Visual P2p component responds to perceived numerosity.

Area of Science:

• Cognitive Neuroscience
• Psychophysics
• Electrophysiology

Background:

• Numerosity perception is crucial for various species, likely involving specific brain mechanisms.
• Electrophysiological (EEG) studies show early and mid-latency signals sensitive to numerosity, but their sensitivity to physical vs. perceived changes is unclear.

Purpose of the Study:

• To investigate whether electrophysiological components track physical or perceived numerosity changes.
• To differentiate the roles of early and mid-latency EEG signals in numerosity processing.

Main Methods:

• Utilized a numerosity adaptation task with electrophysiological recordings (EEG).
• Behavioral measures assessed perceived numerosity judgments under adaptation conditions.
• Analyzed EEG signals, focusing on latency components and their correlation with adaptation effects.

Main Results:

• Behavioral data showed consistent underestimation of test stimuli after high numerosity adaptors.
• A mid-latency EEG component (P2p, ~200 ms) was reduced by illusory numerosity changes, particularly over the left posterior electrodes.
• Early EEG modulations were observed for physical changes, but not for illusory changes, while P2p reflected perceived changes.

Conclusions:

• Mid-latency P2p primarily reflects perceived numerical attributes, while earlier components track physical stimulus characteristics.
• Numerosity adaptation involves short-term plasticity in later visual processing stages, potentially beyond primary visual cortex.
• Mid-latency electrophysiological signals serve as a signature for the internal representation of numerical information.