scholarly journals Layer 4 barrel cortex neurons retain their response properties during whisker replacement

2018 ◽  
Vol 120 (5) ◽  
pp. 2218-2231
Author(s):  
Eduard Maier ◽  
Michael Brecht
Keyword(s):  
Cortical Neurons ◽  
Barrel Cortex ◽  
Field Potential ◽  
Nerve Fibers ◽  
Outer Root Sheath ◽  
Response Properties ◽  
Perceptual Stability ◽  
Root Sheath ◽  
Whisker Length ◽  
Layer 4

Bodies change continuously, but we do not know if and how these changes affect somatosensory cortex. We address this issue in the whisker-barrel-cortex-pathway. We ask how outgrowing whiskers are mapped onto layer 4 barrel neuron responses. Half of whisker follicles contained dual whiskers, a shorter presumably outgrowing whisker (referred to as young whisker) and a longer one (referred to as old whisker). Young whiskers were much thinner than old ones but were inserted more deeply into the whisker follicle. Both whiskers were embedded in one outer root sheath surrounded by a common set of afferent nerve fibers. We juxtacellularly identified layer 4 barrel neurons representing dual whiskers with variable whisker length differences in anesthetized rats. Strength and latency of neuronal responses were strongly correlated for deflections of young and old whiskers but were not correlated with whisker length. The direction preferences of young and old whiskers were more similar than expected by chance. Old whiskers evoked marginally stronger and slightly shorter latency spike and local field potential responses than young whiskers. Our data suggest a conservative rewiring mechanism, which connects young whiskers to existing peripheral sensors. The fact that layer 4 barrel neurons retain their response properties is remarkable given the different length, thickness, and insertion depth of young and old whiskers. Retention of cortical response properties might be related to the placement of young and old whisker in one common outer root sheath and may contribute to perceptual stability across whisker replacement. NEW & NOTEWORTHY A particularly dramatic bodily change is whisker regrowth, which involves the formation of dual whisker follicles. Our results suggest that both whiskers are part of the same mechanoreceptive unit. Despite their distinct whisker length and thickness, responses of single cortical neurons to young and old whisker deflection were similar in strength, latency, and directional tuning. We suggest the congruence of young and old whisker cortical responses contributes to perceptual stability over whisker regrowth.

scholarly journals Comprehensive mapping of whisker-evoked responses reveals broad, sharply tuned thalamocortical input to layer 4 of barrel cortex

2011 ◽  
Vol 105 (5) ◽  
pp. 2421-2437 ◽  
Author(s):  
Noah C. Roy ◽  
Thomas Bessaih ◽  
Diego Contreras
Keyword(s):  
Cortical Neurons ◽  
Barrel Cortex ◽  
Current Source ◽  
Field Potential ◽  
Fundamental Information ◽  
Layer 4 ◽  
Density Analysis ◽  
Evoked Activity ◽  
Rats And Mice

Cortical neurons are organized in columns, distinguishable by their physiological properties and input-output organization. Columns are thought to be the fundamental information-processing modules of the cortex. The barrel cortex of rats and mice is an attractive model system for the study of cortical columns, because each column is defined by a layer 4 (L4) structure called a barrel, which can be clearly visualized. A great deal of information has been collected regarding the connectivity of neurons in barrel cortex, but the nature of the input to a given L4 barrel remains unclear. We measured this input by making comprehensive maps of whisker-evoked activity in L4 of rat barrel cortex using recordings of multiunit activity and current source density analysis of local field potential recordings of animals under light isoflurane anesthesia. We found that a large number of whiskers evoked a detectable response in each barrel (mean of 13 suprathreshold, 18 subthreshold) even after cortical activity was abolished by application of muscimol, a GABAA agonist. We confirmed these findings with intracellular recordings and single-unit extracellular recordings in vivo. This constitutes the first direct confirmation of the hypothesis that subcortical mechanisms mediate a substantial multiwhisker input to a given cortical barrel.

Angular Tuning and Velocity Sensitivity in Different Neuron Classes Within Layer 4 of Rat Barrel Cortex

2004 ◽  
Vol 91 (1) ◽  
pp. 223-229 ◽  
Author(s):  
Soo-Hyun Lee ◽  
Daniel J. Simons
Keyword(s):  
Cortical Neurons ◽  
Barrel Cortex ◽  
Deflection Angle ◽  
Field Potential ◽  
Response Dynamics ◽  
Velocity Sensitivity ◽  
Deflection Amplitude ◽  
Layer 4 ◽  
Local Circuitry ◽  
Local Circuits

Local circuitry within layer IV whisker-related barrels is preferentially sensitive to thalamic population firing synchrony, and neurons respond most vigorously to stimuli, such as high-velocity whisker deflections, that evoke it. Field potential recordings suggest that thalamic barreloid neurons having similar angular preferences fire synchronously. To examine whether angular tuning of cortical neurons might also be affected by thalamic firing synchrony, we characterized responses of layer IV units to whisker deflections that varied in angular direction and velocity. Barrel regular-spike units (RSUs) became more tuned for deflection angle with slower whisker movements. Deflection amplitude had no affect. Barrel fast-spike units (FSUs) were poorly tuned for deflection angle, and their responses remained constant with different deflection velocity. The dependence of angular tuning on deflection velocity among barrel RSUs appears to reflect the same underlying response dynamics that determine their velocity sensitivity and receptive field focus. Unexpectedly, septal RSUs and FSUs are largely similar to their barrel counterparts despite available evidence suggesting that they receive different afferent inputs and are embedded within different local circuits.

scholarly journals Three rules govern thalamocortical connectivity of fast-spike inhibitory interneurons in the visual cortex

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Yulia Bereshpolova ◽  
Xiaojuan Hei ◽  
Jose-Manuel Alonso ◽  
Harvey A Swadlow
Keyword(s):  
Visual Cortex ◽  
Cortical Neurons ◽  
Field Potential ◽  
Inhibitory Interneurons ◽  
Visual Response ◽  
Response Properties ◽  
Layer 4 ◽  
Visual Cortical ◽  
Feed Forward Inhibition ◽  
Fast Spike

Some cortical neurons receive highly selective thalamocortical (TC) input, but others do not. Here, we examine connectivity of single thalamic neurons (lateral geniculate nucleus, LGN) onto putative fast-spike inhibitory interneurons in layer 4 of rabbit visual cortex. We show that three ‘rules’ regulate this connectivity. These rules concern: (1) the precision of retinotopic alignment, (2) the amplitude of the postsynaptic local field potential elicited near the interneuron by spikes of the LGN neuron, and (3) the interneuron’s response latency to strong, synchronous LGN input. We found that virtually all first-order fast-spike interneurons receive input from nearly all LGN axons that synapse nearby, regardless of their visual response properties. This was not the case for neighboring regular-spiking neurons. We conclude that profuse and highly promiscuous TC inputs to layer-4 fast-spike inhibitory interneurons generate response properties that are well-suited to mediate a fast, sensitive, and broadly tuned feed-forward inhibition of visual cortical excitatory neurons.

scholarly journals Sensory computations in the cuneate nucleus of macaques

2021 ◽  
Vol 118 (49) ◽  
pp. e2115772118
Author(s):  
Aneesha K. Suresh ◽  
Charles M. Greenspon ◽  
Qinpu He ◽  
Joshua M. Rosenow ◽  
Lee E. Miller ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Receptive Fields ◽  
Nerve Fibers ◽  
Cuneate Nucleus ◽  
Local Skin ◽  
Response Properties ◽  
Conventional View ◽  
Random Dot Patterns ◽  
Object Features ◽  
Spatiotemporal Response

Tactile nerve fibers fall into a few classes that can be readily distinguished based on their spatiotemporal response properties. Because nerve fibers reflect local skin deformations, they individually carry ambiguous signals about object features. In contrast, cortical neurons exhibit heterogeneous response properties that reflect computations applied to convergent input from multiple classes of afferents, which confer to them a selectivity for behaviorally relevant features of objects. The conventional view is that these complex response properties arise within the cortex itself, implying that sensory signals are not processed to any significant extent in the two intervening structures—the cuneate nucleus (CN) and the thalamus. To test this hypothesis, we recorded the responses evoked in the CN to a battery of stimuli that have been extensively used to characterize tactile coding in both the periphery and cortex, including skin indentations, vibrations, random dot patterns, and scanned edges. We found that CN responses are more similar to their cortical counterparts than they are to their inputs: CN neurons receive input from multiple classes of nerve fibers, they have spatially complex receptive fields, and they exhibit selectivity for object features. Contrary to consensus, then, the CN plays a key role in processing tactile information.

scholarly journals Local and thalamic origins of ongoing and sensory evoked cortical correlations

2016 ◽  
Author(s):  
Katayun Cohen-Kashi Malina ◽  
Boaz Mohar ◽  
Akiva N. Rappaport ◽  
Miao Liu
Keyword(s):  
Barrel Cortex ◽  
Field Potential ◽  
Sensory Response ◽  
Cortical Cells ◽  
Synaptic Inputs ◽  
Correlated Activity ◽  
Layer 4 ◽  
Lower Variability ◽  
Intact Cortex ◽  
Sensory Evoked

Thalamic inputs of layer 4 (L4) cells in sensory cortices are outnumbered by local connections. Thus, it was suggested that robust sensory response in L4 emerges due to synchronized thalamic activity. In order to investigate the role of both inputs in generation of cortical synchronization, we isolated the thalamic excitatory inputs of cortical cells by optogenetically silencing cortical firing. In anesthetized mice, we measured the correlation between isolated thalamic synaptic inputs of simultaneously patched nearby L4 cells of the barrel cortex. In contrast to correlated activity of excitatory synaptic inputs in the intact cortex, isolated thalamic inputs exhibit lower variability and asynchronous spontaneous and sensory evoked inputs. These results were further supported in awake mice when we recorded the excitatory inputs of individual cortical cells simultaneously with the local field potential (LFP) in a nearby site. Our results therefore indicate that cortical synchronization emerges by intracortical coupling.

scholarly journals Cross-Whisker Adaptation of Neurons in Layer 2/3 of the Rat Barrel Cortex

2021 ◽  
Vol 15 ◽  
Author(s):  
Yonatan Katz ◽  
Ilan Lampl
Keyword(s):  
Cortical Neurons ◽  
Barrel Cortex ◽  
Receptive Fields ◽  
Repetitive Stimulation ◽  
Complex Environments ◽  
Cortical Cells ◽  
High Responsiveness ◽  
Layer 2 ◽  
Layer 4 ◽  
Stimulation Of

Neurons in the barrel cortex respond preferentially to stimulation of one principal whisker and weakly to several adjacent whiskers. Such integration exists already in layer 4, the pivotal recipient layer of thalamic inputs. Previous studies show that cortical neurons gradually adapt to repeated whisker stimulations and that layer 4 neurons exhibit whisker specific adaptation and no apparent interactions with other whiskers. This study aimed to study the specificity of adaptation of layer 2/3 cortical cells. Towards this aim, we compared the synaptic response of neurons to either repetitive stimulation of one of two responsive whiskers or when repetitive stimulation of the two whiskers was interleaved. We found that in most layer 2/3 cells adaptation is whisker-specific. These findings indicate that despite the multi-whisker receptive fields in the cortex, the adaptation process for each whisker-pathway is mostly independent of other whiskers. A mechanism allowing high responsiveness in complex environments.

A Selectable Biomarker in Hair Follicle Cycles – Cathepsins: A Preliminary Study in Murine

2021 ◽  
pp. 1-7
Author(s):  
Jingzhu Bai ◽  
Zijian Gong ◽  
Qingfang Xu ◽  
Haiyan Chen ◽  
Qiaoping Chen ◽  
...  
Keyword(s):  
Hair Follicle ◽  
Hair Cycle ◽  
Biological Factors ◽  
Outer Root Sheath ◽  
Physiological Processes ◽  
Intervention Measures ◽  
Root Sheath ◽  
Inner Root Sheath ◽  
Preliminary Study ◽  
Paraffin Method

<b><i>Background/Objective:</i></b> Hair cycle is regulated by many biological factors. Cathepsins are involved in various physiological processes in human skin. Here, we investigated the cathepsin expression and distribution changes in follicular growth cycles for better understanding the hair cycles and to explore new intervention measures. <b><i>Methods:</i></b> The 24 mice (C57BL/6, female, 7-week old) were selected and removed the back hair via rosin/paraffin method. At Day 8, Day 20, and Day 25, biopsy on post-plucking area was done. Immunohistochemical staining, Western blot, and Q-PCR were used to test the cathepsin B/D/L/E. <b><i>Results:</i></b> In anagen, cathepsins (B, D, L, and E) were distributed in the hair follicle matrix, inner hair root sheath, and hair. In catagen, cathepsins were mainly observed in un-apoptosis inner root sheath and outer root sheath. Expression of cathepsins B-mRNA and L-mRNA was decreased from anagen and catagen to telogen. Cathepsin D-mRNA was increased in catagen and then decreased in telogen. Cathepsin E-mRNA was decreased in catagen and slightly increased in telogen. <b><i>Conclusions:</i></b> The distribution and expression of cathepsins B, D, L, and E in hair follicle changed with hair growth process which indicated that cathepsins might act as selectable biomarkers of hair cycle in different stages.

scholarly journals Loss of Calretinin in L5a impairs the formation of the barrel cortex leading to abnormal whisker-mediated behaviors

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Mingzhao Su ◽  
Junhua Liu ◽  
Baocong Yu ◽  
Kaixing Zhou ◽  
Congli Sun ◽  
...  
Keyword(s):  
Information Integration ◽  
Pyramidal Neurons ◽  
Barrel Cortex ◽  
Sensory Information ◽  
Membrane Excitability ◽  
Novelty Preference ◽  
Layer 4 ◽  
Dendritic Complexity ◽  
Cortex System

AbstractThe rodent whisker-barrel cortex system has been established as an ideal model for studying sensory information integration. The barrel cortex consists of barrel and septa columns that receive information input from the lemniscal and paralemniscal pathways, respectively. Layer 5a is involved in both barrel and septa circuits and play a key role in information integration. However, the role of layer 5a in the development of the barrel cortex remains unclear. Previously, we found that calretinin is dynamically expressed in layer 5a. In this study, we analyzed calretinin KO mice and found that the dendritic complexity and length of layer 5a pyramidal neurons were significantly decreased after calretinin ablation. The membrane excitability and excitatory synaptic transmission of layer 5a neurons were increased. Consequently, the organization of the barrels was impaired. Moreover, layer 4 spiny stellate cells were not able to properly gather, leading to abnormal formation of barrel walls as the ratio of barrel/septum size obviously decreased. Calretinin KO mice exhibited deficits in exploratory and whisker-associated tactile behaviors as well as social novelty preference. Our study expands our knowledge of layer 5a pyramidal neurons in the formation of barrel walls and deepens the understanding of the development of the whisker-barrel cortex system.

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