title: Stimulus and optode placement effects on functional near-infrared spectroscopy of visual cortex.
abstract: Functional near-infrared spectroscopy has yet to be implemented as a stand-alone technique within an ophthalmology clinical setting, despite its promising advantages. The present study aims to further investigate reliability of visual cortical signals. This was achieved by: (1) assessing the effects of optode placements using the 10-20 International System of Electrode Placement consisting of 28 channels, (2) determining effects of stimulus size on response, and (3) evaluating response variability as a result of cap placement across three sessions. Ten participants with mean age [Formula: see text] years (five male) and varying types of hair color and thickness were recruited. Visual stimuli of black-and-white checkerboards, reversing at a frequency of 7.5 Hz were presented. Visual angles of individual checker squares included 1 deg, 2 deg, 5 deg, 9 deg, and 18 deg. The number of channels that showed response was analyzed for each participant, stimulus size, and session. 1-deg stimulus showed the greatest activation. One of three data collection sessions for each participant gave different results ([Formula: see text]). Hair color and thickness each had an effect upon the overall HbO ([Formula: see text]), while only color had a significant effect for HbD ([Formula: see text]). A reliable level of robustness and consistency is still required for clinical implementation and assessment of visual dysfunction.
authors.affiliation: Wright State University , Biomedical Imaging Laboratory, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, United States.
authors.forename: Nasser H
authors.initials: NH
authors.lastname: Kashou
authors.affiliation: Wright State University , Biomedical Imaging Laboratory, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, United States.
authors.forename: Brenna M
authors.initials: BM
authors.lastname: Giacherio
keywords: functional near-infrared spectroscopy; near infrared spectroscopy; visual cortex; visual stimulation