Biomedical subjects

Irina A Erchova

Publications and source records attributed to Irina A Erchova.

3 recordsLinked to original sources

PubMed2004

Rapid fluctuations in rat barrel cortex plasticity.

Neuronal populations in the sensory cortex exhibit fluctuations in excitability, and the present experiments tested the hypothesis that these variations coincide with peaks and troughs in cortical modifiability. The activity of multiunit neuronal clusters under light urethane anesthesia was recorded through 100-microelectrode arrays implanted in the infragranular layers of rat barrel cortex. Spontaneous activity was characterized by "bursts" of spikes, synchronized across the barrel cortex. This allowed activity at one selected electrode to be taken as a reliable monitor of widespread cortical bursts. We used spikes at the selected electrode to trigger stimulation of two pairs of whiskers during a 50 min conditioning procedure: (1) for the "burst-conditioned" whisker pair, each stimulus was delivered 1 msec after the triggering spike, activating cortex coincident with the burst; and (2) for the "interburst-conditioned" whisker pair, each stimulus was delivered 300 msec after the triggering spike, activating cortex during the trough between bursts. The cross-correlation between cortical neurons in the pairs of columns matching the stimulated whisker pairs was estimated after the termination of the conditioning procedure. Conditioning produced a twofold increase in the degree of co-firing between infragranular neurons in columns receiving burst-conditioned costimulation but no significant change in connectivity between infragranular neurons in columns receiving interburst-conditioned costimulation, although the two pairs of columns received an equal number of sensory inputs. These findings suggest that the strength of co-activity between columns in the barrel cortex can be modified by sensory input patterns during discrete, intermittent intervals time-locked to bursts.

Action Potentials↗

PubMed2003

Effect of developmental sensory and motor deprivation on the functional organization of adult rat somatosensory cortex.

Most sensory systems are active, in the sense that the animal performs specific motor actions in order to collect information of interest-signals are not merely passively received. We, therefore, expect cortical development to depend not only correct sensory experience, but also on correct motor experience. In this study, we used the rat whisker system as a model to compare the importance of these factors. In one group of animals, we trimmed all whiskers starting from post-natal day 8 (P8). In a second group, we left the whiskers intact, but prevented "whisking" by sectioning the facial (VIIth cranial) nerve on P8. The first group had severely disrupted sensory experience but normal motor patterns ("whisker-cut" rats); the second group had normal sensory pathways within which temporal activity patterns were disrupted by motor impairment ("nerve-cut" rats). When they reached 3 months of age, we recorded multi-unit responses from the infragranular layers of primary somatosensory cortex in response to deflection of either single whiskers or pairs of whiskers in order to compare these two groups to a third group of rats that had normal sensory and motor experience. Cortical topographic organization was unaltered in whisker- and nerve-cut rats. Whisker-cut rats showed a smaller than normal difference between the response magnitudes for the principal and surrounding whiskers, as well as stronger than normal interactions between co-active whisker inputs. Responses in nerve-cut rats were nearly indistinguishable from those in normal animals. Thus, unexpectedly, neither pure sensory nor sensorimotor deprivation caused gross functional disruption of SI according to our measures. It appears that abnormal sensory experience leads to alterations in the fine-tuning of cortical properties, but cortex is unexpectedly resistant to the effects of abnormal sensory and sensorimotor experience.

Action Potentials↗

PubMed2002

Somatosensory cortical neuronal population activity across states of anaesthesia.

Experiments were carried out to learn about changes in sensory cortical processing associated with different levels of anaesthesia. Traditionally this question has been addressed by studying single neurons. Because state changes are likely to influence the relationships between neurons, the present experiments were undertaken to investigate the spatial and temporal firing patterns distributed across cortex. Using 5 x 5 or 10 x 10 microelectrode arrays, spontaneous and stimulus-evoked activity of multineuron clusters was recorded from rat somatosensory 'barrel' cortex (the whisker representation) during a light surgical stage of urethane anaesthesia, and after two supplemental doses of urethane which led to intermediate and deep levels of anaesthesia. At all depths of anaesthesia, spontaneously occurring action potentials at a single electrode tended to be clustered into 'bursts.' With increasing anaesthetic depth, bursts became more prominent and rhythmic, and increasingly synchronized between cortical barrel-columns. Burst frequency decreased and fewer spikes occurred outside bursts, leading to a decrease in the overall spontaneous firing rate. The cortical territory engaged by individual whiskers contracted with increasing depth of anaesthesia, leading to the spatial segregation of whisker representations. At all stages of anaesthesia, whisker stimulation produced the maximal cortical response when delivered close to burst onset. These observations show that ongoing spontaneous activity modulates sensory response properties and makes peripheral tactile information accessible to a cortical territory whose size is determined by the phase of burst cycle. The possible significance of the cyclic cortical responsiveness encountered during urethane anaesthesia to cortical processing in awake rats is considered.

Action Potentials↗