CA2 inhibition reduces the precision of hippocampal assembly reactivation.

The structured reactivation of hippocampal neuronal ensembles during fast synchronous oscillatory events, termed sharp-wave ripples (SWRs), has been suggested to play a crucial role in the storage and use of memory. Activity in both the CA2 and CA3 subregions can precede this population activity in CA1, and chronic inhibition of either region alters SWR oscillations. However, the precise contribution of CA2 to the oscillation, as well as to the reactivation of CA1 neurons within it, remains unclear.

Development of serotonergic projections to the suprachiasmatic nucleus in the mouse brain.

Serotonin (5-HT) and its innervation have been implicated in various neural functions including circadian systems. Although classical studies have examined the 5-HT innervation pattern in the adult suprachiasmatic nucleus (SCN), the fine-grained morphological study of the development of pathway and terminal projections to the SCN remains scarce. Here, we utilize transgenic mice expressing GFP under the serotonin transporter (SERT) promoter to subserve our developmental mapping study.

Encoding of social exploration by neural ensembles in the insular cortex.

The insular cortex (IC) participates in diverse complex brain functions, including social function, yet their cellular bases remain to be fully understood. Using microendoscopic calcium imaging of the agranular insular cortex (AI) in mice interacting with freely moving and restrained social targets, we identified 2 subsets of AI neurons-a larger fraction of "Social-ON" cells and a smaller fraction of "Social-OFF" cells-that change their activity in opposite directions during social exploration. Social-ON cells included those that represented social investigation independent of location and consisted of multiple subsets, each of which was preferentially active during exploration under a particular behavioral state or with a particular target of physical contact.

Comprehensive topographical map of the serotonergic fibers in the male mouse brain.

It is well established that serotonergic fibers distribute throughout the brain. Abnormal densities or patterns of serotonergic fibers have been implicated in neuropsychiatric disorders. Although many classical studies have examined the distribution pattern of serotonergic fibers, most of them were either limited to specific brain areas or had limitations in demonstrating the fine axonal morphology.

Imaging the Neural Circuit Basis of Social Behavior: Insights from Mouse and Human Studies.

Social behavior includes a variety of behaviors that are expressed between two or more individuals. In humans, impairment of social function (i.e.