Neuronal oscillations, attention, and normalization circuits

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Attention aids our ability to perceive our external world in detail and to learn which aspects are relevant for successful behavior. Studies over the last 20-30 years have revealed how attention alters the processing of information at the neuronal level, but the studies have often generated conflicting results. Attention increases the neuronal activity of neurons that represent the attended object. Attention can also change the level of rhythmic activity between different neuronal circuits and thereby improve the communication between channels. This Rhythmic activity has been proposed to play an important role in cognitive functions such as attention, perception, working memory, and other cognitive functions. Disruption of this rhythmicity is associated with cognitive deficits as seen in schizophrenia, autism, Alzheimer disease and Parkinson's disease. Despite these insights, we nevertheless have a poor understanding how increases of neuronal activity or alterations of rhythmic activity are mediated or controlled. We still know little about the neuronal circuits involved. We equally have very limited insight why differences are found in different brain areas or why subtly different tasks can yield very different effects on these measures of brain activity. Recent theoretical models propose a mechanism to reconcile these conflicts. They propose that attention acts on inhibitory (normalization) circuits in the brain and thus controls activity levels and rhythmicity levels. These models, despite their explanatory success in silico, need experimental validation. By doing so, we will gain a more detailed understanding of different circuits involved in cognition, and also obtain a more mechanistic understanding in the genesis of cognitive dysfunctions.