An elaborate sweep-stick code in rat barrel cortex

Abstract

In rat barrel cortex, feature encoding schemes uncovered during broadband whisker stimulation are hard to reconcile with the simple stick-slip code observed during natural tactile behaviors, and this has hindered the development of a generalized computational framework. By designing broadband artificial stimuli to sample the inputs encoded under natural conditions, we resolve this disparity while markedly increasing the percentage of deep layer neurons found to encode whisker movements, as well as the diversity of these encoded features. Deep layer neurons encode two main types of events, sticks and sweeps, corresponding to high angular velocity bumps and large angular displacements with high velocity, respectively. Neurons can exclusively encode sticks or sweeps, or they can encode both, with or without direction selectivity. Beyond unifying coding theories from naturalistic and artificial stimulation studies, these findings delineate a simple and generalizable set of whisker movement features that can support a range of perceptual processes.

Pre-neuronal processing of haptic sensory cues via dispersive high-frequency vibrational modes

“…The DVT hypothesis is consistent with most if not all experimental findings related to verifying the “stick-slip” hypothesis [22, 34-38]. Various coding schemes have been proposed for interpretation of reverse correlation studies [14, 16, 17] of stick-slip induced neural activity including fast variation of whisker curvature [21, 24], of angular velocity [21, 35, 37], associated angular acceleration peaks [17, 34], rotational forces [17], or more complex multiplexed products of kinematic and mechanical variables [64, 65]. The DVT hypothesis implies that all these variables do not form an independent basis in a multi-dimensional textural feature space, but rather they all are dependent variables of the same process that generates higher-order modes: conversion of elastic strain energy stored in a whisker bending that is released into a kinetic energy of angular whisker acceleration and transformed into high-frequency modal vibrations at collision (Fig.6).…”

“…Later vibrational events at the whisker follicle defined by arrival of lower order modes can be detected using sparse rate coding that is slower and less metabolically expensive. The overall sensory intake is multiplexed, therefore, between these slow rate-coded channels and the ultrafast time-coded channels [19, 62, 65].…”

“…The overall sensory intake is multiplexed, therefore, between these slow rate-coded channels and the ultrafast time-coded channels [19,62,65].…”

In vitro neurons learn and exhibit sentience when embodied in a simulated game-world

“…Pilot study 3 adopted the layout in Figure 4 D and changed to the combined rate (4–40Hz) and place-coding method of data input. This combined rate and place coding has compelling biological similarities conceptually to the rodent barrel cortex, suggesting this encoding is physiologically coherent ( Harrell et al., 2020 ; Ly et al., 2012 ; Petersen et al., 2001 ). Gameplay for the final fifteen minutes for each culture type was compared ( Figure 4 E and Table S1 ).…”

Cortical circuitry mediating interareal touch signal amplification

“…Vibrissal S1 and S2 are richly interconnected 2 , 22 , 37 , 38 and respond robustly to whisker touch. 2 , 23 , 39 Do broadly tuned touch neurons contribute disproportionately to the touch signal carried between iso-somatotopic vS1 and vS2 subregions? We labeled projecting neurons in both areas by focally injecting rAAV2- retro -FLEX-tdTomato into L2/3 of either vS1 or vS2 40 ( Figures 3A and 3B ).…”