Today the New York Times has an amazing video breakdown of what makes Roger Federer’s footwork such a powerful, if often overlooked, weapon in his arsenal. For fans of the technical breakdown of sports genius, this is for you. The accompanying article describes how this puts unusual pressure on his opponents, by essentially enlarging the size of the court they are playing on (by depriving them of time to get to balls).
As usual there is no discussion of what’s making all this fancy footwork possible – which is to say, Federer’s brain – so we thought we’d augment with a few reminders. First, you’re looking at a huge habit network – Federer isn’t thinking consciously that he wants to make all of these movements, they are happening to him. In the brain, habits are called ‘central pattern generators’ or CPGs, for short, and are stored in the basal ganglia.
However he wasn’t born with them there – he, like all of us, went through a period of training where he consciously ‘wanted’ to move this way, in which his cortex was heavily involved in learning and adjusting his behavior. Over tens of thousands of iterations, likely closing in on the millions at this point, these motor movement programs were transferred from cortex to basal ganglia through habit learning. One of the overlooked purposes of habit is to save energy. By having a part of the brain execute a motor command independent of it being rewarding, or not, you save on all the neural processing required to decide that you want or don’t want to hit a particular shot – you just hit it. This is what athletes often mean when they say they were ‘unconscious’ during a particularly good run of play.
Many of these habit repertoires are active simultaneously in any given shot, and need to be coordinated. This coordination of coordination occurs in the cerebellum. Here the acronym to know is NOCS – for Neural Optimal Control System. What the cerebellar NOCS is doing is receiving – essentially – requests from the various parts of the basal ganglia to proceed with their movement, and the cerebellar master NOCS coordinates all of these requests into a smooth chronological order.
However there’s a piece of the puzzle missing. Where does Federer decide to make one or or another of the various shots he is capable of? Where do these automatic, habitual and well-coordinated motor movements get chosen? Many readers might instinctively guess the motor cortex, but this is far too late in the game. The motor cortex is where the body is told what to do; not where the decision to move is made. That job falls to the supplementary motor area (SMA), which might be thought of as the advance team of mid-level diplomats who fly to foreign countries a week ahead of the President or Secretary of State, and hammer out the deal that the official then takes credit for at a signing ceremony in full view of the press. Or perhaps a better analogy is that the SMA is the motor cortex’s chief of staff.
As the ball flies towards Federer, he has a variety of options. Each of these, like cabinet members, must vie for attention from the chief of staff, making the case for why their plan is best. The SMA is where this conflict gets resolved; urges to do one thing versus another – with each ‘thing’ in fact being a complex set of movements such as ‘hit a lob to his left’ – being represented as a coherent action set. Part of Federer’s brilliance is how well SMA, basal ganglia and cerebellum are working together to produce his phenomenal string of wins.
Baev. A new conceptual understanding of brain function: basic mechanisms of brain-initiated normal and pathological behaviors. Critical reviews in neurobiology (2009) vol. 19 (2-3) pp. 119-202
Yin and Knowlton. The role of the basal ganglia in habit formation. Nat Rev Neurosci (2006) vol. 7 (6) pp. 464-76
Haggard. Human volition: towards a neuroscience of will. Nat Rev Neurosci (2008) vol. 9 (12) pp. 934-46