Fixation duration on natural scenes is explained by memory encoding not processing demand

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Memory Encoding

Background:

• The brain controls eye movements, deciding how long to fixate on visual information before shifting gaze.
• Understanding the factors influencing fixation duration is crucial for comprehending visual attention and information processing.

Purpose of the Study:

• To investigate whether eye movement fixation durations are determined by perceptual processing limits or memory encoding demands.
• To explore the neural mechanisms underlying fixation duration control during scene viewing.

Main Methods:

• A large-scale scene-viewing experiment involving magnetoencephalography (MEG), eye tracking, and a semantic captioning task.
• Multivariate analysis of MEG source-space patterns, behavioral analyses, and artificial neural network (ANN) modeling.
• Analysis of ventral stream representational dynamics and theta-gamma phase-amplitude coupling.

Main Results:

• Fixation durations were not explained by the temporal variability of ventral stream representational dynamics.
• Longer fixation durations correlated positively with ANN-predicted patch memorability and caption-inclusion.
• Fixation durations were anticorrelated with ANN-estimated patch classification difficulty and associated with increased theta-gamma phase-amplitude coupling in frontal and hippocampal regions.

Conclusions:

• Eye movement timing decisions are primarily driven by memory encoding demands, not perceptual processing limitations.
• The findings suggest a distinct role for memory processes in regulating the duration of visual fixations.