Neuronal Mechanisms and Attentional Modulation of Corticothalamic Alpha Oscillations

Abstract

Field potential oscillations in the ~10 Hz range are known as the alpha rhythm. The genesis and function of alpha has been the subject of intense investigation for the past 80 years. Whereas early work focused on the thalamus as the pacemaker of alpha rhythm, subsequent slice studies revealed that pyramidal neurons in the deep layers of sensory cortices are capable of oscillating in the alpha frequency range independently. How thalamic and cortical generating mechanisms in the intact brain might interact to shape the organization and function of alpha oscillations remains unclear. We addressed this problem by analyzing laminar profiles of local field potential (LFP) and multi-unit activity (MUA) recorded with linear array multielectrodes from the striate cortex of two macaque monkeys performing an intermodal selective attention task. Current source density (CSD) analysis was combined with CSD-MUA coherence to identify intracortical alpha current generators and assess their potential for pacemaking. Coherence and Granger causality analysis was applied to delineate the patterns of interaction among different alpha current generators. We found that: (1) separable alpha current generators are located in superficial, granular and deep layers, with both layer 4C and deep layers containing primary local pacemaking generators, suggesting the involvement of the thalamocortical network, and (2) visual attention reduces the magnitude of alpha oscillations as well as the level of alpha interactions, consistent with numerous reports of occipital alpha reduction with visual attention in human EEG. There is also indication that alpha oscillations in the lateral geniculate cohere with those in V1.

Alpha and gamma oscillations characterize feedback and feedforward processing in monkey visual cortex

“…2D). The Granger causality analysis also revealed a peak around 10 Hz, in accordance with a previous study (42), and a broader peak in the γ-range (SI Appendix, Fig. S15).…”

α-Oscillations in the monkey sensorimotor network influence discrimination performance by rhythmical inhibition of neuronal spiking

“…To this date, only a few intracranial studies have looked specifically into how the α-rhythm relates to spiking and performance (34)(35)(36)(37). Recent work using an intermodal attention paradigm where monkeys had to selectively attend to either a visual or an auditory stimulus has reported that increased α-activity in V2 and V4 resulted in faster auditory stimulus detection (36), and a decrease of α-activity in V1 was associated with visual attention (34).…”

“…Recent work using an intermodal attention paradigm where monkeys had to selectively attend to either a visual or an auditory stimulus has reported that increased α-activity in V2 and V4 resulted in faster auditory stimulus detection (36), and a decrease of α-activity in V1 was associated with visual attention (34). Furthermore, in V1, V2, and V4, coherence between α-band oscillations and (multiunit) spikes that decreased with visual attention was demonstrated (34,37). These findings are in line with our current findings and the inhibition hypothesis.…”

“…The key to understanding the phasic role of α-activity is to relate neuronal firing to both the phase and the magnitude of α-oscillations. Only recently this has become a topic of investigation in intracranial monkey studies focusing on visual areas (34)(35)(36)(37). The main issues to be uncovered are the following: (i) Does α-activity exercise an inhibitory or excitatory influence on local neuronal spiking?…”

MEG-measured visually induced gamma-band oscillations in chronic schizophrenia: Evidence for impaired generation of rhythmic activity in ventral stream regions

“…Alpha generators have been found in different layers of both striate and extra-striate visual areas (Bollimunta et al, 2008(Bollimunta et al, , 2011Mo et al, 2011;Haegens et al, 2015;van Kerkoerle et al, 2014), and are known to be modulated in activity by both cortico-cortical and recurrent thalamo-cortical (TC) communication (Steriade et al, 1990), influenced by thalamic nuclei such as the lateral geniculate nucleus (LGN), the pulvinar nucleus, and the thalamic reticular nucleus (TRN). Evidence is growing that these different thalamic nuclei play different roles in sensory information processing, both spatially (i.e., across the visual hierarchy) and temporally (i.e., during early feedforward and later feedback processing), raising the possibility that aberrant alpha-band activity in visual cortices may in part reflect aberrant TC-interactions.…”