Ha. Swadlow, NEOCORTICAL EFFERENT NEURONS WITH VERY SLOWLY CONDUCTING AXONS - STRATEGIES FOR RELIABLE ANTIDROMIC IDENTIFICATION, Journal of neuroscience methods, 79(2), 1998, pp. 131-141
Although simple in concept, reliable antidromic identification of effe
rent populations poses numerous technical challenges and is subject to
a host of sampling biases, most of which select against the detection
of the neurons with slowly conducting axons. This problem is particul
arly acute in studies of the neocortex. Many neocortical efferent syst
ems have large sub-populations with very slowly conducting, nonmyelina
ted axons and these elements have been relatively neglected in antidro
mic studies of neocortical neurons. The present review attempts to red
ress this problem by analyzing the steps that must necessarily precede
antidromic identification and the sampling biases associated with eac
h of these steps. These steps include (1) initial recognition that the
microelectrode is near a neuron; (2) activation of the efferent axon
via the stimulating electrode; (3) conduction of the antidromic impuls
e from stimulation site to soma; (4) detection of the antidromic spike
in the extracellular record and (5) discriminating antidromic from sy
naptic activation. Experimental strategies are suggested for minimizin
g the sampling biases associated with each of these steps; most of whi
ch can be reduced or eliminated by appropriate experimental procedures
. Careful attention to such procedures will make it possible to better
understand the nature and function of the information flow along the
very slowly conducting axonal systems of the neocortex. (C) 1998 Elsev
ier Science B.V. All rights reserved.