Brain waves process visual signals layer by layer
Your brain processes what you see across multiple layers simultaneously. Researchers have now measured in detail which brain waves are active in which layer. That provides a sharper picture of how the brain organises information, and what goes wrong during cognitive ageing.
Using simultaneous EEG and fMRI (two techniques that measure electrical and blood-flow signals in the brain), scientists investigated how different frequencies of brain waves are linked to specific layers of the visual cortex. The study, published in eLife, shows that gamma waves (fast brain waves) strongly correlate with processing specific visual features in the superficial brain layers.
Alpha waves do more than inhibit
Researchers previously thought that alpha waves (slower brain waves) mainly serve an inhibitory function: suppressing brain areas that are not needed. This study finds that alpha waves also actively contribute to processing specific visual information, in both superficial and deep brain layers. That finding substantially refines the classical picture.
The layer-specific approach is novel. By using EEG and fMRI simultaneously, the researchers could link electrical signals to the precise brain location and layer. This reveals that the same brain wave plays a different role in different layers.
Relevance for ageing
Changes in the strength and organisation of brain waves are associated with cognitive decline in older age. If it becomes better understood which waves do what in which layers, that could improve future diagnostics of early cognitive decline. This research provides a more detailed map for that purpose. Clinical translation requires further study.
Search terms to explore further: cortical layer-specific oscillations EEG fMRI, alpha wave visual processing cortex, gamma oscillations neural coding