The existence of a layer IV in the rat motor cortex

Skoglund, Thomas; Pascher, R.; Berthold, C.‐H.

doi:10.1093/cercor/7.2.178

Cited by 47 publications

(30 citation statements)

References 14 publications

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“…Although we cannot observe conventional cortical six-layered cytoarchitecture in motor cortex with light microscopic observation, optical dissector analysis reveals the existence of layer IV at the bottom of layer III (Skoglund et al, 1997). It corresponds with the middle VGLUT2-positive band.…”

Section: Histology and Immunohistochemistrymentioning

confidence: 64%

Neocortical Inhibitory Terminals Innervate Dendritic Spines Targeted by Thalamocortical Afferents

Kubota¹,

Hatada²,

Kondo³

et al. 2007

J. Neurosci.

164

166

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Fast inhibition in the cortex is gated primarily at GABAergic synapses formed by local interneurons onto postsynaptic targets. Although GABAergic inputs to the somata and axon initial segments of neocortical pyramidal neurons are associated with direct inhibition of action potential generation, the role of GABAergic inputs to distal dendritic segments, including spines, is less well characterized. Because a significant proportion of inhibitory input occurs on distal dendrites and spines, it will be important to determine whether these GABAergic synapses are formed selectively by certain classes of presynaptic cells onto specific postsynaptic elements. By electron microscopic observations of synapses formed by different subtypes of nonpyramidal cells, we found that a surprisingly large fraction (33.4 Ϯ 9.3%) of terminals formed symmetrical synaptic junctions onto a subset of cortical spines that were mostly coinnervated by an asymmetrical terminal. Using VGLUT1 and VGLUT2 isoform of the glutamate vesicular transporter immunohistochemistry, we found that the double-innervated spines selectively received thalamocortical afferents expressing the VGLUT2 but almost never intracortical inputs expressing the VGLUT1. When comparing the volumes of differentially innervated spines and their synaptic junction areas, we found that spines innervated by VGLUT2-positive terminal were significantly larger than spines innervated by VGLUT1-positive terminal and that these spines had larger, and more often perforated, synapses than those of spines innervated by VGLUT1-positive afferent. These results demonstrate that inhibitory inputs to pyramidal cell spines may preferentially reduce thalamocortical rather than intracortical synaptic transmission and are therefore positioned to selectively gate extracortical information.

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Section: Histology and Immunohistochemistrymentioning

confidence: 64%

Neocortical Inhibitory Terminals Innervate Dendritic Spines Targeted by Thalamocortical Afferents

Kubota¹,

Hatada²,

Kondo³

et al. 2007

J. Neurosci.

164

166

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“…Group 1 is defined as Layers I-II (0-400μm), Group 2 as Layers III-IV (400-750μm) and Group 3 as Layers V-VI (750-1800μm) below the cortical surface (Skoglund et al, 1997). We used these groups to compare the effects of CES on different frequency bands of LFPs and ECoGs with unit activity.…”

Section: Methodsmentioning

confidence: 99%

High gamma power in ECoG reflects cortical electrical stimulation effects on unit activity in layers V/VI

2013

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Objective Cortical electrical stimulation (CES) has been used extensively in experimental neuroscience to modulate neuronal or behavioral activity, which has led this technique to be considered in neurorehabilitation. Because the cortex and the surrounding anatomy have irregular geometries as well as inhomogeneous and anisotropic electrical properties, the mechanisms by which CES has therapeutic effects is poorly understood. Therapeutic effects of CES can be improved by optimizing the stimulation parameters based on the effects of various stimulation parameters on target brain regions. Approach In this study we have compared the effects of CES pulse polarity, frequency, and amplitude on unit activity recorded from rat primary motor cortex with the effects on the corresponding local field potentials (LFP), and electrocorticograms (ECoG). CES was applied at the surface of the cortex and the unit activity and LFPs were recorded using a penetrating electrode array, which was implanted below the stimulation site. ECoGs were recorded from the vicinity of the stimulation site. Main results Time-frequency analysis of LFPs following CES showed correlation of gamma frequencies with unit activity response in all layers. More importantly, high gamma power of ECoG signals only correlated with the unit activity in lower layers (V-VI) following CES. Time-frequency correlations, which were found between LFPs, ECoGs and unit activity, were frequency- and amplitude-dependent. Significance The signature of the neural activity observed in LFP and ECoG signals provides a better understanding of the effects of stimulation on network activity, representative of large numbers of neurons responding to stimulation. These results demonstrate that the neurorehabilitation and neuroprosthetic applications of CES targeting layered cortex can be further improved by using field potential recordings as surrogates to unit activity aimed at optimizing stimulation efficacy. Likewise, the signatures of unit activity observed as changes in high-gamma power in ECoGs suggest that future cortical stimulation studies could rely on less invasive feedback schemes that incorporate surface stimulation with ECoG reporting of stimulation efficacy.

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“…Delineation of the cortical layers of the motor cortex was performed according the work of van Brederode et al (1991). In this, and in the publications of Krieg (1946), Skoglund et al (1997), and Hiscock et al (1998), the motor cortex was divided into six layers. Although the rat motor cortex is described as a five-layered cortex similar to the human motor cortex (Donoghue and Wise, 1982;Zilles, 1985;Beaulieu, 1993;Zilles and Wree, 1995), we used the subdivision of van Brederode et al(1991), because Zilles and Wree (1995) described a higher cell packing density in the lower part of layer 3 of the rat motor cortex, that is comparable to layer IV in the sensory regions.…”

Section: Effects Of Rtms On Cortical Protein Expressionmentioning

confidence: 99%

Theta-Burst Transcranial Magnetic Stimulation Alters Cortical Inhibition

Benali¹,

Trippe²,

Weiler³

et al. 2011

J. Neurosci.

177

190

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Human cortical excitability can be modified by repetitive transcranial magnetic stimulation (rTMS), but the cellular mechanisms are largely unknown. Here, we show that the pattern of delivery of theta-burst stimulation (TBS) (continuous versus intermittent) differently modifies electric activity and protein expression in the rat neocortex. Intermittent TBS (iTBS), but not continuous TBS (cTBS), enhanced spontaneous neuronal firing and EEG gamma band power. Sensory evoked cortical inhibition increased only after iTBS, although both TBS protocols increased the first sensory response arising from the resting cortical state. Changes in the cortical expression of the calcium-binding proteins parvalbumin (PV) and calbindin D-28k (CB) indicate that changes in spontaneous and evoked cortical activity following rTMS are in part related to altered activity of inhibitory systems. By reducing PV expression in the fast-spiking interneurons, iTBS primarily affected the inhibitory control of pyramidal cell output activity, while cTBS, by reducing CB expression, more likely affected the dendritic integration of synaptic inputs controlled by other classes of inhibitory interneurons. Calretinin, the third major calcium-binding protein expressed by another class of interneurons was not affected at all. We conclude that different patterns of TBS modulate the activity of inhibitory cell classes differently, probably depending on the synaptic connectivity and the preferred discharge pattern of these inhibitory neurons.

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The existence of a layer IV in the rat motor cortex

Cited by 47 publications

References 14 publications

Neocortical Inhibitory Terminals Innervate Dendritic Spines Targeted by Thalamocortical Afferents

Neocortical Inhibitory Terminals Innervate Dendritic Spines Targeted by Thalamocortical Afferents

High gamma power in ECoG reflects cortical electrical stimulation effects on unit activity in layers V/VI

Theta-Burst Transcranial Magnetic Stimulation Alters Cortical Inhibition

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