Three patterns of brain damage of the WAIS.

Compared four groups of matched Ss (40 each) in order to examine different subtest patterns of brain damage on the WAIS, using F-tests and age mean profiles. The groups were: Normals, diffuse cortical degeneration, right and left hemisphere damage. The results indicated three patterns: (1) a normal pattern; (2) a diffuse degenerative and right hemisphere pattern; and (3) a left hemisphere pattern. The diffuse degenerative results were not significantly different from the right hemisphere results. The left hemisphere pattern had no large verbal vs. performance differences. These patterns appear to be produced by the interaction of three brain damage effects: (1) a general effect; (2) a right hemisphere effect; and (3) a left hemisphere effect. Verbal tests are both "hold" and left hemisphere tests, while three Performance Tests are "don't hold" and right hemisphere tests. The WAIS requires other specific tests of brain damage for an adequate assessment of brain damage.     

Lateralization in motor facilitation during action observation: a TMS study

Action observation facilitates corticospinal excitability. This is presumably due to a premotor neural system that is active when we perform actions and when we observe actions performed by others. It has been speculated that this neural system is a precursor of neural systems subserving language. If this theory is true, we may expect hemispheric differences in the motor facilitation produced by action observation, with the language-dominant left hemisphere showing stronger facilitation than the right hemisphere. Furthermore, it has been suggested that body parts are recognized via cortical regions controlling sensory and motor processing associated with that body part. If this is true, then corticospinal facilitation during action observation should be modulated by the laterality of the observed body part. The present study addressed these two issues using TMS for each motor cortex separately as participants observed actions being performed by a left hand, a right hand, or a control stimulus on the computer screen. We found no overall difference between the right and left hemisphere for motor-evoked potential (MEP) size during action observation. However, when TMS was applied to the left motor cortex, MEPs were larger while observing right hand actions. Likewise, when TMS was applied to the right motor cortex, MEPs were larger while observing left hand actions. Our data do not suggest left hemisphere superiority in the facilitating effects of action observation on the motor system. However, they do support the notion of a sensory-motor loop according to which sensory stimulus properties (for example, the image of a left hand or a right hand) directly affect motor cortex activity, even when no motor output is required. The pattern of this effect is congruent with the pattern of motor representation in each hemisphere.     

Eye dominance and somatosensory asymmetry in relation to motor asymmetry: Evidence from hemiplegic children

Fifty‐four children with congenital hemiplegia (25 left and 29 right hemiplegics) were administered a battery of sensory and perceptual tests, the results of which were related to measures of motor asymmetry obtained from the same children. Asymmetries of visual acuity and eye dominance were largely independent of motor asymmetry. Asymmetries of stereognosis and finger identification, but not graphesthesia, were associated with various measures of motor asymmetry. It appears that the association between tactile and motor asymmetries varies with the motor demands of the tactile task and that there is little intrinsic relationship between somatosensory and motor asymmetry. Even though the development of motor skill in these children was more impaired by left‐hemisphere damage than by right‐hemisphere damage, left‐and right‐hemisphere damage produced equivalent deficits in their sensory and perceptual ability.     

MMPI correlates of performance intellectual deficits in patients with right hemisphere lesions

This study investigated the emotional adjustment of 50 patients with focal brain damage in the right hemisphere (RHD). The impact of functional loss (as assessed by the WAIS Performance IQ) was assessed by a multivariate comparison of the composite MMPI profiles of these patients as classified into three groups: Below Average, Average, and Above Average Performance IQ. Regardless of the extent of decline in Performance-related abilities, right hemisphere impairment was associated with symptoms of mild depression, loss of initiative, anxiety, denial, and somatic preoccupations. MMPI scores were not correlated significantly with their WAIS Performance IQs. Implications for neuropsychological assessment are discussed.     

Left temporal lobe brain damage pattern on the Wechsler Adult Intelligence Scale

This study supports an association of left temporal brain damage with the unusual WAIS subtest pattern of more impaired Information and Vocabulary than Similarities scores. Temporal lesions may impair well-learned verbal memory more than reasoning skills. Thirty-six patients with localized left hemisphere brain damage in the frontal, parietal or occipital, and temporal lobe were compared using an index in which Information and Vocabulary were contrasted to Similiarities. Index scores were adjusted for age. Seventy-five percent of the temporal patients had negative index scores, and 75% of the frontal patients had positive index scores. Temporal patients tended to score more negatively on the index than did frontal patients, p less than .05.     

WAIS performance in young normal,young alcoholic,and elderly normal groups: An evaluation of organicity and mental aging indices

Investigated the effects of alcoholism and advanced age on Wechsler Adult Intelligence Scale (WAIS) performance and tested the validity of indices of „organicity”︁ and „mental aging”︁ derived from WAIS scores. The WAIS was administered to three groups of 20 males each: young normal (mean age 31 years), young alcoholic (mean age 33 years), and elderly normal (mean age 71 years). In terms of scaled scores, the young normal group was generally superior to the other groups on Verbal and Performance subtests, and the alcoholic and elderly groups resembled each other more on the Verbal than the Performance subtests. In view of an almost 40-year difference in age between the young alcoholic and the elderly normal Ss, similarities in pattern of performance provided some evidence for the hypothesis of „premature aging”︁ in alcoholics.     

The characteristics of the nogo-N140 component in somatosensory go/nogo tasks

Nogo-related brain potentials may not be dependent on sensory modalities but reflect common neural activities specific to the inhibitory process. Recent studies reported that nogo potentials were elicited by not only visual and auditory but also somatosensory stimulation. However, the characteristics of this nogo potential evoked by somatosensory stimulation have been unclear because of the small number of reports. In the present study, therefore, to determine the characteristics of this potential, the effects of stimulus site and response hand were investigated. Electrical stimulation was delivered to the second and fifth digit of one hand, and the subjects had to respond to a go stimulus by pushing a button with the thumb contralateral to the stimulated side as quickly as possible. The amplitudes of the nogo-N140 component (N140 evoked by the nogo stimuli), which is very similar to the nogo-N2 components following visual and auditory stimulation, were unrelated to the stimulated digits, the second and fifth digit of the left and right hand. However, differences between go and nogo ERPs were significantly larger in the hemisphere contralateral to the response hand than the ipsilateral hemisphere. This result was inconsistent with visual and auditory go/nogo studies showing a right-hemisphere dominance or bilateral activities in nogo trials. Therefore, nogo-N140 should be considered to reflect the inhibitory process especially in the hemisphere contralateral to the response hand and the sensory modality dependency of nogo potentials.     

The effects of unilateral brain damage on visually guided reaching: hemispheric differences in the nature of the deficit

Summary Groups of patients suffering from unilateral damage to the left or right cerebral hemisphere were compared to a group of age-matched normal controls in a visually guided pointing task. Subjects were required to reach quickly and accurately to small visual targets as soon as they appeared on the screen in front of them. All reaches, which were quite unrestricted, were videotaped by rotary-shutter cameras and analyzed by a computer-assisted system which allowed analysis of the kinematic parameters of the movement in three-dimensional space. The groups were compared on the basis of their latency to initiate a reaching movement, the accuracy with which they achieved the target's position, and various measures derived from the instantaneous velocity of the movement. Both patient groups were found to be less accurate than controls and to require more time after the target was illuminated to complete the reach. But while the right-hemisphere group took longer to initiate a reach, the kinematic parameters of the movements they produced did not differ from those of the control group. In contrast, the left-hemisphere group did not differ from the control group in the time required to initiate a reaching movement but did require a greater period of time to execute the reach once it had been initiated. It is suggested that the right hemisphere group were deficient in the speed with which they could determine the spatial position of the target, while the left hemisphere group were deficient in their ability to select an appropriate motor program to achieve the target position and/or to monitor the movement and update the motor program as it was being executed.     

Relative performance of the two hands in simple and choice reaction time tasks

There is evidence that the left hemisphere is more competent for motor control than the right hemisphere. This study investigated whether this hemispheric asymmetry is expressed in the latency/duration of sequential responses performed by the left and/or right hands. Thirty-two right-handed young adults (16 males, 16 females; 18-25 years old) were tested in a simple or choice reaction time task. They responded to a left and/or right visual target by moving their left and/or right middle fingers between two keys on each side of the midline. Right hand reaction time did not differ from left hand reaction time. Submovement times were longer for the right hand than the left hand when the response was bilateral. Pause times were shorter for the right hand than the left hand, both when the responses were unilateral or bilateral. Reaction time results indicate that the putatively more efficient response preparation by the left hemisphere motor mechanisms is not expressed behaviorally. Submovement time and pause time results indicate that the putatively more efficient response execution by the left hemisphere motor mechanisms is expressed behaviorally. In the case of the submovements, the less efficient motor control of the left hand would be compensated by a more intense attention to this hand.     

Increasing right hand dominance with age on a motor skill task

A standardized pegboard task was used to investigate changes in manipulative skill as a function of age in 119 right-handed subjects. The typical pattern of cognitive impairment in old age indicates a relative preservation of functions which depend on the integrity of the left hemisphere. In accord with these observations, we predicted that, with increasing age, right hand motor skills would be better preserved than left hand skills. We found this on initial exposure to the task (P less than 0.01); however, the phenomenon was masked by practice, because older subjects (over 60 years of age) derived more improvement to their left hand motor skill, as a result of practice, than they did to their right hand skill (P less than 0.05). The asymmetrical effects of ageing on motor skill may be relevant to the increasing prevalence of emotional lability and neurosis in the elderly, since emotional control is thought to be dependent on right hemisphere mechanisms.     

Probing for hemispheric specialization for motor skill learning: a transcranial direct current stimulation study

Convergent findings point to a left-sided specialization for the representation of learned actions in right-handed humans, but it is unknown whether analogous hemispheric specialization exists for motor skill learning. In the present study, we explored this question by comparing the effects of anodal transcranial direct current stimulation (tDCS) over either left or right motor cortex (M1) on motor skill learning in either hand, using a tDCS montage to better isolate stimulation to one hemisphere. Results were compared with those previously found with a montage more commonly used in the field. Six groups trained for three sessions on a visually guided sequential pinch force modulation task with their right or left hand and received right M1, left M1, or sham tDCS. A linear mixed-model analysis for motor skill showed a significant main effect for stimulation group (left M1, right M1, sham) but not for hand (right, left) or their interaction. Left M1 tDCS induced significantly greater skill learning than sham when hand data were combined, a result consistent not only with the hypothesized left hemisphere specialization for motor skill learning but also with possible increased left M1 responsiveness to tDCS. The unihemispheric montage effect size was one-half that of the more common montage, and subsequent power analysis indicated that 75 subjects per group would be needed to detect differences seen with only 12 subjects with the customary bihemispheric montage.     

Instability of hemispheric asymmetry in dyslexic children.

The study tested the hypothesis of abnormal brain asymmetry in dyslexic children. Two dyslexic groups classified as "phonetic disorder" and "language disorder" and a control group participated in two experiments. In both experiments was employed a dichotic listening procedure consisting in recalling pairs of words presented simultaneously to two ears. In Experiment I the children were to recognize four words presented at a level of loudness typical for natural speech. In Experiment II only two words were used in each trial but they were presented at a low intensity level. The recognition scores for stimuli presented to the left and right ears were compared. In Experiment I all groups of children showed a typical right ear/left hemisphere superiority, i.e. their recognition scores were higher for the right than for the left ear. Dyslexics, however, performed significantly less well. In Experiment II the control children and those from "phonetic disorder" group again performed better when words were presented to their right ears. Unlike those two groups, the children from "language disorder group" showed the right hemisphere superiority, i.e. they performed better in the left ear presentation condition. The results do not support the hypothesis that dyslexic children have abnormal lateralization of verbal functions. They suggest that the pattern of hemispheric asymmetry in dyslexics is less stable and depends both on the kind of dyslexia and on task variation.     

Qualitative block design performance in epilepsy patients.

Broken configuration errors on the WAIS-R Block Design subtest have been associated with right hemisphere brain damage. This study examined whether pre-surgical epilepsy patients with seizure foci restricted to the right hemisphere would break configuration more frequently than those with left hemisphere foci. Subjects included 38 patients with unilateral right or left hemisphere epilepsy of frontal or temporal lobe origin. The left and right hemisphere groups did not differ significantly in demographic or disease variables, IQ, or Block Design standard scores. Right hemisphere patients made more broken configurations than did those with left hemisphere foci. In the right hemisphere group, more broken configurations were associated with a lower Block Design Scaled Score and Full Scale IQ. These results suggest that the observation of broken configurations in the Block Design can assist in corroborating the seizure focus and highlight the importance of qualitative Block Design analysis.     

Imaging recovery from stroke

Brain imaging techniques illustrate the plastic potential even of the adult human brain in healthy subjects as in patients with peripheral or central lesions. Recovery of lost function through a persistent structural lesion in the central nervous system is accompanied by a complex and individually variable pattern of reorganisation of the brain. Changes depend on the site of the lesion and are found in both hemispheres, the damaged and the sound one within a pre-existing, widespread and bilateral organised and parallel processing network without the formation of new centres. This implies changes at rest with increased or decreased activity and altered activation patterns during performance of the restituted function. Within the primary motor system an activation at the rim of the infarct, extension into neighbouring representations, which outflow is not disturbed, altered recruitment pattern of motor cortex neurons, and recruitment of ipsilateral direct descending corticospinal tract pathways originating in the sound hemisphere are found. Disruption of the primary system leads to re-weighting of activity between the various representational levels with increased activity in secondary of higher order areas. Early sensory reorganisation indicates the potential for recovery of lost motor function. Behavioural language training in aphasics results in improvement of altered comprehension function, which is related to right hemisphere activation. Thus, reorganisation can be beneficial and training or rehabilitation influence the pattern of reorganisation.     

Brain correlates of right-handedness

Recent development of neuroimaging techniques has opened new possibilities for the study of the relation between handedness and the brain functional architecture. Here we report fMRI measurements of dominant and non-dominant hand movement representation in 12 right-handed subjects using block design. We measured possible asymmetry in the total volume of activated neural tissue in the two hemispheres during simple and complex finger movements performed either with the right hand or with the left hand. Simple movements consisted in contraction/extension of the index finger and complex movements in successive finger-thumb opposition from little finger to index finger. A general predominance of left-hemisphere activation relative to right hemisphere activation was found. Increasing the complexity of the motor activity resulted in an enlargement of the volume of consistently activated areas and greater involvement of ipsilateral areas, especially in the left hemisphere. Movements of the dominant hand elicited large contralateral activation (larger than movements of the non-dominant hand) and relatively smaller ipsilateral activation. Movements of the non-dominant hand resulted in a more balanced pattern of activation in the two hemispheres, due to relatively greater ipsilateral activation. This suggests that the dominant (right) hand is controlled mainly by the contralateral (left) hemisphere, whereas the nondominant hand is controlled by both left and right hemispheres. This effect is especially apparent during execution of complex movements. The expansion of brain areas involved in motor control in the hemisphere contralateral to the dominant hand may provide neural substrate for higher efficiency and a greater motor skill repertoire of the preferred hand.     

The effects of competition and motor reprogramming on visuomotor selection in unilateral neglect

Patients with unilateral neglect following right hemisphere damage may have difficulty in moving towards contralesional targets. To test the hypothesis that this impairment arises from competing motor programs triggered by irrelevant ipsilesional stimuli, we examined 16 right hemisphere patients, eight with left visual neglect and eight without, in addition to eight healthy control subjects. In experiment 1 subjects performed sequences of movements using their right hand to targets on the contralesional or ipsilesional side of the responding limb. The locations of successive targets in each sequence were either predictable or unpredictable. In separate blocks of trials, targets appeared either alone or with a simultaneous distractor located at the immediately preceding target location. Neglect patients were significantly slower to execute movements to contralesional targets, but only for unpredictable movements and in the presence of a concurrent ipsilesional distractor. In contrast, healthy controls and right hemisphere patients without neglect showed no directional asymmetries of movement execution. In experiment 2 subjects were required to interrupt a predictable, reciprocating sequence of leftward and rightward movements in order to move to an occasional, unpredictable target that occurred either in the direction opposite to that expected, or in the same direction but twice the extent. Neglect patients were significantly slower in reprogramming the direction and extent of movements towards contralesional versus ipsilesional targets, and they also made significantly more errors when executing such movements. Right hemisphere patients without neglect showed a similar bias in reprogramming direction (but not extent) for contralesional targets, whereas healthy controls showed no directional asymmetry in either condition. On the basis of these findings we propose that neglect involves a competitive bias in favour of motor programs for actions directed towards ipsilesional versus contralesional events. We suggest that programming errors and increased latencies for contralesional movements arise because the damaged right hemisphere can no longer effectively inhibit the release of inappropriate motor programs towards ipsilesional events. Received: 1 October 1996 / Accepted: 21 October 1997     

Side of symptom onset affects motor dysfunction in Parkinson's disease

The healthy brain appears to have an asymmetric dopamine distribution, with higher levels of dopamine in the left than in the right striatum. Here, we test the hypothesis that this neurochemical asymmetry renders the right striatum relatively more vulnerable to the effects of dopaminergic denervation in Parkinson's disease (PD). Using the pegboard dexterity test, we compared motor performance of both hands between healthy subjects (n=48), PD patients with predominantly right-hemispheric dopamine depletion (PD-RIGHT; n=83) and PD patients with more severe left-hemispheric dopamine depletion (PD-LEFT; n=103). All subjects were right-handed. After adjusting for hand-dominance effects, we found that PD-RIGHT patients exhibited a 55% larger difference between right and left dexterity scores than PD-LEFT patients. This effect could be attributed to greater motor dysfunction of the more-affected hand in PD-RIGHT patients, while the less-affected hand performed similarly in both groups. We conclude that the side of symptom onset affects motor dysfunction in PD, and suggest that the non-dominant right hemisphere may be more susceptible to dopaminergic denervation than the dominant left hemisphere.     

Hemispheric asymmetries and bimanual asynchrony in left- and right-handers

It is known that, when both forearms are rotated rhythmically and symmetrically, the dominant hand leads in time by about 25 ms, irrespective of movement speed. Positron emission tomography was used to test the hypothesis that the asynchrony results from a functional hemispheric asymmetry. We found that in normal, adult right-handers portions of the motor and premotor motor areas are more active in the left than in the right hemisphere. The converse pattern was observed in left-handers. The results suggest that at least some components of the neural processing involved in bimanual coordination are carried out only in the hemisphere contralateral to the dominant hand. In particular, between-hands asynchrony may reflect the time for dispatching pace-setting commands to the contralateral hemisphere.     

Ipsilesional trajectory control is related to contralesional arm paralysis after left hemisphere damage

We have recently shown ipsilateral dynamic deficits in trajectory control are present in left hemisphere damaged (LHD) patients with paresis, as evidenced by impaired modulation of torque amplitude as response amplitude increases. The purpose of the current study is to determine if these ipsilateral deficits are more common with contralateral hemiparesis and greater damage to the motor system, as evidenced by structural imaging. Three groups of right-handed subjects (healthy controls, LHD stroke patients with and without upper extremity paresis) performed single-joint elbow movements of varying amplitudes with their left arm in the left hemispace. Only the paretic group demonstrated dynamic deficits characterized by decreased modulation of peak torque (reflected by peak acceleration changes) as response amplitude increased. These results could not be attributed to lesion volume or peak velocity as neither variable differed across the groups. However, the paretic group had damage to a larger number of areas within the motor system than the non-paretic group suggesting that such damage increases the probability of ipsilesional deficits in dynamic control for modulating torque amplitude after left hemisphere damage.     

Decision strategies in neuropsychology I: determination of lateralized cerebral dysfunction.

This study addressed the issue concerning neuropsychological assessment and the determination of hemispheric lateralization. Based upon the different processing strategies employed by each hemisphere, several neuropsychological tests were hypothesized to discriminate between left hemisphere and right hemisphere damage. Lesion localization was determined by neurological examination, electroencephalography, and/or neuroradiological procedures for the 111 patients (47 right hemisphere, 64 left hemisphere) who were given a neuropsychological evaluation. Two strategies are presented for lateralizing cerebral impairment, a discriminant analysis and a decision process using one standard deviation as a cut-off point. These two strategies are compared with The Key Approach of Russell, Neuringer, and Goldstein (1970) and Simpson and Vega's WAIS Sign Test. The efficacy of decision strategies used to predict lateralization is discussed.