Disrupting the Ventral Premotor Cortex Interferes with the Contribution of Action Observation to Use-dependent Plasticity

Abstract

Action observation (AO), observing another individual perform an action, has been implicated in several higher cognitive processes including forming basic motor memories. Previous work has shown that physical practice (PP) results in cortical motor representational changes, referred to as use-dependent plasticity (UDP), and that AO combined with PP potentiates UDP in both healthy adults and stroke patients. In humans, AO results in activation of the ventral premotor cortex (PMv), however, whether PMv activation has a functional contribution to UDP is not known. Here, we studied the effects disruption of PMv has on UDP when subjects performed PP combined with AO (PP+AO). Subjects participated in 2 randomized-crossover sessions measuring the amount of UDP resulting from PP+AO while receiving disruptive (1Hz) transcranial magnetic stimulation (TMS) over the fMRI activated PMv or over orbito-frontal cortex (FC, Sham). We found that unlike the sham session, disruptive TMS over PMv reduced the beneficial contribution of AO to UDP. To ensure that disruption of PMv was specifically interfering with the contribution of AO and not PP, subjects completed two more control sessions where they performed only PP while receiving disruptive TMS over PMv or FC. We found that the magnitude of UDP for both control sessions was similar to PP+AO with TMS over PMv. These findings suggest that the fMRI activation found in PMv during action observation studies is functionally relevant to task performance, at least for the beneficial effects that AO exerts over motor training.

The Frames of Reference of the Motor-Visual Aftereffect

“…In our opinion the most plausible interpretation of this datum is that the actual joint displacement is causally involved in producing the MVA. This finding is supported by results in non-human primates, in the motor systems of which, the double coding of goals and movements is widespread [15]–[18]. Another interpretation that cannot be ruled out by the present data is that it is the somatosensory rather than the visual information that determines this component of the MVA.…”

Selective enhancement of motor cortical plasticity by observed mirror-matched actions

“…We hypothesise that this influence arises upstream from M1. It is well established that action observation activates the ventral premotor cortex (PMv) (Iacoboni et al, 1999), that the connections between PMv and M1 are enhanced with action observation (Koch et al, 2010), and that disruption of PMv with inhibitory rTMS can disrupt the contribution of action observation to use-dependent plasticity (Cantarero et al, 2011). Based on our findings, we speculate that action observation triggers a locally specific increase in functional connectivity between PMv and M1.…”

Rehabilitation with Poststroke Motor Recovery: A Review with a Focus on Neural Plasticity

“…A previous study in healthy subjects reported that observing another person learn a novel task improves subsequent performance of the same task [126]. Moreover, data from a recent virtual lesion study using TMS further supports the hypothesis that action observation coupled with physical practice may enhance use-dependent plasticity through the mirror neuron system in healthy controls [131]. …”