| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2005: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2004: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Studies have shown that rats have a greater short-term memory in response to auditory information over visual information (ex. Tsutsui, 1998). This phenomenon is known as the modality effect on memory. In this study, the relationship between the modality effect and cholinergic pathways was examined in rats brains. Eighteen rats were trained to perform a successive delayed matching-to-sample (SDMTS) task, using operant chambers with two retractable levers. Paired stimuli (S1-S2), which was divided by a delay interval of 1 second, 3 seconds, or 5 seconds, was presented to the animals. The four types of S1 and S2 combinations were as follows : Light-Light, Light-Tone, Tone-Tone, and Tone-Light. The rats had to press one of the two levers depending on the combination of the stimuli : When the modality of S1 was identical to that of S2, pressing the right lever was rewarded with a food pellet, and when the modality of S1 was different from that of S2, pressing the left lever was rewarded in the same manner. After the acquisition of the SDMTS, half of the rats were given a lesion into the nucleus basalis of Meynert (nbm) unilaterally, and the other half received a sham operation. Lesions given to the nbm disrupted the retention of auditory information, as a function of the length of the delay interval between S1 and S2. Rats whose nbm was destroyed were not able to retain visual information irrespective of the length of the delay interval. As a result, it has been suggested that the nbm has two different roles according to the modality of memory information. There is a possibility that the nbm is related to the short-term memory of auditory information and to the long-term memory of visual information.
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