The Theta-Gamma Neural Code

John E. Lisman, Ole Jensen
2013 Neuron  
Theta and gamma frequency oscillations occur in the same brain regions and interact with each other, a process called cross-frequency coupling. Here, we review evidence for the following hypothesis: that the dual oscillations form a code for representing multiple items in an ordered way. This form of coding has been most clearly demonstrated in the hippocampus, where different spatial information is represented in different gamma subcycles of a theta cycle. Other experiments have tested the
more » ... tional importance of oscillations and their coupling. These involve correlation of oscillatory properties with memory states, correlation with memory performance, and effects of disrupting oscillations on memory. Recent work suggests that this coding scheme coordinates communication between brain regions and is involved in sensory as well as memory processes. Kim, J., Delcasso, S., and Lee, I. (2011). Neural correlates of object-in-place learning in hippocampus and prefrontal cortex. J. Neurosci. 31, 16991-17006. Kim, S.M., Ganguli, S., and Frank, L.M. (2012). Spatial information outflow from the hippocampal circuit: distributed spatial coding and phase precession in the subiculum. J. Neurosci. 32, 11539-11558. King, C., Recce, M., and O'Keefe, J. (1998). The rhythmicity of cells of the medial septum/diagonal band of Broca in the awake freely moving rat: relationships with behaviour and hippocampal theta. Eur. J. Neurosci. 10, 464-477. Koene, R.A., and Hasselmo, M.E. (2007). First-in-first-out item replacement in a model of short-term memory based on persistent spiking.
doi:10.1016/j.neuron.2013.03.007 pmid:23522038 pmcid:PMC3648857 fatcat:iivx4zy7f5e5bo6hojkkfnrdva