Tonic excitation of nucleus reuniens decreases prefrontal-hippocampal coordination during slow-wave states.

The nucleus reuniens of the thalamus (RE) is an important node between the medial prefrontal cortex (mPFC) and the hippocampus (HPC). Previously, we have shown that its mode of activity and its influence in mPFC-HPC communication is dependent upon brain state. During slow-wave states, RE units are closely and rhythmically coupled to the ongoing mPFC-slow oscillation (SO), while during activated (theta) states, RE neurons fire in an arrhythmic and tonically active manner.

Prefrontal-Hippocampal Pathways Through the Nucleus Reuniens Are Functionally Biased by Brain State.

Circuit-level communication between disparate brain regions is fundamental for the complexities of the central nervous system operation. Co-ordinated bouts of rhythmic activity between the prefrontal cortex (PFC) and hippocampus (HPC), in particular, are important for mnemonic processes. This is true during awake behavior, as well as during offline states like sleep.

The Reuniens Nucleus of the Thalamus Has an Essential Role in Coordinating Slow-Wave Activity between Neocortex and Hippocampus.

Sleep is a period of profound neural synchrony throughout the brain, a phenomenon involved in various physiological functions. The coordination between neocortex and hippocampus, in particular, appears to be critical for episodic memory, and, indeed, enhanced synchrony in this circuit is a hallmark of slow-wave sleep. However, it is unclear how this coordination is mediated.

Hyperoxia enhances slow-wave forebrain states in urethane-anesthetized and naturally sleeping rats.

Oxygen (O) is a crucial element for physiological functioning in mammals. In particular, brain function is critically dependent on a minimum amount of circulating blood levels of O and both immediate and lasting neural dysfunction can result following anoxic or hypoxic episodes. Although the effects of deficiencies in O levels on the brain have been reasonably well studied, less is known about the influence of elevated levels of O (hyperoxia) in inspired gas under atmospheric pressure.