The dark matter of the brain

Area of Science:

• Neuroscience
• Cellular Biology

Background:

• The brain's high energy consumption is primarily for neuronal activity.
• Studies indicate a large proportion of neurons in the brain remain silent, not firing action potentials.

Purpose of the Study:

• To review emerging data on the existence and implications of widespread silent neurons in the mammalian nervous system.
• To explore the potential role of these dormant neuronal populations in neuro-psychiatric symptoms and brain plasticity.

Main Methods:

• Review of long-term electrophysiological and neuroimaging studies in animal models.
• Analysis of evolutionary and functional data related to neuronal activity and inhibition.

Main Results:

• Evidence suggests massive redundancy of nerve cells, maintained in an inhibited state at significant energetic cost.
• Dormant neurons and circuits, potentially products of evolution, are largely inactive under normal conditions.
• These silent neuronal populations can become active under stress or disease, contributing to neuropsychiatric symptoms.

Conclusions:

• The prevalence of silent neurons necessitates a re-evaluation of current brain functional models.
• These findings suggest untapped potential for brain rehabilitation and plasticity strategies targeting dormant neuronal networks.