Lecture Notes: Default Mode Network in the Human Brain

Introduction

Default Mode Network (DMN)
- Engages when the mind is at rest, comprising 20% of the brain.
- Initially appears as brain idle, but is active in a unique way.
- Revolutionizes the understanding of the human brain.

Hans Berger and EEG (1920s)
- Invented EEG to record brain's electrical activity.
- Found brain active at rest, but his ideas were not widely accepted.
Washington University Study (70 years later)
- Noted deactivation patterns in certain brain areas during tasks.
- Identified key areas like medial prefrontal cortices, posterior cingulate cortex, and angular gyrus.
- Marcus Raichle's study confirmed findings, introducing the term "default mode."

Vinod Menon's Research at Stanford
- Used fMRI to study resting brain and found connectivity.
- Identified the DMN as a functioning network.

Network Functions
- Compared to a symphony, where parts work together for functions.
- DMN's function was initially unclear.
DMN's Role in Cognition
- Involves coordination between different regions for memory and cognition.
- Important for both autobiographical and semantic memory.

Memory
- Episodic Memory: Past experiences and future planning.
- Semantic Memory: General knowledge and facts.
Self-Awareness and Social Cognition
- Involves self-reflection, social interactions, and theory of mind.

DMN and Attention
- Works with salience network to manage attention.
- Involves switching attention to external stimuli.

Disruption of DMN
- Linked to psychiatric disorders like schizophrenia, Alzheimer's, and depression.
- Vinod Menon's theory on network disruption in mental disorders.
Therapeutic Research
- Psilocybin shows promise in treating disorders by affecting DMN.
- Brain scanning on psilocybin reveals changes in DMN and its potential impacts.

Unified Sense of Self
- DMN potentially creates a cohesive internal narrative.
- Still much to learn about the full capabilities and implications of the DMN.