Re-examining Paul Broca's initial presentation of M. Leborgne: understanding the impetus for brain and language research

How Do We Connect Brain Areas with Cognitive Functions? The Past, the Present and the Future

One of the central goals of cognitive neuroscience is to understand how structure relates to function. Over the past century, clinical studies on patients with lesions have provided key insights into the relationship between brain areas and behavior. Since the early efforts for characterization of cognitive functions focused on localization, we provide an account of cognitive function in terms of localization. Next, using body perception as an example, we summarize the contemporary techniques. Finally, we outline the trajectory of current progress into the future and discuss the implications for clinical and basic neuroscience.

The Long View of Language Localization

For British neurologists, one case was considered to represent significant evidence regarding the organization of language in the brain in the second half of the 19th century. The interpretation of its significance was based on repeated standard clinical assessment of behavioral deficits, the use of a psychological model of processing, and lesion localization to inform understanding of clinic-pathological correlation. The aphasic deficits experienced by a single case were observed and recorded by London neurologist Henry Charlton Bastian (1837-1915) over a period of 18 years and used as a demonstration of clinico-pathological reasoning regarding language function. This case was well documented in many of Bastian's publications; presented in teaching demonstrations; included in discussions at medical society meetings and public lectures; and reported widely in the medical press. When this patient died, the autopsy findings were added to the extensive record of his language deficits. Some aspects of the size and site of the lesion were consistent with Bastian's clinical predictions arising from his model of language processing, while others presented more of a paradox. This single case was a significant source of discussion and reflection in the medical community throughout the second half of the 19th century. Examination of various interpretations of this case reveal the assumptions regarding the functional architecture of language processing and more general theoretical considerations of how evidence from cases of acquired neurogenic aphasia can be employed in developing such models. This long view into a historical case sheds light on the challenges of clinic-pathological correlation methods in the understanding of localization of language functions which remain today.

What does scalp electroencephalogram coherence tell us about long-range cortical networks?

Long-range interactions between cortical areas are undoubtedly a key to the computational power of the brain. For healthy human subjects, the premier method for measuring brain activity on fast timescales is electroencephalography (EEG), and coherence between EEG signals is often used to assay functional connectivity between different brain regions. However, the nature of the underlying brain activity that is reflected in EEG coherence is currently the realm of speculation, because seldom have EEG signals been recorded simultaneously with intracranial recordings near cell bodies in multiple brain areas. Here, we take the early steps towards narrowing this gap in our understanding of EEG coherence by measuring local field potentials with microelectrode arrays in two brain areas (extrastriate visual area V4 and dorsolateral prefrontal cortex) simultaneously with EEG at the nearby scalp in rhesus macaque monkeys. Although we found inter-area coherence at both scales of measurement, we did not find that scalp-level coherence was reliably related to coherence between brain areas measured intracranially on a trial-to-trial basis, despite that scalp-level EEG was related to other important features of neural oscillations, such as trial-to-trial variability in overall amplitudes. This suggests that caution must be exercised when interpreting EEG coherence effects, and new theories devised about what aspects of neural activity long-range coherence in the EEG reflects.

Louis Victor Leborgne ("Tan")

Louis Victor Leborgne was a patient of Paul Broca. "Monsieur Leborgne," as Broca would call him, was also known around in the hospital by the nickname "Tan." His neurologic condition left him with difficulty in speaking, and he could only speak the word "Tan." Leborgne spent nearly half of his entire life in the hospital. He was initially admitted into the psychiatry division of the hospital and was later transferred under the care of Broca toward the end of his life. The story of the Leborgne sits in the crossroads of human thoughts that led to the discovery of cerebral localization. It is the objective of this study to describe the circumstances associated with this patient, which led the great thinkers of that time to discover the language localization in the cerebral cortex. Leborgne's condition was the cornerstone in the evolution of this discovery. More than 150 years have passed since the death of Leborgne, yet Leborgne's brain continues to attract researchers investigating the mysteries of human speech.

Early steps toward understanding neuronal communication

PURPOSE OF REVIEW

The computational power of the brain arises from the complex interactions between neurons. One straightforward method to quantify the strength of neuronal interactions is by measuring correlation and coherence. Efforts to measure correlation have been advancing rapidly of late, spurred by the development of advanced recording technologies enabling recording from many neurons and brain areas simultaneously. This review highlights recent results that provide clues into the principles of neural coordination, connections to cognitive and neurological phenomena, and key directions for future research.

RECENT FINDINGS

The correlation structure of neural activity in the brain has important consequences for the encoding properties of neural populations. Recent studies have shown that this correlation structure is not fixed, but adapts in a variety of contexts in ways that appear beneficial to task performance. By studying these changes in biological neural networks and computational models, researchers have improved our understanding of the principles guiding neural communication.

SUMMARY

Correlation and coherence are highly informative metrics for studying coding and communication in the brain. Recent findings have emphasized how the brain modifies correlation structure dynamically in order to improve information-processing in a goal-directed fashion. One key direction for future research concerns how to leverage these dynamic changes for therapeutic purposes.

The Third Man: Robert Dunn's (1799-1877) Contribution to Aphasia Research in Mid-Nineteenth-Century England

Throughout his medical career, Robert Dunn (1799-1877) published a number of clinical cases with postmortem reports involving acquired language disorders, with the first noted in 1842. He developed a physiologically informed approach to psychological function during the 1850s along with a group of notable colleagues Benjamin Collins Brodie, Henry Holland, Thomas Laycock, John Daniel Morell, and Daniel Noble. He was also active in ethnographic research on human origins and racial diversity. As such, Dunn represents an interesting player in the developing fields of neurology, psychology, and anthropology in England in the latter part of the nineteenth century. These various strands converged at the meeting of the British Association of the Advancement of Science in 1868, where Dunn shared the program of lectures on the cutting-edge topic of aphasia with Paul Broca (1824-1880) and John Hughlings Jackson (1835-1911). Dunn's ideas developed over a longer time frame than his younger colleagues and as such represent a unique blending of concepts from the earlier work of Franz Josef Gall (1758-1828) and Jean-Baptiste Bouillaud (1798-1881) to the perspectives on language organization in the brain developed after 1861.

Broca's faculté du langage articulé: Language or Praxis?

De Oliveira-Souza, Moll, and Tovar-Moll (this issue) historically reevaluate that Paul Broca's aphemia should be considered as a kind of apraxia rather than aphasia. I argue that such a claim is unwarranted, given the interpretation of the faculty of speech Broca derived from his predecessors, Jean-Baptiste Bouillaud and Franz Joseph Gall, and also with a view on the then generally held opinion that the terms aphémie and aphasie were synonyms. I will discuss evidence that patients such as Leborgne, producing only very few words or syllables, suffer from a global aphasia, affecting all modalities, despite Broca's statement that Leborgne's comprehension was intact. I also point to Broca's claim that the faculty of speech, located in the left anterior hemisphere, is independent from hand preference because it is an intellectual and not a motor function, and to his statement that the cerebral convolutions are not motor organs. I finally contend that, in order to determine whether a given language problem should be labeled as aphasia or apraxia, it is crucial to first be clear on the components of old and new models of language production.

Norman Geschwind and the use of history in the (re)birth of behavioral neurology

When Norman Geschwind (1926-1984) attended medical school in the 1940s, his psychiatry professors taught as if behavior were unrelated to neuropathology. The focus of neurology remained the diagnosis and treatment of aphasias and epilepsies, while cognitive impairments and developmental disorders were classified as functional (psychological) disorders. Geschwind was troubled by the fact that many of the patients he saw with neurological deficits also presented with behavioral (developmental) disorders. Geschwind's generation also had been taught that aphasias resulted from global rather than localized or focal neurological lesions. These holists, including the prepsychoanalytic Sigmund Freud, targeted the work of aphasiologist Carl Wernicke as an exemplar of the flaws of the localizationist hypothesis. Reading Wernicke in the original, Geschwind discovered a complex and multilayered explanation for aphasias that implicated lesions located in association pathways that, when extensive, resulted in behavioral disorders. Geschwind also reread the works of the holists, discovering that, while their rhetoric rejected Wernicke, their explanations of aphasias actually reinforced Wernicke's hypothesis. Building on his reading of these historical documents and his clinical experiences, Geschwind urged the resurrection of Wernicke's disconnection syndromes that Geschwind labeled as Behavioral Neurology.

Written language production disorders: historical and recent perspectives

Written language production is often the least examined neuropsychological function, yet it provides a sensitive and subtle sign to a variety of different behavioral disorders. The dissociation between written and spoken language and reading and writing first came to clinical prominence in the nineteenth century, with respect to ideas about localization of function. Twentieth century aphasiology research focused primarily on patients with unifocal lesions from cerebrovascular accidents, which have provided insight into the various levels of processing involved in the cognitively complex task of producing written language. Recent investigations have provided a broader perspective on writing impairments in a variety of disorders, including progressive and diffuse brain disorders, and functional brain imaging techniques have been used to study the underlying processes in healthy individuals.

Mysterious "Monsieur Leborgne": The mystery of the famous patient in the history of neuropsychology is explained

As of spring 2011, 150 years have passed since the death of one of the most famous neurological patients of the nineteenth century. A Frenchman, "Monsieur Leborgne" also known by the nickname "Tan," was hospitalized due to an almost complete loss of speech. His case was presented in 1861, during a seating of the Société d'Anthropologie de Paris by a physician, Pierre Paul Broca (1824-1880), who used this occasion to report that he had discovered, in the middle part of patient's left frontal lobe, the cortical speech center. This area was later named "Broca's area." Both the patient and his medical records were the subject of numerous descriptions and citations in the medical literature. The patient's full identity and social background has remained a mystery until now. This article presents biographical data concerning Leborgne and his family based on archive registers in France.