The amount of stimulus information conveyed by the pulvinar neurons and the number of stimulus-differentiating neurons were consistently higher during the second 50-ms period than during the first 50-ms period. These results suggest that responsiveness to face-like patterns during the first 50-ms period might be attributed to ascending inputs from the superior colliculus or the retina, while responsiveness to the five different stimulus categories during the second 50-ms period might be mediated by descending inputs from cortical regions. These findings provide neurophysiological
evidence for pulvinar involvement in social cognition and, specifically, rapid coarse facial information processing. The pulvinar nuclei are located in the posterior region of the thalamus and are proportionally larger in higher mammals, such as primates, having the largest dimensions in the human Selleckchem Verteporfin brain
(Browne & Simmons, 1984). The pulvinar receives visual inputs from subcortical structures, including the superficial and deep layers of the superior colliculus, and has intimate reciprocal connections with a wide variety of cortical areas (Benevento & Fallon, 1975; Linke et al., 1999; Grieve et al., 2000; Kaas & Lyon, 2007). These neuroanatomical studies suggest that the pulvinar forms a subcortical visual route to the cortex that bypasses the striate cortex (Pessoa & Adolphs, 2010). Indeed, human subjects and monkeys with lesions in the striate cortex (V1) display a wide range of residual visual functions in the blind area (i.e. blindsight; Stoerig & Cowey, 1997). Monkeys with striate cortex selleck lesions can discriminate spatial localization (Solomon et al., 1981), luminous flux (Pasik & Pasik, 1973), colors and figures (Schilder et al., 1972). Human subjects with V1 lesions Palbociclib nmr can
also respond differentially to spatial localization of stationary and moving stimuli (Perenin & Jeannerod, 1975; Blythe et al., 1987), motion direction (Barbur et al., 1980; Perenin, 1991), line orientation (Weiskrantz, 1987), wavelength (Morland et al., 1999) and form (Perenin & Rossetti, 1996). Consistent with these findings, some pulvinar neurons have retinotopically specific receptive fields and respond to moving stimuli with various directions, while the activity of other pulvinar neurons is modulated by spatial attention (Robinson, 1993). These pulvinar neurons might send visual information directly to the middle temporal area, accounting for some residual visual functions, especially spatial functions (Berman & Wurtz, 2010, 2011). The pulvinar also projects to other subcortical areas such as the amygdala and striatum (Day-Brown et al., 2010; Pessoa & Adolphs, 2010; Tamietto & de Gelder, 2010). These subcortical routes might be involved in rapid processing of emotional stimuli (Tamietto & de Gelder, 2010).