Continuous Theta-Burst Stimulation Demonstrates a Causal Role of Premotor Homunculus in Action Understanding

Abstract

Although it is well established that regions of premotor cortex (PMC) are active during action observation, it remains controversial whether they play a causal role in action understanding. In the experiment reported here, we used off-line continuous theta-burst stimulation (cTBS) to investigate this question. Participants received cTBS over the hand and lip areas of left PMC, in separate sessions, before completing a pantomime-recognition task in which half of the trials contained pantomimed hand actions, and half contained pantomimed mouth actions. The results reveal a double dissociation: Participants were less accurate in recognizing pantomimed hand actions after receiving cTBS over the hand area than over the lip area and less accurate in recognizing pantomimed mouth actions after receiving cTBS over the lip area than over the hand area. This finding constrains theories of action understanding by showing that somatotopically organized regions of PMC contribute causally to action understanding and, thus, that the mechanisms underpinning action understanding and action performance overlap.

Action Observation as a Visual Process: Different Classes of Actions Engage Distinct Regions of Human PPC

“…Once one has accepted that action observation is part of vision, it follows that it can be tested very much like other aspects of visual perception, by using discrimination tasks. This circumvents using complex tasks as in past studies (Clerget et al, 2009;Fazio et al, 2009;Michael et al, 2014;Vanuscorps and Caramazza, 2016), the interpretation of which is complicated by the many cognitive aspects associated with the processing of the identities of the observed actions they include. In fact, years ago I proposed the use of discrimination tasks such as identification, successive or simultaneous discrimination, as a way of simplifying the processing taking place in a complex brain , and as an alternative to studying small animal model brains.…”

“…Perhaps mirror neurons should then be renamed OAS motor (OAS-M) neurons. It should be noted that so-called causal experiments such as suppressive TMS (Michael et al, 2014) have only regional specificity and therefore cannot distinguish between the mirror and OAS neurons' role in action observation. Also, it has been argued that the transformation of visual OA-signals into motor format by the mirror neurons explains the impression of owning the action when observing it (Jeannerod, 2001), but this impression may not reflect the source of the perception, but rather be a simple correlate of using a visual representation located in motor planning regions.…”

Mirror neuron research: the past and the future

“…One reason for the opposition of some neuropsychologists to accept the existence of mirror neurons in humans is probably due to the fact that the mirror mechanism was discovered when it was not completely clear whether damage to the areas endowed with this mechanism determines deficits in understanding others' actions (for evidence for the causative role of mirror neurons in action understanding, see [12,16]). Typically, the opposite series of events occurs, that is experimental and/ or clinical studies indicate that a certain cortical region is involved in a particular function (e.g.…”

The Development of Social Attention in Human Infants

“…(2) We reflexively or automatically orient our own attention to the same location resulting in eye contact (direct or mutual gaze) or attention to objects and events (averted gaze) (e.g., Driver et al 1999;Friesen & Kingston, 1998;Frischen, Bayliss, & Tipper, 2007). (3) Our attention to observed actions automatically activates corresponding motor programs Kilner, Marchant, & Frith, 2006;Michael et al, 2014;Rizzolatti & Craighero, 2004). (4) We infer state of mind (i.e., intentions, desires, beliefs) from these actions by others (e.g., Blakemore & Decety, 2001;Gallese, Rochat, Cossu, & Sinigaglia 2009;Wellman, Lopez-Duran, LaBounty & Hamilton, 2008;Woodward, 2009).…”