抄録
We investigated neural plasticity in the rat primary somatosensory cortex after somatosensory frequency discrimination learning with flavoprotein autofluorescence imaging. A water-deprived rat was trained to discriminate the frequency (20 Hz or 40 z) of floor vibration in a Skinner box. Licking a spout only during the floor vibration at either 20 Hz or 40 Hz (S+) was rewarded with water in each rat, while that in response to 40 Hz or 20 Hz stimulation (S-) was not. The rat quickly learned to discriminate between S+ and S- by suppressing behavioral responses to S-. After this learning was achieved in consecutive 3-5 days, the rat was anesthetized with urethane (1.5 g/kg, i.p.), and somatosensory neural activities in response to vibratory skin stimulation at 20 Hz or 40 Hz applied on the contralateral left plantar hindpaw was recorded. Responses were visualized with flavoprotein autofluorescence (500-550 nm) in blue light (450-490 nm) using a cooled CCD camera attached to an epifluorescence binocular microscope. The neural responses to S- were smaller than those to S+ in all of the 8 rats tested. The responses to S- in learned rats were significantly smaller that those in naive rats, while those to S+ were similar to the responses in naive rats. These results suggest that the plastic changes in the somatosensory cortex (suppression of the somatosensory responses to S-) may be a part of essential neural mechanisms underlying the frequency discrimination learning with suppressed behavioral responses to S-. [Jpn J Physiol 54 Suppl:S144 (2004)]
