Why People Who Cannot Move Are Able to Think

Abstract

The first clue in approaching an answer concerns the fact that for the brain, the only difference between planning or imagining an activity and engaging in the activity is the actual execution of that behavior. It is well documented that very similar, if not identical brain areas are recruited during the process of thinking about an activity and when actually performing that behavior [207, 208]. The primary difference is the activation of the motor system when that behavior is executed. The second clue concerns the fact that it is also well documented that mentally rehearsing, or imagining the execution of a behavior, actually improves performance [207, 208]. For example, in one study, it was concluded that viewing tools seemed to generate prehensions and anticipations about using them; the imagined action of using a tool “mirrored” the brain activation underlying the functional use of the tool [259]. The perception of the tool, the contextual coupling of the action of using the tool, and the imagination of the activity generated the precursors or forerunners of overt “action control” over tool use. In addition, it has been documented that the planning of the use of a tool activates or recruits a distributed large scale brain network within the left hemisphere. This network includes the posterior superior temporal sulcus, a brain region necessary for the perception of motion; proximal regions of the middle and superior temporal gyri were also recruited, which are brain regions associated with the memory of the identification of objects and the assignment of appropriate context for objects, in other words, salience assignment; the anterior and posterior supramarginal gyri of parietal regions were recruited, which are brain regions that are necessary for specifying the parameters of action, insofar as grasp of the tool might be determined by its size, shape, and movement; the inferior frontal and ventral premotor cortices were activated, as well as the dorsolateral prefrontal cortex, regions necessary for the execution of movement and for decision making over action. These regions have been described as an “action control” network [2, 75, 110, 260], while it also should be noted that these brain regions include what some investigators have termed the “mirror neuron system” [158, 261, 262]. While activity within the left DLPFC dropped out during action execution (which makes sense after the decision to act was made to choose that particular candidate behavior), adjacent and partially overlapping areas of the left temporal, parietal, and frontal cortex were engaged during action execution. As cited above, when the cerebellum was included as a brain region of interest (ROI), differential regions of the anterior and posterior inferior cerebellum were also activated during actual and imagined tool use. The data identify the lateralized large scale brain network referred to in this and earlier papers as a functional ensemble for the interaction of semantic/declarative and motor/procedural representations upon which meaningful skills depend [263]. Therefore, while in reviewing Pezzulo [116–118] it was concluded that procedural knowledge can lead to the development of declarative knowledge, the opposite relationship is similarly evident. Declarative knowledge can facilitate procedural learning through the process of observation. This was similarly evident in the prior example of attending a brain dissection workshop.