Tracing the formation of perceptual decisions in the human brain: A new approach to the study of visuospatial attention asymmetries

Abstract

Event Abstract Back to Event Tracing the formation of perceptual decisions in the human brain: A new approach to the study of visuospatial attention asymmetries Daniel P. Newman1*, Gerard M. Loughnane2, Simon P. Kelly3, Redmond G. O'Connell4 and Mark Bellgrove1 1 Monash University, School of Psychology and Psychiatry, Australia 2 Trinity College Dublin, Trinity Centre for Bioengineering, Ireland 3 City College of New York, Department of Biomedical Engineering, United States 4 Trinity College Dublin, Institute of Neuroscience and School of Psychology, Ireland BACKGROUND Healthy individuals tend to exhibit a subtle processing bias favouring stimuli in the left over the right visual hemifield, termed pseudoneglect, which is thought to reflect a dominant role of the right hemisphere for attention. Reversal of this leftward advantage marks neurological vulnerability across a number of disorders, including unilateral neglect, ADHD and dyslexia. These disorders share a qualitatively similar behavioural phenotype-leftward inattention- yet this label speaks little to the underlying pathophysiological processes. This study aimed to develop an electrophysiological paradigm to differentiate between attentional, perceptual decision making, and motoric processing asymmetries in relation to visuospatual bias. METHODS A random dot motion patch was continuously presented in each hemifield while healthy participants fixated centrally and reacted via button press to instances of coherent motion occurring on either the left or right at pseudorandom times. Since detecting coherence requires sampling from the entire array of dots, the decision regarding coherent motion is gradual and reflects an accumulation of sensory evidence. Further, the continuous stimuli eliminate sensory-evoked deflections in the ERP trace due to stimulus onset. This allows us to track robust brain signals that index sensory evidence accumulation up to an action-triggering threshold. RESULTS A significant leftward reaction time bias confirmed the task’s sensitivity to pseudoneglect in healthy subjects. Analysis of the decision signal revealed that coherent motion in the left and right visual fields was associated with identical build-up rates and decision thresholds but there was a significant ~23ms lag in the onset of evidence accumulation for right versus left targets. The EEG results suggest that pseudoneglect cannot be attributed to hemispheric differences in motoric processing, evidence accumulation rate or threshold, but are indicative of more efficient attentional orienting towards the left shortly after motion onset- before the coherent motion is consciously perceived. DISCUSSION This paradigm provides a way to identify the specific stages of the perceptual decision process that are related to visuospatial attention asymmetries. This approach has obvious value for clinical populations, such as neglect, ADHD and dyslexia, as a means of ruling out non-attentional influences on spatial asymmetry. Keywords: spatial attention, pseudoneglect, perceptual decision making, hemispheric asymmetry, individual differences Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Attention Citation: Newman DP, Loughnane GM, Kelly SP, O'Connell RG and Bellgrove M (2013). Tracing the formation of perceptual decisions in the human brain: A new approach to the study of visuospatial attention asymmetries. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00132 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Nov 2013; Published Online: 25 Nov 2013. * Correspondence: Mr. Daniel P Newman, Monash University, School of Psychology and Psychiatry, Melbourne, Australia, dan.newman86@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Daniel P Newman Gerard M Loughnane Simon P Kelly Redmond G O'Connell Mark Bellgrove Google Daniel P Newman Gerard M Loughnane Simon P Kelly Redmond G O'Connell Mark Bellgrove Google Scholar Daniel P Newman Gerard M Loughnane Simon P Kelly Redmond G O'Connell Mark Bellgrove PubMed Daniel P Newman Gerard M Loughnane Simon P Kelly Redmond G O'Connell Mark Bellgrove Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.