The role of the arcuate fasciculus in conduction aphasia

Abstract

In aphasia literature, it has been considered that a speech repetition defect represents the main constituent of conduction aphasia. Conduction aphasia has frequently been interpreted as a language impairment due to lesions of the arcuate fasciculus (AF) that disconnect receptive language areas from expressive ones. Modern neuroradiological studies suggest that the AF connects posterior receptive areas with premotor/motor areas, and not with Broca's area. Some clinical and neurophysiological findings challenge the role of the AF in language transferring. Unusual cases of inter-hemispheric dissociation of language lateralization (e.g. Broca's area in the left, and Wernicke's area in the right hemisphere) have been reported without evident repetition defects; electrocortical studies have found that the AF not only transmits information from temporal to frontal areas, but also in the opposite direction; transferring of speech information from the temporal to the frontal lobe utilizes two different streams and conduction aphasia can be found in cases of cortical damage without subcortical extension. Taken altogether, these findings may suggest that the AF is not required for repetition although could have a subsidiary role in it. A new language network model is proposed, emphasizing that the AF connects posterior brain areas with Broca's area via a relay station in the premotor/motor areas.

White Matter Disruptions in Adolescents Exposed to Childhood Maltreatment and Vulnerability to Psychopathology

“…However, the terminations of this tract cover lateral frontal, prefrontal, premotor, dorsolateral parietal, fronto-parietal, pareito-occipital, parieto-temporal, temporal, and insular regions. The extensive cortical connections of this tract suggest that SLF-L may be involved in more brain functions besides language (Bernal and Ardila, 2009). Consistent with our finding, a study of young adults exposed to parental verbal abuse found disruption in the left arcuate fasciculus, the fronto-temporal branch of SLF-L (Choi et al, 2009).…”

Prediction of Aphasia Outcome Using Diffusion Tensor Tractography for Arcuate Fasciculus in Stroke

“…These results seem to support the previous studies about the role of AF in language function: Injury of the AF showed various language dysfunction as well as conduction aphasia. [29][30][31][32] The early AQ score was found to be correlated with the late AQ in regression analysis. These results coincided with the results of previous studies finding that the severity of aphasia at the acute stage is a significant predictor of aphasia outcome.…”

“…According to the previous studies on the recovery mechanism of aphasia, we can assume several other ways of recovery: recovery via other neural tracts such as the superior longitudinal fasciculus, contribution of the unaffected (right) hemisphere, or interhemispheric dissociated lateralization of the Broca and Wernicke areas (Broca and Wernicke areas are located in different hemispheres). 7,30,[36][37][38] Second, it has been reported that the typical type of the AF injury was conduction aphasia, and the prognosis of conduction aphasia was usually good. Kertesz and McCabe 39 reported that 5 (62.5%) of 8 patients with conduction aphasia were completely recovered.…”

“…Kertesz and McCabe 39 reported that 5 (62.5%) of 8 patients with conduction aphasia were completely recovered. 30,40 Moreover, several studies suggested that the AF was not necessary for speech repetition. 31,32,[36][37][38][39][40][41] Third, another possibility might be the small number of subjects.…”

Developmental conduction aphasia after neonatal stroke

“…Wui K. Chong, MD, 2 Frances M. Cowan, PhD, 3,4 and Torsten Baldeweg, MD 1,2 Objective: Impairment of speech repetition following injury to the dorsal language stream is a feature of conduction aphasia, a well-described "disconnection syndrome" in adults. The impact of similar lesions sustained in infancy has not been established.…”