Observations on the pyramidal tract of the slow loris

Doetsch, Gernot S.; Towe, A.L.

doi:10.1007/bf02693481

Cited by 1 publication

(2 citation statements)

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“…If spread uniformly through the cortex that yields an r wave, the density of PT cells bodies would be about 1,300/mm2 (about 3% of the neu rons in that tissue). If the density distribu tion is adjusted to match the observed am plitude of the r wave, a maximum density of about 2,000 PT neurons/mm2 would be found in focus I -only half of that de duced for the slow loris [Doetsch and Towe, 1981b], for which animal a maxi mum surface alpha wave of 0.1 mV was calculated. Clearly, a purely antidromic model cannot account for the observed size of the r wave.…”

Section: Discussionmentioning

confidence: 99%

“…The properties of the response in the rabbit, as described by Woolsey and Chang [1948], by Chang [1955a,b] and by Conway et al [1969], are similar to those in the opossum and woodchuck, suggesting that a similar process may be involved. The antidromic response in these latter two species differs markedly from that in the cat, but is similar to that in the phalanger [Porter, 1955], slow loris [Doetsch and Towe, 1981b], and laboratory rat [Por ter and Sanderson, 1964;Harrison and Towe, 1982], Porter [1955] found that intravenous cu rare had no effect on the antidromic re sponse in the cat, but markedly reduced or abolished the response in both rabbit and phalanger. Chang [1955a] found that the induction of spreading depression in rab bit by needle puncture at the site of record ing markedly diminished the antidromic response; similar behavior followed appli cation of potassium cyanide to the cortex [Chang, 1955b].…”

Section: Introductionmentioning

confidence: 99%

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Cerebral Response to Medullary Pyramid Stimulation in the Rabbit

Chen¹,

Towe²

1984

Brain Behav Evol

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The response evoked in the cerebral cortex of the rabbit by stimulation of the medullary pyramid was studied electrophysiologically. The response was everywhere surface-positive and began 2–3 ms after the stimulus. It exceeded 1 mV in amplitude and generally lasted 2–4 ms. Maps of the response showed it to extend throughout the anterior one-third of the cortex (in the ''motor'' cortex) and into adjacent tissue, including the limbic cortex. Although it depended on antidromic conduction in pyramidal tract fibers for its production, it varied in amplitude, configuration and latency at different sites and at the same sites on repeated trials. It was found to reverse polarity deep in the cortex, to become a large, negative wave in layer V and to maintain that polarity into the underlying white matter. The response disappeared during a spreading depression, though it recovered more rapidly than the primary response evoked by skin stimulation. Maps of the primary response showed a strong overlap with the ''antidromic'' response, though the response was largest slightly caudal to the maximal focus of the ''antidromic'' response and extended more caudally through transitional and into limbic cortex. The ''antidromic'' response showed two major foci on the cortex, with an additional minor focus located more laterally. It is argued that the ''antidromic'' response in the rabbit is the same as that found in the opossum, woodchuck, rat and slow loris, and is markedly different from that found in the cat and macaque monkey. It is postulated that this response reflects synaptic action in pyramidal tract axon collaterals, probably onto cell bodies in layer V, rather than being a purely antidromic event.

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Section: Discussionmentioning

confidence: 99%