FRONTIERS COMMENTARY To summarize, the analytical approach described by Maei et al. (2009) provides a more effective and accurate new measure in terms of its superb sensitivity and statistical validity in water maze studies. Furthermore, the H measure will contribute greatly to the advancement of behavioral assays that, in conjunction with molecular genetic approaches, are designed to elucidate the molecular mechanisms underlying learning and memory. REFERENCES D’Hooge, R., and De Deyn, P. P. (2001). Applications of the Morris water maze in the study of learning and memory. Brain Res. Brain Res. Rev. 36, 60–90. Gallagher, M., and Rapp, P. R. (1997). The use of animal models to study the effects of aging on cognition. Annu. Rev. Psychol. 48, 339–370. Lipp, H. P., and Wolfer, D. P. (1998). Genetically modiﬁed mice and cognition. Curr. Opin. Neurobiol. 8, 272–280. Maei, H. R., Zaslavsky, K., Teixeira, C. M., and Frankland, P. W. (2009). 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Morris water maze:procedures for assessing spatial and related forms of learning and memory. Nat. Protoc. 1, 848–858. Received: 21 September 2009; published: 15 May 2010. Citation: Front. Neurosci. (2010) 4, 1: 1–2. doi: 10.3389/ neuro.01.002.2010 Copyright © 2010 Lee and Kaang. This is an open-access publication subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduc- tion in any medium, provided the original authors and source are credited. Decisions of voluntary action: what vs when Deborah J. Serrien* School of Psychology, University of Nottingham, University Park, Nottingham, UK *Correspondence: deborah.serrien@nottingham.ac.uk A commentary on Dissociating what and when of intentional actions by Veronika Krieghoff, Marcel Brass, Wolfgang Prinz and Florian Waszak Voluntary action is a fundamental characteristic of human behavior and identiﬁes our ability to realize intention- ally driven tasks. Functional imaging work has indicated that intentional perform- ance activates neural circuitry conﬁned to the fronto-medial cortex (Cunnington et al., 2002; Lau et al., 2004; Nachev et al., 2005). This network activity integrates, besides the conscious experience of intend- ing (Haggard and Clark, 2003; Lau et al., 2004), a series of processes in relation to the intentional act (Brass and Haggard, 2007). Accordingly, intentional behav- ior can be viewed as a form of decision making that consists of various compo- nents with different types of information processing (Brass and Haggard, 2008; Haggard, 2008). This distinctive viewpoint is important as voluntary action has often been regarded as a unitary concept without 2 | May 2010 | Volume 4 | Issue 1 little consideration for the component functions. In this respect, it has been sug- gested that voluntary action has at least two decisional processes: what action to per- form (selection component) and when to perform it (timing component), (Mueller et al., 2007). Thus, the “what” decision speciﬁes which action to perform from a range of alternative options, whereas the “when” decision denotes the moment in time at which to execute the action. In their recent contribution to Frontiers in Neuroscience, Krieghoff et al. (2009) presented an fMRI study that provides new insights into voluntary behavior. In particular, the authors proposed a well- designed protocol in which they simulta- neously and independently manipulated the selection and timing component within one experimental paradigm. Moreover, the participants were instructed to perform one of two possible actions at one of two possible moments in time. Furthermore, the action and moment in time were freely chosen or externally triggered by means of a cue. In other words, the “what” (selec- tion) and “when” (timing) decision of the impending action were based on an inter- nal judgment or imposed by an external stimulus. This distinction between inter- nally and externally generated responses is relevant as both types of activities are known to have (partly) dissociable neural circuitry in respect to the component proc- ess of selection, as well as timing (Deiber et al., 1999; Cunnington et al., 2002, 2006; Lau et al., 2006). As the main objective of Krieghoff et al. (2009) was to investigate the decisional processes of voluntary behavior, the data analysis focused primarily on the cue- related activity that speciﬁed the decision making process rather than on the target- related activity that represented the imple- mentation of that decision. In view of that premise, the whole-brain analysis of the cue-related signal showed that two fronto- medial wall areas associated with distinct component functions of voluntary action: whereas the selection component linked strongly with the rostral cingulate zone (RCZ), the timing component tied closely with the superior medial frontal gyrus (SFG), which is localized close to pre-SMA (Rushworth, 2008). These results indicate that separate brain regions are involved in distinct decisional processes, and accord- ingly highlight a functional dissociation of www.frontiersin.org