Neuroscience 2010, the 40th annual meeting of the Society for Neuroscience
会期: 2010.11.13-17
会場: The San Diego Convention Center

発表日:2010.11.16

Program#/Poster#: 581.13/TT12

Title: Time course of neuronal selectivity for facial expression in the temporal visual cortex and the amygdala of monkeys

Authors: *M. INAGAKI, I. FUJITA;
Grad Sch. Frontier Biosci., Osaka Univ., Toyonaka, Japan

Abstract: Facial expression is important for social communication in humans and non-human primates because it provides clues to infer others’ emotional state. Neurons showing selectivity for facial expression of visual images of face have been found in the temporal visual cortex and the amygdala. Although the selectivity for facial expression has been previously assessed, the origin of the selectivity has remained unclear. Because of reciprocal anatomical connections, the activities of temporal cortex neurons can influence those of amygdala neurons and vice versa. Both areas therefore could be the initial source of facial expression selectivity. To address this issue, we compared the time course of the neuronal selectivity for facial expression between the temporal visual cortex and the amygdala. We used two Japanese monkeys (Macaca fuscata) and recorded extracellular neuronal activities while the monkeys were engaged in a simple fixation task. We presented three facial expressions (open-mouth, pout-lips, and neutral) by three different monkeys for a total of nine images. Each image subtended 7.7 × 7.7 degrees in visual angle and was presented for 500 ms. We recorded 117 and 103 face-responsive neurons from the temporal visual cortex (A18 - A24) and the amygdala (A22 - A25), respectively. Among them, 42 and 43 neurons were selective for facial expression (two-way ANOVA; factors, facial expression, face identity; p < 0.05) when we assessed the selectivity using mean responses averaged across stimulus duration. To examine the time course of the selectivity, we measured the responses with a sliding 50 ms time window and repeatedly analyzed selectivity for facial expression along the time axis (two-way ANOVA; factors, facial expression, face identity; p < 0.05, with Bonferroni correction). The percentage of facial-expression selective neurons in the temporal visual cortex first exceeded chance in the time window 57 to 106 ms, whereas that of the amygdala first exceeded chance at 102 to 151 ms. The population latency of the selectivity in the temporal visual cortex was shorter than that of the amygdala by 45 ms, indicating that facial-expression selective responses firstly occur in the temporal visual cortex. From these results, we suggest that selectivity for facial expression is initiated in the temporal visual cortex and then the information spreads into the amygdala.