The anterior temporal lobes support residual comprehension in Wernicke’s aphasia

Holly Robson,Karen Sage,Richard J Binney,James L Keidel,Matthew A Lambon Ralph,Roland Zahn

doi:10.1093/brain/awt373

Abstract

Wernicke's aphasia occurs after a stroke to classical language comprehension regions in the left temporoparietal cortex. Consequently, auditory-verbal comprehension is significantly impaired in Wernicke's aphasia but the capacity to comprehend visually presented materials (written words and pictures) is partially spared. This study used functional magnetic resonance imaging to investigate the neural basis of written word and picture semantic processing in Wernicke's aphasia, with the wider aim of examining how the semantic system is altered after damage to the classical comprehension regions. Twelve participants with chronic Wernicke's aphasia and 12 control participants performed semantic animate-inanimate judgements and a visual height judgement baseline task. Whole brain and region of interest analysis in Wernicke's aphasia and control participants found that semantic judgements were underpinned by activation in the ventral and anterior temporal lobes bilaterally. The Wernicke's aphasia group displayed an 'over-activation' in comparison with control participants, indicating that anterior temporal lobe regions become increasingly influential following reduction in posterior semantic resources. Semantic processing of written words in Wernicke's aphasia was additionally supported by recruitment of the right anterior superior temporal lobe, a region previously associated with recovery from auditory-verbal comprehension impairments. Overall, the results provide support for models in which the anterior temporal lobes are crucial for multimodal semantic processing and that these regions may be accessed without support from classic posterior comprehension regions.

Highlights

Wernicke’s aphasia is the classical aphasic syndrome associated with impaired language comprehension
Wernicke’s aphasia results from lesions to the left posterior temporoparietal cortex (Bogen and Bogen, 1976; Dronkers et al, 1995), thereby affecting core elements of the phonological and semantic systems (Robson et al, 2012a, 2013) that interact during language comprehension
Single-word reading aloud was taken from the Psycholinguistic Assessment of Language Processing in Aphasia (PALPA: Kay et al, 1992)

Summary

Introduction

Wernicke’s aphasia is the classical aphasic syndrome associated with impaired language comprehension. Wernicke’s aphasia results from lesions to the left posterior temporoparietal cortex (Bogen and Bogen, 1976; Dronkers et al, 1995), thereby affecting core elements of the phonological and semantic systems (Robson et al, 2012a, 2013) that interact during language comprehension. The comprehension impairment in Wernicke’s aphasia is modulated by the degree of phonological analysis required (Robson et al, 2012b). Spoken language comprehension, which requires a high degree of phonological analysis for word recognition, is severely impaired in Wernicke’s aphasia. Written word comprehension, which is mediated by both phonological and visual processes, is significantly less impaired in Wernicke’s aphasia in comparison with spoken word comprehension.

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Conclusion