Abstract
In the past decade, studies have shown that attention fluctuates at ∼8 Hz, alternating between intervals of increased and decreased visual performance [Re, D., Karvat, G., & Landau, A. N. Attentional sampling between eye channels. Journal of Cognitive Neuroscience, 35, 1350–1360, 2023; Re, D., Inbar, M., Richter, C. G., & Landau, A. N. Feature-based attention samples stimuli report feature-based attention samples stimuli rhythmically. Current Biology, 1–7, 2019; Helfrich, R. F., Fiebelkorn, I. C., Szczepanski, S. M., Lin, J. J., Parvizi, J., Knight, R. T., et al. Neural mechanisms of sustained attention are rhythmic. Neuron, 99, 854–865, 2018; VanRullen, R. Perceptual cycles. Trends in Cognitive Sciences, 20, 723–735, 2016; Fiebelkorn, I. C., Saalmann, Y. B., & Kastner, S. Rhythmic sampling within and between objects despite sustained attention at a cued location. Current Biology, 23, 2553–2558, 2013; Landau, A. N., & Fries, P. Attention samples stimuli rhythmically. Current Biology, 22, 1000–1004, 2012]. This modulation of performance, which has been observed primarily in the visual modality, also manifests in behavior and has been termed “attentional sampling.” In this study, we investigate whether sampling goes beyond vision and serves as a domain general mechanism shared by other perceptual systems. Specifically, we examined the auditory modality, in which there is contradicting evidence for endogenous sampling at similar frequencies [see VanRullen, R., Zoefel, B., & Ilhan, B. On the cyclic nature of perception in vision versus audition. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 369, 20130214, 2014]. In addition, we sought to investigate a putative role for visual experience in sampling in audition. To this end, sighted (n = 21), sighted blindfolded (n = 26), individuals with acquired blindness (n = 13), and individuals with congenital blindness (n = 12) detected a brief target (an intensity decrement) within an ongoing white noise stimulus. We observed 8- to 10-Hz sampling in the congenitally blind group only. We discuss this finding within the context of two possible, and even compatible, accounts. The first is that brain plasticity in the congenitally blind brings about attentional sampling in audition. It is possible that the lack of early visual experience drives the recruitment of “visual” cortices for auditory inputs, resulting in the same attentional sampling dynamics typically observed in vision, for audition. The second is that auditory sampling also exists in the sighted brain but might be obscured by visual inputs and other reflexive visual processes or might unfold at an entirely different rhythm. In fact, the acquired blind and the two sighted samples exhibited a significant low-frequency fluctuation at 2 Hz in their auditory performance. Although the study was not designed to investigate sampling at delta, this finding is consistent with a role for delta-band activity in audition as well as in temporal expectation mechanisms due to the temporal statistics of the utilized target times [e.g., Herbst, S. K., & Obleser, J. Implicit temporal predictability enhances pitch discrimination sensitivity and biases the phase of delta oscillations in auditory cortex. Neuroimage, 203, 116198, 2019; Wilsch, A., Henry, M. J., Herrmann, B., Maess, B., & Obleser, J. Slow-delta phase concentration marks improved temporal expectations based on the passage of time. Psychophysiology, 52, 910–918, 2015; Stefanics, G., Hangya, B., Hernádi, I., Winkler, I., Lakatos, P., & Ulbert, I. Phase entrainment of human delta oscillations can mediate the effects of expectation on reaction speed. Journal of Neuroscience, 30, 13578–13585, 2010]. Interestingly, delta band sampling was absent in the congenitally blind group. To further substantiate a role for delta band sampling, it would be important to design paradigms better suited to study lower frequencies in behavior, both in sighted individuals and under different degrees of visual input processing.