title: Human scalp potentials reflect a mixture of decision-related signals during perceptual choices.
abstract: Single-unit animal studies have consistently reported decision-related activity mirroring a process of temporal accumulation of sensory evidence to a fixed internal decision boundary. To date, our understanding of how response patterns seen in single-unit data manifest themselves at the macroscopic level of brain activity obtained from human neuroimaging data remains limited. Here, we use single-trial analysis of human electroencephalography data to show that population responses on the scalp can capture choice-predictive activity that builds up gradually over time with a rate proportional to the amount of sensory evidence, consistent with the properties of a drift-diffusion-like process as characterized by computational modeling. Interestingly, at time of choice, scalp potentials continue to appear parametrically modulated by the amount of sensory evidence rather than converging to a fixed decision boundary as predicted by our model. We show that trial-to-trial fluctuations in these response-locked signals exert independent leverage on behavior compared with the rate of evidence accumulation earlier in the trial. These results suggest that in addition to accumulator signals, population responses on the scalp reflect the influence of other decision-related signals that continue to covary with the amount of evidence at time of choice.
authors.affiliation: Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, G12 8QB, United Kingdom, Marios.Philiastides@glasgow.ac.uk.
authors.forename: Marios G
authors.initials: MG
authors.lastname: Philiastides
authors.affiliation: Department of Education and Psychology, Freie Universität Berlin, 14195 Berlin, Germany, Max Planck Institute for Human Development, 14195 Berlin, Germany, and.
authors.forename: Hauke R
authors.initials: HR
authors.lastname: Heekeren
authors.affiliation: Department of Biomedical Engineering, Columbia University, New York, New York 10027.
authors.forename: Paul
authors.initials: P
authors.lastname: Sajda
mesh_terms: D000328:Adult; D002755:Choice Behavior / Q000502:physiology*; D003657:Decision Making / Q000502:physiology; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D010865:Pilot Projects; D011930:Reaction Time / Q000502:physiology; D012535:Scalp / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: EEG; confidence; diffusion model; evidence accumulation; perceptual decision making; single-trial