In the brain, synchronous activity is detected as oscillations at different frequencies. Experimental data from the hippocampus and neocortex link Phase-Amplitude Cross Frequency Coupling (PAC), where the amplitude of fast gamma oscillations aligns with the phase of slower theta/alpha waves, to cognitive functions like attention, learning and navigation. Traditionally, this mechanism was thought to be generated through the slow oscillation modulating the excitability and thus driving the fast gamma wave amplitude. However, recent findings using the Cross-Frequency Directionality (CFD) metric show that in the hippocampus, gamma amplitude reliably precedes in time the locally measured theta phase (CFD<0). In this computational study, we explore how neural connectivity influences these interactions. Specifically, we show that feedforward inhibition modeled by a theta-modulated ING (Interneuron Network Gamma) model results in fast-to-slow interactions. In contrast, feedback inhibition in a theta-modulated PING (Pyramidal Interneuron Network Gamma) model leads to slow-to-fast interactions. The fast-to-slow directionality is attributed to the rapid response of basket cell interneurons in gamma, which anticipates local theta activity. Additionally, we found that each motif is optimized for different types of input: fast-to-slow motifs better integrate non-theta inputs, while slow-to-fast motifs excel at integrating theta inputs. These findings suggest that CFD measurements reflect distinct neural circuit activations, each tailored to different computational demands.
Contact: Dimitrios Chalkiadakis, dimitrios@ifisc.uib.es
Institute for Cross-Disciplinary Physics and Complex Systems (IFISC), Palma de Mallorca, Spain and Institute of Neurosciences (IN), Alicante, Spain
Additional Authors:
Jaime Sánchez-Claros, Institute for Cross-Disciplinary Physics and Complex Systems, jaime@ifisc.uib-csic.es; Santiago Canals, Insute of Neurosciences Alicante, scanals@umh.es; Claudio Miraso, Institute for Cross-Disciplinary Physics and Complex Systems, claudio@ifisc.uib-csic.es