Human striatal activation during adjustment of the response criterion in visual word recognition Lars Kuchinke a,c, ⁎, Markus J. Hofmann a , Arthur M. Jacobs a , Sascha Frühholz b , Sascha Tamm a , Manfred Herrmann b a Department of Psychology, Freie Universität Berlin, Germany b Dept. of Neuropsychology/Behav. Neurobiology, Center for Advanced Imaging – CAI Bremen, University of Bremen, Germany c Experimental Psychology, Department of Psychology, Ruhr-Universität Bochum, Germany abstract article info Article history: Received 3 October 2009 Revised 11 August 2010 Accepted 23 August 2010 Available online 31 August 2010 Keywords: fMRI Striatum Criterion shifting Sequential effects Lexical decision task Results of recent computational modelling studies suggest that a general function of the striatum in human cognition is related to shifting decision criteria in selection processes. We used functional magnetic resonance imaging (fMRI) in 21 healthy subjects to examine the hemodynamic responses when subjects shift their response criterion on a trial-by-trial basis in the lexical decision paradigm. Trial-by-trial criterion setting is obtained when subjects respond faster in trials following a word trial than in trials following nonword trials — irrespective of the lexicality of the current trial. Since selection demands are equally high in the current trials, we expected to observe neural activations that are related to response criterion shifting. The behavioural data show sequential effects with faster responses in trials following word trials compared to trials following nonword trials, suggesting that subjects shifted their response criterion on a trial-by-trial basis. The neural responses revealed a signal increase in the striatum only in trials following word trials. This striatal activation is therefore likely to be related to response criterion setting. It demonstrates a role of the striatum in shifting decision criteria in visual word recognition, which cannot be attributed to pure error- related processing or the selection of a preferred response. © 2010 Elsevier Inc. All rights reserved. Introduction The role of the basal ganglia in higher cognitive processing remains a matter of debate. Basal ganglia are known to support error correction (Lawrence, 2000) and prediction error processing (O'Doh- oherty et al., 2004), response preparation (Monchi et al., 2001), and, more generally, basal ganglia functioning are associated with the planning of actions (Glover, 2004) and action selection (Grillner et al., 2005; Jüptner and Weiller, 1998; Redgrave et al., 1999). Recent neuroimaging research has revealed basal ganglia involvement in higher cognitive tasks such as decision making (Grinband et al., 2006), verbal processing (Friederici and Kotz, 2003; Friederici, 2006; Schirmer, 2004) and semantics (such as word generation; Crosson et al., 2003; 2007). Taken together, these data on basal ganglia involvement in different cognitive functions point to a substantial role of the basal ganglia in higher cognitive processes (Crosson et al., 2007). More recently, modelling studies (Bogacz, 2007; Bogacz and Gurney, 2007; Lo and Wang, 2006) and imaging studies (e.g. Forstmann et al., 2008) have presented evidence that one function of the basal ganglia, and in particular the striatum, is in tuning decision criteria. Response criterion setting on a trial-by-trial basis can be used in decision making to optimize behaviour, for example to control the trade-off between speed and accuracy in simple reaction time tasks and perceptual tasks (Gold and Shadlen, 2007; Smith and Ratcliff, 2004). Models of sequential sampling of information assume that noisy information is integrated over time until a criterion is reached that favours one response over another and stops the decision process (Lo and Wang, 2006; Smith and Ratcliff, 2004). These criteria can be set on a trial-by-trial basis to account for the variability in the stimulus quality. One hypothesis to explain how the basal ganglia affect selection processes refers to the setting of the response criterion in favour of a particular action, e.g. a manual response, depending on the outcome of a fronto-striatal processing loop (Crosson et al., 2003). Thus, (pre-)frontal brain regions might process the contextual cues of a decision task — and, depending on the occurrence of a cue, top down processing elicits strategic shifts or criterion settings that are expected to be processed in the basal ganglia (e.g. Braver and Barch, 2002; Gold and Shadlen, 2007). For example, using a perceptual decision task, Forstmann et al. (2008) could show that brain activation in the striatum covaries with individual adjustments in the response criterion. Here, we want to add neuroimaging evidence to this debate by demonstrating, that the striatum is particularly activated when subjects adjust their response criterion on a trial-by-trial basis in a NeuroImage 54 (2011) 2412–2417 ⁎ Corresponding author. Freie Universität Berlin, AB Allgemeine Psychologie, Habelschwerdter Allee 45, 14195 Berlin, Germany. E-mail address: kuchinke@zedat.fu-berlin.de (L. Kuchinke). 1053-8119/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2010.08.062 Contents lists available at ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg