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Evidence of a sensory processing unit in the mammalian maculaWe cut serial sections through the medial part of the rat vestibular macula for transmission electron microscopic (TEM) examination, computer-assisted 3-D reconstruction, and compartmental modeling. The ultrastructural research showed that many primary vestibular neurons have an unmyelinated segment, often branched, that extends between the heminode (putative site of the spike initiation zone) and the expanded terminal(s) (calyx, calyces). These segments, termed the neuron branches, and the calyces frequently have spine-like processes of various dimensions with bouton endings that morphologically are afferent, efferent, or reciprocal to other macular neural elements. The major questions posed by this study were whether small details of morphology, such as the size and location of neuronal processes or synapses, could influence the output of a vestibular afferent, and whether a knowledge of morphological details could guide the selection of values for simulation parameters. The conclusions from our simulations are (1) values of 5.0 k omega cm2 for membrane resistivity and 1.0 nS for synaptic conductance yield simulations that best match published physiological results; (2) process morphology has little effect on orthodromic spread of depolarization from the head (bouton) to the spike initiation zone (SIZ); (3) process morphology has no effect on antidromic spread of depolarization to the process head; (4) synapses do not sum linearly; (5) synapses are electrically close to the SIZ; and (6) all whole-cell simulations should be run with an active SIZ.
Document ID
20040173197
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Chimento, T. C.
(NASA Ames Research Center Moffett Field, CA United States)
Ross, M. D.
Date Acquired
August 22, 2013
Publication Date
June 19, 1996
Publication Information
Publication: Annals of the New York Academy of Sciences
Volume: 781
ISSN: 0077-8923
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center ARC
NASA Program Space Biology
NASA Discipline Neuroscience
NASA Discipline Number 40-10

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