Effect of Nicorandil on the Spatial Arrangement of Primary Motor Cortical Neurons in the Sub-Acute Phase of Stroke in a Rat Model

AbstractFollowing stroke, the survival of neurons and their ability to re-establish connections is critical to functional recovery. This is strongly influenced by the balance between neuronal excitation and inhibition. In the acute phase of experimental stroke, lethal hyperexcitability can be attenuated by positive allosteric modulation of GABAA receptors (GABAAR). Conversely, in the late phase, negative allosteric modulation of GABAAR can correct the sub-optimal excitability and improves both sensory and motor recovery. Here, we hypothesized that octadecaneuropeptide (ODN), an endogenous allosteric modulator of the GABAAR synthesized by astrocytes, influences the outcome of ischemic brain tissue and subsequent functional recovery. We show that ODN boosts the excitability of cortical neurons, which make it deleterious in the acute phase of stroke. However, if delivered after day 3, ODN is safe and improves motor recovery over the following month in both young and aged mice. Furthermore, we bring evidence that during the sub-acute period after stroke, the repairing cortex can be treated with ODN by means of a single hydrogel deposit into the stroke cavity.

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Spatial Distribution of Contextual Interactions in Primary Visual Cortex and in Visual Perception

Journal of Neurophysiology ◽

10.1152/jn.2000.84.4.2048 ◽

2000 ◽

Vol 84 (4) ◽

pp. 2048-2062 ◽

Cited By ~ 198

Author(s):

Mitesh K. Kapadia ◽

Gerald Westheimer ◽

Charles D. Gilbert

Keyword(s):

Spatial Distribution ◽

Visual Cortex ◽

Primary Visual Cortex ◽

Cortical Neurons ◽

Receptive Fields ◽

Human Perception ◽

Spatial Arrangement ◽

Orthogonal Axis ◽

V1 Neurons ◽

Contextual Interactions

To examine the role of primary visual cortex in visuospatial integration, we studied the spatial arrangement of contextual interactions in the response properties of neurons in primary visual cortex of alert monkeys and in human perception. We found a spatial segregation of opposing contextual interactions. At the level of cortical neurons, excitatory interactions were located along the ends of receptive fields, while inhibitory interactions were strongest along the orthogonal axis. Parallel psychophysical studies in human observers showed opposing contextual interactions surrounding a target line with a similar spatial distribution. The results suggest that V1 neurons can participate in multiple perceptual processes via spatially segregated and functionally distinct components of their receptive fields.

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Hypothetical joint-related coordinate systems in which populations of motor cortical neurons code direction of voluntary arm movements

Neuroscience Letters ◽

10.1016/0304-3940(94)90493-6 ◽

1994 ◽

Vol 180 (2) ◽

pp. 83-86 ◽

Cited By ~ 9

Author(s):

Shoji Tanaka

Keyword(s):

Cortical Neurons ◽

Arm Movements ◽

Coordinate Systems ◽

Motor Cortical

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Computer Simulation of Post-Spike Facilitation in Spike-Triggered Averages of Rectified EMG

Journal of Neurophysiology ◽

10.1152/jn.1998.80.3.1391 ◽

1998 ◽

Vol 80 (3) ◽

pp. 1391-1406 ◽

Cited By ~ 41

Author(s):

S. N. Baker ◽

R. N. Lemon

Keyword(s):

Computer Simulation ◽

Action Potential ◽

Motor Unit ◽

Cortical Neurons ◽

Emg Activity ◽

Motor Unit Action Potential ◽

Cortical Cells ◽

Motor Unit Action ◽

Motor Cortical ◽

Unit Action

Baker, S. N. and R. N. Lemon. Computer simulation of post-spike facilitation in spike-triggered averages of rectified EMG. J. Neurophysiol. 80: 1391–1406, 1998. When the spikes of a motor cortical cell are used to compile a spike-triggered average (STA) of rectified electromyographic (EMG) activity, a post-spike facilitation (PSF) is sometimes seen. This is generally thought to be indicative of direct corticomotoneuronal (CM) connections. However, it has been claimed that a PSF could be caused by synchronization between CM and non-CM cells. This study investigates the generation of PSF using a computer model. A population of cortical cells was simulated, some of which made CM connections to a pool of 103 motoneurons. Motoneurons were simulated using a biophysically realistic model. A subpopulation of the cortical cells was synchronized together. After a motoneuron discharge, a motor unit action potential was generated; these were summed to produce an EMG output. Realistic values were used for the corticospinal and peripheral nerve conduction velocity distribution, for slowing of impulse conduction in CM terminal axons, and for the amount of cortical synchrony. STA of the rectified EMG from all cortical neurons showed PSF; however, these were qualitatively different for CM versus non-CM cells. Using an epoch analysis to determine reliability in a quantitative manner, it was shown that the onset latency of PSF did not distinguish the two classes of cells after 10,000 spikes because of high noise in the averages. The time of the PSF peak and the peak width at half-maximum (PWHM) could separate CM from synchrony effects. However, only PWHM was robust against changes in motor unit action-potential shape and duration and against changes in the width of cortical synchrony. The amplitude of PSF from a CM cell could be doubled by the presence of synchrony. It is proposed that, if a PSF has PWHM <7 ms, this reliably indicates that the trigger is a CM cell projecting to the muscle whose EMG is averaged. In an analysis of experimental data where macaque motor cortical cells facilitated hand and forearm muscle EMG, 74% of PSFs fulfilled this criterion. The PWHM criterion could be applied to other STA studies in which it is important to exclude the effects of synchrony.

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