Time Course of Hemoglobin Concentration Changes in Human Visual Cortex during Visual Stimulation Demonstrated by Near–infrared Spectroscopy

Abstract

Abstract: : Purpose: To investigate the time courses of concentration changes using near–infrared spectroscopy (NIRS) in oxyhemoglobin (oxy–Hb), deoxyhemoglobin (deoxy–Hb), and total hemoglobin (total–Hb) in the occipital cortex during visual stimulation. Methods: Five normal subjects were studied with NIRS during the stimulation with black–and–white checkerboards reversing at 8 Hz. The optodes were carefully positioned based on anatomic MRI marked with vitamin D capsules. Results: An increase in [oxy–Hb] and [total–Hb] and a decrease in [deoxy–Hb] were observed during the visual stimulation in all subjects. All these changes in NIRS parameters were statistically significant and the change in [oxy–Hb] was the largest among the three parameters. The NIRS responses followed the onset and the offset of the visual stimulation with a latency of 9 and 12 seconds, respectively. Conclusions: The time courses of NIRS parameters during visual activation of visual cortex were found to be reproducible across subjects. This method may be useful in non–invasively monitoring visual function in humans together with other methods (e.g., visual evoked potentials).

Keywords: visual cortex • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • neuro–ophthalmology: diagnosis