Finger Tapping and Brain Dysfunction: A Qualitative and Quantitative Study
George P. Prigatano, PhD
Department of Clinical Neuropsychology, Barrow Neurological Institute, Mercy Healthcare Arizona, Phoenix, Arizona
†Department of Psychology, University of Hamburg, Hamburg, Germany
Fifteen brain dysfunctional patients and 15 normal control subjects were videotaped while performing the Halstead Finger Tapping Test. Compared to control patients, finger tapping in brain dysfunctional patients was not only slower but showed a higher frequency of abnormal finger movements. Disturbances of motor inhibition, apraxia, or both may account for these qualitative findings.
Key Words: neuropsychology, rehabilitation, traumatic brain injury
In his search for measures of “biological intelligence,” Ward Halstead identified the Finger Oscillation (or Tapping) Test as one potentially useful measure. In this test, subjects are asked to place their index finger on a key while their hand rests comfortably on a board. Subjects are then instructed to tap as fast as possible for 10 seconds. The procedure is repeated until five trials have been obtained with each hand in which each score is within five taps of one another.
Provided the subject is “motivated” to tap as fast as possible and there are no peripheral injuries that might influence performance negatively, this “simple” task has proven quite useful. Crossvalidation studies have shown that the mean speed of finger tapping can distinguish brain dysfunctional patients from both medical control patients and psychiatric patients. Speed of finger tapping in the dominant and nondominant hands also relates to the severity of a traumatic brain injury (TBI). Dikmen et al. demonstrated that median speeds were related to the time it took TBI patients to respond to commands in a meaningful way.
Motor recovery after a mild to moderate TBI appears to be better for grip strength than for speed of finger tapping. This finding is compatible with the notion that “motor slowing” (in part measured by speed of finger tapping) is related to the severity of brain injury and therefore may be involved with the ability or lack of ability to recover. This latter notion is supported by a study that related speed of finger tapping to the achievement of rehabilitation goals after an acute cerebral vascular accident. Interestingly, it was the speed of finger tapping of the hand ipsilateral to the lesion (the so-called “unaffected hand”) that distinguished patients who achieved rehabilitation goals from those who failed to do so.
Although various studies have documented the usefulness of quantitative measures of finger tapping, to our knowledge no study has investigated qualitative features of finger-tapping performance in brain dysfunctional patients and normal control patients. This lack is curious because various brain lesions are known to affect the motor systems differentially.[1,2] Moreover, clinical observation frequently reveals individual variations, not only in the number of taps/10 sec but in the tempo or consistency of the rate of tapping. Furthermore, some patients have difficulty inhibiting other finger movements while performing this task.
In this exploratory study, we therefore videotaped finger movements of patients performing the Halstead Finger Tapping Test and asked three questions: Do brain dysfunctional patients seen for clinical neuropsychological evaluation show qualitative features of finger movement not observed in normal individuals? If so, can the features be classified with specific patterns? And, finally, what is the frequency of such abnormal movements?
Methods and Materials
Thirty-one patients consecutively referred to the Department of Clinical Neuropsychology at the Barrow Neurological Institute, St. Joseph's Hospital and Medical Center for neuropsychological evaluation served as the initial study sample. Each patient had a known or suspected brain disorder at the time of referral. Patients were evaluated from mid-October to mid-December 1996.
Patients were diagnosed as follows. First, 13 patients had moderate to severe TBIs as defined by an admitting Glasgow Coma Scale (GCS) score of 9 to 12 and 3 to 8, respectively. One patient had a clearly documented mild TBI (GCS = 13 to 15). Five patients met criteria for dementia of the Alzheimer's type. One patient had cerebral anoxia and a resolving amnestic syndrome. Three patients had neoplasms of the brain (one astrocytoma, one oligodendroglioma, and one choroid plexus tumor). One patient had hydrocephalus with spina bifida. One patient met the DSM-IV criteria for dementia, but its etiology was undetermined. One patient met the DSM-IV criteria for moderate mental retardation. One patient met the DSM-IV criteria for specific learning disability. Four patients lacked an adequate medical history or neuropsychological assessment to permit a specific diagnosis.
From this larger sample of 31 patients, 15 patients (12 males, 3 females) were identified and age matched to 15 (6 males, 9 females) normal subjects who had no history of neurological disorder. These latter individuals consisted primarily of visiting students, friends, or family members of the two investigators. Four of the patients with a brain injury were left-handed and 11 were right-handed. All of the control subjects were right-handed. Table 1 compares the demographic characteristics of these two groups as well as the diagnosis of the patients eventually selected for data analysis.
As a part of their clinical neuropsychological evaluation, each patient was administered the Halstead Finger Tapping Test. Signed informed consent was obtained for each individual. Subjects were seated comfortably at a table on which the finger tapper was placed. Subjects were shown the finger-tapping device and its use was explained. They were instructed to tap as fast as possible for 10 sec, using the index finger of their preferred or dominant hand first. Additionally, all subjects were explicitly told to try and keep their other fingers down, resting comfortably on the board when tapping. They were also asked to try and rest the heel of their hand on the board when performing the tapping task. The procedure was demonstrated by one of two investigators who tested all participants.
The standard procedure of the Halstead Finger Tapping Test was slightly altered. Instead of having the patient tap five consecutive trials with their preferred hand, they were given three trials with the preferred hand first, followed by three trials with the nonpreferred or nondominant hand. They were then given two to three more trials with each hand, depending on the range of their scores and signs of fatigue. The number of taps achieved in 10 sec for each trial and with each hand was obtained.
In addition to this quantitative measure, each patient and 11 of the 15 control subjects were videotaped while performing the task. The other four normal subjects were not videotaped, but the qualitative features of their finger tapping were observed and recorded by the examiners during the trials.