Article of the Month, January 2019 (Joshua's lab)

Encoding of Reward and Decoding Movement from the Frontal Eye Field during Smooth Pursuit Eye Movements

Authors:   Adi Lixenberg and Mati Joshua

Published in JNeurosci Journal of Neuroscience 5 December 2018, 38 (49)

From an engineer perspective it might be beneficial to separate the mechanisms that compute the details of an action from those that evaluate its consequences. In the brain however, the same circuitry that process motor commands are also embedded in reward systems. This raises the question of how do representations of reward in the motor system interact with the computations that drive behavior. We recorded activity in smooth pursuit neurons in the frontal eye field of two monkeys while controlling the eye speed by manipulating either reward size or target speed. The neurons encoded the different reward conditions more strongly than the different target speed conditions. This pattern could not be explained by differences in the eye speed, since the eye speed sensitivity of the neurons was also larger for the reward conditions. Pooling the responses by the preferred direction of the neurons attenuated the reward modulation and led to a tighter association between neural activity and behavior. Therefore, a plausible decoder such as the population vector could explain how the frontal eye field both drives behavior and encodes reward beyond behavior.