Tactile perception of direction in relation to hemispheric locus of lesion

The performances of patients with lesions of the right or the left hemisphere on a task involving the perception of the direction of tactile stimulation applied to the palms of the hands were compared with each other and with those of patients without cerebral disease. The results confirmed earlier findings of bilateral impairment in this function in a noteworthy proportion of patients with lesions of the right hemisphere. Patients with lesions of the left hemisphere showed significant impairment only in the right hand. Within the left hemisphere group, aphasic and non-aphasic patients did not differ with respect to level or pattern of performance. The results are interpreted as supporting the conclusion that the right hemisphere plays a distinctively important role in mediating spatial perception in the tactile as well as in the visual and auditory modalities.     

Facial recognition in patients with focal brain lesions

The performances of patients with radiologically or surgically verified focal lesions on a test requiring the identification of unfamiliar faces were investigated. Nonaphasic patients with posterior right hemisphere lesions and aphasic patients with substantial impairment in language comprehension showed a notably high frequency of defect. The frequency of defective performance in nonaphasic patients with right anterior lesions was higher than normal but less than that of the previously mentioned groups. Nonaphasic patients with left hemisphere lesions and aphasic patients without substantial impairment in language comprehension performed on a level comparable with that of control subjects. It is concluded that the identification of unfamiliar faces is a bihemispheric process, possibly involving linguistic as well as visuoperceptive components.     

Further evidence for focal effect of right hemisphere damage on simple reaction time

Changes of simple visual reaction time were analyzed in two groups of unilateral brain damaged patients in order to evaluate to what extent intrahemispheric localization of lesions affects performance. Possible interactions with size were avoided by selecting a localization criterion, i.e. the median section of lesion, uncorrelated with size of damage. By preliminarly establishing that the distribution of lesions in our hemispheric groups did not differ, we were enabled to confirm that intrahemispheric localization of damage has a different bearing on performance depending on side of lesion. In the right hemisphere group slower performances were generally associated with frontal damage whereas in the left hemisphere group localization did not influence the performance. The use of independent indexes for size and locus of lesion proved the existence of an interaction between these parameters in the right hemisphere group.     

Generalized cognitive function after stroke

The present investigation was designed to determine the effect of cerebrovascular lesions upon general neuropsychological function. The performances of 60 patients with lateralized or diffuse cerebrovascular lesions were compared to 20 controls on cognitive and intellectual measures. Multivariate analyses indicated markedly poorer performances by the cerebrovascular groups on measures of generalized cerebral function, and no differences on such measures were found between the left- and right-damaged groups. The lateralized CVD groups demonstrated a differential tendency towards lower performances on VIQ for the left group and on PIQ for the right group. The results indicate significant neuropsychological impairment which extends beyond the expected lateralized dysfunctions, or selected deficits, associated with the damaged hemisphere. These findings indicate the importance of evaluating generalized as well as specific cognitive functions in clinical assessment of cerebrovascular lesions.     

Diagnostic utility of the thurstone word fluency test in neuropsychological evaluations

Abstract

Previous research has found that verbal associative fluency tasks are sensitive to the presence of cerebral lesions and more sensitive to frontal lobe and left hemisphere lesions than to other focal lesions. The present study investigated the diagnostic utility of the Thurstone Word Fluency Test (TWFT), a test of written verbal fluency, in detecting and localizing cerebral lesions. Using results from 203 brain-damaged and 134 normal subjects, we found that TWFT performance is affected by cerebral damage generally. At the same time, it is more impaired by frontal than by nonfrontal, by left than by right hemisphere, and by left frontal than by right frontal lesions. This test does not discriminate focal frontal from diffuse lesions. Stepwise discriminant function analyses indicated that the TWFT adds to the Halstead-Reitan Battery in discriminating focal frontal from nonfrontal lesions, but not in discriminating left hemisphere from right hemisphere lesions. Only markedly impaired TWFT performances had lateralizing significance.     

Ocular dominance in patients with recently and remotely acquired lateralized brain lesions

This study reports a significantly higher proportion of left-eyedness in patients with remotely acquired right hemisphere brain lesions as compared with patients with recently acquired right hemisphere lesions, as well as patients with left hemisphere lesions, regardless of whether they were recently or remotely acquired. It was determined that this finding could not be attributed to a higher incidence of left-handedness among the patients with remotely acquired right hemisphere lesions. The findings were interpreted in terms of a possible mechanism for adjustment to left field neglect.     

Visuospatial performance in left-handed patients with unilateral brain lesions

A test of visuospatial judgment was given to left-handed patients with lesions of either the right or left hemisphere. In right-handed patients impaired performance on the test has been found to be almost exclusively associated with right hemisphere disease, the performance of patients with left hemisphere disease being comparable to that of controls. The left-handed patients in this study showed the same performance pattern: a high proportion of patients with right hemisphere lesions performed defectively while all the patients with left hemisphere lesions performed on a normal level. Thus the findings are in accord with the conclusion that hemispheric cerebral organisation with respect to the mediation of visuospatial performance do not differ in right-handers and left-handers.     

Disturbances of the body schema in relation to language impairment and hemispheric locus of lesion

The relationship of disturbances of the body schema to hemispheric locus of lesion and sensory aphasic disorder was assessed by giving verbal and non-verbal tests of right-left orientation, finger recognition, and autotopagnosis to patients with unilateral cerebral disease. The study was restricted to right-handed patients who were free from general mental impairment or confusion. The tests were also given to a group of control patients whose performances defined the range of normal performance in each test. A significant proportion of patients with sensory aphasic disorder performed defectively on all the tests, non-verbal as well as verbal, the relative frequency of failure in this group ranging from 10 to 67% for the different tests. There were, however, a number of patients with sensory aphasic disorder who performed adequately on most of the tests. Defective performance on the part of non-aphasic patients with lesions of either the left or the right hemisphere was quite rare in the case of 19 of the 20 tests. The exceptional test was the task of imitating lateral movements from Head's battery, on which both non-aphasic groups performed relatively poorly. The patients with lesions of the right hemisphere were significantly inferior to those with left hemisphere disease on this test. The findings are interpreted as indicating that sensory aphasic disorder is a necessary but not sufficient condition for the occurrence of some types of bilateral `body schema' disturbance in patients with unilateral disease. It is postulated that the sufficient condition is a combination of aphasic disorder with somatosensory impairment. Bilateral impairment of the `body schema' does not appear to have a differential relationship to hemispheric locus of lesion per se.     

Impairment in visual recognition of geometric figures in patients with circumscribed retrorolandic brain lesions

Twenty patients with left-sided and 21 patients with right-sided circumscribed retrorolandic brain lesion were given Gottschaldt's Test, Benton's Visual Retention Test and several tests for pertinent control variables. Analyses of variance demonstrated, that aphasic patients were inferior to left-sided patients without aphasia. There was no difference in the performance of aphasic and right brain damaged patients. Visou-spatial disturbance was associated with lesions of either hemisphere. The impairment of the aphasic patients was not due to language disturbance per se, nor to severity of brain lesion. Rather, presence of aphasia indicated a locus of lesion critical for the performances tested.     

Linguistic and non-linguistic abilities in a patient with early left hemispherectomy

A patient who underwent early removal of the left hemisphere because of Sturge-Weber syndrome was submitted to detailed linguistic and visuospatial batteries. The performances were compared to performances of subjects matched for age, education and IQ, but without focal cerebral lesions. Language was mildly impaired but to the same extent as in IQ controls. On the contrary, visuospatial abilities were clearly worse than in IQ controls, and the most preserved visuospatial abilities seemed to be the less sophisticated ones. Non literal comprehension of language, a function generally attributed to the right hemisphere, was intact. This same pattern, that is, preservation of language and impairment of visuospatial abilities, also seems to occur in subjects who have undergone surgical removal of the right hemisphere; in other words, the cognitive pattern seems the same regardless of which hemisphere is removed. These observations suggest that no matter which hemisphere is removed, functional reorganisation follows a hierarchical criterion which privileges the linguistic function, and the visuospatial functions most essential for independent survival.     

The restricted effects of right-hemisphere lesions after age one; Wechsler test data

The late effects of early and later lateralized brain lesions were studied with the Wechsler intelligence test in 50 patients with unilateral nonprogressive cerebral lesions incurred in infancy or in childhood. Results differed according to age at lesion for right but not left hemisphere patients; patients with right hemisphere lesions after age one had normal Verbal ratings impaired Performance ratings; patients with earlier right hemisphere lesions were impaired on both ratings.     

Visual localization in patients with unilateral brain disease.

The accuracy of localization of briefly exposed single dots and pairs of dots was assessed in patients with lesions of the left and right hemispheres and in control patients without history or evidence of brain disease. A remarkably high frequency of impaired performance was found in the patients with right hemisphere lesions. The performance of the patients with left hemisphere lesions was comparable with that of the control patients. Visual field defect was associated with defective localization in the right hemisphere group but not in the left hemisphere group. Aphasic disorder and age were not related to performance level. The relationship of the findings to those of previous studies of visual localization in patients with unilateral brain disease is discussed.     

Proprioceptive feedback performance in patients with focal brain lesions

Summary Utilization of proprioceptive feedback in a manual tracking task was studied in patients with circumscribed unilateral brain lesions. Patients with posterior right hemisphere disease showed severe impairment in performance as compared to those with lesions in other areas of the brain. Increasing the intensity of proprioceptive feedback facilitated the tracking performance of left hemisphere damaged patients while patients with right hemisphere lesions failed to improve. The results were interpreted as supporting the view that the posterior right hemisphere plays a particularly important role in the utilization of proprioceptive information to maintain the position of body parts in space.This investigation was supported by Research Grant NS00616 and Program-Project Grant NS03354 from the National Institute of Neurological Diseases and Stroke.     

Stereopsis and the perception of anomalous contours

A relationship between depth perception and the perception of anomalous contours has been suggested by some investigators. To test this hypothesis, performance on an anomalous contour test was compared to performance on two stereoscopic tests. A conventional stereoacuity test (local stereopsis) and a test of random-letter stereopsis (global stereopsis) were given to patients with unilateral right hemisphere lesions, since only such patients have been shown to be specifically impaired on the latter type of test. The findings demonstrated significant relationship between both types of stereoscopic performances and anomalous contour perception. Implications for a theory of global stereopsis are discussed.     

Effects of localised cerebral lesions and dysphasia on verbal memory.

Twenty-nine patients with unilateral left hemisphere lesions, 22 patients with unilateral right hemisphere lesions, and 19 neurological control patients with extracerebral lesions were assessed on verbal memory recall and recognition tests and on a battery of language tests. The left hemisphere group was significantly impaired in memory and language skills. Significant verbal memory impairment was found both in the subgroup of left hemisphere lesion patients whose lesions involved the temporal lobe and in the subgroup whose lesions did not. However, no significant differences between these left hemisphere subgroups' levels of performance on memory tasks emerged, even when dysphasia was taken into account. This study, therefore, fails to support the notion of a specific anatomical correlate of verbal memory impairment within the left hemisphere. Dysphasic subjects were significantly impaired on verbal memory tasks but displayed the same pattern of sensitivity to the effects of word frequency and word concreteness on verbal memory as control subjects, suggesting that the verbal memory of the dysphasic subjects was quantitatively rather than qualitatively impaired. This impairment could not be attributed to deficits in the comprehension or expression of the memory test items, and it is, therefore, proposed that language disturbances may hinder the efficient use of such language based procedures as may subserve verbal memory.     

Impaired grating discrimination following right hemisphere damage

We investigated the effect of unilateral brain lesions on visual discrimination of low-, middle- and high-frequency gratings. The performance of patients with right hemisphere lesions was significantly impaired compared with that of both controls and patients with left hemisphere lesions. This impairment was largely limited to patients with right posterior hemispheric lesions and was present with all spatial frequencies. These findings run counter to the hypothesis that high and low spatial frequencies are preferentially processed by different hemispheres.     

Recognition of onomatopoeias and animal cries during focalized lesions of the cerebral cortex (author's transl)

The recognition of animal cries and their onomatopoeias was compared during the course of right or left unilateral cortical lesions. A double dissociation is noted; in left-sided affections there is a more severe deficiency to onomatopoeia than to cries, whereas in right-sided lesions the quality of the performances is reversed. These results suggest that the right hemisphere is dominant in the auditive recognition of familiar sounds, and supply information as to the linguistic value of onomatopoeias.     

Impaired working memory for location but not for colour or shape in visual neglect: a comparison of parietal and non-parietal lesions

Patients with spatial neglect due to right hemisphere pathology may show 'revisiting' behaviour during visual search and cancellation tasks, such that previously encountered targets are treated as if they are new discoveries. Revisiting behaviour is particularly evident when no visible trace is left to inform patients that a particular target has already been detected (Husain et al., 2001; Wojciulik et al., 2001), implying that spatial working memory may be impaired in neglect. To test whether working memory for location is selectively impaired relative to memory for colour and shape, we compared performances of right hemisphere neglect patients with parietal (n = 4) and non-parietal (n = 4) lesions on a change detection task. Patients were presented with a matrix containing four objects in different positions, and required to detect a change in the location, colour or shape of one of the objects following presentation of a brief visual mask. Parietal patients were selectively impaired in detecting location changes, regardless of the horizontal position of the object in the matrix, relative to colour and shape changes. This deficit of spatial working memory was not apparent for neglect patients with lesions that spared the parietal cortex. We conclude that the human parietal cortex is crucially involved in the updating and maintenance of spatial representations across saccades, and that neglect arising from parietal damage causes impairment in these re-mapping mechanisms.     

Ipsilesional line bisection bias in patients with chronic parietal lesions

The current study investigated whether an ipsilesional bias in line bisection, a conventional measure for diagnosing hemispatial neglect, persists even in the absence of this syndrome in patients with chronic lesions restricted to posterior association cortex or dorsolateral prefrontal cortex. Both left and right hemisphere parietal lesions produced ipsilesional bisection errors, and to a comparable degree. Patients with lesions in frontal cortex, on the other hand, did not show a consistent bias. We conclude that chronic parietal lesions produce an ipsilesional bias in line bisection, even in the absence of other clinical signs of neglect, and that left hemisphere lesions can affect line bisection to the same degree as right hemisphere lesions.     

Lateralization of deficit in self-awareness of memory in patients with intractable epilepsy

PURPOSE: Memory disorders are prominent among patients with intractable epilepsy. It has, however, been frequently observed that subjective memory complaints of these patients did not match their performance on objective memory tests. This discrepancy may reflect emotional, cognitive, or self-awareness deficits among these individuals. The aim of the current study was to explore the interference of cerebral dysfunction on accuracy of self-appraisal for memory. METHODS: The degree of concordance between self-perception of memory function, as measured by a visual analogue scale, and actual performance on memory tests was computed in 35 patients who were candidates for epilepsy surgery and demographically matched normal control subjects. The difference between the self-estimated memory ability and performance on memory tests and its relation to the laterality of an epileptogenic lesion, cognitive factors, and affective status was then examined. RESULTS: The results show that the discrepancy between the self-estimated memory ability and performance on memory tests in patients with right hemisphere epileptogenic lesions was significantly larger in magnitude compared with that in patients with left hemisphere lesions and demographically matched control subjects (p = 0.001). Furthermore, whereas patients with left hemisphere lesions and normal controls had about an equal number of positive and negative discrepancy scores, all patients with right hemisphere lesions had positive discrepancy scores, suggesting a tendency for overestimation of memory abilities. CONCLUSIONS: These results suggest that right hemisphere lesions may introduce a systematic bias in self-awareness for memory. This bias may color patients' perceptions of self and others, affecting their perceptions of the quality of life, and necessitating an adjustment of the treatment goals and procedures.