Spatial hemineglect in humans

doi:10.1016/S1364-6613(98)01145-0

Trends in Cognitive Sciences

Volume 2, Issue 3, 1 March 1998, Pages 87-97

https://doi.org/10.1016/S1364-6613(98)01145-0 Get rights and content

Abstract

The term `spatial hemineglect' refers collectively to disorders of spatial cognition, which concern specific sectors of space with reference to a given coordinate system. Patients with cerebral lesions involving the posterior-inferior parietal and the premotor cortex, most often in the right hemisphere, sometimes fail to explore the extra-personal and personal sectors of space contralateral to the side of the lesion, are not aware of stimuli presented in these portions of space, or of contralateral body parts and their disordered function. In addition to these negative signs patients may also show positive pathological manifestations, such as avoidance or withdrawal from the contralateral side of space, and delusional views concerning contralateral body parts. The many varieties of this disorder can occur in dissociated forms, suggesting a multifaceted organization of the internal representation of space, of spatial attention, and of their neural correlates. Many manifestations of hemineglect are modulated in a similar fashion by specific sensory stimulation that also affects visuo-motor processes in normal subjects. This ongoing sensory modulation might update the internal representations of space in a continuously changing environment, and contribute to the formation, around the vertical orientation of gravity, of our subjective unitary experience of space.

Section snippets

The compass of spatial hemineglect

The clinical term `spatial hemineglect' should be conceived as the label of a `syndrome' in which a number of symptoms and signs of disordered function are related to one another by a spatial peculiarity. The deficit concerns the contralesional side, with reference to specific spatial co-ordinate systems and processing domains. So far, a number of specific varieties of hemineglect have been reported, which may be distinguished along different, although related, cleavage dimensions (see Appendix

The anatomical basis of hemineglect

Hemineglect, as other human cognitive disorders such as dysphasia and apraxia—typically associated with damage to the left cerebral hemisphere—is characterized by a hemispheric asymmetry. Hemineglect is more frequent and severe after damage to the right cerebral hemisphere of right-handed subjects, concerning therefore the left side1, 40. This asymmetry may be explained assuming that the right hemisphere contains neural networks capable of attending and representing both sides of space, while

The modulation of hemineglect by sensory stimulations

The kinds of spatial representations disrupted in hemineglect are not fixed architectures. Egocentric (e.g. centred on the head, on the trunk) and allocentric frames of reference are computed through the continuous integration of inputs provided by multiple sensory sources (visual, vestibular and proprioceptive-somatosensory) in a changing environment[54]. These processes make available updated spatial representations, intermediate between sensory input (e.g. retinotopic and somatotopic frames

Processing without awareness in spatial hemineglect

In recent years, converging evidence has been accumulated to the effect that patients with spatial hemineglect are able to analyse material presented in the contralesional side of space, which they are unable to report and deny perceiving. The anatomophysiological basis of this preserved processing without awareness includes the sparing of the primary somatosensory and visual cortices in a number of patients with hemineglect (see Fig. 5), and the physiological evidence that the presented

Conclusion

From the neuropsychological vantage point discussed in this review, it appears to be the case that the neural system concerned with spatial cognition has a highly articulated architecture. A main development in this area is likely to involve the further fractionation of spatial hemineglect into more and more specific patterns of `hemi' impairment, resulting from the disordered function of discrete neural networks. In this respect, the anatomical counterparts of the behavioural dissociations in

Outstanding questions

•
Which are the precise features of the distortion of the internal representations of space, found in patients with hemineglect?
•
Why are patients with hemineglect not aware of material they prove to be able to process, or, why is phenomenal experience lacking in this processing without awareness?
•
Which are the relationships between defective and productive manifestations of hemineglect?
•
Which are the precise mechanisms whereby sensory stimulations modulate hemineglect and spatial behaviour?
•
Which are

Acknowledgements

I am grateful to Michele di Francesco for a useful discussion, and to the anonymous referees for their comments and suggestions. This work was supported in part by grants from the MURST, CNR, Ministero della Sanità, and EC Grant BMH1-CT94-1133.

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Trends in Cognitive Sciences

Spatial hemineglect in humans

Abstract

Section snippets

The compass of spatial hemineglect

The anatomical basis of hemineglect

The modulation of hemineglect by sensory stimulations

Processing without awareness in spatial hemineglect

Conclusion

Outstanding questions

Acknowledgements

Neuropsychologia

Neuropsychologia

Neuropsychologia

Neuropsychologia

Cortex

Brain Cognit.

Neuropsychologia

Neuropsychologia

Neuropsychologia

Neuropsychologia

Neuropsychologia

Cortex

Trends Cognit. Sci.

Neuropsychologia

Cognit. Psychol.

Neuropsychologia

Cortex

Neuropsychologia

Neuropsychologia

Neuropsychologia

Neuropsychologia

Brain Cognition

Cortex

Cortex

Neuropsychologia

Neuropsychologia

Arguments concerning representations for mental imagery

Psychol. Rev.

Unilateral `spatial agnosia' (`inattention') in patients with cerebral lesions

Brain

The significance of perceptual rivalry resulting from parietal lesion

Brain

Mental representation in unilateral neglect and related disorders: the twentieth Bartlett memorial lecture

Q. J. Exp. Psychol. A

Left spatial hemineglect: An unmanageable explosion of dissociations?

No Neuropsychol. Rehab.

Left neglect for near but not far space in man

Nature

Unilateral neglect restricted to visual imagery

Nature

Spared awareness for the left side of internal visual images in patients with left-sided extrapersonal neglect

Neurology

Spatial and object-based neglect

Neurocase

A framework for interpreting distinct patterns of hemispatial neglect

Neurocase

Attention to within-object and between-object spatial representations: multiple sites for visual selection

Cognit. Neuropsychol.

Separate coding of space within and between perceptual objects: evidence from unilateral visual neglect

Cognit. Neuropsychol.

Directional hypokinesia: prolonged reaction times for leftward movements in patients with right hemisphere lesions and neglect

Neurology