Purkinje cells in Crus I and II encode the visual stimulus and the impending choice as monkeys learn a reinforcement based visuomotor association task.

Visuomotor association involves linking an arbitrary visual cue to a well-learned movement. Transient inactivation of Crus I/II impairs primates' ability to learn new associations and delays motor responses without affecting the kinematics of the movement. The simple spikes of Purkinje cells in the Crus regions signal cognitive errors as monkeys learn to associate specific fractal stimuli with movements of the left or right hand.

A cerebro-cerebellar network for learning visuomotor associations.

Consensus is rapidly building to support a role for the cerebellum beyond motor function, but its contributions to non-motor learning remain poorly understood. Here, we provide behavioral, anatomical and computational evidence to demonstrate a causal role for the primate posterior lateral cerebellum in learning new visuomotor associations. Reversible inactivation of the posterior lateral cerebellum of male monkeys impeded the learning of new visuomotor associations, but had no effect on movement parameters, or on well-practiced performance of the same task.

Motor "laziness" constrains fixation selection in real-world tasks.

Humans coordinate their eye, head, and body movements to gather information from a dynamic environment while maximizing reward and minimizing biomechanical and energetic costs. However, such natural behavior is not possible in traditional experiments employing head/body restraints and artificial, static stimuli. Therefore, it is unclear to what extent mechanisms of fixation selection discovered in lab studies, such as inhibition-of-return (IOR), influence everyday behavior.

Neck muscle activity reflects neural patterns of sequential saccade planning in head-restrained primates.

Goal-directed behavior involves the transformation of neural movement plans into appropriate muscle activity patterns. Studies involving single saccades have shown that a rapid pathway links saccade planning in frontal eye fields (FEFs) to neck muscle activity. However, it is unknown if the rapid connection between FEF and neck muscle is also maintained during sequential saccade planning.

Mixed Selectivity in the Cerebellar Purkinje-Cell Response during Visuomotor Association Learning.

Although the cerebellum has been traditionally considered to be exclusively involved in motor control, recent anatomic and clinical studies show that it also has a role in reward-processing. However, the way in which the movement-related and the reward-related neural activity interact at the level of the cerebellar cortex and contribute toward learning is still unclear. Here, we studied the simple spike activity of Purkinje cells in the mid-lateral cerebellum when 2 male monkeys learned to associate a right or left-hand movement with one of two visual symbolic cues.

Mid-lateral cerebellar complex spikes encode multiple independent reward-related signals during reinforcement learning.

Although the cerebellum has been implicated in simple reward-based learning recently, the role of complex spikes (CS) and simple spikes (SS), their interaction and their relationship to complex reinforcement learning and decision making is still unclear. Here we show that in a context where a non-human primate learned to make novel visuomotor associations, classifying CS responses based on their SS properties revealed distinct cell-type specific encoding of the probability of failure after the stimulus onset and the non-human primate's decision. In a different context, CS from the same cerebellar area also responded in a cell-type and learning independent manner to the stimulus that signaled the beginning of the trial.

Neural mechanisms underlying the temporal control of sequential saccade planning in the frontal eye field.

Sequences of saccadic eye movements are instrumental in navigating our visual environment. While neural activity has been shown to ramp up to a threshold before single saccades, the neural underpinnings of multiple saccades is unknown. To understand the neural control of saccade sequences, we recorded from the frontal eye field (FEF) of macaque monkeys while they performed a sequential saccade task.

Preparatory activity links the frontal eye field response with small amplitude motor unit recruitment of neck muscles during gaze planning.

A hallmark of intelligent behavior is that we can separate intention from action. To understand the mechanism that gates the flow of information between motor planning and execution, we compared the activity of frontal eye field neurons with motor unit activity from neck muscles in the presence of an intervening delay period in which spatial information regarding the target was available to plan a response. Although spatially specific delay period activity was present in the activity of frontal eye field neurons, it was absent in motor unit activity.

Neural correlates of goal-directed and non-goal-directed movements.

What are the cortical neural correlates that distinguish goal-directed and non-goal-directed movements? We investigated this question in the monkey frontal eye field (FEF), which is implicated in voluntary control of saccades. Here, we compared FEF activity associated with goal-directed (G) saccades and non-goal-directed (nG) saccades made by the monkey. Although the FEF neurons discharged before these nG saccades, there were three major differences in the neural activity: First, the variability in spike rate across trials decreased only for G saccades.

Assessing within-trial and across-trial neural variability in macaque frontal eye fields and their relation to behaviour.

The conventional approach to understanding neural responses underlying complex computations is to study across-trial averages of repeatedly performed computations from single neurons. When neurons perform complex computations, such as processing stimulus-related information or movement planning, it has been repeatedly shown, through measures such as the Fano factor (FF), that neural variability across trials decreases. However, multiple neurons contribute to a common computation on a single trial, rather than a single neuron contributing to a computation across multiple trials.

Neural Correlates of Reinforcement Learning in Mid-lateral Cerebellum.

The role of the cerebellum in non-motor learning is poorly understood. Here, we investigated the activity of Purkinje cells (P-cells) in the mid-lateral cerebellum as the monkey learned to associate one arbitrary symbol with the movement of the left hand and another with the movement of the right hand. During learning, but not when the monkey had learned the association, the simple spike responses of P-cells reported the outcome of the animal's most recent decision without concomitant changes in other sensorimotor parameters such as hand movement, licking, or eye movement.

Simultaneous analysis of the LFP and spiking activity reveals essential components of a visuomotor transformation in the frontal eye field.

The frontal eye field (FEF) is a key brain region to study visuomotor transformations because the primary input to FEF is visual in nature, whereas its output reflects the planning of behaviorally relevant saccadic eye movements. In this study, we used a memory-guided saccade task to temporally dissociate the visual epoch from the saccadic epoch through a delay epoch, and used the local field potential (LFP) along with simultaneously recorded spike data to study the visuomotor transformation process. We showed that visual latency of the LFP preceded spiking activity in the visual epoch, whereas spiking activity preceded LFP activity in the saccade epoch.