Experimental evidence for involvement of monocular channels in mental rotation.

According to the prevailing view, cognitive processes of mental rotation are carried out by visuospatial perceptual circuits located primarily in high cortical areas. Here, we examined the functional involvement of (mostly subcortical) monocular channels in mental rotation tasks. Images of two rotated objects (0°, 50°, 100°, or 150°; identical or mirrored) were presented either to one eye (monocular) or segregated between the eyes (interocular). The results indicated a causal role for low monocular visual channels in mental rotation: Response times for identical ("same") objects at high angular disparities (100°, 150°) were shorter when both objects were presented to a single eye than when each object was presented to a different eye. We suggest that mental rotation processes rely on cortico-subcortical loops that support visuospatial perception. More generally, the findings highlight the potential contribution of lower-level mechanisms to what are typically considered to be high-level cognitive functions, such as mental representation.