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Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat

Anatomical studies report a large proportion of fine myelinated fibers in the primate pyramidal tract (PT), while very few PT neurons (PTNs) with slow conduction velocities (CV) (<~10 m/s) are reported electrophysiologically. This discrepancy might reflect recording bias toward fast PTNs or preve...

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Autores principales: Kraskov, A, Soteropoulos, D S, Glover, I S, Lemon, R N, Baker, S N
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7197198/
https://www.ncbi.nlm.nih.gov/pubmed/32026928
http://dx.doi.org/10.1093/cercor/bhz318
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author Kraskov, A
Soteropoulos, D S
Glover, I S
Lemon, R N
Baker, S N
author_facet Kraskov, A
Soteropoulos, D S
Glover, I S
Lemon, R N
Baker, S N
author_sort Kraskov, A
collection PubMed
description Anatomical studies report a large proportion of fine myelinated fibers in the primate pyramidal tract (PT), while very few PT neurons (PTNs) with slow conduction velocities (CV) (<~10 m/s) are reported electrophysiologically. This discrepancy might reflect recording bias toward fast PTNs or prevention of antidromic invasion by recurrent inhibition (RI) of slow PTNs from faster axons. We investigated these factors in recordings made with a polyprobe (32 closely-spaced contacts) from motor cortex of anesthetized rats (n = 2) and macaques (n = 3), concentrating our search on PTNs with long antidromic latencies (ADLs). We identified 21 rat PTNs with ADLs >2.6 ms and estimated CV 3–8 m/s, and 67 macaque PTNs (>3.9 ms, CV 6–12 m/s). Spikes of most slow PTNs were small and present on only some recording contacts, while spikes from simultaneously recorded fast-conducting PTNs were large and appeared on all contacts. Antidromic thresholds were similar for fast and slow PTNS, while spike duration was considerably longer in slow PTNs. Most slow PTNs showed no signs of failure to respond antidromically. A number of tests, including intracortical microinjection of bicuculline (GABA(A) antagonist), failed to provide any evidence that RI prevented antidromic invasion of slow PTNs. Our results suggest that recording bias is the main reason why previous studies were dominated by fast PTNs.
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spelling pubmed-71971982020-05-07 Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat Kraskov, A Soteropoulos, D S Glover, I S Lemon, R N Baker, S N Cereb Cortex Original Article Anatomical studies report a large proportion of fine myelinated fibers in the primate pyramidal tract (PT), while very few PT neurons (PTNs) with slow conduction velocities (CV) (<~10 m/s) are reported electrophysiologically. This discrepancy might reflect recording bias toward fast PTNs or prevention of antidromic invasion by recurrent inhibition (RI) of slow PTNs from faster axons. We investigated these factors in recordings made with a polyprobe (32 closely-spaced contacts) from motor cortex of anesthetized rats (n = 2) and macaques (n = 3), concentrating our search on PTNs with long antidromic latencies (ADLs). We identified 21 rat PTNs with ADLs >2.6 ms and estimated CV 3–8 m/s, and 67 macaque PTNs (>3.9 ms, CV 6–12 m/s). Spikes of most slow PTNs were small and present on only some recording contacts, while spikes from simultaneously recorded fast-conducting PTNs were large and appeared on all contacts. Antidromic thresholds were similar for fast and slow PTNS, while spike duration was considerably longer in slow PTNs. Most slow PTNs showed no signs of failure to respond antidromically. A number of tests, including intracortical microinjection of bicuculline (GABA(A) antagonist), failed to provide any evidence that RI prevented antidromic invasion of slow PTNs. Our results suggest that recording bias is the main reason why previous studies were dominated by fast PTNs. Oxford University Press 2020-05 2019-02-06 /pmc/articles/PMC7197198/ /pubmed/32026928 http://dx.doi.org/10.1093/cercor/bhz318 Text en © The Author(s) 2019. Published by Oxford University Press. http://creativecommons.org/licenses/by/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
spellingShingle Original Article
Kraskov, A
Soteropoulos, D S
Glover, I S
Lemon, R N
Baker, S N
Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat
title Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat
title_full Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat
title_fullStr Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat
title_full_unstemmed Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat
title_short Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat
title_sort slowly-conducting pyramidal tract neurons in macaque and rat
topic Original Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7197198/
https://www.ncbi.nlm.nih.gov/pubmed/32026928
http://dx.doi.org/10.1093/cercor/bhz318
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