The baller's brain (and his pinky)

Participation in most sports requires agility, impeccable timing and the planning and execution of complex movements, so that actions such as catching a ball or throwing it into a hoop can be performed. Performing well at sports also requires anticipating and accurately predicting the movements of others.

Athletes and sportspersons undergo years of specialized training to hone these abilities, and nobody would sensibly argue that they are not more proficient at them than others. Indeed, numerous behavioural studies show that those who take part in sports have better sensory and motor skills than sports novices. Yet, very little is known about the neural bases of such skills.

Neuroscientists are now beginning to gain some understanding of the neural mechanisms underlying excellence in sport. One recent study showed that professional tennis players have superior speed discrimination and other time-related skills than triathletes and non-athletes. And a paper just published online in Nature Neuroscience shows that elite basketball players are better than others at predicting the outcome of basket shots, and suggests that this accuracy is based on highly detailed motor imagery.

Cosimo Urgesi of Sapienza and his colleagues at the University in Rome recruited 10 elite players from the Italian professional basketball league, 5 sports journalists, 5 sports couches and 10 students who were complete novices. The latter group had no experience whatsoever of playing basketball, whereas the journalists and coaches had stopped playing the sport an average of 9 years previously, and were instead regarded as "expert watchers". Urgesi and his colleagues showed these participants 12 film short film clips of "free" basket shots by a professional player. Each clip was interrupted at one of 10 possible durations, and the participants were asked to predict whether or not the ball would fall through the hoop.

The professional basketball players were found to predict the outcome of the free shots in the film clips significantly more accurately than both the expert watchers and novices. However, the overall difference in accuracy was found to be far less when the clips were stopped at longer durations. Whereas the ballers could predict the outcome accurately when the film clips were interrupted at durations of less than 0.7 seconds (see above), the predictions of the expert watchers and novices only became more accurate when the film clip was long enough to show the trajectory of the ball after it was released from the player's hands.

The researchers then used a technique called transcranial magnetic stimulation (TMS) to test for a relationship between the accuracy of the participants' predictions and activity in the parts of the brain involved in planning and executing movements. A figure-of-eight-shaped magnetic coil was placed over the primary motor cortex, to record the brain activity correlated with predicting the outcome of the same basketball clips. The participants were also shown static images of basketball shots and clips of soccer shots.

This set of experiments showed that film clips of basketball shots elicited higher levels of motor cortex activity than the soccer clips or static images, in the elite players and expert watchers, but not in the novices. Significantly, these experiments also showed that the observation of an erroneous performance elicited an even greater level of motor cortical activity in the elite players. When the ballers observed basket shots that they predicted would miss the hoop, there was a specific increase in the activation of that part of the motor cortex which controls the movements of the little finger (or pinky).

Neurons in this part of the motor cortex project axons into the corticospinal tract to a muscle in the little finger called the abductor digiti minimi. When it flexes, this muscle pulls the little finger away from the body's midline. This muscle, and the movement it generates, turn out to be crucial in controlling the trajectory of a basketball. If the little finger is in the wrong position during the split-second at which the ball leaves the player's hand, it will go off course and miss the hoop.

Thus, observing others perform actions activates the parts of the brain involved in generating those movements. When one becomes an expert at executing specific movements, the brain generates highly detailed simulations, or motor images, of those movements being executed. And the motor imagery in the baller's brain is so detailed that he can predict the outcome of a basket shot by simulating the minuscule movements of the little finger.

Aglioti, S.M. et al (2008). Action anticipation and motor resonance in elite basketball players. Nat. Neurosci. DOI: 10.1038/nn.2182