title: Transcranial electrical brain stimulation modulates neuronal tuning curves in perception of numerosity and duration.
abstract: Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method with many putative applications and reported to effectively modulate behaviour. However, its effects have yet to be considered at a computational level. To address this we modelled the tuning curves underlying the behavioural effects of stimulation in a perceptual task. Participants judged which of the two serially presented images contained more items (numerosity judgement task) or was presented longer (duration judgement task). During presentation of the second image their posterior parietal cortices (PPCs) were stimulated bilaterally with opposite polarities for 1.6s. We also examined the impact of three stimulation conditions on behaviour: anodal right-PPC and cathodal left-PPC (rA-lC), reverse order (lA-rC) and no-stimulation condition. Behavioural results showed that participants were more accurate in numerosity and duration judgement tasks when they were stimulated with lA-rC and rA-lC stimulation conditions respectively. Simultaneously, a decrease in performance on numerosity and duration judgement tasks was observed when the stimulation condition favoured the other task. Thus, our results revealed a double-dissociation of laterality and task. Importantly, we were able to model the effects of stimulation on behaviour. Our computational modelling showed that participants' superior performance was attributable to a narrower tuning curve--smaller standard deviation of detection noise. We believe that this approach may prove useful in understanding the impact of brain stimulation on other cognitive domains.
authors.affiliation: Institute of Behavioural Neuroscience, Department of Experimental Psychology, University College London, WC1H 0AP, London, UK. Electronic address: a.h.javadi@gmail.com.
authors.forename: Amir Homayoun
authors.initials: AH
authors.lastname: Javadi
authors.affiliation: Institute of Behavioural Neuroscience, Department of Experimental Psychology, University College London, WC1H 0AP, London, UK. Electronic address: iva.brunec.11@alumni.ucl.ac.uk.
authors.forename: Iva K
authors.initials: IK
authors.lastname: Brunec
authors.affiliation: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, WC1N 3AR London, UK. Electronic address: vin.walsh@gmail.com.
authors.forename: Vincent
authors.initials: V
authors.lastname: Walsh
authors.affiliation: Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, WC1N 3BG London, UK. Electronic address: wpenny@fil.ion.ucl.ac.uk.
authors.forename: Will D
authors.initials: WD
authors.lastname: Penny
authors.affiliation: Institute of Behavioural Neuroscience, Department of Experimental Psychology, University College London, WC1H 0AP, London, UK. Electronic address: h.spiers@ucl.ac.uk.
authors.forename: Hugo J
authors.initials: HJ
authors.lastname: Spiers
mesh_terms: D000328:Adult; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007600:Judgment / Q000502:physiology*; D008297:Male; D055641:Mathematical Concepts; D008959:Models, Neurological; D010296:Parietal Lobe / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Computational modelling; Duration; Magnitude judgement; Neuronal tuning curve; Numerosity; Receptive field; Time