Rapid Input-Output Transformation between Local Field Potential and Spiking Activity during Sensation but not Action in the Superior Colliculus

Sensorimotor transformation is the sequential process of registering a sensory signal in the environment and then responding with the relevant movement at an appropriate time. For visually guided eye movements, neural signatures in the form of spiking activity of neurons have been extensively studied along the dorsoventral axis of the superior colliculus (SC). In con-trast, the local field potential (LFP), which represents the putative input to a region, remains largely unexplored in the SC. We therefore compared amplitude levels and onset times of both spike bursts and LFP modulations recorded simultaneously with a laminar probe along the dorsoventral axis of SC in 3 male monkeys performing the visually guided delayed saccade task. Both signals displayed a gradual transition from sensory activity in the superficial layers to a predominantly motor response in the deeper layers, although the transition from principally sensory to mostly motor response occurred ;500 lm deeper for the LFP. For the sensory response, LFP modulation preceded spike burst onset by ,5 ms in the superficial and in-termediate layers and only when data were analyzed on a trial-by-trial basis. The motor burst in the spiking activity led LFP modulation by .25 ms in the deeper layers. The results reveal a fast and efficient input-output transformation between LFP modulation and spike burst in the visually responsive layers activity during sensation but not during action. The spiking pat-tern observed during the movement phase is likely dominated by intracollicular processing that is not captured in the LFP.