Effect of Synaptic Connectivity on Long-Range Synchronization of Fast Cortical Oscillations (original) (raw)
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Synchronous cortical gamma-band activity in task-relevant cognition
NeuroReport, 2000
Widespread synchronous oscillatory activity, particularly in the gamma (`40 Hz') band, has been postulated to exist in the brain as a mechanism underlying binding. A new method of examining phase synchronicity across multiple electrode sites in speci®c EEG frequency bands as a function of time was employed, in a conventional cognitive ERP paradigm in 40 normal subjects. A signi®cant late post-stimulus gamma syn-chronicity response occurred for task-relevant stimuli, whereas for task-irrelevant stimuli no such response was evident. However, an early response was seen for both task-relevant and irrelevant stimuli. This is the ®rst empirical demonstration that widespread synchronous high frequency oscillations occur in humans in relation to cognition. NeuroReport 11:669±675 & 2000 Lippincott Williams & Wilkins.
2016
Neuronal gamma-band synchronization shapes information flow during sensory and cognitive processing. A common view is that a stable and shared frequency over time is required for robust and functional synchronization. To the contrary, we found that non-stationary instantaneous frequency modulations were essential for synchronization. First, we recorded gamma rhythms in monkey visual area V1, and found that they synchronized by continuously modulating their frequency difference in a phase-dependent manner. The frequency modulation properties regulated both the phase-locking and the preferred phase-relation between gamma rhythms. Second, our experimental observations were in agreement with a biophysical model of gamma rhythms and were accurately predicted by the theory of weakly coupled oscillators revealing the underlying theoretical principles that govern gamma synchronization. Thus, synchronization through instantaneous frequency modulations represents a fundamental principle of ga...
The European journal of neuroscience, 2015
Neuronal assemblies typically synchronize within the gamma band (30-80 Hz) and are fundamental to information processing. Despite numerous investigations, the exact mechanisms and origins of gamma oscillations are yet to be known. Here, through multiunit recordings in the primary visual cortex of cats we show that the strength of gamma power (20-40 Hz and 60-80 Hz) is significantly stronger between the functionally connected units than the unconnected units within an assembly. Furthermore, there is increased frequency coherence in the gamma range between the connected units than the unconnected units. Lastly, the higher gamma rhythms (60-80 Hz) are mostly linked to the fast-spiking neurons. These results led us to postulate that gamma activity is intrinsically generated between the connected units within cell-assemblies (microcircuits) in relation to the stimulus within an emergent '50 ms-temporal window-of-opportunity'. This article is protected by copyright. All rights res...
Is synchronized neuronal gamma activity relevant for selective attention?
Brain Research Reviews, 2003
Today, much evidence exists that sensory feature binding is accomplished by phase synchronization of induced neuronal gamma activity (30-80 Hz). Recent studies furthermore suggest that phase synchronization of induced gamma activity may represent a general mechanism enabling transient associations of neural assemblies and thus may play a central role in cortical information processing. Here, we describe findings indicating that synchronized gamma activity is moreover specifically involved in selective attention. While feature binding appears to depend primarily on induced gamma synchronization, attentional processes seem to involve both induced and evoked gamma oscillations. Yet it is still an open question, as to which topdown and bottom-up processes are associated with attentional modulation of gamma activity. A possible mechanism to project influences from attentional control structures to areas concerned with stimulus representation and vice versa, may be neuronal synchronization and the resulting firing rate changes of coincidence-detecting neurons in target areas.
Finding synchrony in the desynchronized EEG: the history and interpretation of gamma rhythms
Frontiers in Integrative Neuroscience, 2013
Neocortical gamma (30-80 Hz) rhythms correlate with attention, movement and perception and are often disrupted in neurological and psychiatric disorders. Gamma primarily occurs during alert brain states characterized by the so-called "desynchronized" EEG. Is this because gamma rhythms are devoid of synchrony? In this review we take a historical approach to answering this question. Richard Caton and Adolf Beck were the first to report the rhythmic voltage fluctuations in the animal brain. They were limited by the poor amplification of their early galvanometers. Thus when they presented light or other stimuli, they observed a disappearance of the large resting oscillations. Several groups have since shown that visual stimuli lead to low amplitude gamma rhythms and that groups of neurons in the visual cortices fire together during individual gamma cycles. This synchronous firing can more strongly drive downstream neurons. We discuss how gamma-band synchrony can support ongoing communication between brain regions, and highlight an important fact: there is at least local neuronal synchrony during gamma rhythms. Thus, it is best to refer to the low amplitude, high frequency EEG as an "activated" , not "desynchronized" , EEG.
A quantitative theory of gamma synchronization in macaque V1
eLife
Gamma-band synchronization coordinates brief periods of excitability in oscillating neuronal populations to optimize information transmission during sensation and cognition. Commonly, a stable, shared frequency over time is considered a condition for functional neural synchronization. Here, we demonstrate the opposite: instantaneous frequency modulations are critical to regulate phase relations and synchronization. In monkey visual area V1, nearby local populations driven by different visual stimulation showed different gamma frequencies. When similar enough, these frequencies continually attracted and repulsed each other, which enabled preferred phase relations to be maintained in periods of minimized frequency difference. Crucially, the precise dynamics of frequencies and phases across a wide range of stimulus conditions was predicted from a physics theory that describes how weakly coupled oscillators influence each other’s phase relations. Hence, the fundamental mathematical prin...