Slow Endogenous Fluctuations in Cortical fMRI Signals Correlate with Reduced Performance in a Visual Detection Task and Are Suppressed by Spatial Attention

Abstract

Spatial attention improves performance on visual tasks, increases neural responses to attended stimuli, and reduces correlated noise in visual cortical neurons. In addition to being visually responsive, many retinotopic visual cortical areas exhibit very slow (<0.1 Hz) endogenous fluctuations in functional magnetic resonance imaging signals. To test whether these fluctuations degrade stimulus representations, thereby impairing visual detection, we recorded functional magnetic resonance imaging responses while human participants performed a target detection task that required them to allocate spatial attention to either a rotating wedge stimulus or a central fixation point. We then measured the effects of spatial attention on response amplitude at the frequency of wedge rotation and on the amplitude of endogenous fluctuations at nonstimulus frequencies. We found that, in addition to enhancing stimulus-evoked responses, attending to the wedge also suppressed slow endogenous fluctuations that were unrelated to the visual stimulus in topographically defined areas in early visual cortex, posterior parietal cortex, and lateral occipital cortex, but not in a nonvisual cortical control region. Moreover, attentional enhancement of response amplitude and suppression of endogenous fluctuations were dissociable across cortical areas and across time. Finally, we found that the amplitude of the stimulus-evoked response was not correlated with a perceptual measure of visual target detection. Instead, perceptual performance was accounted for by the amount of suppression of slow endogenous fluctuations. Our results indicate that the amplitude of slow fluctuations of cortical activity is influenced by spatial attention and suggest that these endogenous fluctuations may impair perceptual processing in topographically organized visual cortical areas.

Are neuronal mechanisms of attention universal across human sensory and motor brain maps?

“…We also have ignored exogenously controlled attention since its properties appear to be notably different (Li et al, 2021). We focused primarily on the subprocess of attentional selection/enhancement and did not specifically address other subprocesses such as alerting (Posner, 2012), baseline shifting (Kastner et al, 1999;Seydell-Greenwald et al, 2014), reductions in low-frequency variability (Mitchell et al, 2009), slow fluctuations (Bressler et al, 2020), engagement/disengagement (Buschman & Kastner, 2015), or motivation (Engelmann et al, 2009). Within this restricted context, we assume that the primary role of attention is the selection, enhancement, and/or suppression of information or action alternatives.…”