Nucleus_incertus
The nucleus incertus is a region of the pontine brainstem just ventral to the 4th ventricle.[1] The term was coined by George Streeter (Latin for "uncertain nucleus") based on its unknown function at the time, to name a group of cells he observed near the midline of the floor of the 4th ventricle.[2] It sometimes called the 'nucleus O'.[3]
The nucleus incertus is a bilateral structure which sits near the brainstem, in front of the nucleus prepositus hypoglossi.[4] It consists of mostly ascending GABAergic projection neurons and glutamatergic neurons[5] which innervate a broad range of forebrain regions involved in behavioural activation.
It is part of the theta network acting as a relay from the reticularis pontis oralis nucleus to the septo-hippocampal system.[6] The stimulation of the nucleus incertus activates the hippocampal theta rhythm and either its lesion or inhibition suppress the theta oscillation induced by brainstem stimulation.[7] The nucleus incertus itself presents theta oscillations coupled to the hippocampal theta rhythm.[8]
In addition to hippocampal theta rhythms, the nucleus incertus is involved in the control of locomotor speed and arousal,[9] response to stress[3] and integrating the vestibulo-ocular reflex and gaze holding with hippocampal navigation.[6]