Theta rhythms are electroencephalogram (EEG) waveforms between 4-12 Hz and are correlated with arousal, orientation, exploration, attention, learning and memory, motivational drives and emotions and movements. The last sixty years have been witness to a greatly increasing understanding of the underlying anatomical pathways and mechanisms necessary for theta rhythms. Today, it is well established that cells of the medial septal area (MSA) fire in a rhythmic bursting pattern to pace the theta rhythm in the hippocampus (HPC) and that lesioning the MSA abolishes theta rhythm in the HPC. However, comparatively little is known about the anatomy driving the theta rhythm of non-hippocampal areas, such as the prefrontal cortex (PFC). Therefore, this study examined whether the MSA also drives the theta rhythm in the PFC. Results indicated that selective infusions of the muscarinic receptor antagonist scopolamine into the MSA significantly decreased PFC theta power but had no effect on theta frequency. While this study has not been conducted before, these results coincide with other studies implicating the MSA as a widespread controller of theta power. Thus, it appears that the MSA affects PFC theta in the same manner as HPC theta with regards to both power and frequency.



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