Human visual and parietal cortex encode visual choices independent of motor plans Martin N. Hebart a, b, c, ⁎, Tobias H. Donner d, 1 , John-Dylan Haynes a, b, c, e, ⁎ , 1 a Bernstein Center for Computational Neuroscience, Charité Universitätsmedizin, Berlin, Germany b Berlin Center for Advanced Neuroimaging, Charité Universitätsmedizin, Berlin, Germany c Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Germany d Department of Psychology, University of Amsterdam, The Netherlands e Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany abstract article info Article history: Accepted 5 August 2012 Available online 16 August 2012 Keywords: Decision-making Motion perception Signal detection theory Decoding Multivoxel pattern analysis fMRI Perceptual decision-making entails the transformation of graded sensory signals into categorical judgments. Often, there is a direct mapping between these judgments and specific motor responses. However, when stimulus–response mappings are fixed, neural activity underlying decision-making cannot be separated from neural activity reflecting motor planning. Several human neuroimaging studies have reported changes in brain activity associated with perceptual decisions. Nevertheless, to date it has remained unknown where and how specific choices are encoded in the human brain when motor planning is decoupled from the deci- sion process. We addressed this question by having subjects judge the direction of motion of dynamic ran- dom dot patterns at various levels of motion strength while measuring their brain activity with fMRI. We used multivariate decoding analyses to search the whole brain for patterns of brain activity encoding sub- jects' choices. To decouple the decision process from motor planning, subjects were informed about the re- quired motor response only after stimulus presentation. Patterns of fMRI signals in early visual and inferior parietal cortex predicted subjects' perceptual choices irrespective of motor planning. This was true across several levels of motion strength and even in the absence of any coherent stimulus motion. We also found that the cortical distribution of choice-selective brain signals depended on stimulus strength: While visual cortex carried most choice-selective information for strong motion, information in parietal cortex decreased with increasing motion coherence. These results demonstrate that human visual and inferior parietal cortex carry information about the visual decision in a more abstract format than can be explained by simple motor intentions. Both brain regions may be differentially involved in perceptual decision-making in the face of strong and weak sensory evidence. © 2012 Elsevier Inc. All rights reserved. Introduction Our brain continuously transforms noisy and incomplete sensory signals into categorical judgments about the state of the outside world. Much progress has been made in understanding the neural mechanisms underlying such decision-making processes. Monkey neurophysiology (Gold and Shadlen, 2000; Roitman and Shadlen, 2002; Romo et al., 2002; Salinas et al., 2000; Shadlen and Newsome, 2001) and human neuroimaging studies (Donner et al., 2009; Heekeren et al., 2004, 2006; Ho et al., 2009; Tosoni et al., 2008) provide converging evidence that, in the face of uncertainty, the brain produces perceptual choices by accumulating weak signals from sensory cortical areas. It has, however, remained largely unknown how perceptual choices are encoded when they are decoupled from action planning. Most previous studies directly mapped perceptual choices (e.g. up- ward vs. downward motion) onto motor responses (e.g. right vs. left button press) and in that way treated perceptual decision-making as a problem of action selection (Freedman and Assad, 2011; Gold and Shadlen, 2007). Consequently, the decision process was reflected in neuronal activity in sensorimotor and motor brain regions, both in macaque monkeys (Horwitz and Newsome, 1999; Kim and Shadlen, 1999; Salinas and Romo, 1998; Shadlen and Newsome, 2001) and in humans (Donner et al., 2009; Tosoni et al., 2008). In monkeys, a subset of parietal neurons also encoded perceptual choices when the deci- sion was decoupled from the motor response (Bennur and Gold, 2011), but this study focused on a single brain area in the macaque. It has remained an open question how such abstract perceptual NeuroImage 63 (2012) 1393–1403 ⁎ Corresponding authors at: Charité-Universitätsmedizin Berlin, Bernstein Center for Computational Neuroscience, Haus 6, Philippstraße 13, 10115 Berlin, Germany. Fax: +49 30 2093 6771. E-mail addresses: martin.hebart@bccn-berlin.de (M.N. Hebart), haynes@bccn-berlin.de (J.-D. Haynes). 1 Both of these authors share senior authorship. 1053-8119/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.neuroimage.2012.08.027 Contents lists available at SciVerse ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg