| Budget Amount *help |
¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2000: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
To investigate the subcortical visual function, visual stimuli were projected to the nasal and temporal hemiretinas, and their psychophysical effects were compared. Visual signals projected to the nasal and temporal hemiretinaes are sent to the primary visual cortex via crossed and uncrossed visual pathways, respectively. Compared with the uncrossed visual pathway, the crossed visual pathway is known to have strong neural connections with the subcortical neural structures such as the superior colliculus and the nuclei of the optic tract which are responsible for generating eye movements and visual orienting behavior. Therefore, it is expected that visual stimuli projected to the nasal hemiretina attract more attention than those projected to the temporal hemiretina. To examine this expectation, three experiments were conducted. In the first experiment, reaction latencies of saccadic eye movements to visual stimuli presented to the nasal and temporal hemiretinas were recorded, but no significant difference was shown. In the second experiment, mislocation produced by rapid motion of background scene was compared between the nasal and temporal hemiretinas, but the results were negative. The third experiment was conducted to examine the inhibitory effect of visual distractor stimuli on saccade generation. In this experiment, a visual distractor was presented to one hemiretina and a saccade target was presented to other hemiretina. The saccade latencies were increased by simultaneous presentation of distractors, and the amount of this inhibitory effect was larger for distractors presented to the nasal hemiretina. This result is consistent with the neuroanatomical finding that, compared with the temporal hemiretina, the nasal hemiretina has strong neural connections with subcortical structures. Thus, the experimental method used in this study is expected to be a useful paradigm for psychophysically exploring subcortical visual function of normal subjects.
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