No abstract

Variability in cortical neuronal responses to sensory stimuli and in perceptual decision making performance is substantial. Moment-tomoment fluctuations in waking state or arousal can account for much of this variability. Yet, this variability is rarely characterized across the full spectrum of waking states, leaving the characteristics of the optimal state for sensory processing unresolved. Using pupillometry in concert with extracellular multiunit and intracellular whole-cell recordings, we found that the magnitude and reliability of visually evoked responses in primary visual cortex (V1) of awake, passively behaving male mice increase as a function of arousal and are largest during sustained locomotion periods. During these high-arousal, sustained locomotion periods, cortical neuronal membrane potential was at its most depolarized and least variable. Contrastingly, behavioral performance of mice on two distinct visual detection tasks was generally best at a range of intermediate arousal levels, but worst during high arousal with locomotion. These results suggest that large, reliable responses to visual stimuli in V1 occur at a distinct arousal level from that associated with optimal visual detection performance. Our results clarify the relation between neuronal responsiveness and the continuum of waking states, and suggest new complexities in the relation between primary sensory cortical activity and behavior.

Both vagal nerve stimulation (VNS) and responsive neurostimulation (RNS System) are treatment options for medically refractory focal epilepsy. The mechanism of action of both devices remains poorly understood. Limited prior evidence suggests that acute VNS stimulation may reduce epileptiform activity and cause EEG desynchronization on electrocorticography (ECoG). Our study aims to isolate effects of VNS on ECoG as recorded by RNS System in patients who have both devices, by comparing ECoG samples with and without acute VNS stimulation.Methods: Ten 60-second ECoGs each from 22 individuals at 3 epilepsy centers were obtainedd5 ECoGs with VNS "off" and 5 ECoGs with VNS "on." Electrocorticograps containing seizures or loss of telemetry connection artifact were excluded from analysis (total of 169 ECoGs were included). Electrocorticographs were analyzed for differences in spectral content by generating average spectrograms for "on" and "off" states and using a linear mixed-effects model to isolate effects of VNS stimulation.Results: Acute VNS stimulation reduced average power in the theta band by 4.9%, beta band by 3.8%, and alpha band by 2.5%. The reduction in theta power reached statistical significance with a P value of ,0.05. Conclusions:Our results provide evidence that acute VNS stimulation results in desynchronization of specific frequency bands (salient decrease in theta and beta bands, smaller decrease in alpha band) in ECoGs recorded by the RNS device in patients with dual (VNS and RNS) neurostimulators. This finding offers support for desynchronization as a theorized mechanism of action of VNS. Further research may lead to future improved neurostimulator efficacy by informing optimal stimulation programming parameters.