Microsaccades differentially modulate neural activity in the striate and extrastriate visual cortex

Area of Science:

• Neuroscience
• Visual Perception
• Primate Vision

Background:

• Saccadic eye movements, including microsaccades during fixation, constantly alter retinal stimulus location.
• Despite these shifts, visual perception remains stable and continuous.
• Understanding neural processing during these movements is key to explaining perceptual stability.

Purpose of the Study:

• To investigate the impact of fixational eye movements on single neuron activity in primate visual cortex.
• To identify how different visual areas (V1, V2, V4, IT) respond to saccade-related neural signals.
• To explore the role of these responses in maintaining stable visual perception.

Main Methods:

• Recorded single-unit activity in striate (V1) and extrastriate (V2, V4, IT) visual cortex of macaque monkeys.
• Analyzed neuronal firing patterns in relation to naturally occurring microsaccades and small saccades.
• Correlated neural responses with the timing and amplitude of eye movements.

Main Results:

• Many neurons in V1 showed a transient decrease in firing after saccades.
• Neurons in extrastriate areas V2 and V4 exhibited strong excitatory responses coinciding with V1 depression.
• Inferotemporal cortex (IT) neurons showed no significant activity change related to saccades.

Conclusions:

• Extrastriate visual areas (V2, V4) likely receive extraretinal input related to saccadic events.
• This saccade-related input may be vital for stable object and scene perception during eye movements.
• These signals could bridge central object representations and changing retinotopic input.