How ongoing fluctuations in human visual cortex predict perceptual awareness: baseline shift versus decision bias

Area of Science:

• Neuroscience
• Cognitive Science
• Visual Perception Research

Background:

• Perceptual fluctuations in visual awareness are often linked to ongoing neural activity.
• Top-down attention is hypothesized to modulate this prestimulus activity, influencing subsequent perception.

Purpose of the Study:

• To investigate whether ongoing attentional modulations fully explain the perceptual impact of prestimulus activity.
• To differentiate the roles of prestimulus neural signals and attentional modulations in visual awareness.

Main Methods:

• Magnetoencephalography (MEG) was used to measure brain activity.
• Analysis focused on prestimulus gamma-band and alpha-band fluctuations in lateral occipital (LO) areas.
• A decision-making model was employed to analyze the influence of neural signals on seen-unseen decisions.

Main Results:

• Prestimulus gamma-band fluctuations in LO predicted visual awareness but not attentional focus.
• These gamma-band signals impacted decisions independently of subsequent visual responses, suggesting a decision bias.
• Spatial attention suppressed alpha-band activity and created a sustained baseline shift, also predicting awareness.

Conclusions:

• Prestimulus neural fluctuations influence conscious detection via two mechanisms: a gamma-band decision bias and an alpha-band attention-driven baseline shift.
• These findings distinguish the roles of different neural oscillations in visual awareness and decision-making.
• Ongoing neural activity, not solely attentional modulation, plays a critical role in determining visual perception.