Preserved speech abilities and compensation following prefrontal damage.

Abstract

Lesions to left frontal cortex in humans produce speech production impairments (nonfluent aphasia). These impairments vary from subject to subject and performance on certain speech production tasks can be relatively preserved in some patients. A possible explanation for preservation of function under these circumstances is that areas outside left prefrontal cortex are used to compensate for the injured brain area. We report here a direct demonstration of preserved language function in a stroke patient (LF1) apparently due to the activation of a compensatory brain pathway. We used functional brain imaging with positron emission tomography (PET) as a basis for this study.How the human brain recovers function following injury remains one of the most puzzling scientific mysteries. In particular, the recovery mechanism(s) that allows speech function after injury to brain areas critical to language has been debated for more than a century (1-3). In the past, researchers have sought to understand speech production deficits by examining patients with brain damage and trying to determine what the patients cannot do. The logic applied in these studies is as follows: if a brain area is damaged and a person cannot perform certain speech tasks, then the damaged area, in some way, participates in the lost functions. However, this approach does not provide a powerful methodology for determining how patients might be performing any preserved and/or recovered functions.Recent positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies in normal subjects have characterized the functional anatomy of several speech tasks (4-8). These studies provide a unique context for the study of patients with speech production deficits. Utilizing this context, we have developed an approach to the study of compensation following injury. The unique feature of this approach is to determine which brain area is damaged in a patient and identify tasks that are known to activate that area in neuroimaging studies of normal subjects. By testing the patient on these tasks, preserved performance can be used as a predictor of tasks likely being accomplished by compensatory brain pathways. Then, neuroimaging can be used to determine these compensatory pathways. As a final step, additional behavioral testing can be conducted to determine task capabilities potentially using the compensatory pathways.We report here a case study, of patient LF1, where we used this approach. As a basis for this study, we relied on the finding that a relatively small area in the left-inferior frontal cortex near Broca's area has been activated across many production tasks in normal right-handed subjects (8, 9). Patient LF1 sustained an ischemic stroke that included this portion of left frontal cortex. Using the approach outlined above, we identified preservedThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solel...

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“…This hypothesis has even been used as the conceptual basis for several neuroimaging studies of lesion-related language disorders (e.g., Refs. 54,67,273,402,419). The contribution of specific right-sided regions in language recovery from aphasia has gained support from recent results.…”

Maturation-dependent response of the piglet brain to scaled cortical impact

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Study of Ability of Plastic Motor of Cerebral Cortex in Patients after Stroke (Literature Review)

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