Cortical Columnar Processing in the Rat Whisker-to-Barrel System

Abstract

processing in the rat whisker-to-barrel system. J. Neurophysiol. 82: 1808Neurophysiol. 82: -1817Neurophysiol. 82: , 1999. Controlled whisker stimulation and single-unit recordings were used to elucidate response transformations that occur during the processing of tactile information from ventral posterior medial thalamus (VPM) through cortical columns in the rat whisker/barrel cortex. Whiskers were either deflected alone, using punctate ramp-and-hold stimuli, or in combination with a random noise vibration applied simultaneously to two or more neighboring whiskers. Quantitative data were obtained from five anatomically defined groups of neurons based on their being located in: VPM, layer IV barrels, layer IV septa, supragranular laminae, and infragranular laminae. Neurons in each of these populations displayed characteristic properties related to their response latency and time course, relative magnitudes of responses evoked by stimulus onset versus offset, strength of excitatory responses evoked by the noise stimulus, and/or the degree to which the noise stimulus, when applied to neighboring whiskers, suppressed or facilitated responses evoked by the columnar whisker. Results indicate that within layer IV itself there are at least two anatomically distinct networks, barrel and septum, that independently process afferent information, transforming thalamic input in similar but quantitatively distinguishable ways. Transformed signals are passed on to circuits in supragranular and infragranular laminae. In the case of supragranular neurons, evidence suggests that circuits there function in a qualitatively different fashion from those in layer IV, diminishing response differentials between weak and strong inputs, rather than enhancing them. Compared to layer IV, the greater heterogeneity of receptive field properties in nongranular layers suggests the existence of multiple, operationally distinct local circuits in the output layers of the cortical column.

Layer-specific network oscillation and spatiotemporal receptive field in the visual cortex

“…This observation is consistent with previous findings in cortical slices that L5 inputs are located more proximally than L2/3 inputs (16,35), giving the L5 inputs greater control of postsynaptic responses. In the somatosensory cortex, the sensory response is also found to be more transient in L5 than in L2/3 (36,37), perhaps due to the same mechanism.…”

Coding principles of the canonical cortical microcircuit in the avian brain

“…From layer 4, axonal projections go to the superficial layers 2/3 and then to the deep layers 5/6, where information is distributed to other cortical and subcortical targets (23,25). In primary auditory (A1), visual (V1), and somatosensory (S1) cortices, receptive fields are simple and separable in layer 4 and more complex and nonlinear in superficial and deep layers (26)(27)(28)(29). Sensory evoked responses are generally sparser and more selective in layers downstream of layer 4 (30-32) although firing rates in layers 4 and 5 are similar in some systems (30,33,34).…”

Layer-Specific Touch-Dependent Facilitation and Depression in the Somatosensory Cortex during Active Whisking

“…4, Table 2). In most studies reporting on adaptation during stimulus trains, stimuli were applied to passive (i.e., motionless) whiskers, and responses were depressed from first cycle to steady state (Simons, 1978;Brumberg et al, 1999;Ahissar et al, 2000Ego-Stengel et al, 2001Chung et al, 2002;Castro-Alamancos, 2004;Khatri et al, 2004;Webber and Stanley, 2004;Higley and Contreras, 2006). In only a few studies, response components of some barrel cortex neurons were facilitated in response to passive touch (Brecht and Sakmann, 2002;Garabedian et al, 2003).…”