Serotonergic hyperactivity as a potential factor in developmental, acquired and drug-induced synesthesia

Area of Science:

• Neuroscience
• Psychology
• Genetics

Background:

• Synesthesia research has advanced, yet commonalities among its types remain unclear.
• Known mechanisms involve aberrant brain connectivity, such as direct projections or disinhibited feedback.
• Synesthesia can be developmental, acquired (e.g., after brain injury), or drug-induced.

Purpose of the Study:

• To explore potential mechanistic commonalities among different forms of synesthesia.
• To investigate the role of serotonin in the onset and characteristics of synesthesia.

Main Methods:

• Review of existing research on developmental, acquired, and drug-induced synesthesia.
• Analysis of proposed neurobiological mechanisms, including brain connectivity and neurotransmitter function.
• Focus on the role of serotonin in psychedelic intoxication and acquired synesthesia.

Main Results:

• Psychedelic drugs (psilocybin, LSD, mescaline) can induce synesthesia, with serotonin implicated in perceptual changes.
• Excessive serotonin after brain injury may contribute to acquired synesthesia by causing unusual feature binding.
• Altered serotonergic systems in autism may lead to developmental synesthesia through impaired gating mechanisms.

Conclusions:

• Excessive serotonin levels are proposed as a common factor in some cases of acquired, developmental, and drug-induced synesthesia.
• Elevated serotonin may enhance sensory brain region excitability and connectivity, potentially explaining shared synesthetic experiences.