Interaction between local and global visual orientation signals in subjects with unilateral brain lesions

A general theory concerning the prenatal origins of cerebral lateralization in humans.

“…Penfield (1957) originally suggested that the predominant role of the right parietal lobe in maintaining spatial orientation may arise from its greater involvement in vestibular function. Subsequent research has confirmed that the right hemisphere indeed plays a more critical role in vestibular processing and the maintenance of a gravitational coordinate system (Barlow, 1970;Birch, Belmont, Reilly, & Belmont, 1961;De Ajuriaguerra, Hecaen, & Angelergues, 1960;DeCencio, Leshner, & Voron, 1970;Magnussen, Johnsen, & Reinvang, 1987). A classic vestibularly mediated deficit that accompanies right-parietal damage is spatial disorientation, whose presence in these patients is analogous to the deficit found in labyrinth-defective individuals (Barlow, 1970).…”

“…For example, neglect is created by imbalances in nigrostriatal dopaminergic transmission (Heilman et al, 1987) that may occur naturally in humans because of asymmetric otolith development, whereas unilateral vestibular stimulation evidently alleviates this impairment (Cappa, Sterzi, Vallar, & Bisiach, 1987; Rubens, 1985; Vallar, Sterzi, Bottini, Cappa, & Rusconi, 1990). Finally, the enhanced “field dependence” (i.e., a reliance on the orientation of the visual field to infer the direction of the gravitational vertical) that is found in most right-parietal patients (Magnussen et al, 1987) also appears to reflect a “vestibular” symptom, because it is increased during weightlessness (Young, Shelhamer, & Modestino, 1986) and other situations involving attenuated vestibular input (Ornitz, 1970).…”