Abstract
In this paper, the most effective stimulation durations in the visual, somatosensory, and motor cortices are investigated. To evoke hemodynamic responses (HRs) for the purpose of brain-computer interface (BCI) with functional near-infrared spectroscopy (fNIRS), the best and the minimal durations for three tasks (visual, tapping, and poking) are presented. The examined tasks include the checkerboard, right-hand-index-finger poking, and the right-hand-index-finger tapping tasks in association with the visual, somatosensory, and motor cortices. Upon stimulations, the peak value, time to peak, and the full width at half maximum of the HRs are examined. Six different stimuli durations (i.e., 1, 3, 5, 7, 10 and 15 sec) were tested. Ten male subjects participated in the experiment. Three types of stimulations having the same duration were presented to the subjects randomly. The stimulation durations that showed the maximum peak values in the checkerboard, poking, and tapping tasks were 7, 5, and 10 sec, respectively. The peak value increased with the increase of stimulation duration. But beyond a certain period of time, the peak value did not increase anymore and sometimes it decreased when the stimulation period is too long. It is noted that 1-sec stimulation (for all three tasks) can generate a noticeable peak value. Instead, the initial dip upon poking occurred only with 1-sec poking (i.e., initial dip did not occur in all other poking periods). Conclusively, this work reveals the possibility of a BCI command generation within 1 sec.
Highlights
Brain-computer interface (BCI) characterizes a communication medium between the brain and peripheral devices, constructed to achieve external activities with only brain signals [1]
We aim to suggest the most suitable stimulation durations for three brain regions for functional near-infrared spectroscopy (fNIRS)-based BCI
The concept of desired hemodynamic response function (dHRF) is used to identify the initiation of the real hemodynamic responses (HRs) for both short and long stimulation durations in each target area
Summary
Brain-computer interface (BCI) characterizes a communication medium between the brain and peripheral devices, constructed to achieve external activities with only brain signals [1]. The new era of BCI has developed various ways to detect particular neural signals in the human brain and to decipher those signals as commands that can be used to control the associated external devices. This research has been an area of focus for researchers since 2000, prompting the inventions of several prototype systems. BCI is intended for patients, but it can be used for healthy people like pilots and drivers for specific purposes. The objective of this study is to find out the best and minimal stimulation durations that can produce the maximal and sufficient activations in the hemodynamic response (HR) for BCI.
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