Neuronal Variability of MSTd Neurons Changes Differentially With Eye Movement and Visually Related Variables

Abstract

Neurons in macaque cortical area MSTd are driven by visual motion and eye movement related signals. This multimodal characteristic makes MSTd an ideal system for studying the dependence of neuronal activity on different variables. Here, we analyzed the temporal structure of spiking patterns during visual motion stimulation using 2 distinct behavioral paradigms: fixation (FIX) and optokinetic response. For the FIX condition, inter- and intra-trial variability of spiking activity decreased with increasing stimulus strength, complying with a recent neurophysiological study reporting stimulus-related decline of neuronal variability. In contrast, for the optokinetic condition variability increased together with increasing eye velocity while retinal image velocity remained low. Analysis of stimulus signal variability revealed a correlation between the normalized variance of image velocity and neuronal variability, but no correlation with normalized eye velocity variance. We further show that the observed difference in neuronal variability allows classifying spike trains according to the paradigm used, even when mean firing rates (FRs) were similar. The stimulus-dependence of neuronal variability may result from the local network structure and/or the variability characteristics of the input signals, but may also reflect additional timing-based mechanisms independent of the neuron's mean FR and related to the modality driving the neuron.

Behavioral context determines network state and variability dynamics in monkey motor cortex

“…Furthermore, in vivo intracellular recordings in anesthetized rat somatosensory cortex showed that FF is equal or even slightly smaller than the CV² (FF ≤ CV²) under stationary conditions (Nawrot et al 2007). In visual cortex of behaving monkeys, Brostek et al (2013) showed that spiking statistics of MSTd neurons, both during the presentation of moving visual stimuli and during ocular following, are in good agreement with the renewal prediction. Unfortunately the authors did not test the renewal prediction before stimulus presentation and/or eye movements, which would have been better suited for comparison with our results during wait.…”

Behavioral Context Determines Network State and Variability Dynamics in Monkey Motor Cortex

“…Furthermore, in vivo intracellular recordings in anesthetized rat somatosensory cortex showed that FF is equal or even slightly smaller than the CV 2 (FF ≤ CV 2 ) under stationary conditions (Nawrot et al, 2007 ). In visual cortex of behaving monkeys, Brostek et al ( 2013 ) showed that spiking statistics of MSTd neurons, both during the presentation of moving visual stimuli and during ocular following, are in good agreement with the renewal prediction. Unfortunately the authors did not test the renewal prediction before stimulus presentation and/or eye movements, which would have been better suited for comparison with our results during wait .…”

Distinct dynamics of ramping activity in the frontal cortex and caudate nucleus in monkeys

“…VarCE measures the portion of the spike count variance that can be attributed to the stochastic rate parameter and complements more commonly used measures of total spike count variability, such as Fano factor, coefficient of variation, etc. (Brostek et al 2013). It has been especially useful as a signature of neural computations related to temporal accumulation in the context of decision making (Churchland et al 2011;de Lafuente et al 2015;Marcos et al 2013).…”