Coupling of hippocampal theta and ripples with pontogeniculooccipital waves

The hippocampus has a major role in encoding and consolidating long-term memories, and undergoes plastic changes during sleep(1). These changes require precise homeostatic control by subcortical neuromodulatory structures(2). The underlying mechanisms of this phenomenon, however, remain unknown. Here, using multi-structure recordings in macaque monkeys, we show that the brainstem transiently modulates hippocampal network events through phasic pontine waves known as pontogeniculooccipital waves (PGO waves). Two physiologically distinct types of PGO wave appear to occur sequentially, selectively influencing high-frequency ripples and low-frequency theta events, respectively. The two types of PGO wave are associated with opposite hippocampal spike-field coupling, prompting periods of high neural synchrony of neural populations during periods of ripple and theta instances. The coupling between PGO waves and ripples, classically associated with distinct sleep stages, supports the notion that a global coordination mechanism of hippocampal sleep dynamics by cholinergic pontine transients may promote systems and synaptic memory consolidation as well as synaptic homeostasis. Studies using multi-structure recordings in macaque monkeys show that distinct phasic pontogeniculooccipital waves modulate hippocampal network events similar to those that underlie the learning and formation of memories during sleep.

Automated summary

Studies demonstrate that the brainstem modulates hippocampal network events through PGO waves, promoting the learning and formation of memories. Different types of PGO waves influence events at different frequencies, leading to high neural synchrony within neural populations.