Effect of target probability on pre-stimulus brain activity.

Area of Science:

• Cognitive Neuroscience
• Decision Science

Background:

• Perceptual decision-making performance is modulated by target stimulus proportion.
• Faster response times (RTs) and more errors occur with high target frequency, reflecting a speed-accuracy trade-off.
• Previous electroencephalography (EEG) studies focused on post-stimulus activity; this study investigates pre-stimulus preparatory activity.

Purpose of the Study:

• To examine the neural correlates of response bias during perceptual decision-making.
• To investigate how pre-stimulus activity differs between tasks with high and low target frequencies.
• To link preparatory brain activity to behavioral outcomes in a Go/No-go task.

Main Methods:

• Two versions of a Go/No-go task with differing Go stimulus proportions (88% vs. 12%) were employed.
• Electroencephalography (EEG) was used to record pre-stimulus and post-stimulus brain activity.
• Behavioral data, including response times and error rates, were collected.

Main Results:

• Frequent Go trials showed enhanced motor preparation (Bereitschaftspotential) and faster RTs but higher commission errors.
• A right lateralized prefrontal negativity (lateral pN) was larger in the rare Go trial task.
• Post-stimulus N2 and P3 components were larger for rare trials, regardless of stimulus type.

Conclusions:

• Pre-stimulus motor preparation (Bereitschaftspotential) is enhanced by target frequency, contributing to faster responses.
• The observed preparatory activity changes align with accumulation models of decision-making, where target frequency affects the subjective baseline.
• Findings highlight the role of preparatory neural activity in mediating the speed-accuracy trade-off in perceptual decisions.