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.

A Town Dances the Rite of Spring

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Huddled together like a pack of penguins in a small side chamber stand several dozen people. They are all dressed in suits with plain T-shirts underneath. They all look in one direction: A door leading out onto a stage, before whichsits an anticipating audience. hile these people look uniform, their backgrounds are intrinsically different in a great many respects. There is a lorry driver, a doctor, 6a salesperson, a teacher, an architect, an unemployed, an independent, a pensioner, a child… What unites them are two things: First, they are all from Hoyerswerda, a deprived town in the formerly socialist east of Germany, suffering from an ageing population and the decline of the coal industry. Second, each one of them has made sacrifices for some greater good.

1This sacrifice, this putting oneself back   – sometimes to the brink of despair or illness – for one’s career, children, some obligation or just to fit in, is the main issue to be artistically deconstructed in this year’s theatre dance project by the Kultur Fabrik Hoyerswerda. The idea that in a world that follows the rules of competitiveness and the threat of career redundancy, sacrifices are made in order to withstand the pressure put on oneself by expectation and fear of social downfall. The proposal put forward by this project is that not all of these sacrifices are justified. Some stand in the way of happiness and health. Furthermore, the process of discussing and dancing this state of affairs is meant to bring about relief and courage.

2The musical accompaniment of this expression is Igor Stravinsky’s “Le Sacre du Printemps”. This timeless masterpiece was written just prior to the Great War in a society fixated on power and multi-national tension. It tells the tale of an ancient tribal society, which sacrifices a young woman from within, o that spring may come again. It asks the question what sacrifice we are willing to make as a society so that the earth can bloom once more. Though what are the wishes of that woman? Is she honoured or terrified? Does she at all desire sacrifice for society over her own path to discovery of a life she just began? Moving forward to today, we inquire as to what we are willing to sacrifice. Will our sacrifices lead to renewal and rebirth or something less sustainable and sinister?

3Every one of those people crammed in that room has asked these questions and reflected upon their own sacrifices and whether they led to any blossoming. Many believe that it did not, that in fact their former selves might not be proud of where they are today. One person barely took part in the raising of his child due to his frequent delivery tours throughout Europe. Another tells of a cloud of death surrounding her medical work, which sometimes becomes so dark that she has trouble calling in the next patient. Some speak of their childhood dreams of being artists, and how circumstances shifted them in new directions. A man just out of school reminisces on his planning a model biography to the liking of potential employers.

7Grey and black business jackets lie on stage. As the light come on, the group of about 70 dancers finds theirs and with the first notes of the music put on this uniform. To the beat of the drums, the sweet strokes of the violins or abrupt brass punches, those dancers teeter, balance, tense and convulse their bodies, which are not all dancers’ figures. Through this performance, which is interleaved with interviews of individual dancers, the audience gains a sense of remission of these sacrifices. At the end, one by one the dancers break formation and declare silently that their willingness to participate in their sacrifices has ended. No jackets are worn at the close.

Prior to this performance stood months of rehearsals including hours and hours of strength and stamina training. Given the diversity of the group, this is a tremendous achievement, thanks for which go to Dirk5 Lienig, who took the group through rehearsals and also Judith Gamm, together with whom he devised the choreography. Speaking to the dancers, one cannot help but notice both the pride they take in making this happen next to work and family, but also how intimate and trusting this strange group of people have become over the course of this project.

4One thing left to mention is that I had the privilege of dancing with them, which has been a magnificent experience and brought me close to more people in Hoyerswerda, than I have known here since moving overseas. Also, dancing together with my mother – a veteran withthis project – has improved an already excellent relationship in my family. For that alone, I am very grateful. Those moments of standing behind a stage with others that are likeminded, anticipating and begin nervous, is a superb sensation. Now that it is over, we are all very saddened. Our bodies may revert to a lesser state of athleticism, though I know that many of us will choose more wisely the sacrifices we make in the future.IMG_0325

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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Against an Evolutionary Account of Modularity in Peripheral Cognitive Abilities

A common way of looking at the mind is to say that it is modular, i.e. divided into units, each responsible for a different cognitive ability or domain. A criticism that can be made against this idea comes from its connection to evolutionary psychology. The genetic predetermination of modules as explained by evolutionary pressures is not easily squared with brain plasticity. Here I defend modularity by trying to separate it from evolutionary psychology.

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10 Places Not to be Missed in Edinburgh

This week I move away from Edinburgh to the south of England. I know already that I am going to miss it very much. It is a great and vibrant city, that elegantly united the traditional and forward-looking. Going through my memories of this place, I noticed a few places that I would not want to have missed while living here. They are not secret or unknown, but in case you are in town a little while longer and seek something other than old town and Princes street, these might be places for you.

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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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A Tribute to Bob Ross

When I was in kindergarten, I remember seeing Bob Ross on television. He made painting in oil seem incredibly easy and fun. While at university, a friend moved abroad for just a year and asked me to look after a few things, including his painting supplies. I agreed on the condition that I could try some things out as well. Unfortunately, Bob Ross has already passed away, but his TV show remains and with it some fun anyone can have in oil. Here are a few of the painting that were made in my kitchen. They are not professional, but I hope still enjoyable.

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

Why There Can be No Reliable Relativistic Hypercomputers

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Figure 1: Simple model of computation in an M-H space-time.

A hypercomputer is able to finish infinitely many computations in finite time. Any user could hence get all the answers to any computable question rather quickly, including for instance the greatest prime number. Given our laws of physics, such devices cannot be built. However, there are theories of hypercompuation that makes use of relativistic space-time curvature. These would have to operate though for an infinite amount of time in their little pocket of the universe. This requires a rather reliable machine. Here I argue against such reliability. I start by examining the physical Church-Turing (PhCT) thesis and its interplay with supertasks and hypercomputation. I will introduce Piccinini’s usability constraint for testing the viability of possible counterexamples to PhCT and will examine relativistic hypercomputation to that end. I propose that ontic pancomputationalism is a possible solution of an infinitely persisting computation, but note that instead of the machine, the observer now perishes and also the computing function becomes unusable. Quintessentially, I conclude that on the reliability constraint alone, all hypercomputation will fail in nomologically accessible worlds.

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Review of Chapter 5 “Physics for Philosophers” from Craig Bourne’s “A Future for Presentism”

In his book chapter, Bourne introduces the layman reader to the basic non-mathematical postulates of special relativity. He begins by presenting our common-sense intuitions about the additivity of speeds between objects, which turns out to be violated, since no speed can be added to exceed the speed of light c. This has some counterintuitive consequences for concepts like simultaneity and the uniform passage of time.

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David Lewis Established the Logical Possibility of Time Travel

kdlsj442After just a single episode of Doctor Who, you’ll know that time travel does not come without its share of headaches. There are a great many paradoxes, most famously those that ask how changing the past in a way that eliminates you from existence could allow you to change the past in the first place. Intuitively for many, time travel is consequently an inconsistent notion. Here I defend David Lewis’ claim that backwards time travel (BTT) need not entail logical contradictions. I start by outlining his exposition of BTT, the resulting grandfather paradox and his compossibility solution. I then move to a critique of this answer from unexplained constraints on the traveller. I argue that it misconstructs Lewis’ argument and although puzzling fails to show that BTT entails contradiction. I conclude that prima facie Lewis did establish the logical possibility of BTT.

Picture: A police box on the Grassmarket in Edinburgh

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No More Humean Supervenience about Laws of Nature

1_gammaIf you are a Humean, you may believe that laws of nature do not govern, but rather neatly fit the overall pattern of everything that happens in the universe. A law then would not have much governing to do beyond offer an explanation. Unfortunately, there are empirical reasons to believe that this may not be so. Here I try to make the case for some of these. After constructing Humean Supervenience as conjunction of Modal Combinatorialism, Supervenience and Nomological Reduction, I consider quantum-entanglement to show how Modal Combinatorialism is violated leading to a downfall of HS in general. I will consider a response to this by Loewer and conclude that on empirical grounds HS under Lewis’ formulation fails, although its basic intuition of non-governing laws persists.

 

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The Case for Boyd’s Homeostatic Property Clusters

clustet342What makes a bird a bird? Well, our taxonomy of course. What if this changes though over time and evolution? What if the properties we associate with birds one day no longer exist or only some? Boyd offers an account of classifying natural kinds, such as birds or psychiatric disorders based on properties which usually cluster together because of causal relations between them. I try to defend that view here. After thoroughly setting up the HPC theory in contrast to essentialism, with particular emphasis on its homeostatic causal mechanism, I shall then try to defend this mechanism against essentialist attack. I will examine how clustering is contingent on the causal structure of the world with examples from biological taxa and psychiatry.

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How Persuasive is Wilby’s Solution to the Problem of Common Knowledge in Joint Attention?

I attend to a candle. You attend to the candle. We know of each other doing just that. We jointly attend. Simple enough, right? Unfortunately, philosophically conceptualising this concept is rather difficult. It would have to be some action-enabling, open epistemic notion that is at the same time compatible with empirical evidence from psychology. Here I argue against one such notion from Wilby of shared mental states in joint attention. I also consider Tomasello’s critique of the applicability of philosophical accounts to psychology altogether.

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Against Money as Measure between Prudential Values

Money is not a good common measure for prudential values in one-person cases. When considering opportunity costs in daily decisions, watching Dr Who vs watching Inspector Lynley, it fails quickly to meet the standard we would need in a viable theory of value. I begin the rationale for this by introducing the informed-desire account, move on to the resulting problem of incommensurable values and their measurement. I then propose money as solution to those problems. Afterwards I will discuss three counterexamples from investment, consumer rationality and money as social relation which will lead this post to conclude that although money has merits in explaining how to measure prudential values, it ultimately cannot overcome the counterexamples.

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