Category: Publications

Is something special about beat-based expectations in rhythm? In this paper, we try to find out! The preprint is now fully updated with all the latest analyses, and online on bioRxiv:

Bouwer, F.L., Fahrenfort, J.J., Millard, S.K., Kloosterman, N.A., Slagter, H.A. (preprint). A silent disco: Persistent entrainment of low-frequency neural oscillations underlies beat-based, but not pattern-based temporal expectations. bioRxiv, 2020.01.08.899278; doi: https://doi.org/10.1101/2020.01.08.899278

Temporal expectations (e.g., predicting “when”) facilitate sensory processing, and are suggested to rely on entrainment of low frequency neural oscillations to regular rhythmic input, such as a beat in music (“beat-based” expectations). However, temporal expectations can also be based on predictable repeated patterns (“pattern-based” expectations). These two types of expectations often occur simultaneously, but whether they are subserved by the same neural mechanisms is currently a topic of active debate. Here, we addressed this outstanding issue by examining EEG activity and behavioral responses during silent periods following rhythmic auditory sequences designed to elicit only beat-based or pattern-based expectations, or with random timing. In Experiment 1 (N = 32), participants rated how well probe tones at various time points fitted the previous rhythm. Beat-based expectations affected fitness ratings for at least two beat-cycles, while the effects of pattern-based expectations subsided after the first expected time point in the silence window. In Experiment 2 (N = 27), using EEG, we found a Contingent Negative Variation (CNV) following the final tones of pattern-based, but not beat-based sequences. Moreover, we found enhanced power in the EEG signal at the beat frequency for beat-based sequences both during listening and the silence, while for pattern-based sequences, enhanced power at a pattern-specific frequency was only present during listening, not during the silence. Finally, we show how multivariate pattern decoding and multi scale entropy – measures sensitive to non-oscillatory components of the signal – can be used to probe temporal expectations. Taken together, we show that beat-based and pattern-based expectations affect behavior differentially, with beat-based expectations exerting longer-lasting effects than pattern-based expectations. At a neural level, climbing activity may specifically reflect pattern-based expectations, while persistent low frequency oscillations may be specific to beat-based expectations. When studying responses to complex rhythmic stimuli, like in music and language, both types of expectations should therefore be considered.

My fabulous postdoc supervisor Prof. Heleen Slagter invited me to co-author a commentary about individual differences in the Journal of Cognition. Out now!

Slagter, H. A., & Bouwer, F. L. (2021). Qualitative Versus Quantitative Individual Differences in Cognitive Neuroscience. Journal of Cognition, 4(1), 49. DOI: http://doi.org/10.5334/joc.170

Individual differences in cognitive performance can be quantitative or qualitative in nature. Accounting for qualitative as well as quantitative individual differences is of importance for cognitive neuroscience, where a central goal is not only to relate brain function to behavior generally, but also to understand and predict individual behavior from neural data. In turn, cognitive neuroscience can help determine the nature of individual differences by revealing the underlying neural mechanisms and uncover qualitative individual differences that are not immediately apparent from behavioral data, enhancing our understanding of why and how people behave the way they do.

Two years after the fabulous workshop organised by Henkjan Honing, Sonja Kotz, Andrea Ravignani, and Michael Greenfield, the special theme issue on rhythm and rhythmic interactions came out in Philosophical Transactions B, including a paper co-authored by me on how to test rhythmic abilities in human and non-human animals. More on this in my previous post about the preprint. Note that the preprint is identical to the published version and open access.

Bouwer, F.L., Nityananda V., Rouse, A. A., & ten Cate, C. (2021). Rhythmic abilities in humans and non-human animals: a review and recommendations from a methodological perspective. Philosophical Transactions of the Royal Society B, 376, 20200335. doi: 10.1098/rstb.2020.0335

Rhythmic behaviour is ubiquitous in both human and non-human animals, but it is unclear whether the cognitive mechanisms underlying the specific rhythmic behaviours observed in different species are related. Laboratory experiments combined with highly controlled stimuli and tasks can be very effective in probing the cognitive architecture underlying rhythmic abilities. Rhythmic abilities have been examined in the laboratory with explicit and implicit perception tasks, and with production tasks, such as sensorimotor synchronization, with stimuli ranging from isochronous sequences of artificial sounds to human music. Here, we provide an overview of experimental find- ings on rhythmic abilities in human and non-human animals, while critically considering the wide variety of paradigms used. We identify several gaps in what is known about rhythmic abilities. Many bird species have been tested on rhythm perception, but research on rhythm production abilities in the same birds is lacking. By contrast, research in mammals has primarily focused on rhythm production rather than perception. Many experiments also do not differentiate between possible components of rhythmic abilities, such as processing of single temporal intervals, rhythmic patterns, a regular beat or hierarchical metrical structures. For future research, we suggest a careful choice of paradigm to aid cross-species comparisons, and a critical consideration of the multifaceted abilities that underlie rhythmic behaviour.

In the summer of 2019, I was lucky to be invited to be part of a Lorentz workshop, in which an inspiring group of researchers came together to discuss rhythm from every possible angle. This workshop was instigated by a fabulous organising team:Henkjan Honing, Sonja Kotz, Andrea Ravignani, and Michael Greenfield. The results of all the fruitful discussions will be published soon in a Special Issue in Philosophical Transactions B, including a paper co-authored by me on how to test rhythmic abilities in human and non-human animals.

In the paper, co-authored by Carel ten Cate, Vivek Nityananda, and Andrew Rouse, we discuss how different paradigms are used in different species. For example, birds are often tested on their rhythm perception, while monkeys are often tested on rhythm production, making it very hard to compare their abilities. The paper is now available as a preprint on PsyArxiv!

Bouwer, F.L., Honing, H., & Slagter, H.A. (2020). Beat-based and Memory-based Temporal Expectations in Rhythm: Similar Perceptual Effects, Different Underlying Mechanisms

All data, experimental files, and analysis scripts are available here. An open access pre-print of the paper, which is identical in content, is available here. The publishers version can be found here.

Predicting the timing of incoming information allows the brain to optimize information processing in dynamic environments. Behaviorally, temporal expectations have been shown to facilitate processing of events at expected time points, such as sounds that coincide with the beat in musical rhythm. Yet, temporal expectations can develop based on different forms of structure in the environment, not just the regularity afforded by a musical beat. Little is still known about how different types of temporal expectations are neurally implemented and affect performance. Here, we orthogonally manipulated the periodicity and predictability of rhythmic sequences to examine the mechanisms underlying beat-based and memory-based temporal expectations, respectively. Behaviorally and using EEG, we looked at the effects of beat-based and memory-based expectations on auditory processing when rhythms were task-relevant or task-irrelevant. At expected time points, both beat-based and memory-based expectations facilitated target detection and led to attenuation of P1 and N1 responses, even when expectations were task-irrelevant (unattended). For beat-based expectations, we additionally found reduced target detection and enhanced N1 responses for events at unexpected time points (e.g., off-beat), regardless of the presence of memory-based expectations or task relevance. This latter finding supports the notion that periodicity selectively induces rhythmic fluctuations in neural excitability and furthermore indicates that, although beat-based and memory-based expectations may similarly affect auditory processing of expected events, their underlying neural mechanisms may be different.

F.L. Bouwer, H. Honing, & H.A. Slagter (2019). Beat-based and memory-based temporal expectations in rhythm: similar perceptual effects, different underlying mechanisms

Predicting the timing of incoming information allows the brain to optimize information processing in dynamic environments. Behaviorally, temporal expectations have been shown to facilitate processing of events at expected time points, such as sounds that coincide with the beat in musical rhythm. Yet, temporal expectations can develop based on different forms of structure in the environment, not just the regularity afforded by a musical beat. Little is still known about how different types of temporal expectations are neurally implemented and affect performance. Here, we orthogonally manipulated the periodicity and predictability of rhythmic sequences to examine the mechanisms underlying beat-based and memory-based temporal expectations, respectively.