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Published on: June 29, 2018
Period concatenation underlies interactions between gamma and beta rhythms in neocortex
Anita K Roopun1, Mark A Kramer, Lucy M Carracedo
1Institute of Neuroscience, Newcastle University Newcastle, UK.
Frontiers in Cellular Neuroscience
|October 24, 2008
Summary
Cortical rhythms interact via period concatenation, generating new frequencies like beta1 (15 Hz) from gamma (40 Hz) and beta2 (25 Hz). This process, using the golden mean, may enable parallel information processing across multiple temporal scales.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Brain Rhythms
Background:
- The neocortex exhibits diverse rhythmic electrical activity across frequency bands.
- The functional significance of interactions and transitions between distinct brain frequencies remains unclear.
- Existing models explain interactions for frequencies differing by factors of two or more (phase synchronization, amplitude modulation).
Purpose of the Study:
- To investigate how coexpressed cortical rhythms with frequency differences less than a factor of two interact.
- To elucidate the mechanism by which gamma (40 Hz) and beta2 (25 Hz) rhythms generate a third frequency.
- To explore the potential functional implications of these interactions for information processing.
Main Methods:
- Analysis of coexpressed gamma (40 Hz) and beta2 (25 Hz) rhythms in superficial and deep cortical laminae.
- Investigating the generation of a third frequency (beta1 - 15 Hz) through period concatenation.
- Quantifying frequency ratios and temporal interactions.
Main Results:
- Gamma (40 Hz) and beta2 (25 Hz) rhythms, with low temporal interaction, combine to generate beta1 (15 Hz) rhythms with strong temporal interaction.
- The generation process involves period concatenation, where microcircuits for gamma and beta2 rhythms act as building blocks for beta1.
- The ratio of adjacent frequency components approximated the golden mean, minimizing interactions and enabling frequency transitions.
Conclusions:
- Period concatenation provides a mechanism for generating novel frequencies from existing rhythms in the neocortex.
- The golden mean ratio facilitates flexible frequency transitions and minimizes temporal interference.
- This interaction mechanism may support multiplexing and parallel information processing on multiple timescales within the brain.
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