Dynamic θ Frequency Coordination within and between the Prefrontal Cortex-Hippocampus Circuit during Learning of a...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Systems Neuroscience

Background:

• The role of theta-scale coordination between the medial prefrontal cortex (mPFC) and hippocampus (dorsal and ventral) during spatial learning is not fully understood.
• Existing hypotheses suggest connectivity levels, not cognitive demands, predetermine coordination dynamics.

Purpose of the Study:

• To investigate theta frequency coordination dynamics within and between the mPFC, dorsal hippocampus (dHC), and ventral hippocampus (vHC) during spatial learning.
• To test if coherence levels change during the learning of a complex spatial avoidance task.

Main Methods:

• Adult male rats were implanted with EEG electrodes for local field potential (LFP) recording in the mPFC, dHC, and vHC.
• LFPs were analyzed for theta (θ) coherence between these regions during a spatial avoidance task.

Main Results:

• Contrary to hypotheses, θ coherence increased across mPFC-hippocampal circuits with task learning.
• Coherence was highest in the indirectly connected mPFC-dHC circuit, especially during early training.
• A temporal sequence of coherence peaks emerged before avoidance, with distinct sub-frequency fluctuations within the θ bandwidth.

Conclusions:

• Theta coherence within and between the mPFC and hippocampus changes with spatial avoidance learning and cognitive demand.
• Specific θ coherence sub-bandwidths, particularly an 8-9 Hz mPFC signal, play a role in organizing spatial avoidance behavior.