Is Broca's area critical for speech and language? Evidence from lesion-symptom mapping in chronic aphasia

Introduction The specific role that Broca's area plays in speech and language has been hotly debated in the literature. Some research has pointed to a specific role in particular aspects of speech production, while other findings have suggested additional roles in aspects of language comprehension. In the current study, we had the opportunity to take a broad approach by analyzing lesion and behavioral data from a large cohort of left hemisphere stroke patients. In this brief report, our objective was to identify which speech-language measures show a significant association with Broca's area, specifically pars opercularis and pars triangularis. Methods Lesion site and neuropsychological data from 173 chronic left hemisphere stroke patients were analyzed in the current study. Univariate lesion-symptom mapping (LSM) with rigorous correction was used to identify brain regions associated with individual test performance on a large battery of speech and language tasks. Multivariate LSM analyses were conducted in subsequent runs to confirm findings. Results The LSM results identified many predictable left hemisphere gray and white matter regions significantly associated with the speech-language data, but Broca's area was not implicated in performance on any speech or language measure. Regions adjacent to Broca's area, however, in left central opercular, precentral, and insular cortices were associated with speech production and motor speech performance. Discussion The current study failed to identify a single speech or language measure in our comprehensive test battery that was dependent on Broca's area. This finding could not be attributed to a lack of power, as Broca's area had among the highest power values and substantial lesion coverage. Interrogation of data at the individual patient level revealed the likely source of this null finding: Patients with lesions involving Broca's area varied widely in their speech-language performance, with profiles ranging from non-aphasic to Broca's to global aphasia. Given previous studies in acute stroke patients and healthy participants implicating Broca's area in speech-language, the current findings suggest that Broca's area plays a more supplementary than critical role and can be compensated by surrounding brain regions in chronic stroke

Aphasia · Audiology · Boston Naming Test · Broca's area · Cognition · Cognitive psychology · Functional magnetic resonance imaging · Lateralization of brain function · Neuropsychology · Speech production · Speech recognition · Supplementary motor area · Computer Science · EEG and Brain-Computer Interfaces · Medicine · Neurobiology of Language and Bilingualism · Neuroscience · Psychology · Reading and Literacy Development

• An automated labeling system for subdividing the human cerebral cortex on MRI scans into gyral based regions of interest

  Open Access•Rahul S Desikan, Florent Ségonne et al.•NeuroImage•2006

  Add to list

• Cognitive control and parsing

  Open Access•Jared M Novick, John C Trueswell et al.•Cognitive, Affective, &…•2005

  Add to list

• Dissociation of algorithmic and heuristic processes in language comprehension

  Open Access•Alfonso Caramazza, Edgar Zurif et al.•Brain and Language•1976

  Add to list