Oscillatory Recruitment of Bilateral Visual Cortex during Spatial Attention to Competing Rhythmic Inputs

Abstract

Selective attention uses temporal regularity of relevant inputs to bias the phase of ongoing population-level neuronal oscillations. This phase entrainment streamlines processing, allowing attended information to arrive at moments of high neural excitability. How entrainment resolves competition between spatially segregated inputs during visuospatial tasks is not yet established. Using high-density electroencephalography in humans, a bilateral entrainment response to the rhythm (1.3 or 1.5 Hz) of an attended stimulation stream was observed, concurrent with a considerably weaker contralateral entrainment to a competing rhythm. That ipsilateral visual areas strongly entrained to the attended stimulus is notable because competitive inputs to these regions were being driven at an entirely different rhythm. Strong modulations of phase locking and weak modulations of single-trial power suggest that entrainment was primarily driven by phase-alignment of ongoing oscillatory activity. In addition, interhemispheric differences in entrained phase were found to be modulated by attended hemifield, implying that the bilateral nature of the response reflected a functional flow of information between hemispheres. This modulation was strongest at the third of at least four harmonics that were strongly entrained. Ipsilateral increases in alpha-band (8 -12 Hz) power were also observed during bilateral entrainment, reflecting suppression of the ignored stimulation stream. Furthermore, both entrainment and alpha lateralization significantly affected task performance. We conclude that oscillatory entrainment is a functionally relevant mechanism that synchronizes endogenous activity across the cortical hierarchy to resolve spatial competition. We further speculate that concurrent suppression of ignored input might facilitate the widespread propagation of attended information during spatial attention.

Pre-stimulus alpha oscillations over somatosensory cortex predict tactile misperceptions

“…We found a similar negative relationship between alpha and reporting of touch over ipsilateral somatosensory cortex on touch absent trials as we found over contralateral cortex. Alpha over sensory regions other than the primary region associated with a task may play a key role in suppressing irrelevant information -the gating-by-inhibition hypothesis -as seen in a number of studies of spatial attention (Gray, Frey, Wilson, & Foxe, 2015;Haegens et al, 2011Haegens et al, , 2011Jensen & Mazaheri, 2010). Thus, when attending to the right hand, alpha power increases over right, ipsilateral somatosensory cortices and decreases over left, contralateral somatosensory cortices.…”

Macronutrient composition of a morning meal and the maintenance of attention throughout the morning

“…15,16 Finally, the Spatial CTET is known to produce reliable deployment of alpha activity. 14 It is, therefore, particularly well suited to the current investigation.…”

“…The primary task employed in the present experiment was the Spatial Continuous Temporal Expectancy Task (Spatial CTET 14 ). As a variant of a Continuous Performance Task (CPT), the Spatial CTET requires sustained visuospatial attention to a stream of visual information over a time-scale of several minutes.…”

“…For these reasons, the Spatial CTET is particularly well suited for the current aim. The task is here described briefly, but the reader is encouraged to review Gray et al 14 for another thorough description of the task and characterization of associated neurophysiological findings.…”

“…In a cross-over design, EEG, task performance, and metrics of hunger/fullness were simultaneously recorded as adult participants under three breakfast conditions – two calorie-matched, carbohydrate-rich breakfasts with differing carbohydrate availabilities (oatmeal and cornflakes) as well as a volume-matched water condition-performed a demanding continuous performance task (CPT) variant requiring sustained attention across the morning. While CPT variants have been consistently employed to this end and have successfully revealed interactions between nutrition and attention, 1,2 the current CPT variant has an added advantage: it has been validated in the literature to produce reliable attentional deployment of alpha oscillations, 14 suggesting a unique opportunity to probe the nuanced effects of macronutrient composition, as indexed by available carbohydrate load of the two solid breakfast conditions (oatmeal: 39.77 g, cornflakes: 56.66 g), on both behavior and a fundamental neural mechanism of attention. Relative to cornflakes, it was hypothesized that oatmeal, with its reduced available carbohydrate load and glycemic index, would promote steady glycemic availability throughout the experimental session, enabling increased task performance and sustained attentional deployment of alpha oscillations throughout the morning.…”