Beta oscillations define discrete perceptual cycles in the somatosensory domain

Abstract

Whether seeing a movie, listening to a song, or feeling a breeze on the skin, we coherently experience these stimuli as continuous, seamless percepts. However, there are rare perceptual phenomena that argue against continuous perception but, instead, suggest discrete processing of sensory input. Empirical evidence supporting such a discrete mechanism, however, remains scarce and comes entirely from the visual domain. Here, we demonstrate compelling evidence for discrete perceptual sampling in the somatosensory domain. Using magnetoencephalography (MEG) and a tactile temporal discrimination task in humans, we find that oscillatory alphaand low beta-band (8-20 Hz) cycles in primary somatosensory cortex represent neurophysiological correlates of discrete perceptual cycles. Our results agree with several theoretical concepts of discrete perceptual sampling and empirical evidence of perceptual cycles in the visual domain. Critically, these results show that discrete perceptual cycles are not domain-specific, and thus restricted to the visual domain, but extend to the somatosensory domain.somatosensory perception | beta oscillations | MEG | oscillatory phase

Exploring the relationship of phase and peak-frequency EEG alpha-band and beta-band activity to temporal judgments of stimulus duration

“…This is compatible with existing evidence of pre-stimulus phase effects on the probability of liminal stimulus detection (Busch et al, 2009;Mathewson et al, 2009) and fine-grained temporal judgments (e.g. Baumgarten et al, 2015;Cravo et al, 2015) where all stimulus information was presented and contained within close temporal proximity to stimulus onset. One account of these findings might be that suboptimal phases at onset of a stimulus lead to a slower or less efficient neuronal reception.…”

“…This is depicted for the maximum point of phase difference which was in the alpha-band (13 Hz) which was predicted, and for the maximum point of phase difference in the betaband which was not predicted. et al, 2009) and tactile simultaneity (13%; Baumgarten et al, 2015). Using the same phase bins, results showed no significant effect of pre-stimulus alpha-band phase (F (4,60) = 0.765, MSE = 0.001, p = 0.552, η p 2 = 0.049) and no significant effect of beta-band phase (F (1.426,21.388) = 1.235, MSE = 0.017, p = 0.297, η p 2 = 0.076) on standardized PSE (Figure 4(b)).…”

“…The results were then analysed using a one-way repeated measures ANOVA with 5 levels of phase to look at the effect of phase bin on temporal judgment. This analysis was done at the time-frequency point of greatest significance and therefore reflects an upper-bound of phase effects, but allows comparison with the existing literature (Baumgarten et al, 2015;Busch et al, 2009).…”

“…For comparison with previous findings (Baumgarten et al, 2015;Busch et al, 2009), a post-hoc test explored the influence of phase on temporal judgments by separating trials into 5 phase bins at the time and frequency point where the effect was strongest for the alpha-(13 Hz, −310 ms) and beta-band (23 Hz, −350 ms) (Figure 3(b)). As a post-hoc test at the strongest frequency and time points, this indicated an upper-bound of phase effects.…”

“…Thus when two discrete stimuli occur within the same perceptual frame they are more likely to be experienced as simultaneous rather than as temporally segregated. More recently, a number of findings consistent with this framing hypothesis have demonstrated effects of oscillatory pre-stimulus phase on fine-grained temporal judgments (Baumgarten, Schnitzler, & Lange, 2015;Chakravarthi & Vanrullen, 2012;Cravo, Santos, Reyes, Caetano, & Claessens, 2015;Milton & Pleydell-Pearce, 2016). These studies investigated temporal judgments at or shorter than the hypothesized frame duration, typically thought to involve thẽ 10 Hz (~100 ms) alpha cycle for visual stimuli (Cravo et al, 2015;Milton & Pleydell-Pearce, 2016;Varela et al, 1981).…”