How we Can change your mind: Anodal tDCS to Fp3 alters human stimulus representation and learning.

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The aim of the current work is to advance our understanding of both the mechanisms controlling perceptual learning and the face inversion effect. In the three double blind experiments reported here (total N=144) we have shown that anodal tDCS stimulation (10 mins at 1.5 mA) delivered over the left DLPFC at Fp3 affects perceptual learning and drastically reduces the, usually robust, face inversion effect. In Experiment 1, we found a significantly reduced inversion effect in the anodal group compared to that in the sham group. Experiment 2 replicated the pattern of results found in Experiment 1. In both experiments recognition performance for upright faces in the anodal group was significantly impaired compared to that in the sham group. Finally, using an active control in Experiment 3 (same behavioural task but different tDCS targeted brain area) we showed that the same Fp3 anodal tDCS stimulation effect is not obtained when a different brain area is targeted.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 743702 awarded to Ciro Civile. This project has also received funding from the Economic and Social Research Council (ESRC) New Investigator Grant (Ref. ES/R005532) awarded to Ciro Civile (PI) and I.P.L. McLaren (Co-I)

The Role of Experience-based Perceptual Learning in the Face Inversion Effect

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Perceptual learning of the type we consider here is a consequence of experience with a class of stimuli. It amounts to an enhanced ability to discriminate between stimuli. We argue that it contributes to the ability to distinguish between faces and recognize individuals, and in particular contributes to the face inversion effect (better recognition performance for upright vs inverted faces). Previously, we have shown that experience with a prototype defined category of checkerboards leads to perceptual learning, that this produces an inversion effect, and that this effect can be disrupted by Anodal tDCS to Fp3 during pre-exposure. If we can demonstrate that the same tDCS manipulation also disrupts the inversion effect for faces, then this will strengthen the claim that perceptual learning contributes to that effect. The important question, then, is whether this tDCS procedure would significantly reduce the inversion effect for faces; stimuli that we have lifelong expertise with and for which perceptual learning has already occurred. Consequently, in the experiment reported here we investigated the effects of anodal tDCS at Fp3 during an old/new recognition task for upright and inverted faces. Our results show that stimulation significantly reduced the face inversion effect compared to controls. The effect was one of reducing recognition performance for upright faces. This result is the first to show that tDCS affects perceptual learning that has already occurred, disrupting individuals’ ability to recognize upright faces. It provides further support for our account of perceptual learning and its role as a key factor in face recognition

Transcranial Direct Current Stimulation (tDCS) and the Face Inversion Effect: Anodal stimulation at Fp3 reduces recognition for upright faces

This is the final version of the article. Available from the publisher via the link in this record.Perceptual learning is a key perceptual skill that people possess, in particular, it contributes to their ability to distinguish between faces thus recognize individuals. Recently, we showed that anodal transcranial Direct Current Stimulation (tDCS) at Fp3 abolishes the inversion effect (that would otherwise exist) for familiar checkerboards created from a prototype. Because of the close analogy between the inversion effect obtained with checkerboards, which we use as a marker for perceptual learning, and the traditional face inversion effect (upright faces recognized better than inverted ones), we investigated the effects of anodal tDCS at Fp3 during an old/new recognition task for upright and inverted faces. Results showed that stimulation significantly reduced the face inversion effect compared to controls. The effect was strongest in reducing recognition performance to upright faces. This result supports our account of perceptual learning and its role as a key factor in face recognitio

Directional cue and landmark configurations: The effect of rotating one set of landmarks relative to another

This is the author accepted manuscript. The final version is available from the American Psychological Association via the DOI in this recordIn this article we addressed the question whether rats can use distal landmarks as directional cues that are used in combination with other proximal landmark configurations. The animals were trained with an A, B, C, and D landmark configuration in the Morris pool, where B and C are the near (to platform) landmarks and A and D the far ones. We also added another more distal "directional" cue Z (a white strip attached to the black curtain surrounding the pool). Experiment 1 shows a robust detrimental effect on the time spent by the rats swimming in the platform quadrant when the location of all landmarks was "Inverted" (rotated by 180 degrees) with respect to Z. A similar detrimental effect was found when, after the inversion manipulation, the locations of the near and far landmarks were "Flipped" (B swapped with C and A with D). Rats in both Inverted and Flipped tests spent more time in the Z quadrant compared to the platform quadrant (BC). Experiment 1b provided evidence distinguishing between alternative explanations of how the directional cue Z acts in combination with the other landmarks. The results from both experiments show that Z operates differently to the standard landmarks. It can function as a beacon in its own right. It can also combine with the other landmarks to produce a high level of search performance, in a way that we hypothesize to be distinct from that described by the configural analysis often applied to multiple landmarks.European Union Horizon 2020Economic and Social Research Council (ESRC

Labelling faces as “Autistic” reduces the Inversion Effect

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this recordDoes the belief that a face belongs to an individual with autism affect recognition of that face? To address this question, we used the inversion effect as a marker of face recognition. In Experiment 1, participants completed a recognition task involving upright and inverted faces labelled as either ‘regular’ or ‘autistic’. In reality, the faces presented in both conditions were identical. Results revealed a smaller inversion effect for faces labelled as autistic. Thus, simply labelling a face as ‘autistic’ disrupts recognition. Experiment 2 showed a larger inversion effect after the provision of humanizing versus dehumanizing information about faces labelled as ‘autistic’. We suggest changes in the inversion effect could be used as a measure to study stigma within the context of objectification and dehumanization.S.S.O. is supported by a discovery grant from the Natural Sciences and Engineering Research council of Canada. C.C. is supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie (grant agreement No. 743702) and by the Economic and Social Research Council (ESRC) New Investigator Grant (Ref. ES/R005532)

Switching off perceptual learning: tDCS to left DLPFC eliminates perceptual learning in humans.

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Perceptual learning can be acquired as a result of experience with stimuli that would otherwise be difficult to tell apart, and is often explained in terms of the modulation of feature salience by an error signal based on how well that feature can be predicted by the others that make up the stimulus. In this article we show that anodal transcranial Direct Current Stimulation (tDCS) at Fp3 directly influences this modulation process so as to eliminate and possibly reverse perceptual learning. In 2 experiments, anodal stimulation disrupted perceptual learning (indexed by an inversion effect) compared with sham (Experiment 1) or cathodal (Experiment 2) stimulation. Our findings can be interpreted as showing that anodal tDCS severely reduced or even abolished the modulation of salience based on error, greatly increasing generalization between stimuli. This result supports accounts of perceptual learning based on variations in salience as a consequence of pre-exposure, and opens up the possibility of controlling this phenomenon.IPLM and FV are supported by a grant from the ESRC (ES/J00815X/1), and FV is supported by a starting grant from the European Research Council (ERC) under the European Union's Seventh Framework Programme (FP7/2007-2013)/ ERC Grant Agreement No. 312445. CC was supported by an Overseas Scholarship from the International Office at the University of Exeter and Yixuan Ku by the National Key Fundamental Research (973) Program (2013CB329501) of China

The effect of scrambling upright and inverted faces on the N170

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.The face inversion effect refers to a decrement in performance when we try to recognise familiar faces turned upside down (inverted), compared to familiar faces presented in their usual (upright) orientation. Recently, we have demonstrated that the inversion effect can also be found with checkerboards drawn from prototype-defined categories when the participants have been trained with these categories, suggesting that factors such as expertise and the relationships between stimulus features, may be important determinants of this effect. We also demonstrated that the typical inversion effect on the N170 seen with faces is found with checkerboards, suggesting that modulation of the N170 is a marker for disruption in the use of configural information. In the present experiment, we first demonstrate that our scrambling technique greatly reduces the inversion effect in faces. Following this, we used Event-Related Potentials (ERPs) recorded while participants performed an Old/New recognition study on normal and scrambled faces presented in both upright and inverted orientations to investigate the impact of scrambling on the N170. We obtained the standard robust inversion effect for normal faces: The N170 was both larger and delayed for normal inverted faces as compared to normal upright faces, whereas a significantly reduced inversion effect was recorded for scrambled faces. These results show that the inversion effect on the N170 is greater for normal compared to scrambled faces, and we interpret the smaller effect for scrambled faces as being due to the reduction in expertise for those faces consequent on scramblingThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 74370

Editorial: Special Issue on Recent Advances in Perceptual Learning

This is the author accepted manuscript. The final version is available from the American Psychological Association via the DOI in this recor

Categorisation and perceptual Learning: Why tDCS to Left DLPFC Enhances Generalisation.

In Associative Learning and Cognition, Homage to Prof. N.J. Mackintosh. Editors: Trobalon JB, Chamizo VD. Barcelona 10 Sep 2016This is the author accepted manuscript. The final version is available from University of Barcelona via the link in this record.In the 27 years that have passed since the McLaren, Kaye and Mackintosh (MKM) model of perceptual learning was first proposed, it has undergone considerable theoretical development and been subject to extensive empirical test. But we would argue that the basic principles of the theory remain as valid today as they were in 1989. One of these principles was that salience modulation of stimulus representations based on prediction error was a key component of latent inhibition and perceptual learning. It was this modification of what was otherwise a fairly basic adaptation of the model for categorisation proposed by McCleland and Rumelhart (M&R) that transformed a system that would exhibit enhanced generalisation as category learning progressed, into one that would instead offer an improved capacity for discrimination between exemplars as a consequence of experience with the category. This modification has only been tested indirectly up until now, by looking at the predictions that flow from it and then comparing them to animal and human discrimination following stimulus pre-exposure. In this chapter we test this principle more directly, by using tDCS to disrupt the modulation of salience by prediction error, and show that when this is done, people exhibit the enhanced generalisation predicted by the standard M&R model. We conclude that our results provide further support for the MKM approach to stimulus representation

The effect of tDCS on recognition depends on stimulus generalization: Neuro-stimulation can predictably enhance or reduce the face inversion effect

This is the author accepted manuscript. The final version is available from the American Psychological Association via the DOI in this recordThis paper reports results from three experiments that investigate how a particular neurostimulation procedure is able, in certain circumstances, to selectively increase the face inversion effect by enhancing recognition for upright faces, and argues that these effects can be understood in terms of the MKM theory of stimulus representation. We demonstrate how a specific transcranial Direct Current Stimulation (tDCS) methodology can improve performance in circumstances where error-based salience modulation is making face recognition harder. The three experiments used an old/new recognition task involving sets of normal vs Thatcherised faces. The main characteristic of Thatcherised faces is that the eyes and the mouth are upside down, thus emphasizing features that tend to be common to other Thatcherised faces and so leading to stronger generalization making recognition worse. Experiment 1 combined a behavioural and ERP study looking at the N170 peak component, which helped us to calibrate the set of face stimuli needed for subsequent experiments. In Experiment 2 we used our tDCS procedure (between-subjects and double-blind) in an attempt to reduce the negative effects induced by error-based modulation of salience on recognition of upright Thatcherised faces. Results largely confirmed our predictions. In addition, they showed a significant improvement on recognition performance for upright normal faces. Experiment 3 provides the first direct evidence in a single study that the same tDCS procedure is able to both enhance performance when normal faces are presented with Thatcherised faces, and to reduce performance when normal faces are presented with other normal faces (i.e. male vs female faces). We interpret our results by analyzing how salience modulation influences generalization between similar categories of stimuli.European Union Horizon 2020Economic and Social Research Council (ESRC