Cortically Disparate Visual Features Evoke Content-Independent Load Signals during Storage in Working Memory.

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Human Electrophysiology

Background:

• Working memory (WM) typically involves sustained, stimulus-specific neural activity.
• Previous research has focused on content-specific neural representations in WM.

Purpose of the Study:

• To investigate the existence of a neural signal tracking the number of items in WM, independent of their features.
• To differentiate between content-specific and content-independent neural signals during WM tasks.

Main Methods:

• Electroencephalography (EEG) was used in two studies with young adults.
• Participants performed WM tasks involving maintaining colors, orientations, or color and motion coherence.
• Representational similarity analysis (RSA) was applied to EEG data.

Main Results:

• A consistent neural signal was identified that scaled with the number of items in WM, irrespective of stored features.
• This load signal generalized across different visual features (color, orientation, motion).
• RSA confirmed a content-independent load signal alongside content-specific feature representations.

Conclusions:

• Evidence supports a content-independent neural mechanism for tracking the quantity of information in WM.
• This load signal may function as a 'pointer' binding items to cognitive context.
• Distinct neural processes likely underlie memory load tracking and feature representation.