, 2009): the parametric measure of UPDRS score (Unified Parkinson’s Disease Rating Scale; Fahn, Elton, & Committee, 1987) predicted the parkinsonian SC inflation with such rules and while bilaterally affected Hoehn & Yahr (HY) stage II patients demonstrated a switching deficit, unilaterally affected patients at stage I showed intact switching, even following dopaminergic

withdrawal. We proposed that, in contrast to switching stimulus sets with its established sensitivity to frontostriatal DA (e.g., Cools et al., 2003), impairments in switching both stimulus and response sets, GSI-IX cost due to reconfiguration in the abstract rules that determine their mappings, may reflect non-DAergic, frontoparietal cortical deficits in PD, which emerge as the disease progresses from unilateral to bilateral impairment. Moreover, examination of the magnitude of switch costs across switching paradigms in the neuropsychological studies reviewed here reveals that switching both stimulus and response Selleckchem MK 2206 sets rather than

stimulus sets alone yields significantly greater switch costs. This indicates greater demand on task set reconfiguration processes, and lends further support to the notion that these diverse switching paradigms index different neuropsychological deficits. Task switching studies in patients with frontal lesions reveal a similarly heterogeneous picture (Stablum, Leonardi, Mazzoldi, Umilta, & Morra, 1994). Patients with left (L) frontal lesions exhibit generally increased SC and exaggerated effects of interference from irrelevant task sets in designs employing rule reconfiguration (Aron, Monsell, Sahakian, & Robbins, 2004; Keele & Rafal, 2000; Mayr, Diedrichsen, Ivry, & Keele, 2006). In these studies (Aron et al., 2004; Mayr et al., 2006), right (R) frontal lesions were associated with a switching impairment stemming from a specific inability to inhibit irrelevant responses. The original Rogers et al. (1998) study which indexed stimulus set

reconfiguration demonstrated intact switching in the R frontal lesion group, and inflated switch costs were only apparent in the L frontal group. Another study, however, demonstrated switching deficits in a group of patients who also suffered from language Fossariinae impairment as a result of diffuse L hemisphere damage irrespective of whether it was frontal (Mecklinger, von Cramon, Springer, & Matthes-von Cramon, 1999). Thus, we propose to elaborate on these neuropsychological findings by systematically addressing the effect of the type of reconfiguration in task set elements required on a switch, as a function of the nature of the rules that are switched. Neuroimaging evidence supports the hypothesis that switching between abstract rules that assign categorical responses to stimuli entailing reconfiguration in both stimulus as well as response sets, may rely to a greater extent on prefrontal cortical function compared with switching between stimulus sets alone with concrete rules.