Skilled Motor Learning Does Not Enhance Long-Term Depression in the Motor Cortex In Vivo

2005 ◽  
Vol 93 (3) ◽  
pp. 1486-1497 ◽  
Author(s):  
Jeremy D. Cohen ◽  
Manuel A. Castro-Alamancos
Keyword(s):  
Neural Networks ◽  
Motor Cortex ◽  
Motor Learning ◽  
Primary Motor Cortex ◽  
Short Term ◽  
Long Term Depression ◽  
Short Term Plasticity ◽  
Horizontal Connections

Learning of motor skills may occur as a consequence of changes in the efficacy of synaptic connections in the primary motor cortex. We investigated if learning in a reaching task affects the excitability, short-term plasticity, and long-term plasticity of horizontal connections in layers II–III of the motor cortex. Because training in this task requires animals to be food-deprived, we compared the trained animals with similarly food-deprived untrained animals and normal controls. The results show that the excitability, short-term plasticity, and long-term plasticity of the studied horizontal connections were unaffected by motor learning. However, stress-related effects produced by food deprivation and handling significantly enhanced the expression of long-term depression in these pathways. These results are compatible with the hypothesis that the acquisition of a complex motor skill produces bi-directional changes in synaptic strength that are distributed throughout the complex neural networks of motor cortex, which remains synaptically balanced during learning. The results are incompatible with the idea that learning causes large unidirectional changes in the population response of these neural networks, which may occur instead during certain behavioral states, such as stress.

Short-term and long-term plasticity interaction in human primary motor cortex

2011 ◽  
Vol 33 (10) ◽  
pp. 1908-1915 ◽  
Author(s):  
Ennio Iezzi ◽  
Antonio Suppa ◽  
Antonella Conte ◽  
Pietro Li Voti ◽  
Matteo Bologna ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Short Term

Effects of chronic lead exposure on short-term and long-term depression in area CA1 of the rat hippocampus in vivo

Chemosphere ◽  
2000 ◽  
Vol 41 (1-2) ◽  
pp. 165-171 ◽  
Author(s):  
D.Y Ruan ◽  
K.F Yan ◽  
S.Y Ge ◽  
Y.Z Xu ◽  
J.T Chen ◽  
...  
Keyword(s):  
Lead Exposure ◽  
Rat Hippocampus ◽  
Short Term ◽  
Long Term Depression ◽  
Area Ca1 ◽  
Chronic Lead Exposure

scholarly journals Reversed timing-dependent associative plasticity in the human brain through interhemispheric interactions

2013 ◽  
Vol 109 (9) ◽  
pp. 2260-2271 ◽  
Author(s):  
Virginia Conde ◽  
Henning Vollmann ◽  
Marco Taubert ◽  
Bernhard Sehm ◽  
Leonardo G. Cohen ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Human Brain ◽  
Primary Motor Cortex ◽  
Long Term Potentiation ◽  
Spike Timing ◽  
In Vivo Model ◽  
Sensorimotor Network ◽  
Median Nerve Stimulation

Spike timing-dependent plasticity (STDP) has been proposed as one of the key mechanisms underlying learning and memory. Repetitive median nerve stimulation, followed by transcranial magnetic stimulation (TMS) of the contralateral primary motor cortex (M1), defined as paired-associative stimulation (PAS), has been used as an in vivo model of STDP in humans. PAS-induced excitability changes in M1 have been repeatedly shown to be time-dependent in a STDP-like fashion, since synchronous arrival of inputs within M1 induces long-term potentiation-like effects, whereas an asynchronous arrival induces long-term depression (LTD)-like effects. Here, we show that interhemispheric inhibition of the sensorimotor network during PAS, with the peripheral stimulation over the hand ipsilateral to the motor cortex receiving TMS, results in a LTD-like effect, as opposed to the standard STDP-like effect seen for contralateral PAS. Furthermore, we could show that this reversed-associative plasticity critically depends on the timing interval between afferent and cortical stimulation. These results indicate that the outcome of associative stimulation in the human brain depends on functional network interactions (inhibition or facilitation) at a systems level and can either follow standard or reversed STDP-like mechanisms.

scholarly journals NMDAR-dependent long-term depression is associated with increased short term plasticity through autophagy mediated loss of PSD-95

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Benjamin Compans ◽  
Come Camus ◽  
Emmanouela Kallergi ◽  
Silvia Sposini ◽  
Magalie Martineau ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Short Term ◽  
Long Term Depression ◽  
Short Term Plasticity ◽  
Synaptic Physiology ◽  
Surface Mobility ◽  
Generic Term ◽  
Synaptic Changes ◽  
And Function

AbstractLong-term depression (LTD) of synaptic strength can take multiple forms and contribute to circuit remodeling, memory encoding or erasure. The generic term LTD encompasses various induction pathways, including activation of NMDA, mGlu or P2X receptors. However, the associated specific molecular mechanisms and effects on synaptic physiology are still unclear. We here compare how NMDAR- or P2XR-dependent LTD affect synaptic nanoscale organization and function in rodents. While both LTDs are associated with a loss and reorganization of synaptic AMPARs, only NMDAR-dependent LTD induction triggers a profound reorganization of PSD-95. This modification, which requires the autophagy machinery to remove the T19-phosphorylated form of PSD-95 from synapses, leads to an increase in AMPAR surface mobility. We demonstrate that these post-synaptic changes that occur specifically during NMDAR-dependent LTD result in an increased short-term plasticity improving neuronal responsiveness of depressed synapses. Our results establish that P2XR- and NMDAR-mediated LTD are associated to functionally distinct forms of LTD.

Sensitivity to Stimulus Irregularity Is Inherent in Neural Networks

2019 ◽  
Vol 31 (9) ◽  
pp. 1789-1824
Author(s):  
Teun van Gils ◽  
Paul H. E. Tiesinga ◽  
Bernhard Englitz ◽  
Marijn B. Martens
Keyword(s):  
Neural Networks ◽  
Network Structure ◽  
Recurrent Network ◽  
Local Network ◽  
Short Term ◽  
Short Term Plasticity ◽  
In Vivo Experiments ◽  
Integrate Activity ◽  
Neuron Dynamics

Behavior is controlled by complex neural networks in which neurons process thousands of inputs. However, even short spike trains evoked in a single cortical neuron were demonstrated to be sufficient to influence behavior in vivo. Specifically, irregular sequences of interspike intervals (ISIs) had a more reliable influence on behavior despite their resemblance to stochastic activity. Similarly, irregular tactile stimulation led to higher rates of behavioral responses. In this study, we identify the mechanisms enabling this sensitivity to stimulus irregularity (SSI) on the neuronal and network levels using simulated spiking neural networks. Matching in vivo experiments, we find that irregular stimulation elicits more detectable network events (bursts) than regular stimulation. Dissecting the stimuli, we identify short ISIs—occurring more frequently in irregular stimulations—as the main drivers of SSI rather than complex irregularity per se. In addition, we find that short-term plasticity modulates SSI. We subsequently eliminate the different mechanisms in turn to assess their role in generating SSI. Removing inhibitory interneurons, we find that SSI is retained, suggesting that SSI is not dependent on inhibition. Removing recurrency, we find that SSI is retained due to the ability of individual neurons to integrate activity over short timescales (“cell memory”). Removing single-neuron dynamics, we find that SSI is retained based on the short-term retention of activity within the recurrent network structure (“network memory”). Finally, using a further simplified probabilistic model, we find that local network structure is not required for SSI. Hence, SSI is identified as a general property that we hypothesize to be ubiquitous in neural networks with different structures and biophysical properties. Irregular sequences contain shorter ISIs, which are the main drivers underlying SSI. The experimentally observed SSI should thus generalize to other systems, suggesting a functional role for irregular activity in cortex.

scholarly journals Disengagement of motor cortex from movement control during long-term learning

2019 ◽  
Vol 5 (10) ◽  
pp. eaay0001 ◽  
Author(s):  
Eun Jung Hwang ◽  
Jeffrey E. Dahlen ◽  
Yvonne Yuling Hu ◽  
Karina Aguilar ◽  
Bin Yu ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Motor Learning ◽  
Late Stage ◽  
Primary Motor Cortex ◽  
Motor Task ◽  
Movement Control ◽  
Population Activity ◽  
Two Photon ◽  
Forelimb Movements

Motor learning involves reorganization of the primary motor cortex (M1). However, it remains unclear how the involvement of M1 in movement control changes during long-term learning. To address this, we trained mice in a forelimb-based motor task over months and performed optogenetic inactivation and two-photon calcium imaging in M1 during the long-term training. We found that M1 inactivation impaired the forelimb movements in the early and middle stages, but not in the late stage, indicating that the movements that initially required M1 became independent of M1. As previously shown, M1 population activity became more consistent across trials from the early to middle stage while task performance rapidly improved. However, from the middle to late stage, M1 population activity became again variable despite consistent expert behaviors. This later decline in activity consistency suggests dissociation between M1 and movements. These findings suggest that long-term motor learning can disengage M1 from movement control.

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