Know Your Brain: The Brainstem — Connecting the Lines


We often use the phrase “somewhere in the back of our mind” for thoughts we like to push aside — ones we’d rather not revisit, but know they’re there. You could almost argue that the brainstem fits this description almost literally — maintaining our alertness and regulating our sleep — the main reasons we’re able to shuffle our thoughts in the first place. Of the 13 cranial nerves in our body, 12 of them are in the brainstem — connecting to the cerebral cortex and then relaying sensory messages throughout the central nervous system.

The brainstem is essential to our sense of fine touch as well as indicating pain and body temperature. Rather than think of it as one complex organ, neuroscientists tend to divide the structure into three parts: the midbrain — which is composed of gray matter at the top of the stem and involved in processing vision and hearing — it also contains the red nucleus that descends to lower motor neurons responsible for movement throughout the eyes, face, and tongue; the pons, located below the midbrain, which regulates breathing and activity between both hemispheres of the brain — a network for carrying messages from the cerebrum to the cerebellum and to the stem’s lower half, the medulla oblangata, which controls the heart rate, breathing and blood pressure.

Illustration: OpenStax “Anatomy and Physiology” textbook via CC BY 4.0.

Due to the number of these tasks, and the organs throughout the body that rely upon these three parts, injury to the brainstem can be life threatening — or devastating — in the case of a brainstem stroke, better known by the name of “locked in” syndrome, in which a patient can communicate their thoughts only by basic eye movements. Fortunately, a closer look at the brainstem with the latest in imaging technology can help to shed light on neurological disorders throughout the brain.

Solutions From Within

For many years, patients with epilepsy suffered from memory loss and poor concentration following repeated episodes, problems that weren’t quite understood. Research from Vanderbilt University Medical Center may change that. A study they conducted last spring suggested that continuous seizures may actually reduce brainstem connectivity — the source of these symptoms. Because seizures typically occur in the temporal lobe or throughout the cortex, researchers often overlooked the brainstem.

Dr. Dario Englot, M.D., Ph.D., the study’s lead author, observed that patients with epilepsy often lose consciousness during seizures and set his focus on the brainstem, which is responsible for wakefulness. His paper, published in the journal Neurology, is the first investigation into the impact of epilepsy on what is known as the ascending reticular activating system (ARAS), the neural network that regulates consciousness, located within the brainstem. Scans from fMRI demonstrated that when the ARAS was disrupted, the system suffered decreases in its circuitry.

“Seizures do not start in areas deep below the surface of the brain called subcortical nuclei,” said Englot. “So these areas are not often studied in epilepsy. But we think that problems develop in some deep subcortical circuits that may contribute to some of the unexplained global brain problems in temporal lobe epilepsy, including progressive neurocognitive problems and problems with arousal that can’t be explained by problems in the temporal lobe.”

Memory lapses and attention deficits are not associated with temporal lobe activity, however. Englot’s work on the brainstem further confirms what many in neuroscience have long suspected — that seizures can impact many more regions of the brain than previously thought.

For the study, Englot and his team looked at the scans of 26 patients affected with temporal lobe epilepsy and compared them to 26 people with no epilepsy diagnosis. They matched each pair by age, sex, as well as left or right handedness for controls. The tests established specific connections between the ARAS nuclei and other brain regions that had been altered in patients suffering long term epilepsy.

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