, 1997 and Crammond and Kalaska, 2000) and the posterior parietal cortex (Mountcastle et al., 1975, Snyder et al., 1997, Batista et al., 1999 and Gail and Andersen, 2006). The rule-selection hypothesis predicts that such areas only encode one goal at a time, according to the preliminarily selected Navitoclax rule, but not multiple rule-based potential goals simultaneously (Figure 1B, left). The goal-selection hypothesis predicts that they simultaneously encode all alternative potential movement goals prior to the decision (Figure 1B, right). Therefore, the two hypotheses are distinguishable only at predecision stages,
where the simultaneous existence of multiple, alternative, potential BIBW2992 order motor goals in a rule-selection task would favor the goal-selection hypothesis. Evidence for potential motor goal encoding in spatial rule selection tasks, i.e., in situations like in the example of the striker, is lacking. Several areas of the brain have been thought to
encode multiple potential motor goals in space, but only in experiments involving selection among multiple physical targets (Basso and Wurtz, 1998, Cisek and Kalaska, 2005 and Lau and Glimcher, 2008). However, in such tasks, multiple alternative spatial representations in the neural activity could be associated with multiple physical targets rather than motor goals. Therefore, target selection tasks are unsuitable for distinguishing between the rule- and
the goal-selection hypotheses. We measured the spatial selectivity of neurons in monkey parietal and premotor cortex during reach planning in a novel rule-selection task (Figure 2). We show that two spatial, rule-based potential motor goals can be simultaneously encoded, supporting the goal-selection hypothesis. Potential motor goals can encode all alternative choices as defined by the task (options), or biased representations of all choices based on before previous reward experience (preferences), depending on which stage of the decision process they represent. So far, empirical evidence for preference encoding has been lacking for skeletomotor tasks, even in target selection experiments. Many previous oculomotor studies showed modulation of neural target responses by choice probability or some form of value assignment (preference encoding) in different brain areas of monkey (Basso and Wurtz, 1998, Dorris and Munoz, 1998, Platt and Glimcher, 1999, Sugrue et al., 2004, Dorris and Glimcher, 2004, Yang and Shadlen, 2007, Lau and Glimcher, 2008, Kim and Basso, 2010 and Louie and Glimcher, 2010) and human (Hampton et al., 2006, Kable and Glimcher, 2007, Yanai et al., 2008 and Wunderlich et al., 2009). Target-selection experiments using skeletomotor behavior, like reaching, showed encoding of freely selected targets in the parietal reach region (PRR) (Scherberger and Andersen, 2007 and Pesaran et al.