Chronic neonatal blockade of N-methyl-D-aspartate (NMDA) receptors produces behavioral and physiological changes in adult animals. Temporal information processing was investigated by testing the effects of chronic neonatal NMDA-R blockade with MK-801 (0.4 mg/kg twice per day) on temporal cognition in adult rats. Rats were trained to discriminate between 2-s and 8-s anchor durations, and they were then required to classify probe duration in the bisection task. Neonatal chronic MK-801 treatment did not disrupt duration discrimination. Conversely, MK-801-treated rats showed a leftward shift of their timing function. The results of the present study suggest that chronic blockade of NMDA receptors in the critical period of neurodevelopment induces long-lasting changes in temporal cognition processing. Therefore, MK-801-treated rats present a potential animal model of disorders that involve abnormal temporal cognition.
Russell & Bullock (1985) proposed that facial expressions are emotionally categorized through psychological evaluation consisting of two dimensions, i.e., “pleasure (pleasant feeling -- unpleasant feeling)” and “arousal (high arousal -- sleepiness)”. On the other hand, previous ERP (event-related potential) studies for facial expression recognition suggest that ERP amplitude and latency vary depending on facial emotion categories. In the present study, participants received the neutral face as the first stimulus, which was immediately followed by the facial expression (happy, angry, and surprise) or random dots as the second stimulus. In addition, each facial expression was evaluated by the Affect Grid. Both the arousal score and the P130 amplitude for surprise facial expression were greater than those for happy and angry facial expressions. The amplitude and latency of N170 and P300 were not different among the facial expressions. These results suggest that changes in the arousal dimension elicited by emotional faces may be linked to early visual processing shown in P130.