Visually evoked gamma responses in the human brain are enhanced during voluntary hyperventilation

Area of Science:

• Neuroscience
• Human Brain Activity
• Computational Neuroscience

Background:

• Hypocapnia, induced by hyperventilation (HV), significantly impacts neuronal excitability and synaptic transmission.
• Gamma-band oscillations (30-45 Hz) are crucial for visual processing and cognitive functions.
• Previous in vitro studies suggest enhanced GABAergic transmission stabilizes gamma activity during hypocapnia.

Purpose of the Study:

• To investigate the effect of voluntary hyperventilation on phase-locked gamma-band oscillations in the human visual cortex.
• To explore the underlying neural mechanisms, specifically the role of GABAergic transmission and neuronal excitability.

Main Methods:

• Magnetoencephalography (MEG) was used to record visually evoked responses to pattern-reversal checkerboard stimuli.
• Time-frequency analysis, utilizing wavelets, was applied to assess changes in gamma-band activity during and after hyperventilation.
• Computational modeling of a neuronal network simulated the effects of enhanced GABAergic transmission and excitability.

Main Results:

• Voluntary hyperventilation led to a significant increase in stimulus-locked gamma-band responses in the occipital visual cortex.
• The frequency of these gamma responses remained largely unchanged during hyperventilation.
• Network simulations indicated that increased GABA(A) transmission and enhanced neuronal excitability could replicate the observed increase in evoked gamma activity.

Conclusions:

• Hyperventilation-induced hypocapnia enhances phase-locked gamma-band activity in the human visual cortex.
• The findings support the hypothesis that increased GABAergic transmission and neuronal excitability contribute to this enhancement.
• This study provides insights into the neurophysiological effects of altered CO2 levels on brain oscillations.