Left Hemisphere Lesion Patients Research Articles

Differential Impairment of Patients with Right Versus Left Hemisphere Lesions on the Ruff-Light Trail Learning Test

The Ruff-Light Trail Learning Test (RULIT) was developed as a neuropsychological measure of visuospatial learning and memory. RULIT scores of patients with right hemisphere and left hemisphere damage, as well as matched controls were compared. Right hemisphere lesion patients scored significantly lower on RULIT measures than did left hemisphere lesion patients and controls. The performance of left hemisphere lesion patients and controls did not differ significantly on RULIT measures. Adequate clinical hit rates, sensitivity and specificity in identifying right hemisphere damaged patients were demonstrated.

Superior temporal and premotor brain areas necessary for biological motion perception

We tested biological motion perception in a large group of unilateral stroke patients (N = 60). Both right and left hemisphere lesioned patients were significantly impaired compared with age-matched controls. Voxel-based lesion analyses revealed that lesions in superior temporal and premotor frontal areas had the greatest effect on biological motion perception. Moreover, the effect in each region was independent, and not attributable to indirect effects of lesions in the other area. When we explored functional magnetic resonance imaging (fMRI) data collected from neurologically healthy controls in a separate experiment in relation to the lesion maps, we found that the two methods converged on their findings. We thus establish that superior temporal and premotor areas are not only involved in biological motion perception, but also have causal relationships to deficits in biological motion perception. While the precise functional roles of each region remain to be identified, this network has been implicated in the perception of action stimuli in many studies and as such patients' deficits may reflect an inability to effectively engage the action observation system.

Constructional functions and figure copying in illiterates or low-schooled Hispanics

Figure copying and constructional abilities were examined in 15 healthy adult participants qualifying for illiteracy, following UNESCO criteria. A set of 14 figures was used for copying, 3 of them in perspective. Four figures of the same protocol were used to reproduce with sticks. Mean age of the sample was of 63.86 years old. They were matched for age and gender to schooled (6–7 years) controls. Illiteracy was due to social, cultural or economic factors. The most frequent and relevant findings were an inability to reproduce the perspective (13/15), unfolding (4/15) and unstructured copying (3/15). No errors were made on the stick construction task. None of these findings appeared in control subjects. The pattern is similar to that reported mostly in left-hemisphere lesion patients. Neglecting the cultural or academic background may, then, bias interpretation in these tasks.

Contributions of the left and right cerebral hemispheres to line bisection

Thirty-one right-hemisphere lesioned (RHL) patients, 11 left-hemisphere lesioned patients (LHL) and 10 normal controls (NC) bisected lines in three spatial location and four directional cuing conditions. The error direction and error size were analyzed as separate and combined variables. Seventy-seven percent of RHL patients and 45% of LHL patients made abnormally large errors in line bisection. Right-hemisphere lesioned patients were more sensitive to spatial location and directional cuing than NC subjects. In contrast, LHL patients were less sensitive to either condition than NCs. The error direction and error size emerged as dissociable components of line bisection. Right-hemisphere lesioned patients and NC subjects bisected lines consistently to one side of the true center. Left-hemisphere lesioned patients bisected lines equally often on both sides of the true center. Both RHL and LHL patients made larger absolute bisection errors than NC subjects, but the RHL patient's errors were larger than those of the LHL patients. We propose that the greater sensitivity of RHL patients to spatial location and directional cues and the directional consistency of their bisection errors represent contributions of the intact left cerebral hemisphere to line bisection. In contrast, the LHL patient's unrestrained ability to orient to both ends of the line reflects a contribution of the intact right cerebral hemisphere to line bisection. The failure of both groups to accurately bisect lines reflects a common visuospatial processing deficit that is more pronounced following RHLs than LHLs.

IMPAIRMENTS OF MOVEMENT INITIATION AND EXECUTION IN UNILATERAL NEGLECT

Patients with unilateral neglect may exhibit slowness in the initiation of contralesionally directed movements in peripersonal space (directional hypokinesia). The present study used a sequential movement task to characterize any such impairment in a group of 24 patients with right hemisphere lesions, 18 of whom had left neglect. A further five patients with left hemisphere lesions, one of whom had right neglect, were also tested. We measured movement initiation and execution times for leftward and rightward movements in either hemispace and across the body midline. Most left neglect patients, particularly those with lesions involving posterior cortex, showed directional hypokinesia. Left neglect patients with anterior and/or subcortical lesions also showed directional bradykinesia, i.e. a slowing in the execution phase of contralesionally directed movements. This impairment occurred regardless of the spatial location of the apparatus and was exacerbated as patients moved closer to their neglected side. The patient with right neglect showed directional hypokinesia but not directional bradykinesia. Right hemisphere and left hemisphere lesion patients without neglect performed in a manner comparable to controls, who did not exhibit directional hypokinesia or directional bradykinesia. These results suggest that directional hypokinesia is associated with both left hemisphere and right hemisphere damage, but only in the context of unilateral neglect. Moreover, the site of hemispheric lesion may determine the temporal characteristics of movement impairments in neglect. Damage to posterior cortex produces deficits in detecting contralesional targets and initiating movements toward them, while damage to anterior or subcortical structures may disrupt the internal representation of an intended trajectory.

Change in Response Time of Stroke Patients and Controls during Rehabilitation

In this study we investigated motor response times of stroke patients at admission to a rehabilitation hospital and again after 6 wk of hospitalization. A prospective comparative study was carried out on 164 stroke patients; 48 hospitalized patients served as controls. Mean motor response times to visual stimuli presented in the left and right visual fields and to centrally presented stimuli were studied. The principle finding was that stroke patients improved significantly in their response times from initial to final evaluation. While at initial assessment they performed significantly more slowly than controls, by final assessment the response times of the two groups did not differ. Visual hemineglect influenced change in response time differentially depending on side of lesion: right hemisphere lesion patients with neglect improved, whereas left hemisphere lesion patients with neglect actually deteriorated. The presence of depression influenced right hemisphere lesion patients' response times and change in response times but it did not have any influence for left hemisphere lesion patients. The findings that response time generally improved during rehabilitation has important implications for the treatment of individuals with brain injury. It will be important to identify therapeutic practices which will be effective in the remediation of response time for all patients. Ultimately the goal of intervening in slow response time is to improve performance of functional activities which are influenced by an individual's ability to respond to visual stimuli.

Variations in “same”-“different” judgments in patients with unilateral cortical lesions

Five subject groups (normal controls, left anterior lesion patients, left posterior lesion patients, right anterior lesion patients, right posterior lesion patients) were tested on two perceptual matching tasks. All groups performed comparably accurately, although right hemisphere lesion patients demonstrated longer RT scores for “same” than for “different” judgments, whereas left hemisphere lesion patients demonstrated the reverse effect. Increased perceptual complexity of “same” target produced higher RT scores for “different” responses in right (but not left) hemisphere lesion groups. Finally, high-prototypicality “same” targets yielded lower RT scores than low-prototypicality “same” targets for all groups.

Temporal Sequencing of Verbal and Nonverbal Materials: The Effect of Laterality of Lesion

The effect of laterality of cerebral lesion on sequencing ability, which is an ability to process two or more stimulus events with respect to the order in which they occur, was examined. Patients with either left or right hemisphere lesions performed on verbal and nonverbal sequencing tasks. Left hemisphere lesioned patients were inferior to the right hemisphere lesioned patients on verbal sequencing tasks, while the right hemisphere lesioned patients were inferior to the left hemisphere lesioned patients on nonverbal sequencing tasks. Impaired performance of the right hemisphere lesioned patients on sequencing tasks raises questions with respect to the notion that sequencing per se is processed in the left hemisphere. Our results demonstrate that sequencing ability, as many other abilities, follows the rule of material-specific laterality of hemispheric asymmetry: the left hemisphere associated with verbal sequencing ability and the right hemisphere associated with nonverbal sequencing ability.

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.