WO2001074236A1

WO2001074236A1 - A diagnostic test for attention deficit hyperactivity disorder

Info

Publication number: WO2001074236A1
Application number: PCT/CA2001/000406
Authority: WO
Inventors: Joan N. Vickers; Sergio Tosi Rodrigues
Original assignee: University Technologies International Inc.
Priority date: 2000-03-31
Filing date: 2001-03-30
Publication date: 2001-10-11
Also published as: AU4400601A

Abstract

Disclosed is a method and associated apparatus for the diagnosis of Attention Deficit Hyperactivity Disorder, or ADHD. The method comprises measuring a person's ability to visually track a moving object during the performance of a motor task in relation to the moving object. In particular, the onset and duration of visual tracking and the frequency of tracking deviation is measured during the performance of a motor task. The method further comprises measuring the ability of a person to successfully perform the motor task. These measurements are then compared to non-ADHD standards to diagnose ADHD. An apparatus is disclosed comprising means for visually displaying a moving object to a person, means for measuring the person's visual tracking of the object and means for measuring a person's ability to perform a motor task in relation to the moving object.

Description

A DIAGNOSTIC TEST FOR ATTENTION DEFICIT HYPERACTIVITY DISORDER

FIELD OF THE INVENTION

The present invention relates in general to methods and apparatus for the diagnosis of Attention Deficit Hyperactivity Disorder, or ADHD, and more particularly relates to the use of variables such as gaze pursuit tracking or quiet eye, gaze frequency, arm movement velocity and percent accuracy as criteria for the diagnosis of ADHD.

BACKGROUND OF THE INVENTION

Attention Deficit Hyperactivity Disorder, or ADHD, is usually characterized by a persistent pattern of inattention and/or hyperactivity- impulsivity. Children, adolescents and adults diagnosed with primary attention deficit (ADHD - PI) cannot sustain attention on relevant objects and events in their environment. Those diagnosed with primary hyperactivity (ADHD - H) have inordinately high levels of impulsiveness in motor behavior. Finally, those diagnosed with combined deficit

(ADHD - C) exhibit deficits of both attention and hyperactivity.

ADHD affects approximately 4 to 6 percent of all children, with estimates varying from 1.7 to 17 percent worldwide. Zametkin, AJ. and Ernst, M. (1999), Problems in the Management of Attention-Deficit- Hyperactivity-Disorder, The New England Journal of Medicine, 340(1),

January 1999, 40-46; Elia, J. Ambrosi, PJ. and Rapaport, J.L. (1999), Drug Therapy: Treatment of attention-deficit-hyperactivity-disorder, The New England Journal of Medicine, 340(10), Mar 1999, 780-788. ADHD may continue into adulthood and is more widespread in males than females during childhood and adolescence by a ratio of 4:1, and in adulthood by a ratio of 2:1. The persistence of ADHD into adulthood has been estimated to be as high as 80%. There is no universally prescribed treatment for ADHD; however, psychostimulant medication such as methylphenidate (Ritalin™), dextroamphetamine (Dexedrine™), and other related drugs reportedly boost the capacity to inhibit and regulate impulsive behavior and have been reported to improve the behavior of children in school related tasks over the short term. Barkley, R.A. (1998), Attention-Deficit Hyperactivity Disorder. A Handbook of Diagnosis and Treatment, 2^nd Ed. (New York: Guilford Press). Unfortunately, not all children suffering from ADHD receive any, or receive only marginal, benefit from such medication. There is at present no universally accepted test for diagnosing

ADHD. ADHD is clinically diagnosed using primarily subjective indicia such as observations of a child's behavior, questionnaires and interviews. Recently, however, studies have been done to explore the possible relationsliip between motor co-ordination and ADHD. It was found that the severity of children's inattentive symptomatology was a significant predictor of motor co-ordination difficulties. Other researchers have found that the relevance of the task to the real world situations is also a key factor in effective research on ADHD. Often the tasks used to study ADHD lack much relevance to tasks which are routinely performed in real life settings.

SUMMARY OF THE INVENTION

The present invention is directed to a diagnostic method and apparatus for diagnosing attention deficit hyperactivity disorder (ADHD) in a person.

In particular, the present invention discloses an apparatus for diagnosing ADHD in a person which measures the ability of the person to visually track a moving object while performing a motor task relative to the moving object. An example of such a motor task is returning a served ball with a paddle. The performance of the motor task involves two phases; a pre- motor phase and a motor phase. The pre-motor phase is sometimes referred to as the cognitive phase and it is during this phase that the person mentally assesses the motor task environment, in particular, commences visually tracking the moving object. The motor phase commences with the onset of the movement necessary to perform the motor task relative to the moving object.

The invention further discloses an apparatus capable of measuring motor control of a person by measuring the ability of a person to physically perform a motor task such as returning a served ball by hitting the ball with a paddle. Further, the invention discloses an apparatus capable of measuring both a person's ability to track a moving object and a person's ability to perform a task specific to the moving object.

The present invention also discloses a method for diagnosing ADHD in a person by comparing the person's ability to visually track a moving object and/or the person's ability to perform a motor task specific to a moving object, to a known standard, for example, to persons' performances who are not diagnosed with ADHD.

In its broadest sense, the present invention discloses an apparatus for diagnosing ADHD in a person comprising a means for visually displaying a moving object to the person and a means for measuring the person's ability to visually track the moving object during the performance of the motor task. Suitable means for displaying a moving object include, but is not limited to, graphically displaying a realistic virtual image generated in a computer to the person in such a fashion that the person perceives a 3D sensation of a moving object, presenting to the person a scene taken by a TV camera in such a fashion that the person perceives a 3D sensation of a moving object, or having a real object moving in real time and in real space. In operating the apparatus for the diagnosis of ADHD, the person is asked to perform a motor task in relation to the moving object. Therefore, in order to perform the task, the person will have to first visually track the object. Suitable tasks would be, but are not limited to, pressing a button, for example, when the object nears the person, moving a limb in response to tlie object, or hitting the object with a paddle or a glove that records the velocity of the hand. In a situation where an actual object is used in real time and space, for example a ball which is served to the person, the means for measuring the person's ability to visually track the moving object comprises:

• a mobile eye tracker; • means for tracking the orientation of the mobile eye tracker;

• means for monitoring the flight of the moving object; and

• a programmable computer program to process the information from the mobile eye tracker, the mobile eye tracker tracking means and the flight of the object monitoring means.

Preferably, the apparatus also includes means for measuring the movement of the person. Such measuring means may comprise, and by way of non-limiting examples, at least one video camera means, which is set up for viewing the person while he or she is engaged in the performance of the particular task, digital imaging means, stop watch means, motor sensing and speed measurement means including and by way of non-limiting example, radar emitting means.

In a further aspect of the invention, there is provided a method for diagnosing ADHD in a person, comprising:

• instructing the person to perform a motor task specific to a moving object;

• displaying the moving object to the person; • measuring the ability of the person to visually track the moving object during the performance of a motor task; and

• comparing said ability to visually track the moving object to a known standard, said comparison to diagnose the presence of ADHD.

Preferably, the person's onset of visual tracking of the object, the length of time the person tracks the object and the frequency in which the person deviates or stops tracking the object for an interval of time is measured and compared to a person's tracking ability who has not been diagnosed with ADHD.

In a further aspect of the invention, a person's ability to perform a motor task relative to a moving object is measured as means for further diagnosing ADHD in a person. For example, when the task which the person must perform is to hit a ball with a paddle, measuring a person's percentage of accurate hits and the velocity of the person's arm at the instant of paddle-ball and comparing same to a non-ADHD person provides a method for diagnosing ADHD.

In a further aspect of the invention, the person may be instructed to perform the task either prior to displaying the moving object to the person or after displaying the moving object to the person.

In a further aspect of the invention, a method for diagnosing ADHD in a person is provided, comprising:

• serving a ball to a person;

• instructing the person to hit the ball towards a target with a hand-held paddle after the ball has been served;

• measuring the velocity of the person's arm at the instant the hand-held paddle makes contact with the ball; and • comparing the velocity of the person's arm to a known standard, said comparison to diagnose the presence of ADHD.

These and other aspects of the invention are described in the detailed description of the invention and in the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 a is a schematic of the table tennis table test set up used in the embodiment of the invention, showing subject and location of video cameras with output showing eye motion, field of view of the eye and the position of the subject in the scene.

Figure lb is a schematic of the subject in relation to the set up of the magnetic head tracker.

Figure lc is a schematic of the subject wearing the eye tracker system.

Figure 2 is a representation of the visual angle between line of gaze and ball edge, gaze and x-axis of the transmitter coordinate system, and the angle between the arm and x-axis of the transmitter coordinate system.

Figure 3 is a schematic of an exemplary video monitor displaying the outputs from the video cameras shown in Figures la and lb.

Figure 4 is a plot of gaze pursuit tracking (visual angle to the ball in degrees versus relative time in percent) of a Normal subject. Figure 5 is a plot of gaze pursuit tracking (visual angle to the ball in degrees versus relative time in percent) of an ADHD subject.

Figure 6a is a plot of gaze pursuit tracking (visual angle to the ball in degrees versus relative time in percent) of an ADHD subject during hits (solid line) and misses (hatched line) during early cue conditions. Figure 6b is a plot of gaze pursuit tracking (visual angle to the ball in degrees versus relative time in percent) of a Normal subject during hits (solid line) and misses (hatched line) during early cue conditions. Figure 7 shows the arm velocity at contact (ANC) in cm/sec of ADHD On subjects, ADHD Off subjects and Normal subjects during the early and late cue conditions.

Figure 8 shows the arm velocity at contact (ANC) in cm/sec of ADHD On subjects, ADHD Off subjects and Normal subjects during early and late cue conditions, on hits and misses.

Figures 9a, b and c show the duration of tracking on the ball results (on the left) and arm velocity at contact results under early cue conditions (on the right), of three Normal subjects. Figures 10a, b and c show the duration of tracking on the ball results (on the left) and arm velocity at contact results under early cue conditions (on the right), of three ADHD subjects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The overall combination of apparatus which forms a preferred embodiment of the system of the present invention is shown in Figures la, lb and lc. In the instant embodiment, the system comprises a table tennis test, however similar technology, software and procedures can be used with any task performance test, for example, table hockey.

Figure la shows the modified table tennis table 15, fitted with right and left cue lights 8, 9 and right and left target areas 28, 29. To commence the table tennis test, a table tennis ball 10 is delivered to the subject 3 using a serving device 7 that directs the ball 10 across the table tennis table 15 towards the subject at a moderate speed (flight time of approximately 800 ms). The serving device 7 delivers the ball to a 40 x 60 cm oval 48 chalked on the table 15, denoting the location of the second bounce. Subjects are to hit the ball as accurately and/or as hard as possible. The subject 3 is to return the ball by means of a paddle 24 (the task) to either the right or left target areas 28, 29 depending upon which of the right and left cue lights 8, 9 is illuminated. The right and left target areas 28, 29, respectively, are rectangular and large enough to be easily hit by a returned ball. The right or left cue lights 8, 9 can be lit either 2 seconds prior to the ball 10 being served (early test condition) or after the ball has been served (late test condition). Laser devices 50, 52 are set up 90 cm from the edge of the table 54 (the table edge where the serving device 7 is situated) so that when the served ball 10 passes the laser beam 56, one of the two cue lights 8, 9 will be lit (late test condition). Under late test conditions, the subject only has approximately 600 ms to react to the cue. In the present invention, there are two integrated data collection systems (primary and secondary) which are used to generate the appropriate data.

Primary Data Collection System

In the primary data collection system, the test subject 3 is equipped with an eye tracker system, a magnetic head tracker, and a motion analysis system (MAS). In the present preferred embodiment, the Applied Science Laboratories™ Model 501 (ASL 501) eye tracker was used but it is understood that any eye/gaze tracking system could be used, for example the ISCAN™ system. The preferred magnetic head tracker is the Flock of Birds™ Model developed by Ascension Technology Corporation™.

The operation of the ASL eye tracker system is described in detail in U.S. Patent 4,852,988 issued to Velez et al on August 1, 1989 and is incorporated herein by reference. The magnetic head tracker is described in detail in U.S. Patent Number 5,744,953 issued to Hansen on April 28, 1998 and is incorporated herein by reference.

Briefly, the ASL 501 eye tracker system is a monocular corneal reflection system that measures line-of-gaze with respect to a helmet 17 worn by the subject 3. The helmet 17 has a 30-meter cord (not shown) which is attached to the waist of the subject 3 and interfaced to a first computer 1. This allows the subject 3 to have near normal mobility. The helmet 17 is further equipped with a eye video camera 19 which is mounted to the helmet 17 by a support member (not shown). The eye video camera 19 is directed at the eye 27 of the subject 3 so that the eye 27 of the subject 3 is in the field of view of the eye video camera 19. The eye 27 is illuminated by a near infrared light source (not shown) beamed coaxially with the optical axis of the eye video camera 19. The light from the near infrared light source and the resulting back-lighted bright pupil image are reflected from a visor 20 coated to be transparent in the visible spectrum but reflective to the near infrared. Use of the visor 20 allows unobstructed simultaneous recording of an image of the eye 27 while the eye is occupied in viewing a scene. Optics (not shown) for the eye video camera 19 or image processing may be used so that the eye video shows about a 2.5 cm x 2.5 cm square centered on the eye.

A second light source 18 is also mounted on the helmet 17 using any of various attachment devices and is supported on the helmet 17 to provide a collimated beam of light that reflects from the visor 20 onto the surface of the cornea and returns corneal reflection into the eye video camera 19.

A field-of-view or scene video camera 21 is mounted on a support 22 attached to the helmet 17 which records the external scene viewed by the observer by reflecting external scene light from the back side of the visor 20. The scene video camera 21 is oriented towards the visor 20 so that the field of view of the scene video camera 21 is nearly aligned with the view from the eye 27 being monitored, thus avoiding parallax problems. The scene camera 21 thus appears to see the world from the same position as the subject's eye. The visor 20 is oriented to pick up optimal scene in front of the subject 3. Since the subject 3 is free to move the head, the scene changes with shifts in the subject's head position.

Interfaced with the ASL 501 eye tracker system is the magnetic head tracker system 2 which is used to determine the location of the gaze relative to the ball. The magnetic head tracker, a six degree of freedom measuring device in this instance, tracks the three-dimensional position and orientation of the eye tracker relative to a transmitter 13, which consists of three individual antennae arranged concentrically to generate a multiplicity of DC magnetic fields. The transmitter 13 is generally located above and one meter behind the subject 3. A receiver 14 is positioned on top of the helmet 17 of the eye tracker system, said receiver 14 consisting of three axes of antenna that are sensitive to DC magnetic fields. The signal output fiom the receiver 14 travels to the signal processing electronics 37 which controls, conditions and converts the analog receiver signals into a digital format that can then be read by a computer (in this case, first computer 1). The signal processing electronics 37 is equipped with an algorithm which computes the position and orientation of the receiver 14 with respect to the transmitter 13. This information is then outputted to the host computer (first computer 1). The magnetic head tracker has a static positional accuracy of 0.1" (2.54 mm), a positional resolution of 0.03" (0.76 mm), a static angular accuracy of 0.5 degrees, and angular resolution of 0.1 degrees.

Data generated from the eye tracker system (i.e. the eye video camera 12 output and the scene video camera 21 output) and data generated from the signal processing electronics 37 of the magnetic head tracker are both inputted to the first computer 1 so as to generate the line- of-gaze relative to the environment, rather than the line-of-gaze relative to the helmet 17 (as is the case with the eye tracker system alone). This is referred to as eye-head integration and the software developed for the eye- head integration is an expansion of the eye tracker software as provided by ASL. Eye-head integration data thus generated is updated at 60 Hz, the same frequency as the eye tracker.

The eye tracker and the magnetic head tracker calibration procedures are also fully integrated in the eye-head integration software. Calibration is divided into specification of planes and specification of eye position in space. The planes to be specified to the eye-head integration software are the table tennis table surface plane and the calibration plane. The calibration plane is arrived at as follows. The receiver 14 is placed on a wand having a laser pointer at one end and a gimbal attached to the other end. The gimbal allows motion of the wand in three dimensions relative to the center of the transmitter 13, the origin of the magnetic head tracker coordinate system. By pointing the laser spot in three points of each plane and by using previously measured distances from the transmitter 13 to those same points, the software calibrates the receiver signals to the three dimensional space (i.e. where the table tennis test takes place).

The specification of eye position in space is calibrated as follows. The receiver 14 is placed on the helmet 17 and the subject 3 is then fitted with the helmet 17. Both the eye video camera 19 and the scene video camera 21 are set up on the helmet 17and the visor 20 is oriented to the table tennis table 15. The subject is then positioned in front of a calibration plane consisting of nine points (each spaced from the other by 3 cm) that are attached to a height-adjustable wooden support. While holding the head steady and moving only the eyes, the subject then looks at each of the nine points and the subject's eye position is recorded relative to each point.

In operation, the eye-head integration software outputs the two- dimensional coordinates of the intersection point between the line-of-gaze and the plane of interest (i.e. the surface of the table tennis table) and the three-dimensional position and orientation angles (azimuth, elevation, and roll) of the receiver 14 (i.e. head) with respect to the signal processing electronics 37.

The primary data collection system also includes a motion analysis system which preferably comprises four to seven high-speed video cameras. In the present preferred embodiment, the motion analysis system comprises six high-speed video cameras 31, 32, 33, 34, 35, 36 set to 180 Hz and positioned in the umbrella configuration as shown in Figure la. The motion analysis system detects both the flight of the ball 10 and the arm 16 motion. The ball 10 is painted with reflective paint which renders the ball 10 retro-reflective to the six cameras 31, 32, 33, 34, 35, 36. In addition, the subject's arm 16 is equipped with at least three reflective markers; one attached to the head of the radius (elbow), the second to the ulnar head (wrist) and the third to the shoulder. Having both the ball 10 and the arm 16 of the subject 3 retro-reflective to the six video cameras 31, 32, 33, 34, 35, 36 allows for digital processing to occur. The video images from each of the six video cameras 31, 32, 33,

34, 35, 36 are captured by a second computer 6 at 180 Hz. The second computer 6 recognizes the retro-reflective markers on each camera image and then reconstructs the three-dimensional position of the markers (i.e. ball 10 and arm 16) in space. Hence, the second computer provides three- dimensional position data of arm and ball flight. Synchronization of all components of the motion analysis system is achieved by electrical pulses sent simultaneously to a central control box (not shown).

As the motion analysis system data processing has distinct phases, its accuracy is described in terms of three-dimensional final measures of a known distance. To this end, a wand of one meter (1,000 mm) having reflective markers at each end is recorded during a one minute interval at 10 Hz as moving in a volume of 1.06 m x 3.46 m x 1.36 m. The obtained mean distance between the two markers on the wand was consistently shown to be 1,000.1 mm (SD=2.4). The eye-head integration software provides data for the horizontal and vertical gaze (table coordinate system) and tl ree-dimensional position and orientation of the head (transmitter coordinate system). The motion analysis system provided the three dimensional positions of the elbow, wrist and ball (calibration cube coordinate system). A software program written in Matlab™ is provided for data smoothing, interpolation, coordinate system transformation and calculation of angles of interest (hereinafter referred to as the "gaze3d.m program"). Elbow, wrist and head positions and head orientation data are smoothed with a forth-order Butterworth™ filter at 5 Hz. Ball position data is smoothed using the same filter at 30 Mz.

An interpolation procedure is used to transform the eye-head integration data from 60 Hz to 180 Hz. This procedure is used to generate the final data points in different intervals to match the motion analysis system data acquisition frequency. Linear interpolation calculates the gaze data points to coincide with an imaginary line between each pair of original data points. This is appropriate for gaze data due to the speed and abrupt changes in eye position. Spline interpolation estimates new data points for head movement according to a smoother curve that fits the original data. This is appropriate for head data due to the relatively slow nature of head movements and their smooth trajectories.

To calculate the angles of interest, data in the table coordinate system and data in the cube coordinate system are transformed (translated and rotated) to the transmitter coordination system. These transformations use a Matlab™ routine based on Soederkvist and Wedin's algorithm (Soederkvist, I & Wedin, P.A. (1993), Determining the Movement of the Skeleton Using Well Configured Markers, Journal of Biomechanics, 26, 1473-1477) to determine rigid body rotations and translations. To test the accuracy of these transformations, measurements of three points on the table tennis table in the three coordinate systems are used: cube calibration (motion analysis system), table and transmitter (gimbal laser and ruler). The root mean square value of residuals resulting from cube to transmitter coordinate system was 0.81 cm, and from the table to transmitter coordinate system was 0.96 cm. These transformations are performed for all calibration settings.

Once all the data are in the same coordinate system, three separate angles can be calculated. These three angles are shown in Figures 2a, 2b and 2c. Figure 2a shows the visual angle between the line of gaze 50 and the ball edge 51. Figure 2b shows the visual angle between the line of gaze 50 and the x-axis 52 of the transmitter coordinate system. Figure 2c shows the angle between the lower arm 53 (segment from elbow to wrist) and the x-axis 52 of the transmitter coordinate system. The data generated by the gaze3d.m program was used to determine the following dependent variables: Movement Time (MT) onset, offset, and duration

Movement time is defined as the duration of the forward phase of the arm movement until contact of the ball. This final phase of movement execution has been defined as the impulse phase. Abrams, R.A., Meyer, D., and Kornblum , S. (1990), Eye-hand Co-ordination: Occulomotor

Control in Rapid Aimed Limb Movements, Journal of Experimental Psychology: Human Perception & Performance, 16-2, 248-262. MT is characterized by a decrease in the angle between the arm (elbow-wrist segment) and the x-axis of the transmitter coordinate system as shown in Figure 2c and/or when the first data point of the forward movement of the arm is greater than zero. The MT onset criterion is when there is the greatest angle between the arm and the x-axis of the transmitter coordinate system and MT offset is the last data point before the ball exhibits an abrupt change in the direction of its trajectory (i.e. ball-paddle contact).

Quiet eye (QE) onset, offset, and duration

Quiet eye is a measure of a person's ability to visually track an object while performing a motor task. Specifically, quiet eye is a measure of the location, onset, offset and duration of a final fixation or tracking gaze that occurs relative to the onset of movement. Quiet eye onset occurs prior to the onset of movement time (MT) and quiet eye offset occurs naturally as the gaze deviates from a defined location. Quiet eye can therefore extend into MT. The criteria for quiet eye is that the visual angle between line-of-gaze and a defined location (in this case the ball's edge as shown in Figure 2a) should be maintained for at least 100 ms within three degrees. A value of three degrees was used for ball tracking based on prior literature (see, for example, Bahill, A. and LaRitz, T (1984), Why Can't Batters Keep Their Eyes On the Ball?, American Scientist, 72, 249- 252; Ripoll, H. and Fleurance,P. (1988), What Does Keeping One's Eye on the Ball Mean?, Ergonomics, 31(11), 1647-1654;Nickers, J.Ν. and

Adolphe, R.A. (1997), Gaze Behaviour during a Ball Tracking and Aiming Skill, International Journal of Sports Vision, 6(1), 30-36; Carpenter, R.H.S. (1988), Movements of the Eyes, (London: Pion)), however, smaller or greater values could be used. Onset of QE is prior to the MT onset, and offset is defined as the point were the gaze deviated off the ball edge more than 3 degrees for > 100 ms. Therefore QE duration is defined as QE offset minus QE onset.

Tracking during movement time (TMT) onset, offset, and duration

Tracking during movement time is defined as the duration of tracking on the ball during the arm movement phase (MT). The criteria for TMT is the same as for QE except that it is initiated during MT.

Eye-head stabilization (EHS) onset, offset, and duration

Eye-head stabilization is defined as the period of stable alignment of the eye and head before ball-paddle contact. The criteria for EHS is that the visual angle between the line-of-gaze and the x-axis of the transmitter coordinate system (see Figure 2b) should remain stable in the final part of ball flight. Stability is based on a fixation criterion, adapted from Helsen, W.F., Elliot, D., Starkes, J.L., and Rickers, K.L. (1998), Temporal and Spatial Coupling of Point of Gaze and Hand Movements in Aiming, Journal of Motor Behaviour, 30(3), 249-259. The onset of EHS requires that the aforementioned angle should be maintained with a standard deviation of 1 deg or less for at least 50 ms. If this criterion is satisfied then EHS is considered to have started. The offset of EHS occurs when four sequential gaze angle measurements are all farther away than 1.5 deg from the mean value of the angles within that period of stabilization.

Arm velocity at contact (ANC)

Arm velocity at contact (ANC) is defined as the instantaneous velocity of the wrist or other marker on tl e arm, hand or paddle at the moment of "contact". "Contact" refers to the moment the subject strikes the ball when executing the return. Arm velocity at contact (ANC, deg/sec) is the three-dimensional angular velocity between arm (elbow- wrist segment) and the x-axis of the transmitter coordinate system or other frame of reference (see Figure 2c) at the moment of ball-paddle contact. ANC (cm/sec) is the instantaneous linear velocity of the marker at the time of contact. For both units (deg/sec and cm/sec), velocity was calculated as the change in position from the data point immediately before contact to the data point immediately after contact, divided by the time elapsed (Winter, D.A. (1990), Biomechanics and Motor Control of Human Movement, 2^nd ed., (New York: John Wiley & Sons).

Accuracy

Accuracy (in percent) is measured by recording the number of hits (i.e. the number of times the subject returns the ball to the designated target area 28, 29) and misses (i.e. the number of times the subject misses the designated target area 28, 29). Accuracy scores are the percentage of accurate returns of the ball to the designated target area.

The absolute measures (millisecond) for MT, QE and TMT are routinely converted to relative time (percent) by the following procedures as outlined by Schmidt, R.A. (1975), A Schema Theory of Discrete Motor Skills, New York, Academic Press; and Schmidt, R.A. and Lee, T.D.

(1999), Motor Control and Learning, Champaign, IL: Human Kinetics. A normalization procedure is applied to the data relative to the total test duration (rt%). Thus every test has at its onset an rt% of 0 and at its offset (ball-paddle contact) an rt% of 100. Each point in time is therefore represented as a proportion or percentage of the total time. When one measures QE, it was found that relative time is the stronger of the two measures for QE as it takes into account any variance in terms of ball light. The normalization of time of each data point is proportionally calculated using the following formula:

Relative Time = (absolute time of data point - absolute time of trial onset)* 100 absolute time of trial offset - absolute time of trial onset A secondary computer program to the gaze3d.m is provided to obtain the frequency of gaze-ball angle deviations (hereinafter referred to as the "gazeFreq.m program"), a measure in the spatial dimension only and independent of time. The gazeFreq.m program gives a measure of the smoothness of ball tracking or gaze frequency (GF). The threshold value, or sensitivity, can be set to any real positive number. In the present invention, one, two and three degrees have been used. For example, if one degree is used, any change of greater than one degree is considered a signal, and any change less than one degree is regarded as noise and ignored. In summary, gaze frequency is defined as follows:

Gaze Frequency (GF)

Gaze frequency is defined as the frequency of gaze deviation from the ball's edge during the entire flight of the ball, from serve to contact. In the following examples, GF was defined as the frequency of gaze deviation from the ball's edge more than 3 degrees visual angle. The degrees visual angle can be set at 1, 2, 3 or more.

Secondary Data Collection System

The secondary data collection system is described in detail in Canadian Patent Application 2,209,886 and is incorporated herein by reference. This secondary system is referred to as the Nision-in-Action system and includes an ASL 501 eye tracker for video outputs (as described above), an external camera 5 (SONY™ TRN 82), a time code generator and a video mixer thereby coupling the subject's gaze, motor and ocular behavior in time. The secondary data collection system is used concurrently with the first data collection system in order to ensure the accuracy of the data collection in the present invention. The two video outputs from the ALS 501 eye tracker and the video output from the external camera 5 are integrated into one final video image which provides the gaze in the scene from the subject's point of view, the eye recorded, and the movements of the subject 3, the server 7 and the ball 10.

The Nision-in-Action system is used to calibrate the participant, monitor calibration during data collection and provide information for later clinical use.

Output from the eye view monitor computer (i.e. first computer 1), including scene with gaze cursor and eye video, and output from the external camera 5 are mixed in a mixer having an output formed of sequential frames in which, in each frame of the mixer output, there is included synchronized video information from each of the cameras.

Preferably, the signals are mixed so that, as shown in Fig. 2, each video output occupies a distinct window on a video monitor 100 (e.g. a Sony™ monitor). Various arrangements may perform the function of the mixer. For example, two effects generators, e.g. Nideonics™, Model MX-1, may be cascaded together as described below.

The first effects generator receives scene video from the eye view monitor computer at its first video input, and video of the subject from an external camera 5 (see Figure la) at its second video input. Genlock signal out from blackburst output on the first effects generator is fed back to the external camera 5. A mixed signal comprising both scene video and subject video is output from the first effects generator video output. The second effects generator receives eye video from the first computer 1 at its first video input, mixes scene video, including gaze information, such that a cursor appears at the location of the subject's gaze in the scene (the gaze cursor) and subject video from the first effects generator, and mixes them to produce mixed eye, scene with gaze cursor and subject video at its video output.

The mixer may also be formed of a digital squeezer, itself known in the art, that squeezes each of the images from the eye video camera, scene video camera and external video camera so that a complete, but reduced, image from each camera appears in the displayed image on the display monitor. Mixer output is input to a video time code generator (e.g. a Datum ™ model 9100 A) which adds time code information to the mixer output for display. The combined mixer output and time code information is input to a first video recorder (e.g. a Toshiba™ or Sony™ recorder), where it may be mixed with audio from an audio mixer, and recorded on video tape. The video tape or a direct feed may be then input to a second video recorder, from which the mixer output and time code information may be displayed on the monitor 100. The final mixed data from all cameras can also be recorded on compact disc, video disc, computer, or other recording devices.

Typical video output displayed on the monitor 100 is shown in Fig. 3 for the analysis of the table tennis test. The upper right portion, about 40% of the monitor screen, shows a scene 106 as seen by scene video camera 21, which closely approximates the scene as viewed by the subject 3. The cursor 104 shows the gaze location of the subject 3 as computed by the first computer 1. The lower portion 102 of the screen shows the subject 3 as viewed by the external camera 5. The upper left quarter 108 shows the image of the eye of the subject 3. The eye view image 118 shows the center of the pupil 110 as indicated by the cross-hairs 112 andl l4 and the location of the corneal reflection 116 as indicated by the cross-hairs 118 and 120. Time code information may be superimposed on the displayed image in any convenient location. Each displayed frame of video is assigned a unique time code. Each frame is also preferably coded with a unique identifier in milliseconds to show the frame interval, according to the standard used (30 frames per second, 60 frames per second or 100 frames per second for example). The NTSC rate is 30 Hz (1 frame = 33.33 ms) and the PAL rate is 50 Hz (1 frame = 20 ms).

In operation of the system thus described, a subject 3 performs a motor activity, such as participating in the table tennis test. The eye video camera 19 is directed at the subject's eye after reflection from the visor 20, and eye video is output to the first computer 1. The scene video camera 21 is directed at the scene by reflection from the visor 20, and scene video is also output to the first computer 1. Eye video and scene video is mixed in the mixer (not shown). At the same time, the external video camera 5 is directed at the subject 3 and output from the external video camera 5 is mixed with the output from the eye video camera 19 and scene video camera 21. A frame of video from each camera 19, 21 and 5 is mixed by the mixer such that each mixed frame of video information includes information from each of the video cameras. By information is meant useful information: enough of the video output from each camera must be displayed to be able to assign values to variables representing physical activity viewed by the video cameras. The output from the mixer may then be recorded for later viewing and displayed simultaneously on a monitor. It is preferred that each mixed frame be encoded with a unique time code so that each array of values representing physical and/or eye activity has a unique identifier. Once again, it is preferred that the scene video mixed into the mixer output include gaze information, such that a cursor appears at the location of the subject's gaze in the scene.

Once the mixer output has been recorded, it may be played back and analyzed frame by frame. Data values are assigned to observable physical characteristics of the motor activity of the subject, people or objects in the scene, gaze locations, gaze behaviors, eye movement, and activity performance. Activity performance, or outcome measures, are recorded, such as accuracy of the trial, optimal verses non-optimal use of objects or tools, and effective or ineffective interaction with others and objects. Temporal motor phases are defined based on the mechanics of the motor skills and needs of the subject. Onset, offset and duration, in milliseconds or other time durations, of the skill and phases of the skill are determined as is the movement time of the sldll. Number of steps, onset of the first and last step, step duration, and direction of stepping or other body movements may be assigned data values. Likewise, arm and hand movement and body velocity may also be assigned values.

Gaze locations may be identified and coded, relative to the motor phases of the skill. A gaze behavior is defined as the gaze held stable on a location in the environment, or a shift in gaze from one location to another. Percent of trials in which a gaze behavior is observed is reported, as is the frequency, onset, offset, and duration of important gaze behaviors during each motor phase. Since a shift in gaze is normally initiated by eye movements, four or more gaze behaviors are identified based on definitions originating from the eye movement literature, for example, fixations, saccades, tracking and blink. Each is coded within accepted ranges using minimum duration parameters. For example, minimum fixation duration is 99.9 ms (3 or more frames) and defined as the stabilization of the gaze cursor on a location in the environment. A tracking gaze behavior is coded when the eyes pursue a moving object or person for 3 or more frames or 99.9 ms. A saccade is coded when a shift in gaze is observed from one location to another with movement time (MT) of 66.6 ms or more (2 or more frames). During a saccade, vision is normally suppressed.

Ocular functions are defined by pupil diameter, eye movements (ratio of pupil center to CR), blink rate and duration.

Analysis output includes graphical presentation of the temporal integration of the subject's gaze behaviors, motor behaviors, and ocular function relative to objects, persons and events in the sldll. Imaging techniques (i.e. NIH Image) are also used to temporarily plot the gaze relative to objects (e.g. a ball).

Example 1

Two adolescent boys, both age 14, were tested using the table tennis test as described above. One boy did not suffer from ADHD (normal subject) while the other boy was diagnosed with ADHD-PI (ADHD subject). Each subject was first allowed to practice the task until comfortable, about 10 minutes. The eye tracker was then fitted on each subject and each subject was calibrated to nine points in space that coincide with the table surface. A second fine calibration procedure is carried out during testing to three points on the table located along the path of the ball, before and after trials to ensure accuracy.

Two conditions of testing were used, early and late. In the early condition, the target cue light comes on two seconds before the ball is served. In the late condition, the target cue comes on 300 ms after the ball is served. Trials are mixed using a Latin square design to minimize order effects. Catch trials are used in order to avoid guessing.

Figure 4 shows the pursuit tracking on the ball of the normal subject during 5 hits (solid line) and 5 misses (dashed line). A visual angle of zero means that the subject's eye gaze was on the ball. It can be seen from Figure 4 that the normal subject detected the ball early and was able to track it over about half of the total flight time of the ball.

Figure 5 shows the pursuit tracking on the ball of the ADHD-PI subject during 3 hits (solid line) and 5 misses (dashed line). Here it is evident that the ADHD-PI subject was having a very difficult time maintaining tracking on the ball.

Example 2

In this example, ADHD subjects were recruited using an advertisement in a local newspaper. Forty-three individuals responded and eight were selected after screening interviews using Barkley and Murphy's ADHD Clinical Questionnaire (Barkley, R.A. and Murphy, K.R. (1998), Attention-deficit hyperactivity disorder, A Clinical Workbook, 2^nd Edition (New York: Guilford Press). In addition, each of the subjects' physician and/or psychologist were consulted to confirm a ADHD-PI or ADHD-C diagnosis. The eight selected ADHD subjects were then age matched with seven Normal control subjects. All chosen subjects were screened for learning disabilities, anxiety disorders, reading difficulties, use of other medications and skill level in table tennis.

Each of the eight selected ADHD subjects were on medication. Six of the ADHD subjects were taking Ritalin™ and two of the subjects were taking Dexedrine™, mean dosage 24.4 mg (SD = 6.2). The age, diagnosis and medication status of the aforementioned subjects are summarized in Table 1.

Table 1

Number of participants, age, diagnosis and medication status of ADHD and Normal Subjects

ADHD Normal

Number 8 7

Age (Years)

Mean 14.3 14.9

SD a 1.5 1.1

Range 13-16 14-16

Diagnosis

ADHD PI 5

ADHD C 3

Medication at testing

Ritalin™ 6

Dexedrine™ 2

None a standard deviation

Each of the eight ADHD subjects were first tested while they were on their mediation (ADHD ON). The ADHD subjects would then be tested two weeks later when they had been off their medication for at least 48 hours (ADHD Off).

All subjects were tested under both early and late conditions. In the early condition, the target cue came on 2 seconds before the ball was served. In the late condition, the target cue came on after the serve passed through the laser beam. The laser beam was situated so that the served ball triggered the target cue light about 300 ms after the ball was served.

This left only approximately 600 ms for the subject to respond.

Performance accuracy (%>) was determined using 20 trials of each condition. MT, QE and TMT data were derived from the first five hits in each condition, and five misses, randomly selected. All absolute measures (millisecond) of MT, QE, and TMT were converted to relative time (percent), following procedures outlined above. Missing cells were filled using mean values for Group x Condition x Accuracy x Trial. Missing trials occurred due to equipment malfunction, or the participant being unable to complete the five hits to the target in the 20 trials allowed per condition.

The groups differed significantly, F (2, 12) •= 12.13, p <.001, in the number of trials they were able to complete. The ADHD Off subjects did not complete 21.20% of trials and the ADHD On did not complete 10.00 % of trials. However, Normal subjects did not complete only 4.00% of the trial.

Four steps were followed in the analysis of the data obtained. First, in order to determine if the ball was served at the same speed to each subject, ball flight duration was analyzed using a 1 x 2 (Group, Condition, Trials) ANONA, with repeated measures on the last two factors. Second, in order to determine if the eye tracker affected accuracy, a 1 x 2 (Group, Tracker) design was used which compared the subject's accuracy with or without the tracker. Third, percent accuracy in hitting the targets was determined under both the early cue (E) and in the late cue (L) conditions using a 1 x 1 (Group, Condition) AΝONA, with repeated measures on the last factor. Four, the dependent measures of QE onset, QE offset, QE duration, MT onset, MT duration and ANC, were analyzed separately, using a 1 x 3 (Group, Condition, Accuracy, Trials) AΝONA, with repeated measures on the last three factors. TMT onset, TMT offset, TMT duration were not analyzed due to the low incidence of this gaze (< 4% of trials).

There were no significant differences found in ball flight duration to second bounce, total ball flight, or ball flight to the onset of the cue in the L condition. Mean values and SD's are shown in Table 2. Table 2

Ball Flight Duration In Milliseconds And Relative Time (With Standard Deviations in Brackets) To The First Bounce, Ball Flight To Second Bounce, And Total Ball Flight (Service To Contact) Of ADHD Off, ADHD On And Normal

Ball Flight Ball Flight Ball Flight

Group 1^st Bounce 2^nd Bounce Total

ADHD Off ms 175.10 (18.35) 627.23 907.23 (41.18) (90.23)

% 18.69 (2.17) 69.54 (5.34) 100.00

ADHD On ms 168.26 (17.41) 635.11 908.08 (34.03) (61.83)

% 19.34 (2.17) 70.16 (3.96) 100.00

Normal ms 163.78 (14.61) 594.91 819.07 (30.83) (49.79)

% 0.06 (2.07) 72.74 (3.67) 100.00

No significant differences were detected in accuracy due to the subject having to wear the eye tracker. This result was consistent with previous studies that showed the eye tracker did not significantly affect the accuracy of either adults or children.

Table 3 shows the percent accuracy of the ADHD Off, the ADHD On and the Normal subjects during early and late conditions. The Normal subjects were significantly more accurate than either the ADHD On subjects or the ADHD Off subjects (M = 46% as compared to M = 26% and 30%), respectively). Scheffe post-hoc tests also revealed that the Normal subjects differed from the ADHD On subjects and the ADHD Off subjects. The interaction of Group x Condition was not significant, however, indicating that the subjects in each groups maintained the same level of accuracy during early and late conditions. Table 3

Percent Accuracy (%) Of The Groups (ADHD-Off, ADHD On, Normal Controls) During Two Temporal Conditions (Early And Late Cue) In Hitting to the Target

Measure ADHD ADHD ^{~ ' ~} Post-hoc

O „ff. On Normal Fa ^μ b _?

Group (df2, 20)

< Off = On

26.20 29.50 46.40 8.62 .002 < N

(13.3) (14.2) (13.9)

Conditions x Gi -oup (df

1.04 n/s 2, 20)

E Cue 25.20 31.80 49.10 (14.9) (14.2) (13.9) L Cue 27.20 27.20 43.70 (11.9) (14.1) (14.9)

Standard deviation in parentheses. n/s = non-significant.

% = percent hits made to the cued target a =ANOVA b = Scheffe'

Table 4 displays the group effects for gaze pursuit tracking (QE onset, offset and duration, GF), and arm movement (MT, ANC). .Also shown are the results of the repeated measures AΝONA and post-hoc tests. It can be seen from Table 4 that GF was significantly higher for both the ADHD On and the ADHD Off subjects when compared to the Normal subjects (3.83 for ADHD Off, 2.89 for the ADHD On, 2.44 for Normal). The Scheffe post hoc tests showed ADHD Off did not differ from ADHD On, but both differed from Normal. QE onset was significantly later for both ADHD groups; Normal onset occurred at 14% of ball flight as compared to 20.69% for ADHD Off and 23.17% for ADHD On. Post-hoc tests were non-significant. QE duration was significantly longer for the Normal group, 49.39%, as compared to the ADHD Off group, 38.92%, and the ADHD On group, 36.37%. Post-hoc tests indicated no difference between both ADHD groups, however, both ADHD groups differed from the Normal group. QE offset did not differ amongst the groups; QE offset occurred between 59.13% to 63.91%) of ball flight for all groups.

Table 4

Gaze And Arm Control Of Groups (ADHD-Off, ADHD-On, Normal Controls) In Table Tennis.

Groups ADHD ADHD ^{~ " ~} Post-hoc

^ „ _j „ Normal F _D ■,

Off On ^ b

Gaze Control

Gaze 3.83 2.89 2.44 5.62 <.01 On = Off

Frequency b (1.89) (1.66) (1.48) > N

QE Onset c 20.69 23.17 14.43 3.40 <.05 Off = On

(18.99) (20.47) (14.71) = N

QE Duration c 38.92 36.37 49.39 <.03 Off = On

(18.67) (19.83) (19.61) < N

QE Offset c 59.13 60.49 63.91 .49 n/s

(19.65) (21.89) (16.44)

Arm Control (df2, 80)

MT Onset c 74.75 72.17 73.37 .61 n/s

(8.49) (6.54) (5.32)

MT Duration 25.55 27.28 26.62 .71 n/s c (8.41) (6*54) (5.32)

AYC d 46.30 52.63 50.59 .59 n/s

(14.88) (15.67) (19.51)

AVC d Condition x Group (df2, 80) 6.49 007

Early Cue 42.32 55.21 50.47

(11.98) (18.07) (17.11)

Late Cue 50.28 50.05 50.71

(16.44) (12.41) (21.77)

Group: ADHD Off medication; ADHD On medication; N = Normal controls Standard deviation in parentheses. n/s = non-significant.

% = percent of accurate hits to the cued target a = Repeated measures ANOVA. b = number of gaze deviating from ball edge > 3 degrees visual angle/trial c = relative time - percent of total trial time (0% = ball serve; 100% = ball-bat contact) d = centimeters per second e = Scheffe' The main effects of GF, QE onset and QE duration were significant. GF was significantly higher for both ADHD groups, ADHD Off having a GF of 3.8 and ADHD On having a GF of 2.9 as compared to a GF of 2.4 for the Normal group. Post-hoc tests showed the ADHD Off group did not differ from the ADHD On group; however, the ADHD Off group did differ from the Normal group. QE onset was p < 0.053 and occurred earlier for the Normal Group, 14%,

Figures 6a and 6b provide plots of the gaze pursuit of a Normal and ADHD subject, respectively, expressed as visual angle on the edge of the ball. The horizontal lines denote the three degree threshold for defining pursuit tracking. Figure 6a shows the pursuit tracking of a 14 year old ADHD Off subject under early cue conditions. The ADHD Off subject was unable to maintain continuous tracking on the ball. A higher frequency of GF is shown and QE tracking is of short duration. Also evident is a different temporal pattern for hit and misses. Figure 6b shows the gaze pursuit of a Normal; also age 14, under early cue conditions. The results in Figure 6b show a lower frequency of GF, and a longer duration of QE tracking. Also evident is a similar temporal pattern of gaze control on hits and misses, or greater invariance in the timing of the saccadic and tracking gaze over the course of ball flight.

There were no differences in arm MT onset, MT duration or ANC (cm/sec) under late cue conditions amongst the three groups. However, under early cue conditions, the two-way interaction of Condition x Group, F (2, 80) = 6.49, p < .007 was significant (Figure 7), as was the three-way interaction of Condition x Accuracy x Group, F (2, 80) = 4.44, p < .03

(Figure 8). ANC for the Normal subjects were similar on hits and misses (range 50.3 - 50.9 cm/s) under early and late conditions. The same was true for the ADHD On and Off (range 49.5 - 50.5 cm/s) under late conditions. However, under early conditions, both the ADHD On subjects and the ADHD Off subjects exhibited irregular ANC levels (range 42.3 -

57.2 cm/s). This result indicates that the ADHD subjects had a more difficult time controlling the velocity of their arm when they had more time to process the task. The use of medication affected ANC under early conditions, but not under late conditions. When the ADHD subjects were on their medication, their ANC levels were higher than Normal subjects, and when off their medication their ANC levels were lower. Figures 9a, 9b and 9c show the duration of tracking on the ball results (on the left) and arm velocity at contact results under early cue conditions (on the right), of three Normal subjects, respectively. Figures 10a, 10b and 10c show the duration of tracking on the ball results (on the left) and arm velocity at contact results under early cue conditions (on the right), of three ADHD subjects, respectively. A comparison of the ball tracking abilities of the three Normal subject to the ball tracking abilities of three ADHD subjects clearly shows that the ADHD subjects have a more difficult time tracking the ball for any length of time. Therefore, this is a good parameter to use for diagnosing individuals with ADHD. Similarly, the Normal subjects showed consistent MT onset, MT offset and

ANC, indicating motor invariance. However, while the ADHD subjects showed normal MT onset and MT offset, they differed significantly in ANC. Hence, it would appear that AVC is also a good parameter to use for diagnosing individuals with ADHD. When all of the collected data for the ADHD Off group is compared with the data for the ADHD On group, it is clear that medication did not significantly improve either gaze control or arm movements of those diagnosed with ADHD, under either easy or hard conditions. There appeared to be a slight improvement towards the Normal group in accuracy and GF when an ADHD subject was on medication. Medication also significantly improved the ability of the ADHD subjects to complete the required number of trials.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for diagnosing attention deficit hyperactivity disorder (ADHD) in a person, comprising:

• instructing the person to perform a motor task specific to a moving object, wherein the performance of the motor task comprises a pre-motor phase and a motor phase;

• displaying the moving object to the person;

• measuring the ability of the person to visually track the moving object during the performance of the motor task ; and

2. A^" method according to claim 1 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the object.

3. A method according to claim 1 wherein the ability of the person to visually track the moving object comprises the length of time the subject visually tracks the object during the performance of the motor task.

4. A method according to claim 1 wherein the ability of the person to visually track the moving object comprises the frequency that the subject deviates from tracking the object during tlie performance of the motor task.

5. A method according to claim 1 wherein the ability of the person to visually track the moving object comprises:

• the onset of visually tracking the object;

• length of time the person visually tracks the object during the performance of the motor task; and

• the frequency that the person deviates from tracking the object during the performance of the motor task.

6. A method according to claim 1 wherein the moving object is a ball.

7. A method according to claim 6 wherein the instructed motor task comprises hitting the ball with a hand-held paddle.

8. A method according to claim 7 wherein the ball is displayed to the person by means of a serving device that serves the ball to the person.

9. A method according to claim 8 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the ball.

10. A method according to claim 8 wherein the ability of the person to visually track the moving object comprises the length of time the person visually tracks the ball during the performance of the motor task of hitting the ball with the hand-held paddle.

11. A method according to claim 8 wherein the ability of the person to visually track the moving object comprises the frequency that the person deviates from tracking the ball during the performance of the motor task of hitting the ball with the hand-held paddle.

12. A method according to claim 8 wherein the ability of the person to visually track the moving object comprises:

• the onset of visual tracking of the ball;

• the length of time the person visually tracks the ball during the performance of the motor task of hitting the ball with the hand-held paddle; and

• the frequency that the person deviates from tracking the ball during the performance of the task of hitting the ball with the hand-held paddle.

13. A method according to claim 12 wherein the known standard is a person who is not diagnosed with ADHD.

14. A method according to claim 1 wherein the person is instructed to perform the motor task prior to displaying the moving object to the person.

15. A method according to claim 1 wherein the person is instructed to perform the motor task after displaying the moving object to the person.

16. A method for diagnosing ADHD in a person, comprising:

• displaying the moving object to the person;

• measuring the ability of the person to perform the motor task; and

• comparing said ability to perform the motor task to a known standard, said comparison to diagnose the presence of ADHD.

17. A method according to claim 16 wherein the ability to perform the motor task comprises the number of times the motor task is successfully performed.

18. A method according to claim 16 wherein the moving object is a ball.

19. A method according to claim 18 wherein the motor task to be performed is hitting the ball with a hand-held paddle.

20. A method according to claim 19 wherein the ball is displayed to the person by means of a serving device that serves the ball to the person.

21. A method according to claim 20 wherein the ability to perform the motor task comprises percentage of accurate hits by the person of the ball with the hand-held paddle to a target.

22. A method according to claim 20 wherein the ability to perform the motor task comprises the velocity of the person's arm at the instant the hand-held paddle makes contact with the ball.

23. A method according to claim 20 wherein the ability to perform the motor task comprises:

• percentage of accurate hits by the person of the ball with the hand-held paddle to a target; and

• velocity of the person's arm at the instant the hand-held paddle makes contact with the ball.

24. A method according to claim 20 wherein the known standard is a person who is not diagnosed with ADHD.

25. A method according to claim 16 wherein the person is instructed to perform the motor task prior to displaying the moving object to the person.

26. A method according to claim 16 wherein the person is instructed to perform the motor task after displaying the moving object to the person.

27. A method for diagnosing ADHD in a person, comprising:

• displaying the moving object to the person;

• measuring the ability of the person to visually track the moving object during the performance of the motor task;

• measuring the ability of the person to perform the motor task; and

• comparing said ability to visually track the moving object and said ability to perform the motor task to known standards, said comparisons to diagnose the presence of

ADHD.

28. A method according to claim 27 wherein the moving object is a ball.

29. A method according to claim 28 wherein the instructed motor task comprises hitting the ball with a hand-held paddle.

30. * A method according to claim 29 wherein the ball is displayed to the person by means of a serving device that serves the ball to the person.

31. A method according to claim 27 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the object and the length of time the person visually tracks the object during the performance of the motor task, and the ability to perform the motor task comprises the number of times the task is successfully performed.

32. A method according to claim 27 wherein the ability of the person to visually track the moving object comprises the frequency that the person deviates from tracking the object during the performance of the motor task, and the ability to perform the motor task comprises the number of times the motor task is successfully performed.

33. A method according to claim 29 wherein the ability of the person to visually track the moving object comprises the frequency that the person deviates from tracking the ball during the performance of the motor task of hitting the ball with a hand-held paddle, and the ability to perform the motor task comprises velocity of the person's arm at the instant the hand-held paddle malces contact with the ball.

34. A method according to claim 29 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the ball and the length of time the person visually tracks the ball during the performance of the motor task of hitting the ball with a hand-held paddle, and the ability to perform the motor task comprises velocity of the person's arm at the instant the hand-held paddle makes contact with the ball.

35. A method according to claim 27 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the object and the length of time the person visually tracks the object during the performance of the motor task and the frequency that the person deviates from tracking the object during the performance of the motor task, and the ability to perform the motor task comprises the number of times the task is successfully performed.

36. A method according to claim 29 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the ball and the length of time the person visually tracks the ball during the performance of the motor task of hitting the ball with a hand-held paddle and the frequency that the person deviates from tracking the ball during the performance of the motor task of hitting the ball with a hand-held paddle, and the ability to perform the motor task comprises velocity of the person's arm at the instant the hand-held paddle makes contact with the ball.

37. A method according to claim 29 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the ball and the length of time the person visually tracks the ball during the performance of the motor task of hitting the ball with a hand-held paddle, and the ability to perform the motor task comprises velocity of the person's arm at the instant the hand-held paddle makes contact with the ball and the number of times the person successfully hits the ball with the hand-held paddle.

38. A method according to claim 29 wherein the ability of the person to visually track the moving object comprises the frequency that the person deviates from tracking the ball during the performance of the motor task of hitting the ball with a hand-held paddle, and the ability to perform the motor task comprises velocity of the person's arm at the instant the hand-held paddle makes contact with the ball and the number of times the person successfully hits the ball with the hand-held paddle.

39. A method according to claim 29 wherein the ability of the person to visually track the moving object comprises the onset of visually tracking the ball and the length of time the person visually tracks the ball during the performance of the motor task of hitting the ball with a hand-held paddle and the frequency that the person deviates from tracking the ball during the performance of the motor task of hitting the ball with a hand-held paddle, and the ability to perform the motor task comprises velocity of the person's arm at the instant the hand-held paddle makes contact with the ball and the number of times the person successfully hits the ball with the hand-held paddle.

40. A method according to claim 27 wherein the person is instructed to perform the motor task prior to displaying the moving object to the person.

41. A method according to claim 27 wherein the person is instructed to perform the motor task after displaying the moving object to the person.

42. An apparatus for diagnosing attention deficit hyperactivity disorder (ADHD) in a person, comprising:

• means for visually displaying a moving object to the person; and

• means for measuring the ability of the person to visually track the moving object during the performance of an instructed motor task specific to the moving object.

43. An apparatus according to claim 42 wherein the means for measuring the ability of the person to visually track the moving obj ect comprises :

• a mobile eye tracker;

• means for tracking the orientation of the mobile eye tracker;

• means for monitoring the flight of the moving object; and

44. An apparatus according to claim 43 wherein the means for monitoring the flight of the moving object comprises at least one external camera.

45. An apparatus according to claim 44 wherein the means for tracking the orientation of the mobile eye tracker comprises a magnetic head tracker.

46. An apparatus according to claim 45 wherein the moving object is a ball.

47. An apparatus according to claim 46 wherein the instructed motor task comprises hitting the ball.

48. An apparatus according to claim 47 wherein the means for displaying the ball to the person comprises a serving means for serving the ball to the person,

49. An apparatus for diagnosing attention deficit hyperactivity disorder (ADHD) in a person, comprising:

• means for visually displaying a moving object to the person; and

• means for measuring the ability of the person to perform an instructed motor task specific to the moving object.

50. An apparatus according to claim 49 wherein the means for measuring the ability of the person to perform the motor task comprises:

• a mobile eye tracker;

• means for tracking the orientation of the mobile eye tracker;

• means for monitoring the movement of the moving object;

• means for monitoring the movement of the person during the performance of the motor task; and

• a programmable computer program to process the information from the mobile eye tracker, the mobile eye tracker tracking means, the means for monitoring the object, and the means for monitoring the movement of the person.

51. An apparatus according to claim 50 wherein the means for monitoring the movement of the object comprises at least one external camera.

52. An apparatus according to claim 51 wherein the means for monitoring the movement of the person comprises at least one external camera.

53. An apparatus according to claim 52 wherein the means for tracking the orientation of the mobile eye tracker comprises a magnetic head tracker.

54. An apparatus according to claim 53 wherein the moving object is a ball.

55. An apparatus according to claim 54 wherein the instructed motor task comprises hitting the ball.

56. An apparatus according to claim 55 wherein the means for displaying the ball to the person comprises a serving means for serving the ball to the person.

57. An apparatus for diagnosing attention deficit hyperactivity disorder (ADHD) in a person, comprising:

• means for visually displaying a moving object to the person;

• means for measuring the ability of the person to visually track the moving object during the performance of an instructed motor task specific to the moving object; and

• means for measuring the ability of the person to perform the instructed motor task specific to the moving object.

58. An apparatus according to claim 57 wherein the means for visually displaying a moving object to the person comprises a computer that generates a realistic virtual image of the object to the person in such a fashion that the person perceives the object as moving in space.

59. An apparatus according to claim 58 wherein the means for measuring the ability of a person to perform the instructed motor task specific to the moving object comprises a glove that records the velocity of the hand.

60. A method for diagnosing attention deficit hyperactivity disorder

(ADHD) in a person, comprising:

• serving a ball to the person;

• measuring the velocity of the person's arm at the instant the hand-held paddle makes contact with the ball; and

• comparing the velocity of the person's arm to a known standard, said comparison to diagnose the presence of ADHD.