Anatomical studies on the motor cortex of Macacus rhesus

1922 ◽  
Vol 35 (1) ◽  
pp. 67-96 ◽  
Author(s):  
Juan C. Nañagas
Keyword(s):  
Motor Cortex ◽  
Anatomical Studies

scholarly journals Slowly-conducting pyramidal tract neurons in macaque and rat

2019 ◽  
Author(s):  
A Kraskov ◽  
D Soteropoulos ◽  
I Glover ◽  
RN Lemon ◽  
SN Baker
Keyword(s):  
Motor Cortex ◽  
Pyramidal Tract ◽  
Recurrent Inhibition ◽  
Anatomical Studies ◽  
Slow Conduction ◽  
Pyramidal Tract Neurons ◽  
Conduction Velocities ◽  
Myelinated Fibres ◽  
Anaesthetised Rats

SummaryAnatomical studies report a large proportion of fine myelinated fibres in the primate pyramidal tract (PT), while very few pyramidal tract neurons (PTNs) with slow conduction velocities (CV) (< ∼10 m/s) are reported electrophysiologically. This discrepancy might reflect recording bias towards fast PTNs or prevention of antidromic invasion by recurrent inhibition of slow PTNs from faster axons. We investigated these factors in recordings made with a polyprobe (32 closely-spaced contacts) from motor cortex of anaesthetised rats (n=2) and macaques (n=3), concentrating our search on PTNs with long antidromic latencies. We identified 21 rat PTNs with antidromic latencies > 2.6 ms and estimated CV 3-8 m/s, and 67 macaque PTNs (> 3.9ms, 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 (GABAA antagonist), failed to provide any evidence that recurrent inhibition prevented antidromic invasion of slow PTNs. Our results suggest that recording bias is the main reason why previous studies were dominated by fast PTNs.

scholarly journals Slowly-Conducting Pyramidal Tract Neurons in Macaque and Rat

2019 ◽  
Vol 30 (5) ◽  
pp. 3403-3418
Author(s):  
A Kraskov ◽  
D S Soteropoulos ◽  
I S Glover ◽  
R N Lemon ◽  
S N Baker
Keyword(s):  
Motor Cortex ◽  
Pyramidal Tract ◽  
Recurrent Inhibition ◽  
Anatomical Studies ◽  
Myelinated Fibers ◽  
Slow Conduction ◽  
Anesthetized Rats ◽  
Pyramidal Tract Neurons ◽  
Conduction Velocities ◽  
Gabaa Antagonist

Abstract 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) (&lt;~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 &gt;2.6 ms and estimated CV 3–8 m/s, and 67 macaque PTNs (&gt;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 (GABAA 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.

Ultrastructure of the soil fungus, Geomyces pannorus

1984 ◽  
Vol 42 ◽  
pp. 738-739
Author(s):  
J. A. Traquair ◽  
E. G. Kokko
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fine Structure ◽  
Low Temperatures ◽  
Soil Fungus ◽  
Organic Soils ◽  
Anatomical Studies ◽  
Transmission Electron ◽  
Electron Microscopical ◽  
Scanning Electron

With the advent of improved dehydration techniques, scanning electron microscopy has become routine in anatomical studies of fungi. Fine structure of hyphae and spore surfaces has been illustrated for many hyphomycetes, and yet, the ultrastructure of the ubiquitous soil fungus, Geomyces pannorus (Link) Sigler & Carmichael has been neglected. This presentation shows that scanning and transmission electron microscopical data must be correlated in resolving septal structure and conidial release in G. pannorus.Although it is reported to be cellulolytic but not keratinolytic, G. pannorus is found on human skin, animals, birds, mushrooms, dung, roots, and frozen meat in addition to various organic soils. In fact, it readily adapts to growth at low temperatures.

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