Functional but not obligatory link between microsaccades and neural modulation by covert spatial attention

Area of Science:

• Neuroscience
• Cognitive Science
• Visual Perception

Background:

• Covert spatial attention exhibits two key indicators: spatial modulation of neural activity and directional biases in microsaccades.
• The relationship between these neural and oculomotor 'fingerprints' of attention remains incompletely understood.

Purpose of the Study:

• To investigate the interrelation between spatial modulation of electroencephalography (EEG) alpha activity and microsaccades during internally directed spatial attention.
• To determine if microsaccades are necessary for the manifestation of neural signatures of spatial attention.

Main Methods:

• Recorded 8-12 Hz EEG alpha activity and microsaccades in human participants.
• Participants directed attention internally within a visual working memory task.
• Analyzed the spatial modulation of alpha activity and microsaccade direction.

Main Results:

• Spatial modulation of alpha activity and microsaccades covaried, with stronger alpha lateralization and earlier onset correlating with microsaccades toward the attended location.
• Crucially, significant spatial modulation of alpha activity was observed even in trials lacking attention-driven microsaccades.
• The magnitude of alpha modulation in trials without microsaccades was comparable to trials with them.

Conclusions:

• Directional biases in microsaccades are correlated with neural signatures of spatial attention, suggesting a common underlying mechanism.
• Microsaccades are not strictly necessary for neural modulation by spatial attention to occur.
• Neural mechanisms of spatial attention can operate independently of overt or covert eye movement biases.