A preparatory cranial potential for saccadic eye movements in macaque monkeys

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Electrophysiology

Background:

• Voluntary movement preparation involves gradual neural activity accumulation.
• The lateralized readiness potential (LRP) is a known EEG signal preceding human manual movements.
• Preparatory EEG potentials for saccadic eye movements are less understood, especially in nonhuman primates.

Purpose of the Study:

• To investigate and describe a lateralized readiness potential (LRP) in macaque monkeys during saccadic eye movements.
• To explore the relationship between EEG signals and neural activity in the frontal eye field.
• To assess the potential of EEG as a non-invasive correlate of intracortical spiking activity.

Main Methods:

• Electroencephalography (EEG) recordings in macaque monkeys.
• Observation of lateralized electrical potentials over the frontolateral cortex.
• Correlation of EEG signals with saccadic eye movement execution (rewarded and non-rewarded).
• Comparison with neural spiking data from the frontal eye field.

Main Results:

• A lateralized readiness potential (LRP) was observed in macaque monkeys, preceding saccadic eye movements.
• This potential showed a ramping activity homologous to humans.
• The frontolateral EEG polarization did not differentiate between saccade generation and inhibition, unlike frontal eye field neural spiking.

Conclusions:

• The study describes a non-invasive electrophysiological signature of saccadic preparation in nonhuman primates.
• The findings suggest EEG measures can bridge invasive neural recordings and non-invasive human studies of eye movement control.
• The lateralized readiness potential (LRP) may serve as a non-invasive correlate of frontal eye field activity.