Commentary: Alpha Synchrony and the Neurofeedback Control of Spatial Attention

Gundlach, Christopher; Forschack, Norman · 2020 · Crossref

DOI: 10.3389/fnins.2020.00597

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Summary

This commentary critiques the causal claims made by Bagherzadeh et al. (2019) regarding the relationship between alpha-band neural activity and spatial attention. The original study proposed that upregulating parietal alpha-lateralization via neurofeedback causally induces shifts in visuospatial attention. Gundlach and Forschack argue that this conclusion is flawed because it fails to adequately rule out the reverse causal direction: that participants used covert spatial attention strategies to modulate their alpha-band activity, rather than alpha modulation driving attentional shifts. Bagherzadeh et al. employed a neurofeedback task where participants learned to increase alpha amplitude lateralization while viewing a central stimulus. They reported several findings interpreted as evidence of attentional shifts: enhanced probe-related evoked responses contralateral to the downregulated hemisphere, persistent alpha power and reaction time lateralization in subsequent Posner paradigm trials, and contralateral gaze shifts in free-viewing tasks. To demonstrate that participants did not use spatial attention to achieve these alpha changes, the original authors analyzed microsaccades, finding no directional bias during the neurofeedback task compared to the Posner paradigm. They interpreted this null result as evidence that attention was not covertly shifted during neurofeedback. Gundlach and Forschack challenge this interpretation on methodological and theoretical grounds. First, they argue that null effects in conventional significance testing do not provide evidence for the null hypothesis, making the absence of microsaccade bias inconclusive. Second, they note that the attentional shift required during the neurofeedback task (approximately 3.4 degrees within a central object) is smaller than the shifts typically detected by microsaccade analysis (≥4 degrees), potentially rendering the measure insensitive to the specific strategy used. Third, they highlight that object-based attention may differ from spatial attention in its neural and oculomotor signatures. Crucially, the commentators point out that the original study’s finding of amplified probe responses on the trained side is a classic marker of sensory gain control associated with spatial attention. This finding contradicts the claim that attention was not deployed, suggesting instead that participants likely attended to lateral aspects of the central stimulus to modulate alpha power. The significance of this commentary lies in its call for more rigorous causal inference in neuroscience. The authors conclude that the claim of alpha-lateralization causing attentional shifts is not warranted given the competing explanation of reverse causation. They recommend future studies employ experimental manipulations of different strategies, instrumental variable approaches to control for confounds, and methods capable of detecting non-linear dependencies. This critique underscores the necessity of ruling out strategic confounds when establishing causal links between neural oscillations and cognitive processes.

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• attention selective divided