The field of systems neuroscience is feeling pretty good about itself. Volumes have been written on all the successes over the past half century, yielding many Nobel prizes. Some distinguished recipients have included David Hubel and Thorsten Wiesel for their work on the visual cortex and John O’Keefe, May-Britt Moser, and Edvard Moser for their work on the hippocampal formation. It is commonly accepted that the best worked out system in neuroscience is the visual system of primates (Schiller and Tehovnik 2015). Here are some sobering statistics, however. Of all the muscles in humans, only 12 are devoted to the control of eye movements for vision with the remaining 700 or so being dedicated to other behaviors. Furthermore, in a recent study that used electrical stimulation of 1,162 and 659 sites, respectively, in the neocortex and subcortex of humans(Sarubbo et al. 2020), it was found that up to 6% of sites were dedicated to oculo-visual functions. The majority of sites mediated skeleto-motor movements and somato-sensation (i.e., 49% and 37% for neocortex and subcortex, respectively) and language (i.e., 47% and 51% for neocortex and subcortex, respectively). The remaining sites (i.e., 3% and 6% for neocortex and subcortex, respectively) were involved in some aspects of cognition (see Footnote 1).
Accordingly, when a professor is talking and moving about delivering his or her lecture, expect some 96% of the neocortex and 88% of the subcortex to be engaged. In a recent study on locomoting mice it was discovered to the surprise of the investigators that much of the neocortex was active (Mausell et al. 2019). I am certain if these investigators had been studying subcortex in locomoting mice they would have found a similar result (see Footnote 2). Should we be awed that our most successful field of study, visual neuroscience, has been working at the tip of the iceberg, i.e., at 6%. On a more positive note, this 6% focus can now be used as a guide to how the neocortex and cerebellum, which represent over 95% of the neurons in the brain (Herculano-Houzel 2009), process the remaining behaviors to finish the work of Hans-Lukas Teuber (1916-1977) (Footnote 1).
Footnote 1: Some in cognitive science believe that the study of cognition (i.e., thinking) needs to be detached from the execution of body movements even if the movements are a consequence of thinking: reading, writing, speaking, painting, singing, dancing, and so on. Chomsky (2012) believes that ‘thinking’ is an exclusive human attribute and that its expression through language should never be conflated with communication. This mind-body apartheid has prevented cognitive scientists from fully embracing the comparative neuropsychological-neurophysiological tradition espoused by Hans-Lukas Teuber (1916-1977), the founder of the Department of Brain and Cognitive Sciences at MIT of which Noam Chomsky was an active participant.
Footnote 2: It has been known since the time of Sherrington (1906) that much of the brain is involved in movement control (Vanderwolf 2007), and in the case of humans, in movement and language control (Kimura 1993; Penfield and Roberts 1966).