The pulvinar neurons displayed a broad distribution of response latencies, ranging from 30 to 500 ms. The mean latency of the short latency group was 63.38 ± 1.89 ms, which was comparable to previous studies (Felsten et al., 1983; Benevento & Port, 1995). Because the mean latency in V1, which projects to the pulvinar, is 66 ± 10.7 ms (Schmolesky et al.,

1998), some pulvinar neurons with short latencies, especially those with latencies < 60 ms, might receive inputs from the superior colliculus or directly from the retina. The remaining pulvinar neurons in the short latency group with latencies > 66 ms might receive inputs from the various visual cortices. BTK inhibitor In comparison, the pulvinar neurons in the long latency group might receive inputs from some other structures, such as the temporal association cortices, prefrontal cortex or the amygdala, which project to the pulvinar (Shipp, 2003). In addition, response latencies to frontal faces were significantly lower than those to profile faces. This suggests that the subcortical visual pathway might be tuned better to frontal faces than to profile faces. Total luminance of the face-like patterns was smaller than those of the square and eye-like stimuli, and luminance of the white

areas of the face-like patterns was the same as that of selleck compound the simple geometric patterns, indicating that specific early responses to the face-like patterns are not due to differences in total luminance or luminance. Furthermore, scrambling of the images greatly reduced the pulvinar

responses in the present study. This is the first evidence that pulvinar neuronal responses are dependent on coherent facial patterns. The results also indicate that selective responses to some visual stimuli are attributable to factors other than luminance differences. These findings are consistent with previous studies on face neurons in the prefrontal cortex (Ó Scalaidhe et al., 1999), inferotemporal cortex (Desimone et al., 1984) and superior temporal cortex (Bruce et al., 1981). However, in contrast to these cortical facial areas and the amygdala (Tazumi et al., 2010), the responses of the pulvinar neurons were not specific Dichloromethane dehalogenase to faces; pulvinar neurons also responded to other visual stimuli, such as simple geometric patterns, in the present study. Furthermore, although there was no significant difference in mean response magnitude toward faces with direct and averted gazes, many individual pulvinar neurons differentially responded to gaze directions (i.e. gaze-differential neurons). Neurophysiological and human imaging studies have shown that the amygdala responds stronger to faces with direct gaze (Kawashima et al., 1999; Wicker et al., 2003; Sato et al., 2004; Tazumi et al., 2010). These findings suggest that the pulvinar sends information on gaze direction to higher upstream brain areas in the visual pathway, such as the amygdala (Tazumi et al.