Biology subjects

Kessler, K.

Publications and source records attributed to Kessler, K..

4 recordsLinked to original sources

bioRxiv2018

Dysregulated Oscillatory Connectivity in the Visual System in Autism Spectrum Disorder

Autism Spectrum Disorder is increasingly associated with atypical perceptual and sensory symptoms. Here we explore the hypothesis that aberrant sensory processing in Autism Spectrum Disorder could be linked to atypical intra- (local) and inter-regional (global) brain connectivity. To elucidate oscillatory dynamics and connectivity in the visual domain we used magnetoencephalography and a simple visual grating paradigm with a group of 18 adolescent autistic participants and 18 typically developing controls. Both groups showed similar increases in gamma (40-80Hz) and decreases in alpha (8-13Hz) frequency power in occipital cortex. However, systematic group differences emerged when analysing intra- and inter-regional connectivity in detail. Firstly, directed connectivity was estimated using non-parametric Granger causality between visual areas V1 and V4. Feedforward V1-to-V4 connectivity, mediated by gamma oscillations, was equivalent between Autism Spectrum Disorder and control groups, but importantly, feedback V4-to-V1 connectivity, mediated by alpha (8-13Hz) oscillations, was significantly reduced in the Autism Spectrum Disorder group. This reduction was positively correlated with autistic quotient scores, consistent with an atypical visual hierarchy in autism, characterised by reduced top-down modulation of visual input via alpha-band oscillations. Secondly, at the local level in V1, coupling of alpha-phase to gamma amplitude (alpha-gamma phase amplitude coupling, PAC) was reduced in the Autism Spectrum Disorder group. This implies dysregulated local visual processing, with gamma oscillations decoupled from patterns of wider alpha-band phase synchrony (i.e. reduced PAC), possibly due to an excitation-inhibition imbalance. More generally, these results are in agreement with predictive coding accounts of neurotypical perception and indicate that visual processes in autism are less modulated by contextual feedback information.

neuroscience↗

bioRxiv2017

Oscillatory Networks of High-Level Mental Alignment: A Perspective-Taking MEG Study

Mentally imagining anothers perspective is a high-level social process, reliant on manipulating internal representations of the self in an embodied manner. Recently Wang et al., (1) showed that theta-band (3-7Hz) brain oscillations within the right temporo-parietal junction (rTPJ) and brain regions coding for motor/body schema contribute to the process of perspective-taking. Using a task requiring participants to engage in embodied perspective-taking, we set out to unravel the extended functional brain network and its connections in detail. We found that increasing the angle of disparity between self and other perspective was accompanied by longer reaction times and increases in theta power within rTPJ, right lateral pre-frontal cortex (PFC) and right anterior cingulate cortex (ACC). Using nonparametric Granger-causality, we showed that during later stages of perspective-taking, the lateral PFC and ACC exert top-down influences over rTPJ, indicative of executive control processes required for managing conflicts between self and other perspectives. Finally, we quantified patterns of whole-brain phase coupling (imaginary coherence) in relation to rTPJ during high-level perspective taking. Results suggest that rTPJ increases its theta-band phase synchrony with brain regions involved in mentalizing and regions coding for motor/body schema; whilst decreasing its synchrony to visual regions. Implications for neurocognitive models are discussed, and it is proposed that rTPJ acts as a hub to route bottom-up visual information to internal representations of the self during perspective-taking, co-ordinated by theta-band oscillations. The self is then projected onto the others perspective via embodied motor/body schema transformations, regulated by top-down cingulo-frontal activity.\n\nSignificance StatementHigh-level social processing, such as the ability to imagine anothers visuospatial experience of the world (perspective taking), is a core part of what makes us human. Building on a substantial body of converging previous evidence, our study reveals how concerted activity across the cortex in low frequencies (theta: 3-7 Hz) implements this crucial human process. We found that oscillatory power and connectivity (imaginary coherence, nonparametric Granger causality) at theta frequency linked functional sub-networks of executive control, mentalizing, and sensorimotor/body schema via a main hub located in the right temporo-parietal junction (rTPJ). Our findings inform neurocognitive models of social cognition by describing the co-ordinated changes in brain network connectivity, mediated by theta oscillations, during perspective-taking.

neuroscience↗

bioRxiv2017

The Detection of Phase Amplitude Coupling During Sensory Processing

1.There is increasing interest in understanding how the phase and amplitude of distinct neural oscillations might interact to support dynamic communication within the brain. In particular, previous work has demonstrated a coupling between the phase of low frequency oscillations and the amplitude (or power) of high frequency oscillations during certain tasks, termed phase amplitude coupling (PAC). For instance, during visual processing in humans, PAC has been reliably observed between ongoing alpha (8-13Hz) and gamma-band (>40Hz) activity. However, the application of PAC metrics to electrophysiological data can be challenging due to numerous methodological issues and lack of coherent approaches within the field. Therefore, in this article we outline the various analysis steps involved in detecting PAC, using an openly available MEG dataset from 16 participants performing an interactive visual task. Firstly, we localised gamma and alpha-band power using the Fieldtrip toolbox, and extracted time courses from area V1, defined using a multimodal parcellation scheme. These V1 responses were analysed for changes in alpha-gamma PAC, using four common algorithms. Results showed an increase in gamma (40-100Hz) - alpha (7-13Hz) PAC in response to the visual grating stimulus, though specific patterns of coupling were somewhat dependent upon the algorithm employed. Additionally, post-hoc analyses showed that these results were not driven by the presence of non-sinusoidal oscillations, and that trial length was sufficient to obtain reliable PAC estimates. Finally, throughout the article, methodological issues and practical guidelines for ongoing PAC research will be discussed.

neuroscience↗

bioRxiv2016

THETA-Rhythm makes the world go round: Dissociative effects of TMS theta vs alpha entrainment of right pTPJ on embodied perspective transformations

Introduction Introduction Materials and Methods Results and Discussion References Being able to imagine another persons experience and perspective of the world is a crucial human social ability (Call & Tomasello, 1999) and recent reports suggest that humans \"embody\" anothers viewpoint by mentally rotating their own body representation into the others orientation (Kessler, Cao, OShea, & Wang, 2014; Kessler & Rutherford, 2010; Kessler & Thomson, 2010; Surtees, Apperly, & Samson, 2013). Using Magnetoencephalography (MEG) our group recently reported in Cortex that brain oscillations at theta frequency (3-7 Hz), originating from the right posterior temporo-parietal-junction (pTPJ) reflected cognitive as well as embod ...

neuroscience↗