Mapping REM- and Wake-Active Neurons in the Dorsal Pons

Cox J, Pinto L, Dan Y. Calcium imaging of sleep-wake related neuronal activity in the dorsal pons. Nat Commun 2016;7:10763. doi: 10.1038/ncomms10763.

Background: The dorsal pons has long been recognized as critical for generating rapid eye movement (REM) sleep, but the underlying circuitry and cell-type-specific mechanisms remain unclear. Distinct neuronal populations, including glutamatergic and GABAergic cells, display state-dependent activity across the sleep–wake cycle, yet their spatial organization and specific contributions to REM and wakefulness have not been well defined.

Hypothesis: This study hypothesized that distinct subpopulations of glutamatergic and GABAergic neurons in the dorsal pons exhibit characteristic and spatially organized activity patterns that correlate with specific behavioral states such as REM sleep and wakefulness.

Methods: The authors performed cell-type-specific calcium imaging in freely moving mice expressing GCaMP6s in glutamatergic or GABAergic neurons of the dorsal pons. Activity was recorded through an implanted gradient refractive index (GRIN) lens coupled to a miniaturized fluorescence microscope and analyzed across natural sleep–wake transitions. Two-photon imaging was conducted using a movable objective microscope controlled by ScanImage to confirm signal specificity.

Results: GABAergic neurons were significantly modulated by brain state and mostly active during wakefulness, with smaller subsets active during REM sleep. In contrast, most glutamatergic neurons were maximally active during REM sleep, showing increased activity at transitions into REM and decreased activity when awakening. These REM-active glutamatergic neurons were preferentially located medially, whereas wake-active neurons were more lateral.

Conclusions: This study concluded that dorsal pontine glutamatergic and GABAergic neurons display distinct and spatially organized sleep–wake activity patterns, suggesting that specific subpopulations within this region contribute differentially to REM sleep and wakefulness regulation.