Objective Testing for Attention Disorders

HOW M-MAT™ WORKS
excerpted from an article by

Mark Strecker, M.D.

M-MAT™ (McLean Motion and Attention Test) is a 15-minute non-invasive, office-based test that objectively measures a child's ability to sit still and pay attention, with results that have been directly correlated to the brain function. It provides precise, reliable and reproducible information on symptom severity under controlled conditions, which not only aids in the assessment of ADHD, but also provides a valuable and timesaving method of facilitating appropriate medication selection and dose titration. M-MAT™ is currently available for 6-12 year old children, and our research networks is in the process of norming the test for adolescents and adults.

M-MAT™ was developed by Martin Teicher, M.D., Ph.D., Associate Professor of Psychiatry, Harvard Medical School, and Director, Developmental Biopsychiatry Research Program, McLean Hospital. The following brief summary of how M-MAT™ works is based on the enclosed articles by Dr. Teicher from the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP) and Nature Medicine.

M-MAT™ begins with the child performing a continuous performance task (CPT) on the computer, but then goes far beyond the limitations of traditional CPTs by adding a motion analysis component: "CPT with motion analysis can best be understood as a form of provocative test that isolates and emphasizes some of the difficulties found in children with ADHD".1 M-MAT™ provides a consistent, reproducible and standardized challenge to assess impairments in the capacity of children to inhibit and control their activity level, under demanding and monotonous test conditions.

While taking the CPT, the child wears a headband or hat with a reflector on the back. The infrared motion sensor camera, which is positioned behind the child, detects any movement greater than .04 mm., sampling at a rate of 50 times per second. As a result of this very precise, quantitative description of movement differences, hyperactivity "can be objectively and reliably discerned in the frequency, amplitude and pattern of body movements."2

During the 15-minute test, 12 discreet, objective and biostatistically valid measures of attention, impulse control and motoric activity are recorded. M-MAT™ sends subject data from our office through the Internet to the M-MAT™ central server, where they are analyzed, compared to age and gender adjusted normative data, and returned to our office quickly, as a comprehensive report. (The patient's confidentiality is stringently protected throughout this process.)

Dr. Teicher has tested more than 2,000 children, with excellent reliability scores. He has found that normal children are never objectively hyperactive on M-MAT™, but not every child diagnosed with ADHD is objectively hyperactive either. He has shown that "methylphenidate substantially attenuated the activity of ADHD subjects who are objectively hyperactive, but exerted little effect on ADHD children, who were not objectively hyperactive."3 Hence, it may be more important to know who is or is not objectively hyperactive than to know whether they fit DSM-IV criteria.

A significant percentage of patients with ADHD do have marked abnormalities on M-MAT™, and are objectively hyperactive. These are the patients who are very likely to be good stimulant responders. Dr. Teicher has found that these patients include approximately two-thirds of children diagnosed with ADHD, Combined Type, two-thirds of all girls, regardless of DSM-IV subtype, and one-third of boys diagnosed as Predominantly Inattentive. The greatest value of the M-MAT™ is thus in identifying distinct subtypes of patients diagnosed with ADHD, whose medication response may then be predicted and quantified.

The validity of these findings has been given strong additional support by Dr. Teicher's functional MRI research. This research, published last April in Nature Medicine, confirms both pharmacological and neuroimaging findings correlated with M-MAT™ results, not DSM-IV subtypes. Using a new test he developed, T2 relaxometry, he demonstrated that the more poorly a child tested on M-MAT™, the lower the perfusion of the putamen, which is known to regulate attention and body movements. After taking Ritalin, M-MAT™ positive ADHD patients had increased putamen perfusion, and a robust motoric and attentional response, while M-MAT™ negative ADHD patients actually had even less blood flow into the putamen, marginal improvement in attention, and an ambiguous activity response.

In May 2001 Dr. Teicher presented new research at the Annual Meeting of the American Psychiatric Association, which brings the measurement of attention by M-MAT™ up to the level of significance of its measurement of activity. These are two very powerful tools offered only by M-MAT™, which add invaluable objective data to the evaluation of ADHD, and to determining the right medication and dose for each child.

Because attention is a dynamic process, not a static entity, there can be many shifts in attention and mental state throughout the course of a 15-minute test. Other CPTs only provide aggregate measures of errors of omission, errors of commission, and response latency for the entire test, and thus have a limited capacity to detect abnormalities in the least symptomatic cases. In response, Dr. Teicher has developed new analytical procedures that enhance the capacity of M-MAT™ to detect statistically significant differences between inattentive children and controls.

By saving the accuracy and response latency to every stimulus, M-MAT™ can divide each successive 30-second segment response into "On-Task","Impulsive", "Distracted", "Random Responding", "Minimal Responding", and "Contrary Responding." By microanalysis of response patterns and attention shifts as a dynamic temporal process, M-MAT™ more precisely identifies the nature of the attention disturbance in ADHD, and provides new means for delineating differential medication effects on different forms of inattention.

The CPT component of M-MAT™ has been further re-engineered to offer two more advantages in the measurement of attention. On other CPTs, which have stationary stimuli, the child can "cheat" by focusing on a narrow portion of the monitor screen. This is not possible with the M-MAT™ CPT, because it is the only CPT with moving targets. The use of non-stationary targets challenges the additional components of the attention system, which brings out the propensity to be impulsive on the test in children with ADHD. In addition, unlike some other CPTs, the M-MAT™ CPT uses targets that aren't letters or numbers. Results are thus not confused by the presence of dyslexia, since left-right discrimination is not necessary.

Because stimulants are so fast acting, and M-MAT™ can be performed so quickly, you can test your patients before and after a test dose. This can help to benchmark medication response, within the context of your overall clinical assessment, and allows you and your patients to save time in finding the optimal dose of the correct medication.

Another advantage is that "this procedure may be helpful in resolving disagreements regarding the presence of ADHD".4 Parents may be concerned that "the teacher is not objective and may have a personality conflict";5 divorced parents may disagree on rating scales but "parents appear to be very willing to accept the results of objective computer measures".6 In summary, M-MAT™ provides clinicians, parents, teachers, and children the opportunity to quickly and easily add objective information to the overall assessment and treatment of ADHD. (Please see the enclosed checklist of other common clinical quandaries M-MAT™ can help resolve.)

For additional information on how easy it is to refer a patient or to make an appointment for your child for an M-MAT™ evaluation, please call our office at 708-403-3200.

1 Teicher et al., Objective Measurement of Hyperactivity and Attentional Problems in ADHD. Journal of the American Academy of Child and Adolescent Psychiatry 35, March 1996, p. 341.
2 Ibid.p. 340.
3 Teicher et al., Functional deficits in basal ganglia of children with attention-deficit/hyperactivity disorder shown with functional magnetic resonance imaging relaxometry. Nature Medicine 6, April 2000, p. 472.
4 Teicher et al., JAACP article, p. 341.
5 Ibid. p. 342.
6 Ibid. p. 342.