The rodent whisker sensorimotor

system is an attractive and relatively simple model system for studying mammalian active sensory processing (reviewed in Brecht, 2007, Petersen, 2007 and Diamond et al., 2008). During exploratory behavior, rodents move their whiskers back and forth at high frequencies (typically 5–20 Hz) scanning their surroundings to obtain check details tactile information about nearby objects. Rodents can use their whiskers to actively gather spatial (Hutson and Masterton, 1986, Harris et al., 1999, Krupa et al., 2004, Knutsen et al., 2006, Curtis and Kleinfeld, 2009 and O’Connor et al., 2010) and textural tactile sensory information (Guić-Robles et al., 1989, learn more Carvell and Simons, 1990, von Heimendahl et al., 2007 and Jadhav et al., 2009). Extracellular recordings in the barrel cortex

of awake behaving rodents have begun to shed light on the action potential coding of tactile sensory information (Krupa et al., 2004, von Heimendahl et al., 2007, Stüttgen and Schwarz, 2008, Jadhav et al., 2009, Curtis and Kleinfeld, 2009, Gerdjikov et al., 2010 and O’Connor et al., 2010). However, little is known about the mechanisms driving the spike coding of whisker sensory perception. Action potentials are driven by synaptic interactions, with the majority of cortical unitary postsynaptic potentials being small in amplitude evoking only subthreshold changes in membrane potential (Vm) (Crochet et al., 2005, Bruno and Sakmann, 2006 and Lefort et al., 2009). Previous studies have investigated subthreshold Vm dynamics evoked by passive whisker stimuli in anesthetised animals

(Moore and Nelson, 1998, Zhu and Connors, 1999, Petersen et al., 2003, Brecht et al., 2003, Wilent and Contreras, 2005, Katz et al., 2006, Higley and Contreras, 2006 and Heiss et al., 2008). However, there are important changes in cortical dynamics during active sensory exploration compared to quiet wakefulness or anesthesia. Quiet wakefulness is characterized in layer 2/3 neurons of mouse barrel cortex by large-amplitude, slow (1–5 Hz), whatever and highly synchronized Vm fluctuations; a low firing rate of pyramidal cells and non-fast-spiking GABAergic neurons; but a high firing rate of fast-spiking GABAergic neurons (Crochet and Petersen, 2006, Poulet and Petersen, 2008 and Gentet et al., 2010). During active whisking in air, the slow activity is suppressed and barrel cortex neurons exhibit fast low-amplitude Vm fluctuations that are less correlated in nearby neurons and the input resistance of pyramidal cells is slightly reduced (Crochet and Petersen, 2006, Poulet and Petersen, 2008 and Gentet et al., 2010).