Consistently, low-frequency faces specifically

activate the subcortical visual pathway, including the superior colliculus, pulvinar and amygdala (Vuilleumier et al., 2003). Furthermore, residual visual ability MG-132 was tuned to low spatial frequency in a patient with blindsight due to lesions in the visual cortical areas (Sahraie et al., 2002). This fast activation of the pulvinar might be due to direct inputs from the superior colliculus, contributing to the ability of newborns to orient toward faces. The present study provides neurophysiological evidence of pulvinar involvement in fast and coarse facial information processing. The second hypothesis proposes that interactive activity based on reciprocal connections between the subcortical and cortical areas is important for stimulus recognition and attention (Bullier, 2001;

Pessoa & Adolphs, 2010). These cortico-pulvino-cortical circuits might be involved in coordinating and amplifying signals, and improving signal-to-noise ratios (Shipp, 2003; Pessoa & Adolphs, 2010), as well as modulating interactions between oscillatory processes in different cortical areas, which contributes to visual attention (Serences & Yantis, 2006; Saalmann & Kastner, 2009). Our results here indicate that pulvinar neurons detect face-like patterns in epoch 1, while they categorize the visual stimuli into one of the five stimulus categories in epoch 2. Furthermore, the amount of stimulus information conveyed by the pulvinar neurons and the number of stimulus-differential neurons was higher in epoch 2 than in Cobimetinib order epoch 1. These results indicate that before pulvinar neurons become more sensitive to other categories of stimuli after epoch 1 (i.e. epoch 2 or later), during which cortical neurons also become active (for response latencies of cortical neurons, see a review by Lamme & Roelfsema, 2000).

These findings suggest that pulvinar responsiveness to a variety of stimuli in epoch 2 might be due to reciprocal connections with cortical areas with similar response latencies. Consistent with this, a neuropsychological study of human patients with pulvinar lesions suggests that the pulvinar is involved in enhancing stimulus saliency (Snow et al., 2009), which might contribute to neural computation in an early stage of stimulus categorization (Meeren et al., 2008). Our results provide direct neurophysiological evidence that pulvinar neurons respond to face-like patterns with short latencies, which seems to be consistent with the view that the pulvinar nuclei comprise a subcortical pathway that rapidly processes coarse facial information. Following the initial recognition of the facial stimulus, the population activity of the pulvinar neurons participates in classifying the facial pattern, with a concomitant increase in the amount of information processed.