EEG and fNIRS Measurement of Brain Activity in Response to Affective Images

Abstract

This pilot study utilizes a multimodal neuroimaging approach, combining electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) to explore neural responses to images which elicit basic emotions: disgust, fear, happiness, and neutrality. Combining techniques that measure brain activity based on different physiological mechanisms, such as in this case neural electrical activity and hemodynamic activity, enables a more comprehensive insight into brain function [1].

Pioneering research in emotional processing indicates that both pleasant and unpleasant stimuli elicit stronger neural responses than neutral stimuli, reflected in amplitude changes across early, middle, and late ERP components [2]. Unlike many previous studies that focus primarily on the valence dimension (positive vs. negative emotions), this study emphasizes basic emotions as distinct categories. Participants passively viewed a sequence of 75 images, drawn from three verified and standardized datasets, designed to elicit basic emotions. The sample included 10 participants (9 females, 1 male; mean age 22), with one outlier in her late 50s. A 32-channel EEG system, arranged according to the international 10/5 system, was used to measure electrical brain activity, particularly event-related potentials (ERPs) such as P3 and late positive potential (LPP), while an 8-channel fNIRS array was used to measure hemodynamic changes in the prefrontal cortex.

Based on our measurements and prior research, we anticipate that emotional images will evoke stronger ERP components (particularly in the prefrontal and centro-parietal regions) than neutral images [3]. We also expect to observe increased blood oxygenation in the left prefrontal cortex, as seen in prior studies regardless of emotion type [1]. Furthermore, we hypothesize that the EEG and fNIRS data will correlate, reflecting complementary aspects of brain activity during emotional stimulus processing. If the hypothesis is confirmed, this methodology may prove valuable for future studies investigating emotional responses.

References

[1] M. Balconi, E. Grippa, and M. E. Vanutelli, "What hemodynamic (fNIRS), electrophysiological (EEG) and autonomic integrated measures can tell us about emotional processing," Brain and Cognition, vol. 95, pp. 67–76, 2015. doi: 10.1016/j.bandc.2015.02.001.

[2] L. Carretié, J. A. Hinojosa, and F. Mercado, "Cerebral patterns of attentional habituation to emotional visual stimuli," Psychophysiology, vol. 40, no. 3, pp. 381–388, 2003. doi: 10.1111/1469-8986.00041.

[3] T. Štrempfel, “Passive Viewing of Affective Images: A Multimodal Functional Near Infrared Spectroscopy and Electroencephalography Study”, Master’s thesis, T. Štrempfel, Ljubljana, 2024. [Online]. Available: https://repozitorij.uni-lj.si/IzpisGradiva.php?id=160739.