Is there an intrinsic relationship between LFP beta oscillation amplitude and firing rate of individual neurons in monkey motor cortex?

Abstract

Beta oscillations are prominent in motor cortical local field potentials (LFPs), and their relationship to the local neuronal spiking activity has been extensively studied. Many studies have shown that in motor cortex, spikes of individual neurons tend to lock to the phase of LFP beta oscillations. However, there are contradictory results concerning whether there is also an intrinsic relationship between the amplitude of LFP beta oscillations and the firing rate of individual neurons. To resolve this controversial issue, we correlated the LFP beta oscillation amplitude recorded in macaque motor cortex with spike counts of individual neurons during visuomotor behavior, in two different manners.First, in an analysis termed task-related correlation, we included data obtained across all behavioral task epochs. These task-related correlations were frequently significant, and of either negative or positive sign. Second, in an analysis termed trial-by-trial correlation, we included only data from a welldefined steady-state pre-cue epoch, and calculated the correlations across trials. Such trial-by-trial correlations were weak and rarely significant. We conclude that there is no intrinsic relationship between the spike count of individual neurons and LFP beta oscillation amplitude in macaque motor cortex, beyond each of these signals being modulated by external factors such as the behavioral task.

Beta Oscillations in Working Memory, Executive Control of Movement and Thought, and Sensorimotor Function

“…To compare beta modulations across different studies, it is important to first understand the underlying relationship between the LFP and neuronal spiking activity. Many studies have shown that sensorimotor LFP beta at least partly reflects local activity, with the spikes of inhibitory interneurons and pyramidal tract neurons locking to the phase of beta (Murthy and Fetz, 1996;Donoghue et al, 1998;Baker et al, 1999;Jackson et al, 2002;Denker et al, 2011;Canolty et al, 2012;Confais et al, 2019). However, whether there is also an intrinsic relationship between the amplitude of beta oscillations and neuronal spike rates has been controversial (Canolty et al, 2012;Rule et al, 2017).…”

“…However, whether there is also an intrinsic relationship between the amplitude of beta oscillations and neuronal spike rates has been controversial (Canolty et al, 2012;Rule et al, 2017). A recent study resolved this issue (Confais et al, 2019) by showing that spike rates and beta amplitude have no intrinsic correlation, but are both modulated by external factors, such as a behavioral task.…”

“…Second, in humans, some evidence suggests beta frequency is effector specific, with frequencies Ͼ20 Hz associated with lower limbs and frequencies Ͻ20 Hz with upper limbs (Pfurtscheller et al, 2000;Neuper and Pfurtscheller, 2001). Third, in the macaque monkey, two beta bands, at ϳ20 and ϳ30 Hz, are present in motor cortical LFPs (Kilavik et al, 2012), and phase-locking analysis of neuronal spiking activity suggests that both bands have at least partly a local origin within motor cortex (Confais et al, 2019). Whereas those particular studies found similar modulations of both bands with behavioral context and movement direction, other work found that prestimulus beta frequencies Ͻ20 Hz were positively correlated with reaction times, whereas higher beta frequencies (Ͼ20 Hz) were negatively correlated (Zhang et al, 2008;Chandrasekaran et al, 2019).…”