Fine-scale plasticity of microscopic saccades

Area of Science:

• Neuroscience
• Ophthalmology
• Vision Science

Background:

• Humans make constant microscopic eye movements, including microsaccades, to maintain steady gaze.
• The role of microsaccades in fixation maintenance has been debated due to contradictory evidence.

Purpose of the Study:

• To investigate whether microsaccades undergo adaptation similar to larger saccades.
• To determine if the motor control of microsaccades is modified by visual feedback during fixation.

Main Methods:

• A miniaturized saccadic adaptation procedure was employed.
• Participants were exposed to systematic intrasaccadic target displacements during microsaccade occurrence.

Main Results:

• Microsaccade amplitude distribution changed after exposure to target shifts.
• Microsaccades showed larger amplitudes when shifts were in their direction and smaller amplitudes when against it.
• This indicates microsaccades are monitored and their motor programs adjusted based on postsaccadic target location.

Conclusions:

• Saccadic adaptation occurs even for fine-grained eye movements near the foveal center.
• Adaptation of microsaccades supports the need for consistent motor control-visual consequence relationships.
• These findings suggest a multimodal spatial representation is active even during visual fixation.