The neural organization in parietal cortex serving communication related to representation and cognition of facial expression.

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The intraparieatal cortex of monkeys is related to an integration of motor and sensory information (e.g.,vision, audition and somatosensory), and is known to an area controlling the oral and facial movements. Accordingly, for the oral and facial movement, it is supposed that the intraparietal cortex subserves an information processing related to communication of meaning between different individuals. If we record neurons in the intrapaeital cortex which respond to both representing a specific facial expression of one's own and observing a specific facial expression of others, it is possible to interpret that the monkey's intraparietal cortex subserbes an important role on communication of meaning related to facial expression. In this study, we executed behavioral and electrophysiological techniques to investigate our theory on communication of meaning.In behavioral experiments, monkey's facial movement and eye movement are measured by an image-analyzing apparatus in the following steps. First, we decided characteristic points on monkey's face (e.g., angle of mouth and eyeball). Second, motions of these characteristic points are measured and are digitized. As a result, monkey's facial expression was classified into three categories, that is, menacing face, frightened face and smacking face.In electrophysiological experiments, we recorded neurons in the intraparietal cortex of awake monkeys. To identify response properties of these neurons, these neuronal activities were analyzed according to their behavior patterns. As a result, we recorded neurons which responded to both executing a specific action of one's own and observing the similar action of others. The existence of these neurons in the intraparietal cortex indicates that the intraparietal cortex is related to coding of action meaning. It is considered that similar neurons related to communication of facial expression also exist in the intraparietal cortex.