title: Action Planning and the Timescale of Evidence Accumulation.
abstract: Perceptual decisions are based on the temporal integration of sensory evidence for different states of the outside world. The timescale of this integration process varies widely across behavioral contexts and individuals, and it is diagnostic for the underlying neural mechanisms. In many situations, the decision-maker knows the required mapping between perceptual evidence and motor response (henceforth termed "sensory-motor contingency") before decision formation. Here, the integrated evidence can be directly translated into a motor plan and, indeed, neural signatures of the integration process are evident as build-up activity in premotor brain regions. In other situations, however, the sensory-motor contingencies are unknown at the time of decision formation. We used behavioral psychophysics and computational modeling to test if knowledge about sensory-motor contingencies affects the timescale of perceptual evidence integration. We asked human observers to perform the same motion discrimination task, with or without trial-to-trial variations of the mapping between perceptual choice and motor response. When the mapping varied, it was either instructed before or after the stimulus presentation. We quantified the timescale of evidence integration under these different sensory-motor mapping conditions by means of two approaches. First, we analyzed subjects' discrimination threshold as a function of stimulus duration. Second, we fitted a dynamical decision-making model to subjects' choice behavior. The results from both approaches indicated that observers (i) integrated motion information for several hundred ms, (ii) used a shorter than optimal integration timescale, and (iii) used the same integration timescale under all sensory-motor mappings. We conclude that the mechanisms limiting the timescale of perceptual decisions are largely independent from long-term learning (under fixed mapping) or rapid acquisition (under variable mapping) of sensory-motor contingencies. This conclusion has implications for neurophysiological and neuroimaging studies of perceptual decision-making.
authors.affiliation: Department of Experimental Psychology, Oxford University, 9 South Parks Road, Oxford, OX1 3UD, United Kingdom.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Tsetsos
authors.affiliation: Department of Psychology, University of Amsterdam, Weesperplein 4, 1018 XA, Amsterdam, The Netherlands; Amsterdam Brain and Cognition, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS, Amsterdam, The Netherlands; Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg- Eppendorf, 20246, Hamburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pfeffer
authors.affiliation: Department of Psychology, University of Amsterdam, Weesperplein 4, 1018 XA, Amsterdam, The Netherlands; Netherlands Institute for Neuroscience, Meibergdreef 47, 1105 BA, Amsterdam Zuidoost, The Netherlands.
authors.forename: Pia
authors.initials: P
authors.lastname: Jentgens
authors.affiliation: Department of Psychology, University of Amsterdam, Weesperplein 4, 1018 XA, Amsterdam, The Netherlands; Amsterdam Brain and Cognition, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS, Amsterdam, The Netherlands; Bernstein Center for Computational Neuroscience, Charitein Center for Comput, Haus 6, Philippstrast 13, 10115, Berlin, Germany.
authors.forename: Tobias H
authors.initials: TH
authors.lastname: Donner
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D001931:Brain Mapping; D003657:Decision Making; D005260:Female; D006801:Humans; D008297:Male; D011597:Psychomotor Performance