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At least 595 records · Page 33Linked to original sources
PubMed1977

Global spatial disorientation. Clinico-pathologic correlations.

Two patients presenting with the acute onset of bilateral parietal lobe damage showed initially the features of Balint's syndrome. After most of its manifestations had cleared, both patients exhibited severe disorders of spatial orientation: acoustic ataxia, inability to localize objects in space. In addition, 1 patient showed a topographical disorientation and abnormalities of whole body movements. This patient came to post-mortem examination, which revealed bilateral and fairly symmetrical old and recent infarctions of the superior parietal lobules. In the light of these observations and previous reports, it is suggested that the reported abnormalities of whole body movements can be explained on the basis of a visuo-motor intrahemispheric disconnection due to the bilateral lesion of the dorsal parietal lobe. In addition, the global spatial disorientation is analysed and is thought to be the manifestation of a derangement of a specific function centered in the parietal lobe. Moreover, it is pointed out that topographic disorientation does not require the concomitant failure of oculomotor mechanisms for its production. The topography of the anatomical lesion is considered in relation to current concepts on brain damage after severe hypotension and cardiac arrest. It is concluded that this group of patients is most likely at risk of developing behavioural abnormalities akin to the ones here reported.

Adult↗
PubMed1983

The selective impairment of phonological processing: a case study.

A case study is reported of an aphasic patient with fluent speech and markedly superior comprehension of written vs. spoken words. Results of extensive testing supported the hypothesis that the patient suffers from a phonological processing deficit that affects performance in all tasks that require the generation of a phonological code. This selective deficit is interpreted as the underlying cause of diverse symptoms such as asyntactic comprehension of written sentences, the commission of spelling errors in writing, and the production of literal paraphasias and neologisms in spontaneous speech. Alternative possibilities for the classification of this patient are discussed.

Adult↗
PubMed2005

A simple method to dissociate sensory-attentional and motor-intentional biases in unilateral visual neglect.

A variant of a line bisection test was devised. Patients with unilateral visual neglect and control subjects were asked to perform the test, which consisted of two subtasks: a verbal and a manual task. The verbal task was newly designed and did not require manual responses from the subjects. The manual task was similar to conventional line bisection tasks. This paper reports and discusses the results obtained from each task and their correlations. This technique is compatible with bedside examinations, does not require a complex apparatus, and provides useful data for the assessment of unilateral visual neglect.

Aged↗
PubMed2005

Differential constraints on the working memory and reading abilities of individuals with learning difficulties and typically developing children.

This study examined the factors that constrain the working memory span performance and reading ability of individuals with generalized learning difficulties. In the study, 50 individuals with learning difficulties (LD) and 50 typically developing children (TD) matched for reading age completed two working memory span tasks. Participants also completed independent measures of the processing and storage operations involved in each working memory span task and Raven's Coloured Progressive Matrices. The results showed that despite an equivalent level of working memory span, the relative importance of the constraints on working memory differed between the groups. In addition, working memory span was not closely related to word recognition or sentence comprehension performance in the LD group. These results suggest that the working memory span performance of LD and TD individuals may reflect different working memory limitations and that individuals with generalized learning difficulties may approach cognitive tasks in a qualitatively different way from that of typically developing individuals.

Child↗
PubMed2006

A role for the 'magnocellular advantage' in visual impairments in neurodevelopmental and psychiatric disorders.

Evidence exists implicating abnormal visual information processing and visually driven attention in a number of neurodevelopmental and psychiatric disorders, suggesting that research into such disorders may benefit from a better understanding of more recent advances in visual system processing. A new integrated model of visual processing based on primate single cell and human electrophysiology may provide a framework, to understand how the visual system is involved, by implicating the magnocellular pathway's role in driving attentional mechanisms in higher-order cortical regions, what we term the 'magnocellular advantage'. Evidence is also presented demonstrating visual processing occurs considerably faster than previously assumed, and emphasising the importance of top-down feedback signals into primary visual cortex, as well as considering the possibility of lateral connections from dorsal to ventral visual areas. Such organisation is argued to be important for future research highlighting visual aspects of impairment in disorders as diverse as schizophrenia and autism.

Animals↗
PubMed1986

Covariant defects in visuospatial abilities and recall of verbal narrative after right hemisphere stroke.

Eighteen patients with right hemisphere strokes and 10 age-matched normal controls were tested for visuospatial abilities and for recall of brief narrative passages. Visuospatial and verbal abilities were evaluated using an objective scoring protocol that quantified accuracy in reproducing individual details, appreciation of structural relationships, and the appearance of unwarranted intrusions. The right hemisphere damaged group was found to be impaired on all measures of verbal recall. Across subjects these defects, particularly the inability to abstract information from the narrative passages, correlated with the degree of constructional apraxia. Analysis of CT scans failed to define a discrete region of the right hemisphere selectively associated with either the visuospatial or verbal defects, but indicated that both are exacerbated by the presence of premorbid brain atrophy.

Aged↗
PubMed2001

Spatial working memory deficit in unilateral neglect.

Based on the similarity of brain areas lesioned in neglect and those activated by spatial working memory (WM) tasks in normals, we hypothesized that neglect may involve spatial WM impairments. A left neglect patient with right inferior frontal and basal ganglia damage performed cancellation tasks, making either highly visible marks (to provide a reminder of visited items), or invisible marks (so only spatial WM could represent cancelled items). Invisible marks led to repeated cancellations for targets that differed only in location, but not for targets with memorable unique identities, suggesting a deficit of spatial WM, with non-spatial WM spared. Neglect was greater for cancellation with invisible marks, consistent with a role for deficient spatial WM in cancellation deficits, but contrary to account solely in terms of attention capture by salient visible marks made in ipsilesional space.

Attention↗
PubMed2001

Are Alzheimer's disease patients able to learn visual prototypes?

Recently, controversial results emerged regarding visual prototype learning in Alzheimer's disease (AD). The aim of this study was to elucidate this issue in a larger population of AD patients. The AD patients (N=72) and age-matched healthy control subjects (N=25) learned to recognize and to categorize visual dot patterns. In comparison with the control subjects, the AD patients as a group showed dysfunctions in the recognition task, whereas categorization was relatively spared in their case. Recognition was impaired in patients with mild AD (Mini-Mental score: 18-23) and moderate AD (Mini-Mental score<18), whereas categorization was impaired only in patients with moderate AD. These results suggest that while the medio-temporal/diencephalic explicit memory system is markedly affected even in early AD, the sensory neocortical areas mediating implicit category learning display a sufficient degree of functional capacity until later stages of the disease.

Aged↗
PubMed2002

Selective deficit of auditory localisation in patients with visuospatial neglect.

Possible auditory deficits in neglect were examined by comparing the performance of four right brain-damaged (RBD) patients with left visuospatial neglect, versus four RBD patients without neglect, in three auditory tasks. The first task required speeded discrimination of sound elevation, by moving a central lever up or down according to the vertical position of a peripheral target sound, regardless of its side. The other two auditory tasks were non-spatial, requiring either speeded pitch discrimination (moving the central lever up for high pitch, down for low pitch) or speeded target detection. Neglect patients' performance was impaired with respect to RBD controls only when the auditory task required spatial coding of the target sound (the up/down spatial discrimination). This demonstrates a selective deficit of auditory space perception in neglect patients. This auditory spatial deficit was more pronounced for left than right sounds. Since auditory space perception was impaired in the vertical dimension, the observed deficit cannot be attributed to a systematic rightward shift in sound localisation. Instead, the results suggest increased spatial uncertainty in sound localisation by neglect patients, particularly for auditory targets on the contralesional side. These findings are related to multimodal coding of space in the parietal cortex, which was damaged in the neglect patients, but not in the RBD controls.

Adult↗
PubMed2002

Spatial working memory span, delayed response and executive function in schizophrenia.

This study investigated the spatial working memory span (SWMS) as well as the immediate memory span of schizophrenic patients, and examined the contribution of each span to the patients' executive function deficit in the visuospatial domain. SWMS measured the visuospatial working memory capacity that simultaneously processes and stores visuospatial information. Immediate memory span was measured with the spatial span (SS), a variant of Corsi's block-tapping test. A total of 16 patients diagnosed with schizophrenia and 16 normal control subjects participated in the study. SWMS, as well as the forward and backward SS, was significantly reduced in schizophrenia. The SWMS deficit observed in this study and previous findings of deficit in verbal working memory spans suggest that impairment in working memory capacity in schizophrenia is general, and not limited to the verbal domain. Executive function as assessed with the self-ordered pointing task (SOPT) was also impaired in the patients, which is consistent with clinical observations of self-monitoring impairment in schizophrenia. SWMS was able to account for the performance on the SOPT, but its contribution in the patients' impairment did not reach statistical significance. Backward span deficit explained this executive function impairment. SWMS was effective in explaining schizophrenic patients' impaired performance on the spatial delayed response, a prefrontal function task. Implications of the relations observed between the spans and the prefrontal function tasks are discussed.

Adult↗
PubMed2002

Patterns of impaired verbal, spatial, and object working memory after thalamic lesions.

Working memory processes in six individuals with isolated thalamic lesions were assessed. Participants were given a verbal, spatial, and object n-back task, each at three levels of task load (1-back, 2-back, and 3-back). Relative to a control group, the patients were impaired on the verbal and spatial n-back tasks, and possibly on the object n-back task as well. None of the patients showed impaired short-term memory as measured by digit span. Group differences on trials measuring matching, sequencing, and inhibitory abilities were consistent with other reports suggesting that thalamic lesions may impair the operation of executive processes.

Aged↗
PubMed2004

Memory for faces dissociates from memory for location following anterior temporal lobectomy.

It has been suggested that the right and left mesial temporal lobes are specialized for processing different types of information for long-term memory (LTM). Although findings have been consistent in regard to the dominant role of the left mesial temporal lobe (MTL) in verbal memory, the role of the right MTL in non-verbal memory remains debatable. Given the existence of two cortical pathways specialized for processing different types of visuospatial information, we examined whether memory processing for these two types of information might also be differentially localized. The effect of unilateral anterior temporal lobectomy (ATL) was compared for memory for unfamiliar faces and a novel sequence of spatial locations in 86 ATL patients (left ATL (LATL) = 35; right ATL (RATL) = 51) pre- and post-surgery to examine the contributions of right and left MTL structures to LTM for pattern and spatial information. Memory for spatial location was not related to side of ATL or time of testing. On the facial memory task, RATL patients showed impairments relative to LATL patients prior to surgery, which became magnified after surgery. These results extend the proposed dissociation between an occipitotemporal and an occipitoparietal pathway for processing visuospatial information by demonstrating dissociations in LTM systems for these two types of information. Lesions in the right MTL, adjacent to the cortical structures believed to be specialized for facial recognition, specifically impair the memory encoding of new faces, but not spatial locations.

Adult↗