Fkd. Nahm et al., IN-VIVO MICROELECTRODE LOCALIZATION IN THE BRAIN OF THE ALERT MONKEY - A COMBINED RADIOGRAPHIC AND MAGNETIC-RESONANCE-IMAGING APPROACH, Experimental Brain Research, 98(3), 1994, pp. 401-411
A technique is described for in vivo localization of microelectrodes d
uring single-unit recording in the alert monkey. Four hollow glass sph
eres filled with copper sulfate and iohexol were affixed to the surfac
e of the animal's skull prior to the acquisition of a series of corona
l magnetic resonance (MR) images. These reference beads were visible i
n both X-ray and MR images. Cranial recording chambers were then impla
nted bilaterally over the amygdaloid complex. A microelectrode was adv
anced to various depths in the subject's brain. At each selected micro
electrode site, five radiographs were obtained and a small electrolyti
c lesion was made. Based on the data from the radiographs, we computed
the position of the microelectrode tip at each site relative to the r
eference beads. With a precision of 625 mu m, this method was used to
predict the neuroanatomical location of ten microlesions placed in bot
h subcortical and cortical structures. Postmortem histological analysi
s revealed that the actual location of the lesions closely matched pre
dictions arrived at using the X-ray/MRI localization technique. This t
echnique thus provides an accurate, reliable and noninvasive method fo
r in vivo localization of microelectrode recording sites.