Slow cortical potential shifts modulate the sensory threshold in human visual system

Area of Science:

• Neuroscience
• Cognitive Science
• Psychophysics

Background:

• Spontaneous slow cortical potentials (SCPs) are slow voltage fluctuations in the electroencephalogram (EEG).
• SCPs are hypothesized to reflect underlying changes in cortical excitability.
• Understanding SCPs' role in sensory perception is crucial for explaining trial-to-trial variability in detection.

Purpose of the Study:

• To investigate the relationship between spontaneous slow cortical potential shifts and the detection of visual stimuli at sensory threshold.
• To determine if the polarity of SCPs influences the ability to detect near-threshold visual stimuli.

Main Methods:

• Participants performed a visual stimulus detection task at sensory threshold.
• Slow cortical potentials preceding detected and missed stimuli were analyzed.
• EEG data was recorded to measure SCPs.

Main Results:

• Mean SCPs preceding detected stimuli were significantly more negative than those preceding missed stimuli.
• Stimulus detection performance was significantly higher during negative SCP shifts compared to positive shifts.
• Cortical negativity correlated with enhanced neural network excitability.

Conclusions:

• Cortical negativity reflects increased neural network excitability, facilitating the detection of threshold visual stimuli.
• Cortical positivity is associated with decreased neural excitability and impaired stimulus detection.
• Variability in EEG baseline, specifically SCPs, may explain why near-threshold stimuli are sometimes detected and sometimes missed across trials.