More recently the notion of a central role for the cerebellum has been questioned (Harrington, Lee, Boyd, Rapcsak, & Knight, 2004), although this view still has its adherents (Ivry & Spencer, 2004). The advent of brain imaging has caused a shift emphasis away from the cerebellum towards fronto- striatal pathways.

The advent of brain imaging has caused a shift in emphasis away from the cerebellum towards fronto- striatal pathways. Initial PET results suggested that the basal ganglia, particularly the striatum, and the cingulate cortex are active during time processing tasks (Jueptner et al., 1995; Lejeune et al., 1997). FMRI studies lead to similar conclusions. Rao et al. (1997) reported that generating a rhythm by finger-tapping causes differential activity for self-generated rhythms in the left putamen and left supplementary motor area (SMA). Rao et al. (2001) found similar results with a time perception task, and in addition showed that activity in the basal ganglia evolves earlier than that in the cerebellum, possibly suggesting a more fundamental role. Nenadic et al. (2003) found timing-related activity in the right putamen in a duration discrimination task, while Coull, Vidal, Nazarian, and Macar (2004) also reported timing-related activity in the striatum and showed that the activity increases with the level of attention paid to the timing task (as opposed to a competing control task). Also emphasised in the latter study are pre-SMA and the frontal operculum, which the authors see as parts of a fronto-striatal timing network. Other studies have also identified pre- SMA as important (e.g. Pastor, Day, Macaluso, Friston, & Frackowiak, 2004; Pouthas et al., 2005). Recent theoretical treatments of timing (e.g. Meck and Benson, 2002; Buhusi & Meck, 2005) give fronto-striatal circuits a key role, while evidence of disruption to timing processes in Parkinson’s disease (Malapani et al., 1998), which involves degeneration of nigrostriatal dopamine systems, is consistent with such an account.