Fractionation of parietal function in bistable perception probed with concurrent TMS-EEG

After a long journey, my second research article is now published! Coauthors include members of the Sackler Centre of Consciousness Science in Sussex, such as Acer Chang, David Schwartzman, Charlotte Rae, Heather Iriye and Ryota Kanai. Lots of thanks to my colleagues! You can find the online article here: [www.nature.com/articles/sdata201665] [full text pdf] [researchgate]. In it we describe a dataset that includes TMS-EEG and sMRI measurements, which can be downloaded from an open source online repository.

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When visual input has conflicting interpretations, conscious perception can alternate spontaneously between these possible interpretations. This is called bistable perception. Previous neuroimaging studies have indicated the involvement of two right parietal areas in resolving perceptual ambiguity (ant-SPLr and post-SPLr). Transcranial magnetic stimulation (TMS) studies that selectively interfered with the normal function of these regions suggest that they play opposing roles in this type of perceptual switch. In the present study, we investigated this fractionation of parietal function by use of combined TMS with electroencephalography (EEG). Specifically, while participants viewed either a bistable stimulus, a replay stimulus, or resting-state fixation, we applied single pulse TMS to either location independently while simultaneously recording EEG. Combined with participant’s individual structural magnetic resonance imaging (MRI) scans, this dataset allows for complex analyses of the effect of TMS on neural time series data, which may further elucidate the causal role of the parietal cortex in ambiguous perception

 

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Parietal theta burst TMS: Functional fractionation observed during bistable perception not evident in attention tasks

A new research article published with Ryota Kanai and Jan Brascamp in Consciousness & Cognition 40 (2016). [Full text pdf] [Article on ResearchGate]

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When visual input is ambiguous, perception spontaneously alternates between interpretations: bistable perception. Studies have identified two distinct sites near the right intra- parietal sulcus where inhibitory transcranial magnetic stimulation (TMS) affects the frequency of occurrence of these alternations, but strikingly with opposite directions of effect for the two sites. Lesion and TMS studies on spatial and sustained attention have also indicated a parcellation of right parietal cortex, into areas serving distinct attentional func- tions. We used the exact TMS procedure previously employed to affect bistable perception, yet measured its effect on spatial and sustained attention tasks. Although there was a trend for TMS to affect performance, trends were consistently similar for both parietal sites, with no indication of opposite effects. We interpret this as signifying that the previously observed parietal fractionation of function regarding the perception of ambiguous stimuli is not due to TMS-induced modification of spatial or sustained attention.

Simultaneous TMS-EEG in Structure from Motion Dataset Available

We recently collected a large dataset using ant_SPLr_brainconcurrent TMS-EEG in bistable perception. Our preliminary analyses of these data have not revealed many interesting ERPs, but a great deal of analyses can potentially be done on this data, including complexity measures, Granger connectivity analyses on the MRI guided source localised data, looking at pre-stimulus alpha power and phase, ect. Unfortunately, we do not have the time at the moment to look at all these things. However, we would very like to advertise this data to anyone with the necessary expertise, who might want to take a look. You can find a pdf summary of the data here, and there is a description below. If you are interested, please drop me an email. The address can be found under ‘about me’.

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Oxytocin is Good for More Than Love: How it Biases Social Perception

IMG_0144The neuropeptide oxytocin (OT) is associated with modulation of a variety of cognitive functions, especially related to sexual preference and trust. This led to its image as the mediator of the “social brain” (Adolphs, 2009). In this blogpost, I will first outline recent research on the effect of oxytocin on social behaviour, focussing mainly on humans. Then I will present and critique the anxiety-reduction hypothesis of OT function as well as explanations of OT altering motivational states. Then I move on to a perceptual model which posits that OT affects the salience of social stimuli. I will attempt to place this idea within the predictive coding framework by arguing that oxytocin biases priors in social perception.

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Transcranial Magnetic Stimulation Cookbook

This is a user manual that I wrote for using TMS. It has two parts. The first deals with the actual stimulation using a MagStim Rapid 2. The second outlines the use of BrainSight 2 as neuronavigation tool. It will take you from receiving the raw structural MRI images of your participant through data preparation, all the way to applying the TMS pulse.

Link: TMS Cookbook

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Methodological Constraints on Neuroscientifically Investigating Meditation

Meditation is an altered state of consciousness. Its investigation is not only spiritual, but has recently been given a neuroscientific dimension in a number of papers. There are great methodological problems with previous research however. Here I outline a few of these and propose ways for future studies to address and overcome them.

Picture: Dr Richard Davidson of the University of Wisconsin with Buddhist monk Matthieu Ricard. Image link to the University of Wisconsin-Madison. Continue reading