Spatial neglect: hypothetical mechanisms of disturbed interhemispheric crosstalk for orientation

Schematic drawings are presented of the major anatomical structures involved, along with their functional excitatory and inhibitory connections as the basis of a hypothetical model of visuospatial neglect. It is assumed that multisensory integration centers for attention and orientation (MSO) are represented in the temporo-parietal cortex of both hemispheres, with the dominant MSO being in the right hemisphere (nondominant hemisphere in right-handedness). A lesion of the dominant MSO will cause a left-sided neglect due to a lack of ipsilateral activation of the visual cortex, which is further enhanced by increased inhibition from the contralateral visual cortex. The nondominant MSO in the left hemisphere might be involved in the manifestation of the less frequent and more transient right-sided neglect and in the plastic mechanisms of gradual recovery from a left-sided neglect or extinction.