Figure 14.

Simplified diagram of neural connections from auditory periphery to the motor system. Each node represents a neural structure of interest to this study, and arrows represent efferent connections. Broadly, there are three possible audiomotor “streams” by which timing and frequency processing could be mediated: the canonical route through sensory cortex (Stream 1 in teal), a thalamostriatal route (Stream 2 in saffron) and a route from the inferior to superior colliculus (Stream 3 in green). Our experiments suggest that the extended auditory cortex is not required for timing in these tasks, and neither is the medial prefrontal cortex. One possibility suggested by these eliminations is that duration perception is mediated by the subcortical streams. An alternate possibility is that cortical structures not targeted by our experiments, but which receive direct input from auditory brainstem, mediate the ability to perceive pure tone durations. Projection key: blue-dashed: corticofugal; red: to/from the hippocampus; green: subcortical; thick black: corticocortical.(Neuroanatomy references: Donoghue and Parham, 1983; Roger and Arnault, 1989; Sesack et al., 1989; Arnault and Roger, 1990; Romanski and LeDoux, 1993; Condé et al., 1995; Burwell and Amaral, 1998; Winer and Schreiner, 2005; García Del Caño et al., 2006).