Spatial generalization of peripherally encoded memories emerges before selection for report

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Human Perception

Background:

• Visual working memory (VWM) representations are known to evolve from location-specific to spatially generalized.
• The precise timing and neural underpinnings of VWM spatial generalization remain poorly understood.
• Investigating the temporal dynamics of VWM representations is crucial for understanding cognitive processing.

Purpose of the Study:

• To determine the time course of spatial generalization in visual working memory.
• To identify the information processing stages and neural signals associated with VWM spatial generalization.
• To differentiate between pre-report and post-report generalization mechanisms.

Main Methods:

• Electroencephalography (EEG) was employed to record neural activity in 30 healthy participants.
• Participants memorized two peripheral visual stimuli (orientations) presented at different locations.
• Impulse signals were used during delay periods to probe memory representations, followed by a selection cue.

Main Results:

• Spatially generalized representations emerged 400-600 ms after stimulus onset in broadband EEG signals, preceding report selection.
• Oscillatory alpha signals did not show clear spatial generalization during this early phase.
• Post-selection cue, both location-specific and generalized codes were observed in alpha and broadband data, indicating mixed representations.

Conclusions:

• Early stages of spatial generalization in VWM occur at sensory, pre-report processing levels.
• Later stages of generalization are linked to the selection of response-relevant spatial features.
• Distinct neural signals (broadband vs. alpha) may underpin different temporal phases of VWM spatial representation.