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Masamitsu Harasawa, Akiko Obata, Toshiya Morita, Takayuki Ito, Takahiro Saito, Takao Sato, Kiyoharu Aizawa; Hemodynamic changes in visual motion detection measured by near infrared spectroscopy. Journal of Vision 2006;6(6):572. doi: 10.1167/6.6.572.
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© ARVO (1962-2015); The Authors (2016-present)
Optical topography (OT) is an apparatus to measure cortical hemodynamic changes using near infrared spectroscopy and can be handled and maintained much more easily than fMRI, MEG and PET. However, there are few previous studies on relationship between OT signal and early visual processing. We investigated effects of motion signal intensity on OT signal, and suggested the usefulness of OT for vision sciences. Method: 100 white dots were randomly positioned within a 9.4° circular aperture in left visual hemifield. All dots moved in random direction with lifetime of 30 ms. Several seconds after the onset of random motion, a fraction (0, 20, 40 or 80%) of dots moved leftward or rightward coherently for 3 sec, and subsequently all dots disappeared. Participants pressed a button with their right hands as quickly as possible if they detected coherent motion. Hemoglobin concentrations were detected by an optical topography (Hitachi Medical Systems, ETG-100) every 0.1 sec at 24 measurement points. We positioned them on left and right side of participants' inions and repeated measurements at least 100 times for every condition. Results and Discussion: OT signals induced by coherent motion were obtained as differences of hemoglobin concentrations between “hit” and “correct rejection” trials. For every participant the higher motion signal intensity induced the shorter behavioral reaction time and the higher OT signals in right hemisphere. Our results indicated the relationship among stimulus intensity, behavioral response and hemodynamic response, and suggested the usefulness of this newly emerging apparatus.
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