Coupled Spike Activity in Micropopulations of Motor Cortex Neurons in Rats

Abstract

Using eight-channel metal microelectrodes (diameter of a separate channel 12 µm), we extracellularly recorded the impulse activity of 186 single neurons or their small groups (usually, pairs) localized in the motor cortex of rats anesthetized with ketamine. In 60 cases (32.3%), action potentials (APs) of two single neurons were generated in a parallel manner and demonstrated fixed time relations with each other. This is interpreted as being a result of excitation of two neighboring functionally connected (coupled) cells. These AP pairs could be recorded via one and the same or two neighboring microelectrode channels. Second APs in the pair were elicited exclusively in the case where an AP was preliminarily generated by another neuron, while APs of the latter in some cases could arrive independently. Therefore, "leading" and "accompanying" cells could be identified in such neuronal pairs. The coupling coefficient in the generation of APs by an accompanying unit with respect to APs generated by a leading cell was close to 100%, with no dependence on the discharge frequency in the latter. Intervals between APs of two neurons in different coupled pairs varied from about 1.0 to 22-23 msec. In the case of minimum values of these interspike intervals, APs generated by coupled neurons overlapped each other; this resulted in the formation of spikes looking like "complex APs." Within some time intervals, interspike intervals could increase, and such APs began to be decomposed. The above-described data are considered electrophysiological proof of the existence of tight functional coupling between a significant part of cortical neurons spatially close to each other, i.e., members of a micropopulation, which was obtained in an in vivo experiment.

Assessment of the Diagnostic Value of the Method of Computer Olfactometry

“…Thus, a structural scheme of the method for the objective diagnosis of respiratory and olfactory disturbances was developed, taking into account the measurements of both aerodynamic indices of nasal breathing and the calculation of energy characteristics [9,16,23], by which the olfactory sensitivity was determined (see Figure 2) [5,6].…”

“…Since the analysis of recent researches and publications has shown that the method of rhinomatometry is the most objective functional method of modern otorhinolaryngology diagnosis, and the method of dynamic active posterior rhinomanometry (APR) is more reliable than the anterior active rhinomatometry, then it is proposed to add a definition to the standard APR method some parameters related to the function of the smell [16,23].…”

Concept and Realization of Backpack-Type System for Multichannel Electrophysiology in Freely Behaving Rodents

“…Using custom made micro-manipulator, the electrode array was moved into the targeted brain area with the 5m step, until stable neural signal was recorded. Verification of a single unit activity was proved with wireless 8-channel system for extracellular electrophysiology [12,14,23] with simultaneous visualization of signal on oscilloscopes [6,26].…”