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Neuronal connections of direct and indirect pathways for stable value memory in caudal basal ganglia
Author(s) -
Amita Hidetoshi,
Kim Hyoung F.,
Smith Mitchell K.,
Gopal Atul,
Hikosaka Okihide
Publication year - 2019
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.13936
Subject(s) - basal ganglia , direct pathway of movement , indirect pathway of movement , globus pallidus , superior colliculus , neuroscience , putamen , striatum , anatomy , biology , medium spiny neuron , pars reticulata , axon , substantia nigra , dopamine , central nervous system , dopaminergic
Abstract Direct and indirect pathways in the basal ganglia work together for controlling behavior. However, it is still a controversial topic whether these pathways are segregated or merged with each other. To address this issue, we studied the connections of these two pathways in the caudal parts of the basal ganglia of rhesus monkeys using anatomical tracers. Our previous studies showed that the caudal basal ganglia control saccades by conveying long‐term values (stable values) of many visual objects toward the superior colliculus. In experiment 1, we injected a tracer in the caudate tail ( CD t), and found local dense plexuses of axon terminals in the caudal‐dorsal‐lateral part of substantia nigra pars reticulata (cdl SN r) and the caudal‐ventral part of globus pallidus externus (cv GP e). These anterograde projections may correspond to the direct and indirect pathways, respectively. To verify this in experiment 2, we injected different tracers into cdl SN r and cv GP e, and found many retrogradely labeled neurons in CD t and, in addition, the caudal‐ventral part of the putamen (cvPut). These cdl SN r‐projecting and cv GP e‐projecting neurons were found intermingled in both CD t and cvPut (which we call “striatum tail”). A small but significant proportion of neurons (<15%) were double‐labeled, indicating that they projected to both cdl SN r and cv GP e. These anatomical results suggest that stable value signals (good vs. bad) are sent from the striatum tail to cdl SN r and cv GP e in a biased (but not exclusive) manner. These connections may play an important role in biasing saccades toward higher valued objects and away from lower valued objects.