Steady-state visual evoked potentials differentiate between internally and externally directed attention

• Published in: NeuroImage (Orlando, Fla.) Vol. 254; p. 119133
• Main Authors: Kritzman, Lior, Eidelman-Rothman, Moran, Keil, Andreas, Freche, Dominik, Sheppes, Gal, Levit-Binnun, Nava
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2022; Elsevier Limited; Elsevier
• Subjects: EEG; Heart; Heartbeat-evoked potential; Information processing; Internal attention; Sensory integration; Steady-state visual evoked potential (ssVEP); Synchronization; Visual evoked potentials; Visual perception; Visual stimuli; Steady-state visual evoked potential (ssVEP); Internal attention; EEG; Heartbeat-evoked potential
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2022.119133

•Steady-state visually evoked potentials are modulated by internal attention.•Internal attention increases alpha-band activity and the heartbeat evoked potential.•Low-level visual processing trades-off with cardiac signal processing.•A limited cortical capacity is shared between sensory and interoceptive processing. While attention to external visual stimuli has been extensively studied, attention directed internally towards mental contents (e.g., thoughts, memories) or bodily signals (e.g., breathing, heartbeat) has only recently become a subject of increased interest, due to its relation to interoception, contemplative practices and mental health. The present study aimed at expanding the methodological toolbox for studying internal attention, by examining for the first time whether the steady-state visual evoked potential (ssVEP), a well-established measure of attention, can differentiate between internally and externally directed attention. To this end, we designed a task in which flickering dots were used to generate ssVEPs, and instructed participants to count visual targets (external attention condition) or their heartbeats (internal attention condition). We compared the ssVEP responses between conditions, along with alpha-band activity and the heartbeat evoked potential (HEP) - two electrophysiological measures associated with internally directed attention. Consistent with our hypotheses, we found that both the magnitude and the phase synchronization of the ssVEP decreased when attention was directed internally, suggesting that ssVEP measures are able to differentiate between internal and external attention. Additionally, and in line with previous findings, we found larger suppression of parieto-occipital alpha-band activity and an increase of the HEP amplitude in the internal attention condition. Furthermore, we found a trade-off between changes in ssVEP response and changes in HEP and alpha-band activity: when shifting from internal to external attention, increase in ssVEP response was related to a decrease in parieto-occipital alpha-band activity and HEP amplitudes. These findings suggest that shifting between external and internal directed attention prompts a re-allocation of limited processing resources that are shared between external sensory and interoceptive processing.