What and When: Parallel and Convergent Processing in Motor Control

Abstract

Successful motor behavior requires making appropriate response (response selection) at the right time (timing adjustment). Earlier psychological studies have suggested that the response selection and timing adjustment processes are performed serially in separate stages. We tested this hypothesis using functional magnetic resonance imaging. The subjects performed a choice reaction time task in four conditions: two (on-line response selection required or not) by two (on-line timing adjustment required or not). We found that the neural correlates for the two processes were indeed separate: the anterior medial premotor cortex (presupplementary motor area) was selectively active in response selection, whereas the cerebellar posterior lobe was selectively active in timing adjustment. However, the functional separation was only partial in that the lateral premotor cortex and the intraparietal sulcus were active equally for response selection and timing adjustment. The lateral premotor cortex was most active when both processes were required, suggesting that it integrates the information on response selection and the information on timing adjustment; alternatively, it might contribute to the allocation of attentional resources during dual information processing. The intraparietal sulcus was equally active when either response selection or timing adjustment was required, suggesting that it modifies, rather than integrates, these processes. Furthermore, our results suggest that these activations related to response selection and timing adjustment were distinct from sensory or motor processes.

Pathophysiology of NSS in ADHD

“…In an fMRI study, Sakai et al (2000) showed some of the interactions between the pre-SMA area and the posterior lobe of the cerebellum. The authors found that the pre-SMA area was selectively active in response selection, whereas the cerebellar posterior lobe was selectively active in timing adjustment, and that the primary motor cortex received connections from both the pre-SMA and the cerebellum (Sakai et al 2000).…”

“…The authors found that the pre-SMA area was selectively active in response selection, whereas the cerebellar posterior lobe was selectively active in timing adjustment, and that the primary motor cortex received connections from both the pre-SMA and the cerebellum (Sakai et al 2000). Both the basal ganglia and the cerebellum have recurrent connections with the prefrontal cortex, which is the site of high-level information processing because of its activity related to working memory, action planning and decisionmaking.…”

Emergence of rhythm during motor learning

“…Automatic timing processes include performance of a well-learned rhythm [17], control of the acceleration and deceleration of a learned sequential hand movement [18], or synchronous tapping to the beat of a rhythm [19,20] especially as performed by professional musicians [8]. Controlled timing processes include encoding of time duration [21,22], explicit discrimination of time intervals [23], on-line adjustment of the timing of motor or cognitive action [19,24,25], or those in early phases of rhythm learning [26].…”

“…Recent studies have shown that, when temporal processing and spatial processing are done explicitly, they are associated with separate neural structures. Specifically, the cerebellar posterior lobe is involved in processing of temporal information whereas the pre-SMA or parietal area is involved in processing of spatial information [6,24,51,52]. However, a controversy remains as to whether the cerebellum is the area dedicated specifically to temporal processing [53,54].…”

“…It also remains unclear whether other cognitive processes that involve the cerebellum can be explained in terms of timing. Integration of temporal and spatial information is shown to be carried out within motor-related areas, including the lateral premotor cortex [24,51,52]. It remains controversial whether or not implicit learning of the two types of information can occur independently [55,56].…”