Locating the human frontal eye fields with transcranial magnetic stimulation

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neurophysiology

Background:

• The frontal eye fields (FEFs) are crucial for controlling voluntary eye movements.
• Previous research suggests FEFs are located in the prefrontal cortex.
• Understanding the precise location and functional variability of FEFs is important for interpreting neuroimaging and stimulation studies.

Purpose of the Study:

• To investigate the inter-individual variability in the location and function of human frontal eye fields (FEFs).
• To determine if transcranial magnetic stimulation (TMS) can reliably identify functional FEF regions.
• To assess the impact of FEF stimulation on saccadic eye movement execution.

Main Methods:

• Utilized transcranial magnetic stimulation (TMS) to probe the prefrontal cortex.
• Employed a saccadic eye movement task known to be influenced by FEF activity.
• Systematically stimulated points over the prefrontal cortex to identify sites disrupting contralateral saccade execution.

Main Results:

• Successfully localized a functional FEF region in 7 out of 10 subjects (70%).
• Stimulation of these localized regions resulted in delays in contralateral saccadic eye movements.
• The functional FEF location varied across subjects, averaging approximately 1.5 cm anterior to the motor hand area.
• No effective stimulation site was found in 3 subjects within the tested area.

Conclusions:

• Significant inter-individual variability exists in both the location and functional engagement of human FEFs.
• Functional localization using methods like TMS is essential, complementing anatomical landmarks.
• These findings underscore the need for personalized approaches when targeting or interpreting FEF activity in research and clinical settings.