The downs and ups of sensory deprivation: evidence for firing rate homeostasis in vivo

Abstract

Homeostatic adjustment of neuronal firing rates is considered a vital mechanism to keep neurons operating in their optimal range despite dynamically changing input. Two studies in this issue of Neuron, Hengen et al. (2013) and Keck et al. (2013), provide evidence for firing rate homeostasis in the neocortex of freely behaving rodents.

Figure 1. Schematic representation of evidence for firing rate homeostasis in vivo

A. Hengen et al. used chronic multielectrode recordings fromall layers of the visual cortex offreely behaving juvenile rats to show that firing rates of inhibitory neurons (pink line) and putative pyramidal neurons (red line),which decreased following monocular lid suture, returned to baseline 24 hrs later despite continued visual deprivation. Controls (black line) were unchanged. B. Keck et al. used calcium imaging of GCaMP signals from neurons in L2/3 and L5 ofthe visual cortex ofawake adult mice to show that overall activity levels, which decreased withinsix hrs of bilateral retinal lesions (red line), returned to mock-lesioned control levels (black line) within 24 hrs, despite the irreversible loss of visual input.