A Parisian spring: the debate on language localization at the Imperial Academy of Medicine, Paris, April 4-June 13, 1865.

The localization of articulate language (speech) to the posterior third of the third left frontal convolution-Broca's area-did not occur to Broca as he reported the case of his first aphasic patient in 1861. Initially Broca localized articulate language to both frontal lobes, a position that he maintained for 4 years after publishing his first case. In the interval, the Academy of Medicine in Paris had received a copy of a paper authored in 1836 by Marc Dax, in which Dax claimed that the ability to speak resides within the left hemisphere alone. The Academy of Medicine convened in the spring of 1865 to adjudicate the issue. All of the distinguished speakers argued against Dax's contention by citing the prevailing paradigm, that bilaterally symmetrical organs, such as the eyes and ears, and the hemispheres of the brain, must perform the same function. The lone dissenting voice was that of Jules Baillarger, the discoverer of the laminar organization of the cerebral cortex, whose argument in favor of what he called "Dax's law" was so lucid that it carried the day. During his address to the Academy, Baillarger not only supported left-hemisphere dominance for speech, but for the first time described two forms of aphasia, fluent and nonfluent, now referred to as Wernicke's and Broca's aphasias, respectively, as well as the ability of aphasics to speak during emotional outbursts, to which we now refer as Baillarger-Jackson aphasia. It was 9 days after Baillarger's address that Broca, for the first time, unequivocally localized speech to the left frontal lobe.This paper is based on the author's reading of Dax's and Broca's original texts and of the texts read before the Academy of Medicine meeting held at the National Library of France between April 4, 1865, and June 13, 1865. From these primary sources it is concluded that the Academy of Medicine's debate was the last serious challenge to left-hemisphere dominance for speech and to the localization of articulate language to the left frontal lobe-and that Jules Baillarger played a pivotal role in what was a defining moment in neurobiology.

Fundamental or forgotten? Is Pierre Paul Broca still relevant in modern neuroscience?

The ability to speak is a unique human capacity, but where is it located in our brains? This question is closely connected to the pioneering work of Pierre Paul Broca in the 1860s. Based on post-mortem observations of aphasic patients' brains, Broca located language production in the 3rd convolution of the left frontal lobe and thus reinitiated the localizationist view of brain functions. However, contemporary neuroscience has partially rejected this view in favor of a network-based perspective. This leads to the question, whether Broca's findings are still relevant today. In this mini-review, we discuss current and historical implications of Broca's work by focusing on his original contribution and contrasting it with contemporary knowledge. Borrowing from Broca's famous quote, our review shows that humans indeed "speak with the left hemisphere"- but Broca's area is not the sole "seat of articulatory language".

Beyond descriptive neurology: Broca, cerebral hemodynamics, and cortical function.

Pierre-Paul Broca's studies in neurobiology remain of interest. I review a previously neglected aspect of Broca's work in which he presages the use of modern scanning techniques. Broca's goal was to correlate cerebral metabolism to regional cerebral blood flow (CBF) using a novel method, to which he referred as cerebral thermometry. Broca attempted to measure changes in temperatures from the ischemic area and across the watershed regions during a stroke, and the increased CBF produced by performing a cognitive task such as reading aloud. The method involved measurements of local temperatures at specific points about the head with an array of strategically placed thermometers much as EEG electrodes are arrayed to record the electrical activity of the brain. Although his technique was inaccurate and unreliable, the concept of measuring CBF as a diagnostic aid and as a cognitive research tool was prescient. Broca's limitation was not conceptual but purely technological. Broca's attempt to measure CBF as a surrogate for cerebral metabolism was conceptually valid but premature because he lacked the technology necessary to do so.