50 Biological Psychology
half century earlier, that specific parts of the brain mediate
specific behaviors.
Both Gall and Bouillaud seemed to be vindicated in 1861
with the publication of the proceedings from a meeting of
the Société d’Anthropologie de Paris. Broca, assisted by
Alexandre Ernest Aubertin, Bouillaud’s son-in-law and a
strong believer in localization and in Bouillaud’s hypothesis,
presented the neuropathological findings from the brain of
his patient, Monsieur Leborgne. [This patient subsequently
was referred to by the name “Tan,” the only utterance Broca
ever heard Monsieur Leborgne make (Broca, 1861).]
Broca’s finding from his patient Tan has been regarded by
some historians as the most important clinical discovery in
the history of cortical localization. Moreover, within the
decade, what some historians regard as the most important
laboratory discovery pertaining to cortical localization was
reported when Gustav Fritsch and Eduard Hitzig (1870) dis-
covered the cortical motor area in the dog and proved that
cortical localization was not restricted to a single function
(Finger, 1994). The discoveries of the speech area by Broca
and the motor area by Fritsch and Hitzig were seen as vindi-
cation for Gall’s ideas and reestablished him as the father of
localization.
Following the pioneering study by Fritsch and Hitzig on
the localization and organization of the motor area of the
cerebral cortex, localization of function quickly won the day,
at least for sensory and motor systems. In the last three
decades of the nineteenth century, the general locations of
the visual and auditory areas of the cortex were identified.
The field of physiology, in particular neurophysiology—for
example, in the work of Sir Charles Sherrington—together
with clinical neurology and neuroanatomy, were exciting
new fields at the beginning of the twentieth century.
At this time, the only experimental tools for studying brain
organization and functions were ablation and electrical stim-
ulation. Neuroanatomy was in its descriptive phase; thanks in
part to the Golgi method, the monumental work of Ramon y
Cajal was completed over a period of several decades begin-
ning near the end of the nineteenth century. Neurochemistry
was in its descriptive phase, characterizing chemical sub-
stances in the brain.
The first recording of a nerve action potential with a
cathode-ray tube was done by Gasser and Erlanger in 1922,
but the method was not much used until the 1930s. The human
EEG was rediscovered in 1929 by H. Berger, and the method
was applied to animal research and human clinical neurology,
particularly epilepsy, in the 1930s by, for example, Alexander
Forbes, Hallowell Davis, and Donald Lindsley.
The pioneering studies of Adrian in England (1940) and of
Wade Marshall, Clinton Woolsey, and Philip Bard (1941) at
Johns Hopkins were the first to record electrical evoked po-
tentials from the somatic sensory cortex in response to tactile
stimulation. Woolsey and his associates developed the de-
tailed methodology for evoked potential mapping of the
cerebral cortex. In an extraordinary series of studies, they de-
termined the localization and organization of the somatic
sensory areas, the visual areas and the auditory areas of the
cerebral cortex, in a comparative series of mammals. They
initially defined two projection areas (I and II) for each sen-
sory field; that is, they found two complete functional maps
of the receptor surface for each sensory region of the cerebral
cortex, for example, two complete representations of the skin
surface in the somatic-sensory cortex.
In the 1940s and 1950s, the evoked potential method was
used to analyze the organization of sensory systems at all
levels from the first-order neurons to the cerebral cortex. The
principle that emerged was strikingly clear and simple—in
every sensory system the nervous system maintained recep-
totopic maps or projections at all levels from receptors—skin
surface, retina, basilar membrane—to cerebral cortex. The
receptor maps in the brain were not point-to-point; rather,
they reflected the functional organization of each system—
fingers, lips, and tongue areas were much enlarged in the pri-
mate somatic cortex, half the primary visual cortex repre-
sented the forea, and so on.
The evoked potential method was very well suited to analy-
sis of the overall organization of sensory systems in the brain.
However, it could reveal nothing about what the individual
neurons were doing. This had to await development of the mi-
croelectrode (a very small electrode that records the activity of
a single cell). Indeed, the microelectrode has been the key to
analysis of the fine-grained organization and “feature detec-
tor” properties (most neurons respond only to certain aspects,
or features, of a stimulus) of sensory neurons. The first intra-
cellular glass pipette microelectrode was actually invented by
G. Ling and R. W. Gerard in 1949; they developed it to record
intracellularly from frog muscle. Several investigators had
been using small wire electrodes to record from nerve fibers,
for example, Robert Galambos at Harvard in 1939 (auditory
nerve; see Galambos & Davis, 1943) and Birdsey Renshaw at
the University of Oregon Medical School in the 1940s (dorsal
and ventral spinal roots). Metal electrodes were generally
found to be preferable for extracellular single-unit recording
(i.e., recording the spike discharges of a single neuron where
the tip of the microelectrode is outside the cell but close
enough to record its activity clearly). Metal microelectrodes
were improved in the early 1950s; R. W. Davies at Hopkins
developed the platinum-iridium glass-coated microelectrode,
D. Hubel and T. Wiesel at Harvard developed the tungsten mi-
croelectrode, and the search for putative stimulus coding