Coinciding decreases in discharge rate suggest that spontaneous pauses in firing of external pallidum neurons are network driven.
The external segment of the globus pallidus (GPe) is one of the core nuclei of the basal ganglia, playing a major role in normal control of behavior and in the pathophysiology of basal ganglia-related disorders such as Parkinson's disease. In vivo, most neurons in the GPe are characterized by high firing rates (50-100 spikes/s), interspersed with long periods (∼0.6 s) of complete silence, which are termed GPe pauses. Previous physiological studies of single and pairs of GPe neurons have failed to fully disclose the physiological process by which these pauses originate. We examined 1001 simultaneously recorded pairs of high-frequency discharge GPe cells recorded from four monkeys during task-irrelevant periods, considering the activity in one cell while the other is pausing. We found that pauses (n = 137,278 pauses) coincide with a small yet significant reduction in firing rate (0.78 ± 0.136 spikes/s) in other GPe cells. Additionally, we found an increase in the probability of the simultaneously recorded cell to pause during the pause period of the "trigger" cell. Importantly, this increase in the probability to pause at the same time does not account for the reduction in firing rate by itself. Modeling of GPe cells as class 2 excitability neurons (Hodgkin, 1948) with common external inputs can explain our results. We suggest that common inputs decrease the GPe discharge rate and lead to a bifurcation phenomenon (pause) in some of the GPe neurons.
Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem 91904, Israel, and eitan.schechtman@mail.huji.ac.il.
Eitan
E
Schechtman
Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem 91904, Israel, and.
Avital
A
Adler
Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem 91904, Israel, and Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah School of Medicine, Jerusalem 91120, Israel.
Marc
M
Deffains
Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah School of Medicine, Jerusalem 91120, Israel.
Hila
H
Gabbay
Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah School of Medicine, Jerusalem 91120, Israel.
Shiran
S
Katabi
Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah School of Medicine, Jerusalem 91120, Israel.
Aviv
A
Mizrahi
Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem 91904, Israel, and Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah School of Medicine, Jerusalem 91120, Israel.
Hagai
http://orcid.org/0000-0002-2402-6673
H
Bergman
D000200:Action Potentials / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D002522:Chlorocebus aethiops; D005260:Female; D005917:Globus Pallidus / Q000166:cytology*; D008252:Macaca fascicularis; D008297:Male; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011336:Probability; D011930:Reaction Time
basal ganglia; globus pallidus; network; pause