Alpha Power Predicts Persistence of Bistable Perception

Abstract

Perception is strongly affected by the intrinsic state of the brain, which controls the propensity to either maintain a particular perceptual interpretation or switch to another. To understand the mechanisms underlying the spontaneous drive of the brain to explore alternative interpretations of unchanging stimuli, we repeatedly recorded high-density EEG after normal sleep and after sleep deprivation while participants observed a Necker cube image and reported the durations of the alternating representations of their bistable perception. We found that local alpha power around the parieto-occipital sulcus within the first second after the emergence of a perceptual representation predicted the fate of its duration. An experimentally induced increase in alpha power by means of sleep deprivation increased the average duration of individual representations. Taken together, these findings show that high alpha power promotes the stability of a perceptual representation and suppresses switching to the alternative. The observations support the hypothesis that synchronization of alpha oscillations across a wide neuronal network promotes the maintenance and stabilization of its current perceptual representation. Elevated alpha power could also be key to the poorly understood cognitive deficits, that typically accompany sleep deprivation, such as the loss of mental flexibility and lapses of responsiveness.An important feature of the perceptual system is its flexibility to process identical physical stimuli in different ways depending on the circumstances. It enables, for example, the maintenance of attention to stimulus properties with expected reward and prevents interference from distracting aspects of the same stimulus. This flexibility is highly dependent on and tightly controlled by ongoing brain activity 1, 2 . Even at rest, when faced with an unchanging physical stimulus, the brain continues to explore alternative perceptual interpretations, a property that becomes manifest when the stimulus is an ambiguous figure [3][4][5] . There have been continued efforts to identify the neuronal correlates of this perceptual flexibility. One of the most likely candidates are the oscillations of neuronal origin, because the numerous combinations of frequency, amplitude, and phase modulation offer a sophisticated and precise mechanism to entrain diverse neuronal populations that encode the same perceptual object 6,7 . The ability of oscillations, in particular alpha (~10 Hz), to encode multiple sources of information is demonstrated by the correlation of alpha power with the number of items in working memory 8 . This process is thought to be mediated by the inhibition that alpha exerts on task-irrelevant brain regions, thereby favoring focused attention 9-12 . Spontaneous fluctuations in alpha power [13][14][15][16] have been shown to determine the subject's ability and accuracy to process stimuli [17][18][19][20][21] . These observations support the interpretation that alpha reflects a neural mechanism that regulates the amount of...

Frequency of alpha oscillation predicts individual differences in perceptual stability during binocular rivalry

“…Our data did not, however, show a relationship between percept duration and individual alpha amplitude. This is in contrast to a recent report that alpha amplitude can influence perceptual stability of the Necker cube within individuals (Piantoni, Romeijn, Gomez‐Herrero, Van Der Werf, & Van Someren, ). There are two possibilities for this discrepancy.…”

Inhibition in selective attention

“…Rather than playing a role in inhibition per se, alpha oscillations may thus enhance tuning to task‐relevant features in visual regions by selectively suppressing the activity of neurons tuned to other features. Interestingly, and furthermore in line with this possibility, recent studies have related increased alpha‐band activity to more stable visual percepts, leading to the proposal that alpha oscillations may not signal inhibition of cortical activity per se, but stabilization of the current configuration of neuronal activity . From this perspective, the observed distractor location learning–related increase in prestimulus alpha activity in the study by Wang and colleagues discussed above could also denote sharper representation of distracting information (Fig.…”

“…Given the tight link between alpha‐band activity and spatial attention, suppression operating at spatial priority maps likely relies on modulations of alpha oscillations. More work, however, is necessary to determine the functional significance of alpha‐band oscillatory activity, especially since recent work indicates that alpha oscillations may not signal top‐down inhibition of cortical activity per se, but stabilization of the current configuration of neuronal activity, possibly through enhancing signal‐to‐noise . Distractor expectation–dependent increases in prestimulus alpha activity thus may not necessarily reflect preparatory inhibition (Fig.…”

“…1C). We will also discuss recent findings that show that alpha‐band oscillations may play an important role in facilitating processing of goal‐relevant information, by suppressing noise or stabilizing the representation of the attended stimulus . We explore the possibility that alpha oscillations could similarly modulate the representation of distracting information.…”

Pre-stimulus feedback connectivity biases the content of visual experiences

“…That the connectivity pathway is in the feedback direction and in the lower frequencies is also well in line with the finding that alpha/beta oscillations subserve feedback connectivity among human (53) and monkey (54) visual cortical areas. Additionally, occipital alpha oscillations have been shown to predict the persistence of bistable perception (55), and percept-dependent changes in occipital oscillatory activity have been suggested to reflect top-down modulations of V1 by extrastriate areas (56). Our findings therefore suggest that in the absence of visual stimulation, mechanisms that mimic known dynamics of unambiguous as well as ambiguous visual object perception are at play.…”