Fig. 5.

a Schematic depiction of four of the ‘fronto-striatal loops’, ranging from a ‘motor’ loop involving the putamen and supplementary motor area through to an ‘affective’ loop comprising the nucleus accumbens and certain areas of the orbitofrontal cortex, with two prominent ‘cognitive’ loops in between (reproduced from Lawrence et al. [36]). Also shown is the hypothesised gradient of dopamine depletion for PD which is greatest in the dorsal striatum and weakest in the ventral striatum. SMA = Supplementary motor area; SSC = somatosensory cortex; PMC = premotor cortex; PPC = posterior parietal cortex; DL-PF = dorsolateral prefrontal cortex; VL- PF = ventrolateral prefrontal cortex; ST = superior temporal cortex; OFC = orbitofrontal cortex; Cing = cingulate cortex; HC = hippocampus; BLA = basolateral amygdala; V putamen = ventral putamen; GPi = globus pallidus, internal segment; VP = ventral pallidum; SNpr = substantia nigra pars reticulata; cv = caudoventral; cl = caudolateral; dm = dorsomedial; r = rostral; rm = rostromedial; VLo = ventrolateral thalamus; VA = ventral anterior thalamus; MD = mediodorsal thalamus; mc = magnocellular; pc = parvocellular. b Schematic rendering of typical forms of behaviour associated with each loop after withdrawal of dopaminergic medication. Note on the extreme left, tasks such as task set switching and spatial working memory are mildly improved by dopamine medication. By contrast, on gambling and reversal learning, tasks associated with ventral frontal mediation, l-DOPA withdrawal significantly impairs performance. Reproduced with permission from Swainson et al. [33] and the publishers.