The nucleus incertus is a region of the rodent pontine

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is ...

just ventral to the 4th ventricle. The term was coined by

George Streeter George Wellington "Cap" Streeter (1837 – January 22, 1921) was an American who became infamous in Chicago for his real estate schemes and oftentimes bizarre eccentricity. From 1886 to 1921, Streeter, often through forgery and other manipula ...

(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. The nucleus incertus is a bilateral structure which sits near the brainstem, and is often also called 'nucleus O'. It consists of mostly ascending

GABAergic In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter GABA. For example, a synapse is GABAergic if it uses GABA as its neurotransmitter, and a GABAergic neuron produces GABA. A ...

projection neuron The projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord. In human neuroanatomy, bundles of axons (nerve fibers) called tracts, within the brain, can be cat ...

s and

glutamatergic Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid agonist, excitato ...

neurons which innervate a broad range of

forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three prima ...

regions involved in behavioural activation and the response to stress. This tegmental nucleus is part of the theta network. The nucleus incertus is a relay from the reticularis pontis oralis nucleus to the septo-hippocampal system. The stimulation of the nucleus incertus activates the

hippocampal theta rhythm The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, an ...

and either its lesion or inhibition suppress the theta oscillation induced by brainstem stimulation. The nucleus incertus itself presents theta oscillations coupled to the hippocampal theta rhythm. In addition to hippocampal theta rhythms, a recent study in rodents implicates the nucleus incertus in the control of locomotor speed and arousal.

References

{{reflist Animal nervous system