Week 4

Spatial neglect

Spatial neglect describes a condition in which the attention to stimuli is withdrawn from one side of the visual field. Neglect arises after brain damage to the inferior parietal lobule (defines the location of stimuli) and always affects the contralateral side (opposite the brain damage) of the visual field. Even though, it can occur in either side of the brain, right hemispatial neglect is reported to be the more common one. This could be due to the fact that left hemispatial neglect is normally presented as less severe.

Spatial neglect can be further divided into two subtypes. The space around a person is described in two areas, the space within the reach of the person (peripersonal space) and the space within walking distance (extrapersonal space). Some patients might display neglect in only one of the two, while the other one is still normally functioning.

Neglect can be tested in several ways, using tests like cancelling out stimuli on a paper or copying images, which all show clear inattention to the contralateral side. The patient however, in most cases, is completely unaware of this disfunction (anosagnosia) and can only notice his deficit (missed stimuli on one side of the paper, copy of only one side of the image) when pointed out to him/her. The realization then, of having neglect, arises after several months and is part of it's recovery.

Extinction:

Extinction is seen as a milder version of neglect, since patients attend to the contralateral side when a stimulus is shown. However, when stimuli are presented on the contralateral side, as well as on the ipsilateral side (same side than the lesion), the patients will only be able to focus their attention on the stimui presented on the ipsilateral side and therefore show the symptoms of neglect in this situation.

Most people are shown to recover from spatial neglect in only few months. However, this does not apply to every patient. Recovery can last several years, or can not occur at all, depending on the patient.