When someone is entirely absorbed in themselves, whether due to narcissism, extreme self-focus, or just habitual self-absorption, several brain and cognitive patterns come into play:

1. Attention is limited – The brain has finite attentional resources. If someone is constantly monitoring their own needs, image, or thoughts, there’s very little “bandwidth” left to notice or process others’ emotions, cues, or subtle behaviors.
2. Empathy circuitry under-activated – Empathy involves the medial prefrontal cortex, temporoparietal junction, and anterior insula. In highly self-absorbed people, these areas aren’t engaged when interacting with others. They might cognitively “understand” your feelings but rarely feel or respond to them.
3. Mirror neurons and social resonance – Normally, mirror neurons help us automatically pick up on others’ emotions and intentions. Self-absorbed individuals often fail to mirror properly, so they don’t pick up on your nonverbal cues. You can be right there, speaking, or showing distress, and their brain literally doesn’t register it.
4. Perception filter – Over time, the brain forms habitual “filters” for what it notices. Someone fixated on themselves literally filters out the external world unless it directly relates to them. That’s why decades together can feel like they never really knew you.

In short, neuroscience confirms that deep self-absorption isn’t just emotional—it’s wired into attention, perception, and social processing circuits. The tragic irony is that presence alone doesn’t equal awareness: someone can be physically close for decades but neurologically tuned out to you.