The many characters of visual alpha oscillations

Abstract

A central feature of human brain activity is the alpha rhythm: a 7-13 Hz oscillation observed most notably over occipitoparietal brain regions during periods of eyes-closed rest. Alpha oscillations covary with changes in visual processing and have been associated with a broad range of neurocognitive functions. In this article, we review these associations and suggest that alpha oscillations can be thought to exhibit at least five distinct 'characters': those of the inhibitor, perceiver, predictor, communicator and stabiliser. In short, while alpha oscillations are strongly associated with reductions in visual attention, they also appear to play important roles in regulating the timing and temporal resolution of perception. Furthermore, alpha oscillations are strongly associated with top-down control and may facilitate transmission of predictions to visual cortex. This is in addition to promoting communication between frontal and posterior brain regions more generally, as well as maintaining ongoing perceptual states. We discuss why alpha oscillations might associate with such a broad range of cognitive functions and suggest ways in which these diverse associations can be studied experimentally.

A review of plasticity induced by auditory and visual tetanic stimulation in humans

“…Moment‐to‐moment fluctuations in the power, phase, and lateralization of the alpha wave are associated with variability in visual signal detection, attention allocation, and balancing of task requirements (e.g. Clayton, Yeung, & Cohen Kadosh, ; Foxe & Snyder, ; Limbach & Corballis, , ). The synchronous firing of neurons associated with the generation of alpha can be disrupted by the presentation of visual stimulation, resulting in momentary desynchronization of the alpha rhythm when some neurons in the population respond to the stimulus and fire out of phase with the idling rhythm (e.g., Pfurtscheller, Neuper, & Mohl, ; Pfurtscheller, Stancák, & Neuper, ).…”

Generative modelling of the thalamo-cortical circuit mechanisms underlying the neurophysiological effects of ketamine

“…Oscillations in visual cortex typically demonstrate prominent oscillations in theta / alpha (4 -7, 8 -13 Hz), through beta (13 -30 Hz) up into the gamma (30+ Hz) range [16][17][18][19][20][21][22] . Subanaesthetic doses of ketamine, a uncompetitive NMDA receptor antagonist, have been shown to modulate both ends of this spectrum during task, with decreases in the amplitude of lower frequencies 23,24 and increases in the amplitude of higher frequencies 11,23 .…”

“…While the laminar and network generators of frequency-specific oscillations remain equivocal, prevailing theories propose distinct dominant laminar generators for oscillations of different frequencies. One particular proposal is that high frequencies tend to be formed by current densities in supragranular layers, while lower frequencies appear to predominate in deeper regions of cortex, around layer V/VI 20,25 or in thalamo-cortical loops 26,27 . Under this model, the noted effects of ketamine on both low and high frequency bands suggest altered neuronal functioning across much of the cortical laminae, and possibly in thalamo-cortical connectivity.…”

A sound-sensitive source of alpha oscillations in human non-primary auditory cortex

“…Second, primary and non-primary auditory fields have distinct architectonic and connectivity profiles (Clarke and Morosan, 2012), which may give rise to intrinsic dynamics at different timescales (Başar and Güntekin, 2008;Honey et al, 2013;Murray et al, 2014). Third, alpha oscillations have been associated with a range of neural operations and processes that may differentially engage lower versus higher levels of the cortical hierarchy (Clayton et al, 2018). These include functional inhibition (Klimesch et al, 2007;Jensen and Mazaheri, 2010), inter-areal synchronization (Palva et al, 2010), and the communication of sensory predictions (Bauer et al, 2014;Sedley et al, 2016;Auksztulewicz et al, 2017;Chao et al, 2018).…”

“…Most of what we know of human alpha oscillations derives from study of the dominant occipital and parietal sources detectable in scalp electroencephalography (EEG), particularly when the eyes are closed or during manipulations of visuo-spatial attention (Berger, 1931;Clayton et al, 2018). However, ongoing oscillations at the lower end of the alpha frequency range (7-10 Hz) have also been recorded from superior temporal cortex.…”