Visuospatial Ability in Healthy Subjects and in Patients with Left or Right Hemi- Sphere Damage

Spatial neglect refers to the defective ability of patients to identify and respond to stimuli presented in the contralesional hemifield, following unilateral brain injury (mainly right hemisphere damage). Spatial neglect can occur in specific sectors of space regarding a given coordinate system. Neurophysiological and neuroimaging data underline the role of posterior parietal cortex (PPC) in visualspatial functions. Healthy subjects show a tendency to overestimate left side of visual field. This phenomenon, known as pseudoneglect, happens mainly in peripersonal (hand reaching) space than in extrapersonal one. These findings highlight that separate neural circuits underline spatial cognition, and that these ones work synergically to elaborate information. Recent studies conducted by using non-invasive transcranial stimulation techniques, such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), strengthened this hypothesis and also suggested that these stimulation techniques may be a useful therapeutic tool in patients with brain damage and visuo-spatial deficits.