A Theta-Gamma Neural Code for Feature Set Composition with Phase-Entrained Delta Nestings*

Continuing a recent line of research into the functional role of neural oscillations in language and cognition, I propose that a central computational system (implemented via gamma, theta and delta interactions) interfaces with external interpretive and attentional systems (implemented via beta and alpha modulations) to derive certain core features of phrasal construction. These interactions are achieved through the coupling of the phase and amplitude of distinct rhythms. A theta-gamma code generates the initial feature-set while thalamic and occipital alpha is used to inhibit irrelevant information sources. This code is itself embedded within left-cortical delta rhythms while an increasing beta rhythm, which finds its source within a cortico-basal ganglia-thalamo-cortical loop, is used to maintain the existing cognitive set in memory. Neuroethological arguments are presented in favour of the species-specific nature of this neural code, and it is argued that the unique hierarchies exhibited in natural language emerge from this human-specific rhythmic profile.