Abstract
To investigate the integration process of motion involved in the dorsal stream and shapes involved in the ventral stream, we examined the neuronal activities of the area MT in the shape from motion (SFM) condition, in which shapes were made visible by dots within invisible contours of shapes moving coherently in one direction. Monkeys performed a shape discrimination task and a direction discrimination task. In the shape task, one of 4 shapes in the white solid condition was presented centrally as a sample stimulus, and after a delay period the same shape was presented peripherally as a target with a distracter presented on the opposite side. Two shapes were defined by moving dots against static dots during this period. Moving directions were selected from the preferred and null directions of the recording cell. Monkeys were required to select the same shape as the sample stimulus. In the direction task, moving dots were presented during the sample period and monkeys were required to ignore the shape difference and to select the same direction of movement as the sample stimulus during the discrimination period. The physical conditions during the discrimination period were identical between two tasks. About 30% of MT neurons showed significantly greater response in the shape task and about 20% showed significantly greater response in the direction task. These results may suggest the involvement of the area MT in the shape discrimination under the SFM condition. [Jpn J Physiol 55 Suppl:S165 (2005)]
