Images of time: temporal aspects of auditory and movement imagination

Research on mental imagery has shown that when we imagine something, the related neural processes overlap with those related to actually perceiving or performing that same percept or action (Kosslyn et al., 2001). Although visual imagery has long been the dominant modality for the investigation of sensory imagery, involvement of modality-specific brain regions (i.e., visual areas being implicated in visual imagery, and so on) has now also been reported for auditory, olfactory and tactile imagery (Halpern, 2001; Plailly et al., 2012; Schmidt et al., 2014). Movement or action imagery has informed theories of action representation (Jeannerod and Decety, 1995) and has recently gained interest in the context of mental practice for expert skill acquisition such as sports or surgery (Cocks et al., 2014) and movement rehabilitation (Malouin and Richards, 2010). Increasingly, the neural underpinnings of imagery have become clearer, and both modality-specific and modalityunspecific neural activations related to imagery have been found (Daselaar et al., 2010; Zvyagintsev et al., 2013). However, the growing body of neuroimaging literature on imagination has yet to include an account of temporal imagery. Although the reproduction of time intervals has been a research topic of interest, the contribution of temporal imagery—namely internal timekeeping or creating the temporal aspects of imagery in other modalities—is largely unexplored. As such it is unclear whether, similar to other perceptual modalities, imagery for time shares cerebral substrate with brain networks involved in time perception or regularity detection. Specifically for actions or sounds, the temporal structure of the imagined stimulus or action is crucial in conjuring a faithful image, suggesting that in scientific findings of auditory and motor imagery, temporal imagery is included. The temporal patterns we create internally arguably lie at the basis of any self-paced movement, be it a fast sprint, a musical performance, or an easy walk in the park. Here, I argue that the shared components between movement and auditory (specifically music) imagery may offer a window into timing and temporal skills, which may carry cognitive importance beyond movement or auditory functions. Whereas the reciprocal influences of rhythmic sound and movement have been shown, with rhythmic movement supporting auditory acuity (Su and Pöppel, 2012) and rhythmic sound supporting movement efficiency (Bood et al., 2013), few studies have looked at the extent to which imagery can functionally replace perception or action and show similar interactions, which may point to shared processing in their temporal structure. Music imagination was reported to affect finger tapping similarly to perceived music (Repp, 2001) and has been used to support movement in clinical settings (Satoh and Kuzuhara, 2008). Anecdotal observation from music imagery experiments (such as described in Schaefer et al., 2011b), suggests that tapping a finger along to music imagery supported accurate imagery timing, and auditory cues are reported to increase motor imagery vividness (Heremans et al., 2009). Furthermore, motor timing skills and anticipatory music imagery ability appear to be related (Pecenka and Keller, 2009; Keller and Appel, 2010). These findings suggest that the links between motor and music processing may extend into imagined stimuli or actions, and the contribution of the current piece is to bring together findings from temporal processing, music and motor research, and to assert that firstly, the commonalities between music and motor imagery may reveal more about internally driven timing mechanisms, and secondly, one might speculate that these internal timing patterns are related to expertise, and as such may be seen in the context of findings on temporal skills and cognitive abilities (Madison et al., 2009; Holm et al., 2011).