Movement in Space


Nikolai Bernstein, perhaps the sharpest thinker of all twentieth-century motor scientists, is mostly quoted for his incisive treatment of the degrees-of-freedom matter in linked limb movements, a topic well covered in Chapter 2 of this book. He is also frequently cited for drawing attention to spatially and effector invariant attributes of complex movements, such as free drawing of a circle with the arm, leg or tongue. I will focus my discussion below on a less discussed topic that Bernstein brought up, namely the pervasive presence of extrapersonal space in motor control (Chapter 5), especially in relation to the evolutionary development of telereceptors, a combination that ultimately proved crucial to the dominance of animals with well-developed telereceptors, especially visual, and a spatially adapted motor apparatus to match. More specifically, I will discuss the brain mechanisms underlying visuospatial motor coordination, as have been revealed by the recordings of neurons in behaving monkeys. The picture that has emerged from those studies over three decades has fully validated and neurally substantiated Bernstein's insights.