The Reticular Activating System, located in the brainstem, plays a pivotal role in brain function. Activated as the baby passes through the birth canal via compression and movement of the head, it readies the newborn to transition from the sleep-like state it has been in during gestation to a more awake and alert state outside the womb. It allows the baby to be aware of its surroundings, process sensory information, and engage with the outside world.
But wait, there's more! The RAS is involved in many processes in the brain, including:
Helps regulate sleep patterns and the sleep-wake transition throughout our lives
Maintains a level of consciousness and raises brainwave activity to do so
Helps mediate transition from relaxed wakefulness (theta and alpha waves) to periods of high attention (beta waves)
Is involved in postural control
Activates the thalamus for sensory processing
Is involved in the fight-or-flight reflex
Acts as a filter for sensory information
Interacts with the vestibular system for balance
Releases neurotransmitters like dopamine, serotonin, acetylcholine, norepinephrine
Has a modulating effect on the prefrontal cortex, the home of attention and executive function
Has a protective effect against brain inflammation
Helps regulate motivation
An interesting function of the RAS is to filter incoming information and arouse the brain to an awake state if its important. Here's a great example I read on the web. A study was done of couples with newborns who lived near airports. The parents would sleep soundly through the noise of an airplane taking off or landing, but the mother would wake if her infant made a sound from the next room. What accounts for this? The RAS acted as a filter to block out the noise that was unimportant to her. Fascinating.
Our brains partially run on neurotransmitters. We have many receptors in our brain for dopamine, GABA and other neurotransmitters. The thalamus, which is deeply involved in auditory and visual processing, has many GABA receptors. Dopamine receptors are located in various areas of the central nervous system, most notably in the hippocampus, the home of long-term memory. Dopamine is associated with memory, attention, general cognition (thinking, learning, and processing), impulse control, sleep, and motivation. So, an underactive RAS can result in low dopamine and other neurotransmitters. ADD medications, like methylphenidate, work by increasing the time dopamine stays in the brain.
An underactive RAS, whether that is from a C-section delivery or other cause, can have a significant impact on a child's (or adult's ability) to focus and attend, to process sensory information, to sleep regularly, to process information efficiently, and more. Children with an underactive RAS may struggle with
Focus and attention
Working memory
Sensory processing (auditory, visual, proprioceptive/tactile, and vestibular)
Physical Self-regulation
Emotional Self-regulation
Processing Speed
Learning, especially reading
Receptive and Expressive Language
Balance
Sleep
Low motivation
After children are born, their developmental milestones, enabled through primitive reflex patterns, continue to stimulate the RAS to stay active. Playing, physical activities like jumping, rocking, and climbing, along with experiences in their everyday environment continue to stimulate the RAS to do its job.
So what should you do if a child (or adult) presents with these symptoms? There is no quick fix, to be honest, but the RAS can be activated in various ways.
The most important one: make sure their reflex patterns are mature and integrated. There are far more than the "big five" that some programs promote. There are many, many reflexes that are activated or partially integrated during the birth process, including the crowing reflex, Babkin Palmomental, TLR, ATNR, rooting, sucking, etc. These reflexes will help activate the RAS and build connections to the midbrain and neocortex.
Proprioceptive input activates the RAS. Proprioception is the first sense to develop and is "turned on" fully from the compression in the birth canal. We have seven types of proprioceptors that give our brains a tremendous amount of information about our bodies. Proprioceptive input could be embracing squeezes (from MNRI), standing on a vibration plate (this is very effective), weighted blankets, rough play, big hugs, massage, etc.
Chewing! Chewing activates the trigeminal nerve which, in turn, activates the RAS. Research has shown that chewing, via its action on the RAS, can improve cognitive processing speed, alertness, attention and improve reaction times.
Vestibular input. The vestibular, or balance, system has a synergistic relationship with the RAS. Balance activities activate the RAS, and the RAS regulates the vestibular system. Both the auditory and visual systems are intertwined with the vestibular system through the 8th cranial nerve and the vestibular-ocular reflex.
Working with a qualified practitioner or team to address these concerns could make a world of difference for someone struggling with these issues. If you would like to talk about how to help your child, please reach out at mary@brain-works.org. I work with people remotely and at my office in Clackamas, Oregon.
References
Allen A. P., Smith A. P. (2012). Effects of chewing gum and time-on-task on alertness and attention. Nutr. Neurosci. 15, 176–185. 10.1179/1476830512y.0000000009
De Cicco V, Tramonti Fantozzi MP, Cataldo E, Barresi M, Bruschini L, Faraguna U, Manzoni D. Trigeminal, Visceral and Vestibular Inputs May Improve Cognitive Functions by Acting through the Locus Coeruleus and the Ascending Reticular Activating System: A New Hypothesis. Front Neuroanat. 2018 Jan 8;11:130. doi: 10.3389/fnana.2017.00130. PMID: 29358907; PMCID: PMC5766640.
Garcia-Rill, E., ed. (2015). Waking and the reticular activating system. Health and Disease.
Hirano Y., Obata T., Takahashi H., Tachibana A., Kuroiwa D., Takahashi T., et al.. (2013). Effects of chewing on cognitive processing speed. Brain Cogn. 81, 376–381. 10.1016/j.bandc.2012.12.002
Powers, D. (2021). The mighty vestibular system: Balance and beyond. Medbridge. www.medbridge.com/blog/2021/7
Tucha O., Mecklinger L., Maier K., Hammerl M., Lange K. W. (2004). Chewing gum differentially affects aspects of attention in healthy subjects. Appetite 42, 327–329.
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