Direct cortical electrical recording (electrocorticography, ECoG) will be applied to problems in the understanding of the functional and neural bases of language and language-related functions. This work is made feasible because some patients requiring focal cerebral resections (e.g., for epilepsy, arteriovenous malformations, or brain tumors) receive extensive indwelling subdural electrode arrays as part of their clinical evaluation. As a result, electrical recording can be done with an awake, cooperative, fully-functioning individual. This project has the following specific scientific aims: (l) To determine what indices of regional cortical electrical activity, such as spectral changes, reflect regional cerebral processing with language and related cognitive functions in humans, (2) To use the indices of regional cerebral involvement determined in #1 to analyze the processes and subprocesses involved in human language and related functions -- in particular, to identify the functional components, their interrelationships, and their time courses, (3) To determine how the results obtained with direct cortical recording compare with those obtained from other techniques, such as direct cortical stimulation, cortically-recorded evoked potentials, PET and/or functional MRI, and focal lesions. Many of these comparisons will be made within the same subject, undergoing investigation with the different techniques. Other comparisons will be made across subjects and subject groups.
These aims will be pursued concurrently, through detailed comparisons of the patterns of electrocortical activity, and of their neuroanatomic correlations, in each individual subject under a variety of different task and stimulus conditions. The standard logic of cognitive neuroscience will be used to interpret patterns of task performance in terms of underlying cognitive operations. Standard methods of electrical signal analysis, and standard and advanced methods of statistical analysis, will be used to interpret the patterns of electrocortical activity and to relate it to functional components and to neuroanatomic regions. Preliminary studies have established that the proposed studies are feasible, that analyses using regional spectral changes in the ECoG appear to reflect regional cerebral involvement in motor, sensory, and cognitive processes, and that a direct comparison with the results of another technique, cortical stimulation, can strengthen the conclusions drawn from either method separately.
