scholarly journals Synaptic Interactions Between Forelimb-Related Motor Cortex Neurons in Behaving Primates

2009 ◽  
Vol 102 (2) ◽  
pp. 1026-1039 ◽  
Author(s):  
W. S. Smith ◽  
E. E. Fetz
Keyword(s):  
Motor Cortex ◽  
Central Peak ◽  
Response Patterns ◽  
Cortical Cells ◽  
Common Input ◽  
Excitatory Connection ◽  
Synaptic Interactions ◽  
Central Trough ◽  
Linear Fit ◽  
Layer V

We investigated the synaptic interactions between neighboring motor cortex cells in monkeys generating isometric ramp-and-hold torques about the wrist. For pairs of cortical cells the response patterns were determined in response-aligned averages and their synaptic interactions were identified by cross-correlation histograms. Cross-correlograms were compiled for 215 cell pairs and 84 (39%) showed significant features. The most frequently found feature (65/84 = 77%) was a central peak, straddling the origin and representing a source of common synaptic input to both cells. One third of these also had superimposed lagged peaks, indicative of a serial excitatory connection. Pure lagged peaks and lagged troughs, indicative of serial excitatory or inhibitory linkages, respectively, both occurred in 5% of the correlograms with features. A central trough appeared in 13% of the correlograms. The magnitude of the synaptic linkage was measured as the normalized area of the correlogram feature. Plotting the strength of synaptic interaction against response similarity during alternating wrist torques revealed a positive relationship for the correlated cell pairs. A linear fit yielded a positive slope: the pairs with excitatory interactions tended to covary more often than countervary. This linear fit had a positive offset, reflecting a tendency for both covarying and countervarying cells to have excitatory common input. Plotting the cortical location of the cell pairs showed that the strongest interactions occurred between cells separated by <400 microns. The correlational linkages between cells of different cortical layers showed a large proportion of common input to cells in layer V.

scholarly journals Synaptic Linkages Between Corticomotoneuronal Cells Affecting Forelimb Muscles in Behaving Primates

2009 ◽  
Vol 102 (2) ◽  
pp. 1040-1048 ◽  
Author(s):  
W. S. Smith ◽  
E. E. Fetz
Keyword(s):  
Motor Cortex ◽  
Synaptic Input ◽  
Action Potentials ◽  
The Other ◽  
Response Patterns ◽  
Cortical Cells ◽  
Synaptic Interactions ◽  
Corticomotoneuronal Cells ◽  
Synergistic Muscles ◽  
Forelimb Muscles

To elucidate the cortical circuitry controlling primate forelimb muscles we investigated the synaptic interactions between neighboring motor cortex cells that had postspike output effects in target muscles. In monkeys generating isometric ramp-and-hold wrist torques, pairs of cortical cells were recorded simultaneously with independent electrodes and corticomotoneuronal (“CM”) cells were identified by their postspike effects on target forelimb muscles in spike-triggered averages (SpTAs) of electromyographs (EMGs). The response patterns of the cells were determined in response-aligned averages and their synaptic interactions were identified by cross-correlograms of action potentials. The possibility that synchronized firing between cortical cells could mediate spike-correlated effects in the SpTA of EMG was examined in several ways. Sixty-two pairs consisted of one CM cell and a non-CM cell; 15 of these had correlogram peaks of the same magnitude as that of other pairs, but the synchrony peaks did not mediate any postspike effect from the non-CM cell. Twelve pairs of simultaneously recorded CM cells were cross-correlated. Half had features (usually synchrony peaks) in their cross-correlograms and the cells of these pairs also shared some target muscles in common. The other half had flat correlograms and, in most of these pairs, the CM cells affected different muscles. The latter group included pairs of CM cells that facilitated synergistic muscles. These results indicate that common synaptic input specifically affects CM cells that have overlapping muscle fields. Reconstruction of the cortical locations of CM cells affecting 12 different muscles showed a wide and overlapping distribution of cortical colonies of forelimb muscles.

Dendritic changes of the pyramidal neurons in layer V of sensory-motor cortex of the rat brain during the postresuscitation period

Resuscitation ◽  
1997 ◽  
Vol 35 (2) ◽  
pp. 157-164 ◽  
Author(s):  
Victor A Akulinin ◽  
Sergey S Stepanov ◽  
Valeriy V Semchenko ◽  
Pavel V Belichenko
Keyword(s):  
Motor Cortex ◽  
Rat Brain ◽  
Pyramidal Neurons ◽  
Postresuscitation Period ◽  
Sensory Motor ◽  
Layer V

Effects of Common Excitatory and Inhibitory Inputs on Motoneuron Synchronization

2001 ◽  
Vol 86 (6) ◽  
pp. 2807-2822 ◽  
Author(s):  
K. S. Türker ◽  
R. K. Powers
Keyword(s):  
Background Noise ◽  
Cross Correlation ◽  
Discharge Rate ◽  
Central Peak ◽  
Common Input ◽  
Synaptic Inputs ◽  
Input Waveform ◽  
The Common ◽  
Repetitive Discharge ◽  
Current Transients

We compared the effects of common excitatory and inhibitory inputs on motoneuron synchronization by simulating synaptic inputs with injected current transients. We elicited repetitive discharge in hypoglossal motoneurons recorded in slices of rat brain stem using a combination of a suprathreshold injected current step with superimposed noise to mimic the synaptic drive likely to occur during physiological activation. The effects of common inputs to motoneurons were simulated by the addition of a waveform composed of from 6 to 300 trains of current transients designed to mimic excitatory and/or inhibitory synaptic currents. We compared the discharge records obtained in several trials in which the same “common input” waveform was applied repeatedly in the presence of different background noise waveforms. The effects of the common input on motoneuron discharge probability and discharge rate were determined by compiling a cross-correlation histogram (CCHist) and a perispike frequencygram (PSFreq) between the discharges of the same cell at different times. Both excitatory and inhibitory common inputs induced synchronous discharge that was evident by a large central peak in the CCHist. The CCHists produced by common excitatory inputs were characterized by larger and narrower central peaks than those generated by common inhibitory inputs. The PSFreqs produced by common excitatory inputs indicated an increase in the discharge rate of motoneurons around time 0 that coincided with the narrow and large central peak in the CCHist. On the other hand, inhibitory inputs often generated very little, if any, change in the discharge rate around time 0 corresponding with the small and wide central peak in the CCHist. These results suggest that the CCHist indicates the effective strength of the net common input but not its sign. Although correlated changes in discharge rate are often quite different for net excitatory and inhibitory common input, except in some restricted conditions, the PSFreq analysis also cannot be used to unambiguously distinguish net excitation from net inhibition.

scholarly journals Induction of BDNF Expression in Layer II/III and Layer V Neurons of the Motor Cortex Is Essential for Motor Learning

2020 ◽  
Vol 40 (33) ◽  
pp. 6289-6308 ◽  
Author(s):  
Thomas Andreska ◽  
Stefanie Rauskolb ◽  
Nina Schukraft ◽  
Patrick Lüningschrör ◽  
Manju Sasi ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Motor Learning ◽  
Bdnf Expression ◽  
Layer V

scholarly journals Dopamine D2 receptors modulate intrinsic properties and synaptic transmission of parvalbumin interneurons in the mouse primary motor cortex

2019 ◽  
Author(s):  
Jérémy Cousineau ◽  
Léa Lescouzères ◽  
Anne Taupignon ◽  
Lorena Delgado-Zabalza ◽  
Emmanuel Valjent ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Synaptic Transmission ◽  
Motor Skills ◽  
Primary Motor Cortex ◽  
Pyramidal Neurons ◽  
D2 Receptors ◽  
Receptor Subtypes ◽  
Parvalbumin Interneurons ◽  
Layer V ◽  
Gabaergic Synaptic Transmission

AbstractDopamine (DA) plays a crucial role in the control of motor and higher cognitive functions such as learning, working memory and decision making. The primary motor cortex (M1), which is essential for motor control and the acquisition of motor skills, receives dopaminergic inputs in its superficial and deep layers from the midbrain. However, the precise action of DA and DA receptor subtypes on the cortical microcircuits of M1 remains poorly understood. The aim of this work was to investigate how DA, through the activation of D2 receptors (D2R), modulates the cellular and synaptic activity of M1 parvalbumin-expressing interneurons (PVINs) which are crucial to regulate the spike output of pyramidal neurons (PNs). By combining immunofluorescence, ex vivo electrophysiology, pharmacology and optogenetics approaches, we show that D2R activation increases neuronal excitability of PVINs and GABAergic synaptic transmission between PVINs and PNs in layer V of M1. Our data reveal a mechanism through which cortical DA modulates M1 microcircuitry and might participate in the acquisition of motor skills.Significance StatementPrimary motor cortex (M1), which is a region essential for motor control and the acquisition of motor skills, receives dopaminergic inputs from the midbrain. However, precise action of dopamine and its receptor subtypes on specific cell types in M1 remained poorly understood. Here, we demonstrate in M1 that dopamine D2 receptors (D2R) are present in parvalbumin interneurons (PVINs) and their activation increases the excitability of the PVINs, which are crucial to regulate the spike output of pyramidal neurons (PNs). Moreover the activation of the D2R facilitates the GABAergic synaptic transmission of those PVINs on layer V PNs. These results highlight how cortical dopamine modulates the functioning of M1 microcircuit which activity is disturbed in hypo- and hyperdopaminergic states.

scholarly journals Cortical inhibitory network selects cerebellar signals for movement initiation

2020 ◽  
Author(s):  
Abdulraheem Nashef ◽  
Oren Cohen ◽  
Steve I. Perlmutter ◽  
Yifat Prut
Keyword(s):  
Motor Cortex ◽  
Ampa Receptors ◽  
Cortical Neurons ◽  
Signal To Noise Ratio ◽  
Large Population ◽  
Pyramidal Cells ◽  
Movement Initiation ◽  
Cortical Cells ◽  
Sequence Of Events ◽  
The Right

SUMMARYThe onset of voluntary movements is driven by coordinated firing across a large population of motor cortical neurons. This pattern of activity is determined by both local interactions and long-range corticocortical and subcortical inputs. The way remote areas of the brain communicate to effectively drive movement is still unclear. We addressed this question by studying an important pathway through which the cerebellum communicates, via the motor thalamus, with the motor cortex. We found that similar to the sensory cortices, thalamic input to the motor cortex triggers feedforward inhibition by directly contacting inhibitory cells via particularly effective GluR2- lacking AMPA receptors blocked by NASPM. Based on these results, we constructed a classifier for SCP-responsive cortical cells to identify pyramidal and PV interneurons and study their role in controlling movements. The findings indicate that PV and pyramidal cells are co-driven by TC input in response to activation of the CTC pathway. During task performance, PV and pyramidal cells had comparable relations to movement parameters (directional tuning and movement duration). However, PV interneurons exhibited stronger movement-related activity that preceded the firing of pyramidal cells. This seemingly counterintuitive sequence of events where inhibitory cells are recruited more strongly and before excitatory cells may in fact enhance the signal-to-noise ratio of cerebellar signals by suppressing other inputs and prioritizing the excitatory synchronized volley from the TC system which occurs at the right time to overcome the inhibitory signal. In this manner, the CTC system can shape cortical activity in a way that exceeds its sheer synaptic efficacy.

scholarly journals Categorical encoding of speech sounds: beyond auditory cortices

2021 ◽  
Author(s):  
Basil C Preisig ◽  
Lars Riecke ◽  
Alexis Hervais-Adelman
Keyword(s):  
Decision Making ◽  
Motor Cortex ◽  
Categorical Perception ◽  
Response Selection ◽  
Activity Patterns ◽  
Response Patterns ◽  
Speech Sounds ◽  
Acoustic Feature ◽  
Auditory Cortices ◽  
The Right

What processes lead to categorical perception of speech sounds? Investigation of this question is hampered by the fact that categorical speech perception is normally confounded by acoustic differences in the stimulus. By using ambiguous sounds, however, it is possible to dissociate acoustic from perceptual stimulus representations. We used a binaural integration task, where the inputs to the two ears were complementary so that phonemic identity emerged from their integration into a single percept. Twenty-seven normally hearing individuals took part in an fMRI study in which they were presented with an ambiguous syllable (intermediate between /da/ and /ga/) in one ear and with a meaning-differentiating acoustic feature (third formant) in the other ear. Multi-voxel pattern searchlight analysis was used to identify brain areas that consistently differentiated between response patterns associated with different syllable reports. By comparing responses to different stimuli with identical syllable reports and identical stimuli with different syllable reports, we disambiguated whether these regions primarily differentiated the acoustics of the stimuli or the syllable report. We found that BOLD activity patterns in the left anterior insula (AI), the left supplementary motor cortex, the left ventral motor cortex and the right motor and somatosensory cortex (M1/S1) represent listeners' syllable report irrespective of stimulus acoustics. The same areas have been previously implicated in decision-making (AI), response selection (SMA), and response initiation and feedback (M1/S1). Our results indicate that the emergence of categorical speech sounds implicates decision-making mechanisms and auditory-motor transformations acting on sensory inputs.

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