The role of neuronal synchronization in selective attention (original) (raw)
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Journal of Neuroscience, 2008
In addition to the modulation of synchronization during visual stimulation, selective attention significantly changed the prestimulus pattern of synchronization. Attention inside the receptive field of the recorded neuronal population enhanced gamma-band synchronization and strongly reduced ␣-band (9 -11 Hz) synchronization in the prestimulus period. These results lend further support for a functional role of rhythmic neuronal synchronization in attentional stimulus selection.
Rhythmic Neuronal Synchronization Subserves Selective Attentional Processing
Selective attention relies on dynamic restructuring of cortical information flow to prioritize neuronal communication between those neuronal groups conveying information about behaviorally relevant information while reducing the influence from groups encoding irrelevant and distracting information. Electrophysiological evidence suggests that such selective neuronal communication is instantiated and sustained through selective neuronal synchronization of rhythmic gamma band activity within and between neuronal groups. Attentionally modulated synchronization patterns evolve rapidly, are evident even before sensory inputs arrive, follow closely subjective readiness to process information in time, can be sustained for prolonged time periods, and convey specific information about perceptually selected sensory features and motor plans. These functional implications of selective synchronization patterns are complemented by recent insights about the mechanistic origins of rhythmic synchronization at micro- and macro- scales of cortical neuronal processing, suggesting that selective attention is subserved by precise neuronal synchronization that is selective in space, time and frequency.
Buia CI, Tiesinga PH. Role of interneuron diversity in the cortical microcircuit for attention. fields of neurons in cortical area V4 are large enough to fit multiple stimuli, making V4 the ideal place to study the effects of selective attention at the single-neuron level. Experiments have revealed evidence for stimulus competition and have characterized the effect thereon of spatial and feature-based attention. We developed a biophysical model with spiking neurons and conductance-based synapses. To account for the comprehensive set of experimental results, it was necessary to include in the model, in addition to regular spiking excitatory (E) cells, two types of interneurons: feedforward interneurons (FFI) and top-down interneurons (TDI). Feature-based attention was mediated by a projection of the TDI to the FFI, stimulus competition was mediated by a cross-columnar excitatory connection to the FFI, whereas spatial attention was mediated by an increase in activity of the feedforward inputs from cortical area V2. The model predicts that spatial attention increases the FFI firing rate, whereas feature-based attention decreases the FFI firing rate and increases the TDI firing rate. During strong stimulus competition, the E cells were synchronous in the beta frequency range (15-35 Hz), but with featurebased attention, they became synchronous in the gamma frequency range (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50). We propose that the FFI correspond to fast-spiking, parvalbumin-positive basket cells and that the TDI correspond to cells with a double-bouquet morphology that are immunoreactive to calbindin or calretinin. Taken together, the model results provide an experimentally testable hypothesis for the behavior of two interneuron types under attentional modulation.
Journal of Neuroscience, 2010
In this computational work, we investigated gamma-band synchronization across cortical circuits associated with selective attention. The model explicitly instantiates a reciprocally connected loop of spiking neurons between a sensory-type (area MT) and an executive-type (prefrontal/parietal) cortical circuit (the source area for top-down attentional signaling). Moreover, unlike models in which neurons behave as clock-like oscillators, in our model single-cell firing is highly irregular (close to Possion) while local field potential exhibits a population rhythm. In this "sparsely synchronized oscillatory" regime, the model reproduces and clarifies multiple observations from behaving animals. Top-down attentional inputs have a profound effect on network oscillatory dynamics while only modestly affecting single-neuron spiking statistics. In addition, attentional synchrony modulations are highly selective: Inter-areal neuronal coherence occurs only when there is a close match between the preferred feature of neurons, the attended feature and the presented stimulus, a prediction that is experimentally testable. When inter-areal coherence was abolished attention-induced gain modulations of sensory neurons were slightly reduced. Therefore, our model reconciles the rate and synchronization effects, and suggests that interareal coherence contributes to large-scale neuronal computation in the brain through modest enhancement of rate modulations as well as a pronounced attention-specific enhancement of neural synchrony.
NeuroImage, 2013
Groups of neurons tend to synchronize in distinct frequency bands. Within a given frequency band, synchronization is defined as the consistency of phase relations between site pairs, over time. This synchronization has been investigated in numerous studies and has been found to be modulated by sensory stimulation or cognitive conditions. Here, we investigate local field potentials (LFPs) and multi-unit activity (MUA) recorded from area V4 of two monkeys performing a selective visual attention task. We show that phase relations, that are consistent over time, are typically diverse across site pairs. That is, across site pairs, mean phase relations differ substantially and this across-site-pair phase-relation diversity (SPHARED, for Spatial PHAse RElation Diversity) is highly reliable. Furthermore, we show that visual stimulation and selective attention can shift the pattern of phase relations across site pairs. These shifts are again diverse and this across-site-pair phase-relation-shift diversity (SPHARESD) is again highly reliable. We find SPHARED for LFP-LFP, LFP-MUA and MUA-MUA pairs, stimulus-induced SPHARESD for LFP-LFP and LFP-MUA pairs, and attention-induced SPHARESD for LFP-LFP pairs. SPHARESD is a highly interesting signal from the perspective of impact on downstream neuronal activity. We provide several pieces of evidence for such a role.
Modulation of the synchronization between cells in visual cortex by contextual targets
European Journal of Neuroscience, 2001
It has been suggested that synchronization of action potentials encodes diverse features of a single image. However, properties of the synchronization, which occurs on a time scale of » 1±5 ms, are still poorly understood. We have tested the modulation of synchronization by manipulating the contextual targets introduced in the surround of the receptive ®eld. Experiments were carried out on anaesthetized cats prepared for multiunit and single-cell recordings in area 17. Initially, a patch of sine-wave drifting grating was positioned over the overlapping receptive ®elds of several neurons. If this coherent motion produced a signi®cant synchronization in cross-correlograms, contextual targets were added. The ®rst contextual stimuli were two sine-wave patches placed above and below the central compound receptive ®eld. Only the contrast of contextual targets changed. Results show that the larger the differential contrast the higher the synchronization. The second contextual stimulus was a lateral shift of a sinewave patch. Data show that the wider the distance between the central and peripheral patches the better the synchronization. Furthermore, results suggest that the synchrony pattern computed by cross correlating multiunit recordings from two sites differs when the cross correlation is carried out between individual units belonging to each multiunit recording. Together with our previous results it appears that synchronization is stimulus dependent and its strength increases with larger disparities included in the whole stimulating image.
Entrainment of Neuronal Oscillations as a Mechanism of Attentional Selection
Science, 2008
The following resources related to this article are available online at Whereas gamma-band neuronal oscillations clearly appear integral to visual attention, the role of lower-frequency oscillations is still being debated. Mounting evidence indicates that a key functional property of these oscillations is the rhythmic shifting of excitability in local neuronal ensembles. Here, we show that when attended stimuli are in a rhythmic stream, delta-band oscillations in the primary visual cortex entrain to the rhythm of the stream, resulting in increased response gain for task-relevant events and decreased reaction times. Because of hierarchical cross-frequency coupling, delta phase also determines momentary power in higher-frequency activity. These instrumental functions of low-frequency oscillations support a conceptual framework that integrates numerous earlier findings.
Temporal dynamics of attention-modulated neuronal synchronization in macaque V4
Neurocomputing, 2003
It was recently observed that neurons in area V4 exhibited enhanced gamma band (35 -90 Hz) synchronization when monkeys attended to a visual stimulus as compared to when they were not attending to the same stimulus (Science 291 (2001) 1560). Spike-triggered averaging of local ÿeld potentials (LFPs) was used to show attentional modulation in an early period from 50 to 150 ms after stimulus onset (Science 291 ). In this work we further studied the ÿne temporal structure in the same data by focusing only on the LFPs without reference to the concurrent spike trains. With the method of adaptive multivariate autoregressive (AMVAR) modeling, we discovered that attentional modulation of gamma power (∼65 Hz) in V4 can be as brief as about 25 ms. Gamma coherence between two V4 recording sites revealed similar attention e ects, as well as a second peak around 45 Hz. Directional in uences between two V4 populations revealed that one can play a more dominant role than another. These results implicate gamma oscillation as a possible agent in carrying out attention-biased competition among visual stimuli in favor of those that are behaviorally relevant. The AMVAR method was instrumental in revealing the dynamics of gamma frequency synchronization with high temporal and frequency resolution.