Modulation of brain signal variability in visual cortex reflects aging, GABA, and behavior.

Area of Science:

• Neuroscience
• Cognitive Science
• Human Physiology

Background:

• Neural variability, the moment-to-moment fluctuations in brain activity, scales with stimulus complexity.
• The underlying mechanisms for adapting neural variability to input complexity remain largely unknown.
• Aging and neurotransmitters, particularly GABA, are potential modulators of neural processing.

Purpose of the Study:

• To investigate the role of aging and GABA in modulating neural variability during visual processing.
• To explore the relationship between GABA levels, neural variability, and visual performance.

Main Methods:

• Utilized a multimodal approach including behavioral tasks, computational modeling, fMRI, MR spectroscopy, and pharmacological interventions.
• Assessed neural variability in response to visual stimuli of varying complexity.
• Measured baseline GABA levels and manipulated GABAergic activity pharmacologically.

Main Results:

• Neural variability positively correlated with visual stimulus complexity, consistent with prior findings.
• Variability modulation was associated with higher baseline visual GABA levels and diminished in older adults.
• Pharmacological enhancement of GABA increased variability modulation in individuals with lower baseline GABA, suggesting an inverted-U relationship.

Conclusions:

• GABA plays a critical role in the brain's ability to adapt neural variability to visual input complexity.
• Age-related decline in GABAergic function may impair neural adaptability.
• Optimal GABAergic function is crucial for effective neural processing and visual discrimination performance.