Laminar‐specific encoding of texture elements in rat barrel cortex

Abstract

Texture discrimination by rats is exquisitely guided by fine-grain mechanical stick-slip motions of the face whiskers as they encounter, stick to and slip past successive texture-defining surface features such as bumps and grooves. Neural encoding of successive stick-slip texture events will be shaped by adaptation, common to all sensory systems, whereby receptor and neural responses to a stimulus are affected by responses to preceding stimuli, allowing resetting to signal novel information. Additionally, when a whisker is actively moved to contact and brush over surfaces, that motion itself generates neural responses that could cause adaptation of responses to subsequent stick-slip events. Nothing is known about encoding in the rat whisker system of stick-slip events defining textures of different grain or the influence of adaptation from whisker protraction or successive texture-defining stick-slip events. Here we recorded responses from halothane-anaesthetized rats in response to texture-defining stimuli applied to passive whiskers. We demonstrate that: across the columnar network of the whisker-recipient barrel cortex, adaptation in response to repetitive stick-slip events is strongest in uppermost layers and equally lower thereafter; neither whisker protraction speed nor stick-slip frequency impede encoding of stick-slip events at rates up to 34.08 Hz; and layer 2 normalizes responses to whisker protraction to resist effects on texture signalling. Thus, within laminar-specific response patterns, barrel cortex reliably encodes texture-defining elements even to high frequencies.

The Neural Origin of Nociceptive-Induced Gamma-Band Oscillations

“…As a result, electrophysiological data from 31 sessions were included in the analysis, as follows: 16 sessions in which the microelectrode sampled activity from superficial layers (,0.9 mm from cortical surface, mainly layers II-IV) and 15 sessions in which the microelectrode-sampled activity from deep layers (.1.1 mm from cortical surface, mainly layers V/VI). The rationale for looking separately at data sampled from superficial and deep layers was the fact that gammaband oscillations are more prominent in superficial layers, where local recurrent connections are more abundant than in deep layers (Allitt et al, 2017;Bruyns-Haylett et al, 2017).…”

Rats Generate Vibrissal Sensory Evidence until Boundary Crossing Triggers a Decision

“…The use of high-speed imaging techniques has allowed the study of kinematics at elevated temporal and spatial resolutions as the whiskers of an awake rat or mouse come into contact with a surface. A consensus is forming that the critical element supporting texture discrimination is the stick-slip event [1,9,[14][15][16][17][18]. This may also be true for fingertips, where lateral forces create stick-slip skin micromotion that is especially effective in exciting primary afferents [16,19,20].…”

Physiological noise optimizes multiplexed coding of vibrotactile-like signals in somatosensory cortex

“…Several in vivo studies have already established that at least some S1 neurons -depending on their afferent input (Saal et al, 2015) -respond to vibrotactile stimuli with precisely times spikes (Allitt et al, 2017;Arabzadeh et al, 2005;Ewert et al, 2015;Ewert et al, 2008;Harvey et al, 2013;Jadhav et al, 2009;Lieber and Bensmaia, 2019). The rate of those spikes can also carry information; for instance, Jadhav et al (2009) found that firing rate and synchrony both increase with roughness, but synchrony varied more consistently than rate for subtle differences in texture.…”