Oscillations in many regions of the cortex have common temporal characteristics with dominant frequencies centered around the 40 Hz (gamma) frequency range and the 5-10 Hz (theta) frequency range. Experimental results also reveal spatially synchronous oscillations which are stimulus dependent (Gray and Singer, 1987; Gray et al., 1989; Engel et al., 1992). This rhythmic activity suggests that th...

In the spiked population model introduced by Johnstone [10], the population covariance matrix has all its eigenvalues equal to unit except for a few fixed eigenvalues (spikes). The question is to quantify the effect of the perturbation caused by the spike eigenvalues. Baik and Silverstein [6] establishes the almost sure limits of the extreme sample eigenvalues associated to the spike eigenvalue...

What is the 'meaning' of a single spike? Spike-triggered averaging ('reverse correlations') yields the typical input just before a spike. Similarly, cross-correlations describe the probability of firing an output spike given (one additional) presynaptic input spike. In this paper, we analytically calculate reverse and cross-correlations for a spiking neuron model with escape noise. The influenc...

Advances in neuronal recording techniques are leading to ever larger numbers of simultaneously monitored neurons. This poses the important analytical challenge of how to capture compactly all sensory information that neural population codes carry in their spatial dimension (differences in stimulus tuning across neurons at different locations), in their temporal dimension (temporal neural respon...

Correlated neural activity has been observed at various signal levels (e.g., spike count, membrane potential, local field potential, EEG, fMRI BOLD). Most of these signals can be considered as superpositions of spike trains filtered by components of the neural system (synapses, membranes) and the measurement process. It is largely unknown how the spike train correlation structure is altered by ...

There is controversy concerning whether orthodromic action potentials originate from the apical or basal dendrites of CA1 pyramidal cells in vivo. The participation of the dendrites in the initialization and propagation of population spikes in CA1 of urethan-anesthetized rats in vivo was studied using simultaneously recorded field potentials and current source density (CSD) analysis. CSD analys...

We present a novel non-parametric method for finding a subspace of stimulus features that contains all information about the response of a system. Our method generalizes similar approaches to this problem such as spike triggered average, spike triggered covariance, or maximally informative dimensions. Instead of maximizing the mutual information between features and responses directly, we use i...

Synaptic efficacy is modified following a brief train of high-frequency stimulation (HFS) to a cell's afferent fibers (long-term potentiation; LTP). An alteration in the postsynaptic response to endogenous neurotransmitter, as a result of an increase in the number of postsynaptic receptors, has been proposed (Baudry and Lynch, 1980). We tested this hypothesis in the CA1 hippocampus by intracell...

Visual processing in the cortex involves various aspects of neuronal properties such as morphological, electrophysiological and molecular. In particular, the neural firing pattern is an important indicator of dynamic circuitry within a neuronal population. Indeed, in microcircuits, neurons act as soloists or choristers wherein the characteristical activity of a 'soloist' differs from the firing...

The nature of the neural codes for pitch and loudness, two basic auditory attributes, has been a key question in neuroscience for over century. A currently widespread view is that sound intensity (subjectively, loudness) is encoded in spike rates, whereas sound frequency (subjectively, pitch) is encoded in precise spike timing. Here, using information-theoretic analyses, we show that the spike ...