@article {46987,
	title = {Low-noise encoding of active touch by layer 4 in the somatosensory cortex.},
	journal = {eLife},
	volume = {4},
	year = {2015},
	month = {2015 Aug 6},
	abstract = {<p>Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with \&gt;70\% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise.</p>
},
	issn = {2050-084X},
	doi = {10.7554/eLife.06619},
	author = {Andrew Hires, Samuel and Gutnisky, Diego A and Yu, Jianing and O{\textquoteright}Connor, Daniel H and Svoboda, Karel}
}
@article {47354,
	title = {Neural coding in barrel cortex during whisker-guided locomotion.},
	journal = {eLife},
	volume = {4},
	year = {2015},
	month = {2015 Dec 23},
	abstract = {<p>Animals seek out relevant information by moving through a dynamic world, but sensory systems are usually studied under highly constrained and passive conditions that may not probe important dimensions of the neural code. Here, we explored neural coding in the barrel cortex of head-fixed mice that tracked walls with their whiskers in tactile virtual reality. Optogenetic manipulations revealed that barrel cortex plays a role in wall-tracking. Closed-loop optogenetic control of layer 4 neurons can substitute for whisker-object contact to guide behavior resembling wall tracking. We measured neural activity using two-photon calcium imaging and extracellular recordings. Neurons were tuned to the distance between the animal snout and the contralateral wall, with monotonic, unimodal, and multimodal tuning curves. This rich representation of object location in the barrel cortex could not be predicted based on simple stimulus-response relationships involving individual whiskers and likely emerges within cortical circuits.</p>
},
	issn = {2050-084X},
	doi = {10.7554/eLife.12559},
	author = {Sofroniew, Nicholas James and Vlasov, Yurii A and Andrew Hires, Samuel and Freeman, Jeremy and Svoboda, Karel}
}
