At a first glance, our results are surprising because it is usually assumed that stimuli are first processed in the visual system, then a binary decision is made in the decision unit (e.g., left or right offset), which is then mapped onto an arbitrary motor response (e.g., button presses, saccades, or verbal responses). Hence, visual processing should be independent of procedural and motor processing. We suggest that, during intensive training, strong stimulus-response associations are formed as in riding a bike, where strong sensorimotor contingencies prevail. We do not claim that stimuli are in general coded together with actions. We propose rather that the coding of actions is coded together with stimuli when both are coupled through extensive learning. In this respect our results support theories where stimuli are coded together with the corresponding actions, such as in the ecological approach (Gibson,
1979), the sensorimotor theory (O'Regan & Noë,
2002), the common coding theory (Prinz,
1997), and the theory of event coding (Hommel, Müsseler, Aschersleben, & Prinz,
2001). Our results are in line with current studies showing strong and direct links between sensory and motor processing (Beets et al.,
2010; Beets, Rosler, & Fiehler,
2010; Brown, Wilson, Goodale, & Gribble,
2007; Casile and Giese,
2006; Hecht, Vogt, & Prinz,
2001; Vahdat, Darainy, & Ostry,
2014; Vahdat, Darainy, Milner, & Ostry,
2011; for reviews, see
Cisek & Kalaska, 2010. Ostry and Gribble,
2016; Schütz-Bosbach & Prinz,
2007). For example, Beets, Rösler, et al. (
2010) trained participants in a cyclical arm movement task. Training improved performance for this motor task and transferred to a visual task consisting in discrimination of elliptical shapes. Likewise, electrophysiological studies have shown that neural responses in primary visual cortex (V1) can be strongly modified by ongoing motor activity in mice (Poort et al.,
2015; Saleem, Ayaz, Jeffery, Harris, & Carandini,
2013) and that somatosensory cortex can
directly control the muscles involved in whisker retraction (Matyas et al.,
2010). Similarly, evidence from human imaging studies showed that the mere visual exposure to movements activates motor-related brain areas (Engel, Burke, Fiehler, Bien, & Rösler,
2008; Reithler, van Mier, Peters, & Goebel,
2007). Interestingly, these activations were higher when the movements in question were trained. Moreover, evidence for
simultaneous changes in the sensory and motor cortices were found in monkey and human following sensorimotor learning (Arce-McShane et al.,
2014; Vahdat et al.,
2011,
2014) supporting claims (Censor et al.,
2012) that perceptual and motor learning share analogous properties in terms of temporal dynamics and the engagement of higher order brain areas.