Neuronal density and proportion of interneurons in the associative, sensorimotor and limbic human striatum
The striatum (caudate nucleus, putamen and nucleus accumbens) is the main input structure of the basal ganglia. It receives cortical projections from the vast majority of the cortex, as well as from other subcortical structures such as the thalamus and amygdala. Its role in planning, preparation and execution of voluntary movements is known to be fine-tuned by the interaction between projection neurons and interneurons. Since the 1990s, it has been accepted that the proportion of interneurons increases phylogenetically, being about 5% in rodents and 26% in humans. However, these data have not been confirmed with unbiased techniques, such as stereology. In the present report, we have divided the human striatum into functional territories (associative, sensorimotor and limbic) and we have quantified the numerical density of all striatal neurons (using Nissl staining) in each area. Taking into account our past research on the estimation of striatal interneurons, we have calculated the proportion of interneurons in each territory. This value was on average 17.1% for the whole striatum, although interneurons were more abundant in the associative (21.9%) than in the sensorimotor (12.8%) and limbic (11.1%) aspects. Therefore, we demonstrate with unbiased stereology that the overall proportion of striatal interneurons is slightly lower than that reported in previous studies, and that it varies in the functional territories of this structure.
KeywordsBasal ganglia Caudate nucleus Nucleus accumbens Putamen Stereology
We are indebted to Dr. Elisa Mengual for making possible this research. We are grateful to Pedro García, Beatriz Paternáin and Esther Luquín for technical support, Jose Ullán and María García Amado for supporting microscope setup and stereology, Gonzalo Arrondo, Maite Aznárez and Jose Miguel Carrasco for statistical advice, and Jose Manuel Giménez-Amaya and Lucía Prensa for their contribution to the study of interneurons. We also acknowledge the suggestions of anonymous reviewers.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interests.
The authors have no funding to report.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Next-of-kin of the deceased authorized the autopsy and collection of tissue.
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