The Role of the Left Anterior Temporal Lobe for Unpredictable and Complex Mappings in Word Reading

Abstract

The anterior temporal lobes (ATLs) have been consistently associated with semantic processing which, in turn, has a key role in reading aloud single words. This study aimed to investigate (1) the reading abilities in patients with the semantic variant of primary progressive aphasia (svPPA), and (2) the relationship between gray matter (GM) volume of the left ATL and word reading performance using voxel-based morphometry (VBM). Three groups of participants (svPPA, Alzheimer’s Disease, AD and healthy elderly adults) performed a reading task with exception words, regular words and pseudowords, along with a structural magnetic resonance imaging scan. For exception words, the svPPA group had a lower accuracy and a greater number of regularization errors as compared to the control groups of healthy participants and AD patients. Similarly, for regular words, svPPA patients had a lower accuracy in comparison with AD patients, and a greater number of errors related to complex orthography-to-phonology mappings (OPM) in comparison to both control groups. VBM analyses revealed that GM volume of the left ATL was associated with the number of regularization errors. Also, GM volume of the left lateral ATL was associated with the number of errors with complex OPM during regular word reading. Our results suggest that the left ATL might play a role in the reading of exception words, in accordance with its role in semantic processing. Results further support the involvement of the left lateral ATL in combinatorial processes, including the integration of semantic and phonological information, for both exception and regular words.

Executive Profile of the Logopenic Variant of Primary Progressive Aphasia: Comparison with the Semantic and Non-Fluent Variants and Alzheimer’s Disease

“…Thus, these results provide additional information to help differential diagnosis and support the data from the literature. For instance, verbal working memory, flexibility, inhibition, initiation, and planning are all less efficient in AD than in the semantic form of PPA [ 23 , 32 , 37 , 40 , 72 , 73 , 75 , 76 ]. Only verbal short-term memory does not differentiate the two groups [ 37 , 73 , 76 ].…”

Distinguishing Semantic Variant Primary Progressive Aphasia from Alzheimer’s Disease

“…Finally, fully testing for svPPA involves asking patients to describe a named item, select an item from an array, identify or sort associated items that go together, and draw a specific item. Writing and reading irregular words further screens for surface dysgraphia and dyslexia, which may result because the ATL degeneration impairs semantic integration of exceptional or irregular word forms [32,33].…”

Using neurostimulation to understand the impact of pre-morbid individual differences on post-lesion outcomes

“…Indeed, there have been a number of semantic dementia cases reported who have had marked surface dyslexia without any evidence of hypometabolism extending into the left ventral occipito-temporal cortex ( 29 ). Furthermore, recent lesion-symptom mapping work has demonstrated a significant relationship between the regularization errors in reading and the degree of left ATL atrophy among semantic dementia patients ( 43 ). Taken together, these results from neurostimulation and neuropsychology combine to support a specific role of the ATL in atypical word reading.…”