Left Lesioned Research Articles

Self-initiated movements in chronic prefrontal traumatic brain injury: An event-related functional MRI study

Electrophysiological studies found traumatic lesions of the prefrontal cortex (PFC) to affect the preparation of self-initiated movements. However, a precise localization of the observed effects has not been reported yet. Moreover, previous reports did not account for effects of lesion location. Therefore, the present study utilized functional MRI to investigate the influence of predominantly left or right hemispheric PFC lesions on movement preparation in chronic traumatic brain injury (TBI) patients. 18 TBI patients with MRI-defined contusions of the PFC as well as 18 healthy control subjects matched for age and gender were examined. Patients were divided into subgroups of predominantly left or right hemispheric lesions. During functional image acquisition, subjects performed self-initiated abductions of their right index finger. Neuropsychological tests of attention and working memory, which are supposed to modulate preparatory processes, were conducted. Patients with predominantly left contusions demonstrated enhanced activity of the dorsal lateral premotor cortex in comparison to healthy control subjects. In predominantly right lesioned patients, reduced activity within the right caudate head was observed. Compared to predominantly left lesioned patients, neuropsychological tests yielded reduced task performances in the right lesion subgroup. In line with previous electrophysiological research, imaging results of the present study are interpreted to represent altered preparatory networks in chronic prefrontal TBI patients. Since attentional and working memory functions are supposed to modulate preparatory processes, differences between the patient subgroups are suggested to result from the more pronounced cognitive impairments in the right-lesioned group.

Early effects of unilateral lesions of substantia nigra on immune reactivity

It has recently been demonstrated that central dopaminergic pathways are asymmetrically involved in the modulation of the immune response. Mitogen-induced proliferation of T lymphocytes was shown to be enhanced 4–6 weeks after right lesion of the substantia nigra (SN) in mice, when compared to left lesioned and control animals. In order to study the involvement of post lesion neuronal reorganization in these results, the same immunological parameters were detemined as early as 2 weeks after right or left lesion of the SN. We showed that the lymphoproliferation induced by αCD 3 and concanavalin A was decreased in both lesioned groups, but phytohemagglutinin-induced mitogenesis was more impaired in the right than in the left lesioned animals. Hence, the time course effects of the right lesions of SN shifted from depression to enhancement of the T lymphocyte responsiveness. This shift appeared to occur around the two weeks period following the lesion. These immunomodulatory effects of unilateral SN lesioning, which depended on time and side of lesion, were similar to those observed after hemidecortication. Based on these findings, it is reasonable to suggest that asymmetry in brain immunomodulation involves functionally related dopaminergic and cortical networks.

Reading among children with left and right brain lesions

Twenty left hemisphere lesioned and 10 right hemisphere lesioned children between 6 and 20 years old were administered a battery of tests assessing phonetic analysis and segmentation, single word decoding, reading comprehension, and spelling. Although group mean performance on all tasks was consistently below that of controls matched for age, sex, race, and social class, few differences reached statistical significance. These findings demonstrate that the majority of children with unilateral brain lesions learn to read quite adequately, evidencing considerable functional reorganization of higher cognitive abilities following brain lesions sustained early in life. Yet five left‐ and two right‐lesioned children did present marked reading deficits in contrast to 1 of the 30 control subjects. A family history for reading disorders was implicated in one left lesioned, one right lesioned and the control subject, suggesting the contribution of a genetic basis. Age of lesion onset was not found to be related to r...

Fluency of conversational speech in children with unilateral brain lesions

The spontaneous conversational speech of 20 children with unilateral left hemisphere lesions and 13 with right lesions was compared to normally developing peers matched by age, sex, race, and social class for instances of stuttering type nonfluencies, normal nonfluencies, and rate of speech. Both left and right lesioned children provided quantitatively more and qualitatively different patterns of nonfluencies than their neurologically normal peers. Left and right lesioned children produced more stuttering types of nonfluencies than their controls, but neither lesioned group produced a greater number of normal nonfluencies than controls. Left lesioned children also had a slower rate of speech as measured by number of syllables per second during either stuttered or fluent speech. Considerable variability was observed among lesioned children. Implications for neurogenic theories of developmental fluency disorders are discussed.

Decision strategies in neuropsychology III: The relationship among lateralized dysfunction, etiology and depression

The present study examines depression as a function of lateralized dysfunction and etiology. The proposed hypothesis is: patients with left hemisphere lesions would be depressed, whereas patients with right hemisphere lesions would not. A total of 61 patients (26 right hemisphere, 35 left hemisphere) having either a stroke, tumor, or penetrating head wound, completed the MMPI and were given a neuropsychological evaluation. Lesion localization was based on electroencephalography and neuroradiological procedures. A regression formula derived from the MMPI assessed depression. Two analyses were performed between: (i) right and left lesioned groups of mixed etiology and a control group, and (ii) right and left cerebrovascular lesioned groups and a control group. Potentially confounding factors, such as, diagnosis, demographic factors, degree of neuropsychological impairment, presence or absence of aphasia, and lesion localization were examined. Regardless of etiology, left and right lesioned patients did not significantly differ in their depression score, nor was either group considered depressed based on the criteria used in this study to measure depression.

Auditory temporal perception of children with left or right brain lesions

Twenty left and 12 right brain lesioned children were administered Tallal's Repetition Task in which they were required to discriminate, associate and sequence two nonverbal auditory stimuli. Unlike adults with left hemisphere injury or children with developmental language disorders previously described by Tallal, neither left nor right brain-lesioned children differ significantly from control subjects matched by age, sex, race and social class. These results contrast with earlier reports of impaired spoken syntax and delayed lexical retrieval among many of these same left lesioned children, suggesting that prelinguistic auditory processing and higher language deficits may be dissociable among young left hemisphere impaired children. The findings demonstrate that the higher level language deficits seen in the left brain lesioned children cannot be attributed to difficulty in more preliminary analyses of the acoustic stimuli.

Lexical retrieval in left and right brain lesioned children

Performance on two measures of lexical retrieval for 19 left and 13 right brain lesioned children was compared to that of control subjects matched by age, sex, race, and social class. On the Word-Finding Test, left lesioned subjects were significantly slower in response time than left controls when given semantic and visual cues and made more errors when given rhyming cues. On the Rapid Automatized Naming Test, left lesioned subjects were significantly slower than left controls in naming all semantic categories, including colors, numbers, objects, and letters. In contrast, right lesioned subjects responded as quickly as or more quickly than did right controls in all access conditions and in naming semantic categories yet tended to produce more errors than their controls, suggesting a speed-accuracy tradeoff. Children sustaining left brain lesions before 1 year of age appeared to be as impaired as those whose lesions occurred after 1 year of age. Diverse lesion sites within the left hemisphere were associated with increased lexical retrieval latencies.

VERBAL AND NONVERBAL MEMORY AMONG CHILDREN WITH RIGHT OR LEFT BRAIN LESIONS

No previous studies of memory in children with left or right brain lesions have been reported, despite known sequelae in other aspects of learning. Memory for verbal (V) and nonverbal (NV) stimuli was evaluated here through a selective reminding task in which animal names (V) and dot patterns (NV) were learned over 8 trials. Measures of V and NV long-term storage (LTS) and cumulative long-term retrieval (CLTR) were made. 18 left lesioned (LL), 13 right lesioned (RL), and 31 age, sex, and SES matched control (C) children were included. All LLs and RLs had CT scan confirmation of unilateral lesions of vascular origin and were >1 yr. post lesion onset. M age at lesion onset was 4.05±4.59; M age at test was 9.42±3.89. M IQ for all groups was within normal limits, but IQ for RLs was significantly lower than for Cs. M T-scores, derived from age norms, SD and Ms adjusted for IQ differences+ were:Multivariate analyses revealed significant differences as noted above. These findings suggest that LLs store V and NV information, but do not retrieve V information normally. RLs have difficulty retrieving NV and also storing V information, possibly due to attentional limitations. These memory deficits correspond to lesion lateralization and hold implications for education.

Cognitive profiles of children with early onset of unilateral lesions

The level and pattern of Wechsler Intelligence Scale for Children‐Revised (WISC‐R) performance for 18 left‐lesioned (LL) and 13 right‐lesioned (RL) children with clearly defined unilateral involvement and no ongoing seizure disorders were compared to normal controls matched by age, sex, race, and social class. Verbal IQ (VIQ), Performance IQ (PIQ), and Full Scale IQ (FIQ) were well within normal limits for all groups, although RL children scored significantly lower than right controls. No significant differences between VIQ, PIQ, and FIQ were found within the LL or RL or control groups; thus VIQ and PIQ discrepancy was not found to relate to lesion laterally. When WISC‐R subtests were recategorized according to Kaufman's factors, the Freedom from Distractibility factor was impaired in both LL and RL children, whereas RL children were also deficient on the Perceptual Organization factor. Level and pattern of cognitive performance are discussed in relation to age of lesion onset and site of lesion within a hemisphere.

The Basis of Visual Constructional Disability in Patients with Unilateral Cerebral Lesions

Patients with left and right unilateral hemispheric lesions were compared on the Form Assembly Task, a visual construction task requiring perceptual but not executive, motor, or verbal skills. Right lesioned patients were inferior to lefts and normals in both degree and frequency of impairment. Performances on the assembly task and two visual discrimination tasks were correlated among right but not left lesioned patients. Left lesioned patients took significantly longer to achieve maximum level of performance than either rights or normals. Neither sex nor duration of lesion affected Form Assembly performance. Results were consistent with the hypothesis that visual perceptual deficits underlie constructional difficulties among right but not left lesioned patients.

General systems theory, brain organization, and early experiences.

Three hypothetical brain processes--interhemispheric coupling, hemispheric activation, and interhemispheric inhibition--are derived from an equation characterizing general systems theory. To investigate these processes, experimental rats were reared under differing early experience conditions. When adult, they had their right or left neocortex lesioned, had a sham operation, or were left undisturbed. Interhemispheric coupling was measured by means of a correlation coefficient between the right and left hemispheres. The presence of a significant positive correlation is taken as evidence of a negative feedback loop between the hemispheres. In one experimental population, in which rats did not receive any extra stimulation in infancy, the correlation was not significantly different from zero, thus implying that the two hemispheres were operating independently. In another population, in which rats had received handling stimulation in infancy, the correlation coefficient was significant (0.543), indicating that the hemispheres were coupled in a systems arrangement. The processes of hemispheric activation and interhemispheric inhibition were assessed by comparing the mean performance of the two unilateral lesion groups and the group with intact brain. The two rat populations had different forms of brain organizations as measured by these processes. These analyses show that the behavior of the isolated hemisphere cannot be directly extrapolated to the behavior of the connected hemisphere. If there is hemispheric coupling via a negative feedback loop or if there is interhemispheric inhibition, then the disconnected hemisphere may show behaviors that are not evident in the normal connected condition.

Patterns of Behavioral Deficit Associated with Visual Spatial Neglect

Visual-spatial neglect as measured by an empirically derived response position preference score on the Raven Coloured Progressive Matrices (RCPM) was examined in 70 patients with cerebral lesions and 63 controls. Patients with right cerebral lesions showed poorer RCPM performance and a higher incidence of response position preference for the side ipsilateral to their lesions than did patients with left lesions. Position preference was significantly associated with homonymous visual field defects, constructional dyspraxia, and in patients with left cerebral lesions mixed or receptive aphasia. The pattern and severity of deficits seemed alike in both right and left lesioned groups. Electroencephalographic evidence indicated that the right lesion group contained a greater number of patients with severe or post-rolandic lesions than did the left lesion group.