The first recordings of subcortical potentials of man fall into the pre-stereotactic
era of movement disorder surgery. In the early 1940s, Meyers inserted manually an
electrode through a craniotomy into the striatum of Parkinsonian patients under direct
inspection, but found no correlation between his electrocaudatograms on the one hand
and the clinically estimated degree of Parkinsonian symptoms on the other. However,
Meyers' demonstration of the potential benefits of basal ganglia surgery together
with the high mortality rates of these „open“ procedures led Spiegel to introduce
the less invasive stereotactic method to the human brain in 1947. Functional exploration
of subcortical structures by means of macroelectrode techniques complemented conventional
electrical stimulation and was soon routinely performed by many other stereotaxic
research groups all over the world. Nevertheless, the results of macroelectrode recordings
were heterogeneous and somewhat disappointing, since the relatively crude EEG-like
signals did not allow for a differentiation of the various structures. The introduction
of microelectrode recordings into functional stereotaxy by Madame Albe-Fessard and
her collaborators in the early 1960s was therefore welcomed enthusiastically by the
stereotactic community because the finer recording probes provided the first recordings
of multiple unit spike activities, enabling a reliable differentiation and delineation
of various human thalamic nuclei. An enormous amount of electrophysiological investigations
were carried out until the introduction of levodopa for the treatment of Parkinsonian
patients in 1967 and resulted in a detailed anatomophysiological description of the
human thalamus and pallidum. Thereafter, interest in functional stereotaxy waned and
the accompanying neurophysiological investigations were only sporadically continued,
until the introduction of new imaging techniques and the implementation of deep brain
stimulation as a substitute for ablative surgery led to a resurrection of functional
stereotactic surgery in the late 1980s. Besides giving a survey of the historical
development of this exciting field of applied neurophysiology, the present report
highlights both practical and methodological challenges of intraoperative microphysiology
in the context of non-invasive imaging techniques and an increased impact of observations
from animal studies.
