[Presentation of an assessment battery for visual mental imagery and visual perception]. / Normalisation d'une batterie d'évaluation de l'imagerie mentale visuelle et de la perception visuelle.

INTRODUCTION: The relationship between visual perception and visual mental imagery are at the center of a lively theoretical debate between those postulating common neurocognitive processes between perception and imagery and those who emphasize the differences between these two entities. Neuropsychology can make an important contribution to this debate, by assessing associations and dissociations between perceptual and imaginal deficits in patients with brain damage. However, currently there is no standardized test battery available for such assessments. MATERIAL AND METHODS: Here we present a battery of paper-and-pencil tests assessing different domains of visual mental imagery and visual perception abilities: object form and color, animals, orthographic material, numbers, faces, and space. We also explored the effects of age, educational level and gender on performance on a group of 103 participants free of neurological damage. RESULTS: The battery includes two parts: one composed of 14 tests assessing mental imagery and the second part composed of eight tests assessing the abilities of visual perception. We calculated the correlations between the tests, and found that, with the exception of orthographic material, there were generally poor correlations between imagery and perceptual tests. CONCLUSION: This result seems inconsistent with hypotheses postulating a strict correspondence between perceptual and imagery abilities.

Looking while imagining: the influence of visual input on representational neglect.

BACKGROUND: Subjects with hemispatial neglect often exhibit representational neglect: a failure to report details from the left side of mentally visualized images. This failure could reflect impaired ability to generate the left side of the mental image, or it could reflect failure to explore the left side of a normally generated mental image. When subjects with hemispatial neglect look at pictures or drawings, their attention tends to be drawn to objects on the right side, thereby aggravating their failure to explore the left side. If representational neglect represents a failure to explore the left side of a normally generated mental visual image, then it should be improved by blindfolding, which removes the attention-catching right-sided stimuli. However, if representational neglect represents a failure to generate the left side of the mental visual image, then blindfolding should have little impact on reporting of details of the image. METHODS: To determine which of these explanations is correct, we asked eight normal participants and eight brain-damaged patients with left representational neglect to imagine the map of France and to name as many towns as possible in 2 minutes. In different sessions, participants performed the task with eyes open or while blindfolded. RESULTS: Normal participants mentioned more towns while blindfolded than with vision, thus suggesting a distracting effect of visual details on mental imagery. Patients with neglect, however, showed no appreciable effect of blindfolding on reporting of details from either side of mental images. CONCLUSION: Representational neglect may represent a failure to generate the left side of mental images.

Multiple-domain dissociation between impaired visual perception and preserved mental imagery in a patient with bilateral extrastriate lesions.

A brain-damaged patient is described whose pattern of performance provides insight into both the functional mechanisms and the neural structures involved in visual mental imagery. The patient became severely agnosic, alexic, achromatopsic and prosopagnosic following bilateral brain lesions in the temporo-occipital cortex. However, her mental imagery for the same visual entities that she could not perceive was perfectly preserved. This clear-cut dissociation held across all the major domains of high-level vision: object recognition, reading, colour and face processing. Our findings, together with other reports on domain-specific dissociations and functional brain imaging studies, provide evidence to support the view that visual perception and visual mental imagery are subserved by independent functional mechanisms, which do not share the same cortical implementation. In particular, our results suggest that mental imagery abilities need not be mediated by early visual cortices.

Confabulation following rupture of posterior communicating artery.

In this study we report a patient, MG, who following rupture of left posterior communicating artery exhibited an amnesic-confabulatory syndrome. Neuropsychological examination showed severe impairment on episodic memory tasks, which were marred by florid but plausible and semantically appropriate confabulation. Performance on tasks involving various kinds of semantic knowledge was normal or only mildly impaired. Performance on tasks traditionally considered sensitive to frontal dysfunction was severely impaired with the exception of Cognitive Estimates where MG's performance was completely normal. There was no evidence of structural (CT scan) or metabolic (SPECT) damage to the frontal lobe. It is argued that tasks traditionally considered sensitive to frontal dysfunction are not specifically implemented by cognitive resources based on frontal structures. MG's confabulation is discussed in terms of a possible disruption of cognitive functions involved in the control of the subjective experience of feeling of remembering.

Preserved imagery for colours in a patient with cerebral achromatopsia.

We report the case of a patient who, after sequential bilateral strokes in the occipital regions sparing the primary visual cortex, developed a severe deficit of colour perception. At variance with other reports of acquired achromatopsic patients, she showed a perfectly vivid visual imagery for colours. These findings, together with similar data in domains other than colour processing, challenge the theories which posit that the same cognitive processes are involved in both the perception and the retrieval from memory of a given stimulus.

Infection after autologous blood-derived stem cell transplantation.

Ten patients who underwent autologous blood-derived stem cell transplantation (APBSCT) were studied retrospectively to determine the frequency and outcome of transplant associated infections during the hemopoietic reconstitution. Six patients developed an infection after transplant. Severe bacterial infections were unfrequent and mostly caused by gram-positive cocci. In no case pneumonia was observed and this scarce morbility of infection could be the result of early engraftment. None of them died for infection. The frequency of infections in APBSCT patients appears lower than the one observed in autologous bone marrow transplant patients.