The Reticular Activating System (RAS), a small but mighty player in the brain
The RAS (often called the reticular activating system or reticular activating network) is a network of neurons in the brainstem that acts like your brain’s attention gatekeeper.
What it does (in plain terms)
The RAS decides:
- What gets your attention
- What stays in the background
- When you’re awake, alert, or drowsy
It filters the overwhelming amount of sensory information coming at you every second and lets only the relevant stuff reach conscious awareness.
Classic example:
- You don’t notice the hum of the air conditioner…
- …until it turns off.
That’s your RAS at work.
Core functions
- Arousal & wakefulness – keeps you conscious and alert
- Attention & focus – selects what you notice
- Sleep–wake regulation – helps control transitions between sleep and waking
- Sensory filtering – prevents overload
Damage to the RAS can lead to coma or severe consciousness disturbances, which shows how foundational it is.
Why it matters psychologically
The RAS is strongly influenced by:
- Beliefs
- Expectations
- Goals
- Emotional salience
This is why:
- When you learn a new word, you suddenly hear it everywhere
- When you’re anxious, you notice threats more easily
- When you’re depressed, your mind “finds” evidence that supports hopelessness
The RAS doesn’t judge truth, it filters for importance.
Clinical & applied relevance
In psychology and behavior:
- Anxiety = RAS is tuned toward danger
- Trauma = RAS stays hypervigilant
- ADHD = dysregulation of attention filtering
- CBT / mindfulness = retraining attentional filters
- Goal-setting = activating RAS toward opportunities
In therapy, changing what the RAS is tuned to often precedes cognitive change.
One-line summary
The RAS is the brain’s spotlight operator, deciding what gets illuminated in your conscious experience.
Shervan K Shahhian
LIBERTY PSYCHOLOGICAL ASSOCIATION 