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Masamitsu Harasawa, Hiroshi Ishikane; Continuously moving RSVP task revealed neuronal activities related to position of spatial attention: an fNIRS study. Journal of Vision 2011;11(11):219. doi: 10.1167/11.11.219.
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© ARVO (1962-2015); The Authors (2016-present)
Variation of position of visuospatial attention causes modulation of neural activities. This phenomenon has been clear in early visual cortex revealed by fMRI studies. Here, we demonstrate that this effect could occur even in lateral parietal cortices and superior temporal cortices by using functional near-infrared spectroscopy. In order to investigate the relationship between the position of visuospatial attention and the cortical activities, the recently developed technique using continuously modulated visual stimuli and differential neural responses (Tajima et al., 2010) was introduced. Subjects performed the RSVP task detecting number figures among the 12 alphabets circularly arranged 4.5 deg peripherally from the center fixation point. The target appeared every about 3.5 sec. The target position continuously moved clockwise around the center FP at the speed of 360°/min. The initial position of the target was right above or below the FP. The initial position was cued before the task period lasting 75 sec. The brain activity (changes of oxy-Hb concentration) was measured at 47 points covering lateral and posterior parietal cortices and parts of temporal and occipital cortices. Differential Hb changes by the initial target position were fitted by sinusoidal curves with the wavelength of 60 sec and the other parameters were optimized for each measurement point and subject. The optimized phases for all data points distributed bimodally. The measurement points with higher phase mainly distributed on the left cortical areas including PPC, STG, and LOC, while the points with lower phases mainly distributed on the right cortical areas. In the control experiment where the peripheral stimuli were neglected and the subjects performed the center RSVP task such bimodal distribution was not observed. These results suggest that there could be the neural activities related to the position of visuospatial attention in relatively higher cortical areas.
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