Neuronal activity in the globus pallidus internus in patients with tics

Area of Science:

• Neuroscience
• Movement Disorders
• Neurology

Background:

• Tourette syndrome is characterized by involuntary, repetitive movements or vocalizations called tics.
• The precise neural mechanisms underlying tic generation remain incompletely understood.
• The basal ganglia, particularly the globus pallidus internus (GPi), are implicated in motor control and may play a role in tic disorders.

Purpose of the Study:

• To investigate the relationship between neuronal activity in the globus pallidus internus (GPi) and the execution of tic movements.
• To explore the temporal dynamics of GPi neuronal firing patterns preceding tic onset.

Main Methods:

• Studied 8 patients with Tourette syndrome undergoing pallidotomy for intractable tics.
• Performed simultaneous microelectrode recordings in the GPi and electromyogram (EMG) recordings of relevant muscle groups.
• Analyzed the correlation between GPi neuronal firing patterns and EMG activity during tics.

Main Results:

• Recorded 232 neurons, with 45% showing tic-related activity (bursts or pauses).
• Tic-related GPi neuronal activity was observed preceding electromyogram (EMG) onset, with initial changes occurring 50 ms to 2 seconds before the movement.
• Specific patterns included synchronous activity, bursts preceding EMG, and pauses preceding EMG.

Conclusions:

• Tic-related neuronal activity in the GPi supports the involvement of the basal ganglia motor circuit in tic generation.
• Early GPi neuronal activity preceding tics may represent the neural correlates of premonitory sensations experienced by patients.
• These findings provide preliminary insights into the pathophysiology of tics and potential therapeutic targets.