Call for Papers – Rhythms in cognition: re-visiting the evidence

Special issue at the European Journal of Neuroscience now open for submissions.

Guest Editors Christian Keitel (University of Stirling, UK), Manuela Ruzzoli (University of Glasgow, UK), Chris Benwell (University of Dundee, UK), Niko Busch (University of Muenster, Germany), and Laura Dugué (Paris Descartes University, France).

Call for Papers: November 2019
Submission Deadline: July 20, 2020
Online Publication within One Week of Acceptance
Estimated Date of Publication of Final Issue: Spring 2021

Everyday experience may arise from a fundamentally discrete sampling of our sensory environment, just like a movie consists of still frames shown in rapid succession. Already Bishop (1932, Am J Physiol Leg) suggested such a sampling process. He further identified rhythmic brain activity as the phasic neural analogue of a shutter mechanism subserving discrete sampling. Although it contrasts starkly with our intuition of a continuous perceptual flow the sampling idea has been reiterated over the past 90 years. Ever-more precise recordings of human brain activity and novel analysis techniques have seen an unprecedented surge of interest over the last decade. Consequently, we have come to see brain rhythms as the neural implementation of perceptual sampling and the basis of cognitive functions such as attention, memory and language. In an interesting twist however, more recent negative findings on the role of pre-stimulus oscillatory phase on perception suggest that support for discrete sampling as a fundamental mechanism remains equivocal.

In our Special Issue, we call for methodologically principled studies, irrespective of their outcome, to provide us with the most detailed picture to-date as to the conditions under which perceptual sampling, and its consequences for cognition, can (not) be observed. These studies can be original contributions, replication attempts, pre-registered studies or file-drawer experiments that have to follow a thorough methodology and thus allow clear interpretations also of negative findings. We also welcome dedicated reviews, opinion pieces and methodological advances. Studies can address perceptual sampling in vision, audition or other senses by testing its impact on neurophysiological or behavioural performance measures (psychophysics). We encourage authors to make their data openly accessible along with their experimental and analysis codes in order to foster reproducibility and transparency. We invite human studies adopting neuroimaging (EEG, iEEG, MEG, fMRI) and neurostimulation techniques (tES, TMS, sensory entrainment). Animal studies will be a highly welcome supplement.

We are very much looking forward to your submissions to our EJN Special Issue “Rhythms in Cognition: Revisiting the Evidence”.

 

Alpha rhythms: Some slow down, some grow stronger

Researchers usually assume alpha brain waves to behave relatively similarly over time. In a new study, led by Chris Benwell and just accepted for publication in NeuroImage, we find that this is not necessarily true for the 1-2 hrs that a typical EEG experiment lasts.

In a re-analysis of data from two previous EEG experiments we saw that alpha underlies two major trends – alpha power increases (an effect previously described) and alpha frequency decreases consistently over time. Both effects maybe related to growing fatigue, the depletion of cognitive resources or a transition from a volitional to a more automatic task performance.

We also found that different sources of alpha rhythms in the brain can show different trends. While some showed both, power increases and frequency decreases, others showed only one if the two trends. Further analysis revealed that both trends do not necessarily depend on each other.


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Figure We usually assume that alpha varies “spontaneously” around a mean and higher alpha leads us to observe a different behaviour. This relationship however could simply be a consequence of both, alpha and behaviour changing “deterministically”, i.e. trending over time. In experiments, we likely observe a “mix” of both sources of variance (also see Benwell et al. 2017 or here).


These findings need to be taken into account when testing for links between brain rhythms (brain state) and behaviour – a link might be reported accidentally just because both, brain state and behaviour change over time – and when attempting to manipulate alpha through stimulation – stimulation frequencies may need to be adapted on the fly, stimulation will need to target a specific alpha generator while leaving others unbothered.

 

Anne wins Biomag 2018 Young Investigator Award

[28 Aug 2018]

Anne has been one of three Early Career Researchers rewarded with a BIOMAG Young Investigator Award at the 2018 International Conference on Biomagnetism, held in Philadelphia, USA. Nominated as one of 10 finalists she won the award for a presentation of her recent work into the neural foundations of speech comprehension [1].

2018BIOMAG-YIA

The award ceremony took place at the conference gala in the Philadelphia Museum of Art, not only known for its collection of contemporary art, but also for its iconic set of stairs famously featured in the “Rocky” movies.


[1] Keitel A, Gross J, Kayser C (2018) Perceptually relevant speech tracking in auditory and motor regions reflects distinct linguistic features. PLoS Biology ~pdf

New preprint on speech tracking in auditory and motor cortices

The tracking of temporal information in speech is frequently used to study speech encoding in dynamic brain activity. Often, studies use traditional, generic frequency bands in their analysis (for example delta [1 – 4 Hz] or theta [4 – 8 Hz] bands). However, there are large inter-individual differences in speech rate. For example, audiobooks are typically narrated with 150 words per minute (2.5 Hz), while the world’s fastest speaker can talk at 637 words per minute (10.6 Hz). We therefore reasoned that speech tracking analyses should take into account the specific regularities (e.g. speech rate) of the stimuli. This is exactly what we did in this study: We extracted the time-scales for phrases, words, syllables and phonemes in our sentences and based our analyses on these stimulus-specific bands.

Previous studies also mainly used continuous speech to analyse speech tracking. This is a fantastic, “real-world” paradigm, but it lacks the possibility to directly analyse comprehension. We therefore played single sentences to our participants and asked, after each sentence, to indicate which out of four words they had heard in the sentence. This way, we obtained a single-trial comprehension measure. We also recorded participants’ magnetoencephalography (MEG) and did our analyses on source projections of brain activity.

We show two different speech tracking effects that help participants to comprehend speech and both act concurrently at time-scales within the traditional delta band: First, the left middle temporal cortex (MTG) tracks speech at the word time-scale, which is probably useful for word segmentation and mapping the sound-to-meaning. And second, the left premotor cortex (PM) tracks speech at the phrasal time-scale, likely indicating the use of temporal predictions during speech perception.

AVentrain_MIoverlap

Previous studies have shown that the motor system is involved in predicting the timing of upcoming stimuli by using its beta rhythm. We therefore hypothesised that a cross-frequency coupling between beta-power and delta-phase at the phrasal time-scale could drive the effect in the motor system. This is indeed what we found and this was also directly relevant for comprehension.

By using stimulus-specific frequency bands and single-trial comprehension, we show specific functional and perceptually relevant speech tracking processes along the auditory-motor pathway. In particular, we provide new insights regarding the function and relevance of the motor system for speech perception.

If you would like to read the full manuscript, you can find a preprint on bioRxiv here.

First WoRB – Workshop on Rhythms in the Brain – concluded

Last week the first Workshop on Rhythms in the Brain – WoRB – took place here in Glasgow, at the Institute of Neuroscience & Psychology. The organisers thank our speakers Satu Palva, Ayelet Landau, Hartwig Siebner & Niko Busch for their inspiring talks, great discussions and joining our hike up Conic Hill.

Also thanks to everyone who attended the talks, found the time to meet with our guests and our fantastic Admin team, who made it all happen.


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Accepted paper: Spontaneous and deterministic fluctuations of pre-stimulus alpha power govern biases in visual line bisection

Chris Benwell’s most recent study shows that an observer’s brain state, just before seeing a transected line, influences their judgment of its centre. Also, these critical brain states do not seem to fluctuate randomly from instant to instant, but trend systematically over time.

Brain states can be defined by rhythmic activity in characteristic frequency bands. We know that the alpha rhythm (roughly ten cycles per second) plays its role in how we take in the visual world around us. For example, strong alpha can shield us from visual impressions. Weak alpha allows for more sensory intake.

Until recently this role of alpha had mostly been shown for briefly presented light flashes just bright enough to be on the verge of being visible. But Chris’ study suggests that alpha may be a gatekeeper for other aspects of visual processing in the brain, too. Here, observers judged whether a line was transected left or right of its centre. Crucially, alpha power before line presentation influenced this judgment.

Line stimuli – Observers had to judge whether lines were interrupted left or right of their actual centre.

More surprising however was that fluctuations in alpha power didn’t come as spontaneous or random as previously thought. Instead, the time observers spent on the task seemed to play a role – at least to some extent. Alpha simply increased over the course of the experiment. And here’s the novel aspect: This deterministic trend predicted a gradual shift in line centre judgments from trial to trial. On average, observers judged the centre to be more to the right than it actually was.

In brief, Chris’ experiment showed that alpha not only influences whether we see very faint stimuli but also how we make judgments about the centre of a visual object. Also, alpha does not just fluctuate randomly but has a deterministic component: When performing a task for an extended period of time alpha inclines gradually. This leads to a sustained and predictable change in our visual perception.

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Schematic of spontaneous and deterministic influences of alpha (a neurometric) on reported line center (a psychometric) – the colour gradient towards purple indicates that observers showed an increased rightward bias over time meaning that they increasingly judged the line centre more right than it actually was.

These findings beg an interesting question for future research: Can we find other determinants of alpha (i.e. brain state) fluctuations? Moreover, can all ‘spontaneous’ fluctuations ultimately be described by deterministic processes?

The paper has just been accepted for publication in the European Journal of Neuroscience, and can be found here.

Reference
Benwell CSY, Keitel C, Harvey M, Gross J, Thut G (accepted) Trial-by-trial co-variation of pre-stimulus EEG alpha power and visuospatial bias reflects a mixture of stochastic and deterministic effects. European Journal of Neuroscience

This paper is part of the EJN special issue “Neural Oscillations”.

WoRB – Workshop on Rhythms in the Brain – ready to go

Proudly we announce the first Workshop on Rhythms in the Brain (WoRB) held in Glasgow on Monday, 11 Sep 2017. WoRB sets the stage for four leading experts – Satu Palva, Ayelet Landau, Hartwig Siebner & Niko Busch – show-casing and discussing their state-of-the-art research in this intense half-day programme.

WoRB aims to gather a broad audience interested in the significance of rhythmic brain activity for cognitive function.
Two key aspects will be in the spotlight:
1) What do brain rhythms code for and how do they give rise to the complexity and efficiency in human behaviour?
2) How can we drive brain rhythms and establish their causal role in cognition through brain stimulation?

The WoRB format delivers condensed talks with opportunity to discuss and get together with the speakers during breaks.
It is our hope that WoRB fosters scientific exchange and spawns future perspectives for research into the functional role of intrinsic brain rhythms.

Programme:

  • 09:00 Registration
  • 09:20 Welcome
  • 09:30 Hartwig Siebner:
    Perspectives of state-informed non-invasive transcranial brain stimulation (NTBS): Creating a “state” or targeting a “state” with NTBS?
  • 10:15 Ayelet Landau:
    Attentional Sampling: a human exploration mechanism
  • 11:00 Coffee Break
  • 11:15 Niko Busch:
    Alpha Oscillations, Neuronal Excitability, and Perceptual Decisions
  • 12:00 Satu Palva:
    Entraining and modulating oscillations with TMS
  • 12:45 Lunch
  • 13:30 End of Session

More info here

Organised by Joachim Gross & Gregor Thut Organising Committee Christian Keitel (Chair), Domenica Veniero, Hyojin Park, Roberto Cecere & Christopher Benwell Website Marc Becirspahic WoRB logo courtesy of Christoph Daube Administrative support Lindsay Wilson & Alice Lee