scholarly journals Development of Thalamocortical Response Transformations in the Rat Whisker-Barrel System

2008 ◽  
Vol 99 (1) ◽  
pp. 356-366 ◽  
Author(s):  
Michael Shoykhet ◽  
Daniel J. Simons
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Receptive Fields ◽  
Second Phase ◽  
Adult Rats ◽  
Response Latencies ◽  
Thalamic Neurons ◽  
Response Properties ◽  
Temporal Domain

Extracellular single-unit recordings were used to characterize responses of thalamic barreloid and cortical barrel neurons to controlled whisker deflections in 2, 3-, and 4-wk-old and adult rats in vivo under fentanyl analgesia. Results indicate that response properties of thalamic and cortical neurons diverge during development. Responses to deflection onsets and offsets among thalamic neurons mature in parallel, whereas among cortical neurons responses to deflection offsets become disproportionately smaller with age. Thalamic neuron receptive fields become more multiwhisker, whereas those of cortical neurons become more single-whisker. Thalamic neurons develop a higher degree of angular selectivity, whereas that of cortical neurons remains constant. In the temporal domain, response latencies decrease both in thalamic and cortical neurons, but the maturation time-course differs between the two populations. Response latencies of thalamic cells decrease primarily between 2 and 3 wk of life, whereas response latencies of cortical neurons decrease in two distinct steps—the first between 2 and 3 wk of life and the second between the fourth postnatal week and adulthood. Although the first step likely reflects similar subcortical changes, the second phase likely corresponds to developmental myelination of thalamocortical fibers. Divergent development of thalamic and cortical response properties indicates that thalamocortical circuits in the whisker-to-barrel pathway undergo protracted maturation after 2 wk of life and provides a potential substrate for experience-dependent plasticity during this time.

Synaptic Interactions Between Thalamic and Cortical Inputs Onto Cortical Neurons In Vivo

2004 ◽  
Vol 91 (5) ◽  
pp. 1990-1998 ◽  
Author(s):  
Pablo Fuentealba ◽  
Sylvain Crochet ◽  
Igor Timofeev ◽  
Mircea Steriade
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Input Resistance ◽  
Maximal Effect ◽  
Time Intervals ◽  
Neocortical Neurons ◽  
Synaptic Interactions ◽  
Cortical Responses ◽  
Cortical Inputs

To study the interactions between thalamic and cortical inputs onto neocortical neurons, we used paired-pulse stimulation (PPS) of thalamic and cortical inputs as well as PPS of two cortical or two thalamic inputs that converged, at different time intervals, onto intracellularly recorded cortical and thalamocortical neurons in anesthetized cats. PPS of homosynaptic cortico-cortical pathways produced facilitation, depression, or no significant effects in cortical pathways, whereas cortical responses to thalamocortical inputs were mostly facilitated at both short and long intervals. By contrast, heterosynaptic interactions between either cortical and thalamic, or thalamic and cortical, inputs generally produced decreases in the peak amplitudes and depolarization area of evoked excitatory postsynaptic potentials (EPSPs), with maximal effect at ∼10 ms and lasting from 60 to 100 ms. All neurons tested with thalamic followed by cortical stimuli showed a decrease in the apparent input resistance ( Rin), the time course of which paralleled that of decreased responses, suggesting that shunting is the factor accounting for EPSP's decrease. Only half of neurons tested with cortical followed by thalamic stimuli displayed changes in Rin. Spike shunting in the thalamus may account for those cases in which decreased synaptic responsiveness of cortical neurons was not associated with decreased Rin because thalamocortical neurons showed decreased firing probability during cortical stimulation. These results suggest a short-lasting but strong shunting between thalamocortical and cortical inputs onto cortical 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 Widely Different Correlation Patterns Between Pairs of Adjacent Thalamic Neurons In vivo

2021 ◽  
Vol 15 ◽  
Author(s):  
Anders Wahlbom ◽  
Hannes Mogensen ◽  
Henrik Jörntell
Keyword(s):  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Thalamic Nuclei ◽  
Thalamic Neurons ◽  
Low Weight ◽  
Afferent Inputs ◽  
Cortical Inputs ◽  
Unique Relationship ◽  
Spike Firing

We have previously reported different spike firing correlation patterns among pairs of adjacent pyramidal neurons within the same layer of S1 cortex in vivo, which was argued to suggest that acquired synaptic weight modifications would tend to differentiate adjacent cortical neurons despite them having access to near-identical afferent inputs. Here we made simultaneous single-electrode loose patch-clamp recordings from 14 pairs of adjacent neurons in the lateral thalamus of the ketamine-xylazine anesthetized rat in vivo to study the correlation patterns in their spike firing. As the synapses on thalamic neurons are dominated by a high number of low weight cortical inputs, which would be expected to be shared for two adjacent neurons, and as far as thalamic neurons have homogenous membrane physiology and spike generation, they would be expected to have overall similar spike firing and therefore also correlation patterns. However, we find that across a variety of thalamic nuclei the correlation patterns between pairs of adjacent thalamic neurons vary widely. The findings suggest that the connectivity and cellular physiology of the thalamocortical circuitry, in contrast to what would be expected from a straightforward interpretation of corticothalamic maps and uniform intrinsic cellular neurophysiology, has been shaped by learning to the extent that each pair of thalamic neuron has a unique relationship in their spike firing activity.

Disruption of Balanced Cortical Excitation and Inhibition by Acoustic Trauma

2008 ◽  
Vol 100 (2) ◽  
pp. 646-656 ◽  
Author(s):  
Ben Scholl ◽  
Michael Wehr
Keyword(s):  
Receptive Field ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Acoustic Trauma ◽  
Tone Frequency ◽  
Synaptic Excitation ◽  
Before And After ◽  
High Level ◽  
Whole Cell Recordings

Sensory deafferentation results in rapid shifts in the receptive fields of cortical neurons, but the synaptic mechanisms underlying these changes remain unknown. The rapidity of these shifts has led to the suggestion that subthreshold inputs may be unmasked by a selective loss of inhibition. To study this, we used in vivo whole cell recordings to directly measure tone-evoked excitatory and inhibitory synaptic inputs in auditory cortical neurons before and after acoustic trauma. Here we report that acute acoustic trauma disrupted the balance of excitation and inhibition by selectively increasing and reducing the strength of inhibition at different positions within the receptive field. Inhibition was abolished for frequencies far below the trauma-tone frequency but was markedly enhanced near the edges of the region of elevated peripheral threshold. These changes occurred for relatively high-level tones. These changes in inhibition led to an expansion of receptive fields but not by a simple unmasking process. Rather, membrane potential responses were delayed and prolonged throughout the receptive field by distinct interactions between synaptic excitation and inhibition. Far below the trauma-tone frequency, decreased inhibition combined with prolonged excitation led to increased responses. Near the edges of the region of elevated peripheral threshold, increased inhibition served to delay rather than abolish responses, which were driven by prolonged excitation. These results show that the rapid receptive field shifts caused by acoustic trauma are caused by distinct mechanisms at different positions within the receptive field, which depend on differential disruption of excitation and inhibition.

scholarly journals Calculating Event-Triggered Average Synaptic Conductances From the Membrane Potential

2007 ◽  
Vol 97 (3) ◽  
pp. 2544-2552 ◽  
Author(s):  
Martin Pospischil ◽  
Zuzanna Piwkowska ◽  
Michelle Rudolph ◽  
Thierry Bal ◽  
Alain Destexhe
Keyword(s):  
Membrane Potential ◽  
Cortical Neurons ◽  
Time Course ◽  
Spike Generation ◽  
Nonlinear Contribution ◽  
Central Neurons ◽  
Time Courses ◽  
Model Subject ◽  
Synaptic Conductances

The optimal patterns of synaptic conductances for spike generation in central neurons is a subject of considerable interest. Ideally such conductance time courses should be extracted from membrane potential ( Vm) activity, but this is difficult because the nonlinear contribution of conductances to the Vm renders their estimation from the membrane equation extremely sensitive. We outline here a solution to this problem based on a discretization of the time axis. This procedure can extract the time course of excitatory and inhibitory conductances solely from the analysis of Vm activity. We test this method by calculating spike-triggered averages of synaptic conductances using numerical simulations of the integrate-and-fire model subject to colored conductance noise. The procedure was also tested successfully in biological cortical neurons using conductance noise injected with dynamic clamp. This method should allow the extraction of synaptic conductances from Vm recordings in vivo.

Simultaneous Reorganization in Thalamocortical Ensembles Evolves Over Several Hours After Perioral Capsaicin Injections

1999 ◽  
Vol 82 (2) ◽  
pp. 963-977 ◽  
Author(s):  
Donald B. Katz ◽  
S. A. Simon ◽  
Aaron Moody ◽  
Miguel A. L. Nicolelis
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Cortical Plasticity ◽  
Population Analysis ◽  
Receptive Fields ◽  
Somatosensory System ◽  
Spontaneous Firing ◽  
Neural Responses ◽  
Spatial Coupling ◽  
Neural Ensembles

Reorganization of the somatosensory system was quantified by simultaneously recording from single-unit neural ensembles in the whisker regions of the ventral posterior medial (VPM) nucleus of the thalamus and the primary somatosensory (SI) cortex in anesthetized rats before, during, and after injecting capsaicin under the skin of the lip. Capsaicin, a compound that excites and then inactivates a subset of peripheral C and Aδ fibers, triggered increases in spontaneous firing of thalamocortical neurons (10–15 min after injection), as well as rapid reorganization of the whisker representations in both the VPM and SI. During the first hour after capsaicin injection, 57% of the 139 recorded neurons either gained or lost at least one whisker response in their receptive fields (RFs). Capsaicin-related changes continued to emerge for ≥6 h after the injection: Fifty percent of the single-neuron RFs changed between 1–2 and 5–6 h after capsaicin injection. Most (79%) of these late changes represented neural responses that had remained unchanged in the first postcapsaicin mapping; just under 20% of these late changes appeared in neurons that had previously shown no plasticity of response. The majority of the changes (55% immediately after injection, 66% 6 h later) involved “unmasking” of new tactile responses. RF change rates were comparable in SI and VPM (57–49%). Population analysis indicated that the reorganization was associated with a lessening of the “spatial coupling” between cortical neurons—a significant reduction in firing covariance that could be related to distances between neurons. This general loss of spatial coupling, in conjunction with increases in spontaneous firing, may create a situation that is favorable for the induction of synaptic plasticity. Our results indicate that the selective inactivation of a peripheral nociceptor subpopulation can induce rapid and long-evolving (≥6 h) shifts in the balance of inhibition and excitation in the somatosensory system. The time course of these processes suggest that thalamic and cortical plasticity is not a linear reflection of spinal and brainstem changes that occur following the application of capsaicin.

scholarly journals Regional distribution, developmental changes, and cellular localization of CNTF-mRNA and protein in the rat brain.

1991 ◽  
Vol 115 (2) ◽  
pp. 447-459 ◽  
Author(s):  
K A Stöckli ◽  
L E Lillien ◽  
M Näher-Noé ◽  
G Breitfeld ◽  
R A Hughes ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Olfactory Bulb ◽  
Cellular Localization ◽  
Time Course ◽  
Regional Distribution ◽  
Developmental Expression ◽  
Adult Rats

Ciliary neurotrophic factor (CNTF) is a potent survival molecule for a variety of embryonic neurons in culture. The developmental expression of CNTF occurs clearly after the time period of the physiological cell death of CNTF-responsive neurons. This, together with the sites of expression, excludes CNTF as a target-derived neuronal survival factor, at least in rodents. However, CNTF also participates in the induction of type 2 astrocyte differentiation in vitro. Here we demonstrate that the time course of the expression of CNTF-mRNA and protein in the rat optic nerve (as evaluated by quantitative Northern blot analysis and biological activity, respectively) is compatible with such a glial differentiation function of CNTF in vivo. We also show that the type 2 astrocyte-inducing activity previously demonstrated in optic nerve extract can be precipitated by an antiserum against CNTF. Immunohistochemical analysis of astrocytes in vitro and in vivo demonstrates that the expression of CNTF is confined to a subpopulation of type 1 astrocytes. The olfactory bulb of adult rats has comparably high levels of CNTF to the optic nerve, and here again, CNTF-immunoreactivity is localized in a subpopulation of astrocytes. However, the postnatal expression of CNTF in the olfactory bulb occurs later than in the optic nerve. In other brain regions both CNTF-mRNA and protein levels are much lower.

scholarly journals Response Properties of Whisker-Related Neurons in Rat Second Somatosensory Cortex

2004 ◽  
Vol 92 (4) ◽  
pp. 2083-2092 ◽  
Author(s):  
Ernest E. Kwegyir-Afful ◽  
Asaf Keller
Keyword(s):  
Somatosensory Cortex ◽  
Receptive Fields ◽  
Stimulus Onset ◽  
Similar Response ◽  
Activity Levels ◽  
Response Latencies ◽  
Response Properties ◽  
Fast Spiking ◽  
Evoked Activity ◽  
Lemniscal System

In addition to a primary somatosensory cortex (SI), the cerebral cortex of all mammals contains a second somatosensory area (SII); however, the functions of SII are largely unknown. Our aim was to explore the functions of SII by comparing response properties of whisker-related neurons in this area with their counterparts in the SI. We obtained extracellular unit recordings from narcotized rats, in response to whisker deflections evoked by a piezoelectric device, and compared response properties of SI barrel (layer IV) neurons with those of SII (layers II to VI) neurons. Neurons in both cortical areas have similar response latencies and spontaneous activity levels. However, SI and SII neurons differ in several significant properties. The receptive fields of SII neurons are at least five times as large as those of barrel neurons, and they respond equally strongly to several principal whiskers. The response magnitude of SII neurons is significantly smaller than that of neurons in SI, and SII neurons are more selective for the angle of whisker deflection. Furthermore, whereas in SI fast-spiking (inhibitory) and regular-spiking (excitatory) units have different spontaneous and evoked activity levels and differ in their responses to stimulus onset and offset, SII neurons do not show significant differences in these properties. The response properties of SII neurons suggest that they are driven by thalamic inputs that are part of the paralemniscal system. Thus whisker-related inputs are processed in parallel by a lemniscal system involving SI and a paralemniscal system that processes complimentary aspects of somatosensation.

The Development of Multisensory Integration in the Brain

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 35-35 ◽  
Author(s):  
M T Wallace
Keyword(s):  
Multisensory Integration ◽  
Time Course ◽  
Receptive Fields ◽  
Developmental Time ◽  
Response Latencies ◽  
Sensory Stimuli ◽  
Sensory Inputs ◽  
Response Enhancement ◽  
Sensory Responses ◽  
The Brain

Multisensory integration in the superior colliculus (SC) of the cat requires a protracted postnatal developmental time course. Kittens 3 – 135 days postnatal (dpn) were examined and the first neuron capable of responding to two different sensory inputs (auditory and somatosensory) was not seen until 12 dpn. Visually responsive multisensory neurons were not encountered until 20 dpn. These early multisensory neurons responded weakly to sensory stimuli, had long response latencies, large receptive fields, and poorly developed response selectivities. Most striking, however, was their inability to integrate cross-modality cues in order to produce the significant response enhancement or depression characteristic of these neurons in adults. The incidence of multisensory neurons increased gradually over the next 10 – 12 weeks. During this period, sensory responses became more robust, latencies shortened, receptive fields decreased in size, and unimodal selectivities matured. The first neurons capable of cross-modality integration were seen at 28 dpn. For the following two months, the incidence of such integrative neurons rose gradually until adult-like values were achieved. Surprisingly, however, as soon as a multisensory neuron exhibited this capacity, most of its integrative features were indistinguishable from those in adults. Given what is known about the requirements for multisensory integration in adult animals, this observation suggests that the appearance of multisensory integration reflects the onset of functional corticotectal inputs.

Visual Response Properties of Neurons in the LGN of Normally Reared and Visually Deprived Macaque Monkeys

2001 ◽  
Vol 85 (5) ◽  
pp. 2111-2129 ◽  
Author(s):  
Jonathan B. Levitt ◽  
Robert A. Schumer ◽  
S. Murray Sherman ◽  
Peter D. Spear ◽  
J. Anthony Movshon
Keyword(s):  
Receptive Field ◽  
Receptive Fields ◽  
Optic Chiasm ◽  
Monocular Deprivation ◽  
Specific Cell ◽  
Visual Response ◽  
Response Latencies ◽  
Macaque Monkeys ◽  
Response Properties ◽  
Parvocellular Neurons

It is now well appreciated that parallel retino-geniculo-cortical pathways exist in the monkey as in the cat, the species in which parallel visual pathways were first and most thoroughly documented. What remains unclear is precisely how many separate pathways pass through the parvo- and magnocellular divisions of the macaque lateral geniculate nucleus (LGN), what relationships—homologous or otherwise—these pathways have to the cat's X, Y, and W pathways, and whether these are affected by visual deprivation. To address these issues of classification and trans-species comparison, we used achromatic stimuli to obtain an extensive set of quantitative measurements of receptive field properties in the parvo- and magnocellular laminae of the LGN of nine macaque monkeys: four normally reared and five monocularly deprived of vision by lid suture near the time of birth. In agreement with previous studies, we find that on average magnocellular neurons differ from parvocellular neurons by having shorter response latencies to optic chiasm stimulation, greater sensitivity to luminance contrast, and better temporal resolution. Magnocellular laminae are also distinguished by containing neurons that summate luminance over their receptive fields nonlinearly (Y cells) and whose temporal response phases decrease with increasing stimulus contrast (indicative of a contrast gain control mechanism). We found little evidence for major differences between magno- and parvocellular neurons on the basis of most spatial parameters except that at any eccentricity, the neurons with the smallest receptive field centers tended to be parvocellular. All parameters were distributed unimodally and continuously through the parvo- and magnocellular populations, giving no indications of subpopulations within each division. Monocular deprivation led to clear anatomical effects: cells in deprived-eye laminae were pale and shrunken compared with those in nondeprived eye laminae, and Cat-301 immunoreactivity in deprived laminae was essentially uniformly abolished. However, deprivation had only subtle effects on the response properties of LGN neurons. Neurons driven by the deprived eye in both magno- and parvocellular laminae had lower nonlinearity indices (i.e., summed signals across their receptive fields more linearly) and were somewhat less responsive. In magnocellular laminae driven by the deprived eye, neuronal response latencies to stimulation of the optic chiasm were slightly shorter than those in the nondeprived laminae, and receptive field surrounds were a bit stronger. No other response parameters were affected by deprivation, and there was no evidence for loss of a specific cell class as in the cat.

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