Whisking-Related Changes in Neuronal Firing and Membrane Potential Dynamics in the Somatosensory Thalamus of Awake Mice

• Published in: Cell reports (Cambridge) 2015-10, Vol.13 (4), p.647-656
• Main Authors: Urbain, Nadia, Salin, Paul A., Libourel, Paul-Antoine, Comte, Jean-Christophe, Gentet, Luc J., Petersen, Carl C.H.
• Format: Article
• Language: English
• Subjects: Action Potentials - physiology; Animals; Electroencephalography; Electromyography; Life Sciences; Male; Membrane Potentials - physiology; Mice; Mice, Inbred C57BL; Neocortex - cytology; Neocortex - physiology; Neurons - cytology; Neurons - physiology; Thalamus - cytology; Thalamus - physiology; Vibrissae - physiology
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2015.09.029

The thalamus transmits sensory information to the neocortex and receives neocortical, subcortical, and neuromodulatory inputs. Despite its obvious importance, surprisingly little is known about thalamic function in awake animals. Here, using intracellular and extracellular recordings in awake head-restrained mice, we investigate membrane potential dynamics and action potential firing in the two major thalamic nuclei related to whisker sensation, the ventral posterior medial nucleus (VPM) and the posterior medial group (Pom), which receive distinct inputs from brainstem and neocortex. We find heterogeneous state-dependent dynamics in both nuclei, with an overall increase in action potential firing during active states. Whisking increased putative lemniscal and corticothalamic excitatory inputs onto VPM and Pom neurons, respectively. A subpopulation of VPM cells fired spikes phase-locked to the whisking cycle during free whisking, and these cells may therefore signal whisker position. Our results suggest differential processing of whisking comparing thalamic nuclei at both sub- and supra-threshold levels. [Display omitted] •Intracellular and extracellular recordings in somatosensory thalamus of awake mice•State dependence and heterogeneity of activity of thalamic cells•During whisking, selective increase in fast-rising EPSPs in VPM neurons•Whisking-cycle phase-locked action potential firing in a subset of VPM neurons Urbain et al. measure membrane potential and action potential firing in the somatosensory thalamus of awake mice during whisker movement. Whisking increased large fast synaptic inputs specifically in VPM cells. Compared to Pom neurons, VPM cells increased firing more strongly during whisking and were more strongly modulated by whisking phase.