Abstract
Purpose: We investigate the susceptibility of the prefrontal cortex to the odd visual stimuli measuring hemodynamic response. The subject observes the Motion Induced Blindness (MIB), which is odd enough to attract one's attention. We search the locus where the hemodynamic response is detectable. We study issues such that the response is transient or sustained and that the neurovascular coupling is oxygenated or deoxygenated. Method: We utilized Near InfraRed HemoEncephaloGraphy (NIR HEG). Preliminarily, different length of time sessions were examined. The attentional response was transient. For reliable HEG response, one second or more period was needed. The stimulus condition therefore was that the target figure disappeared by MIB effects for 500ms. The next 500ms had no MIB. The episode repeated 5 times. For the control condition, the similar stimulus was presented without MIB. The subject observed 5 second control, i.e. without MIB, episode then observed 5 second MIB episode. The 10 second episode composed a single session. A short break was taken at the disposal of the subject. He repeated the session. By trial and error, we searched the measurement site where HEG ratio difference was detectable. We obtained a couple of reliable data by the intensive search. Results: At Brodmann 10, where the light source was on the sinus and the light detector was 3cm horizontally apart to the right hemisphere, the HEG ratio was high for MIB and low for the control conditions. Discussion: At right Brodmann 46, we found that for MIB period HEG ratio was low. If we accept neurovascular coupling hypothesis, whether the light detector was close to artery or to vein determines the increase or decrease of HEG ratio Conclusions: We found a few seconds transient hemodynamics responding to the odd visual stimuli. HEG ratio not necessarily increased but also decreased.
Meeting abstract presented at VSS 2016