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E Vaadia

Publications and source records attributed to E Vaadia.

40 records · Page 3Linked to original sources
PubMedDate not supplied

Hebbian-like functional plasticity in the auditory cortex of the behaving monkey.

In this study, the necessary conditions, including those related to behavior, for lasting modifications to occur in correlated activity ('functional plasticity') were examined in the behaving monkey. Previously, in-vitro studies of neuronal plasticity yielded important information about possible mechanisms of synaptic plasticity, but could not be used to test their functionality in the intact, behaving brain. In-vivo studies usually focused on analysis of the responsiveness of single cells, but did not examine interactions between pairs of neurons. In this study, we combined the two approaches. This was achieved by recording extracellularly and simultaneously the spike activity of several single cells in the auditory cortex of the behaving monkey. The efficacy of neuronal interactions was estimated by measuring the correlation between firing times of pairs of single neurons. Using acoustic stimuli, a version of cellular conditioning was applied when the monkey performed an auditory discrimination task and when it did not. We found that: (i) functional plasticity is a function of the change in correlation, and not of the correlation or covariance per se, and (ii) functional plasticity depends critically on behavior. During behavior, an increase in the correlation caused a short-lasting strengthening of the neuronal coupling efficacy, and a decrease caused a short-lasting weakening. These findings indicate that neuronal plasticity in the auditory cortex obeys a version of Hebb's associative rule under strong behavioral control, as predicted by Thorndike's "Law of Effect".

Acoustic Stimulation↗
PubMedDate not supplied

Emergence of spatio-temporal patterns in neuronal activity.

This paper explores if dynamic modulation of coherent firing serves cortical functions. We recorded neuronal activity in the frontal cortex of behaving monkeys and found that temporal coincidences of spikes firing of different neurons can emerge within a fraction of a second in relation to the animal behavior. The temporal patterns of the correlation could not be predicted from the modulations of the neurons firing rate and finally, the patterns of correlation depend on the distance between neurons. These findings call for a revision of prevailing models of neural coding that solely rely on firing rates. The findings suggest that modification of neuronal interactions can serve as a mechanism by which neurons associate rapidly into a functional group in order to perform a specific computational task. Increased correlation between members of the groups, and decreased or negative correlation with others, enhance the ability to dissociate one group from concurrently activated competing groups. Such modulation of neuronal interactions allows each neuron to become a member of several different groups and participate in different computational tasks.

Animals↗
PubMedDate not supplied

Temporal firing patterns of single units, pairs and triplets of units in the auditory cortex.

The spontaneous and acoustically driven activities of single units, pairs and triplets of units in the auditory cortex were analyzed. Data were obtained in two sets of experiments from nonbehaving awake cats and from a behaving monkey. The results of the two sets of experiments indicated that neighboring neurons usually fire independently. The weak correlations found between pairs of adjacent neurons were mostly indicative of a common input driving both units. In some cases, signs of synaptic interaction between the neurons were found. When triplets of units were considered, it was found that several independent inputs exist, even within a small group of adjacent neurons. When such small groups of neurons were studied in the behaving monkey, it was found that the temporal firing pattern of single neurons and the interactions between pairs of neurons were in some cases dependent on the behavioral state and on the sensorimotor association.

Animals↗