Anterior temporal lobes mediate semantic representation: mimicking semantic dementia by using rTMS in normal participants.

Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 01/2008; 104(50):20137-41. DOI: 10.1073/pnas.0707383104
Source: PubMed

ABSTRACT Studies of semantic dementia and PET neuroimaging investigations suggest that the anterior temporal lobes (ATL) are a critical substrate for semantic representation. In stark contrast, classical neurological models of comprehension do not include ATL, and likewise functional MRI studies often fail to show activations in the ATL, reinforcing the classical view. Using a novel application of low-frequency, repetitive transcranial magnetic stimulation (rTMS) over the ATL, we demonstrate that the behavioral pattern of semantic dementia can be mirrored in neurologically intact participants: Specifically, we show that temporary disruption to neural processing in the ATL produces a selective semantic impairment leading to significant slowing in both picture naming and word comprehension but not to other equally demanding, nonsemantic cognitive tasks.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Retrieving the names of friends, loved ones, and famous people is a fundamental human ability. This ability depends on the left anterior temporal lobe (ATL), where lesions can be associated with impaired naming of people regardless of modality (e.g., picture or voice). This finding has led to the idea that the left ATL is a modality-independent convergence region for proper naming. Hypotheses for how proper-name dispositions are organized within the left ATL include both a single modality-independent (heteromodal) convergence region and spatially discrete modality-dependent (unimodal) regions. Here we show direct electrophysiologic evidence that the left ATL is heteromodal for proper-name retrieval. Using intracranial recordings placed directly on the surface of the left ATL in human subjects, we demonstrate nearly identical responses to picture and voice stimuli of famous U.S. politicians during a naming task. Our results demonstrate convergent and robust large-scale neurophysiologic responses to picture and voice naming in the human left ATL. This finding supports the idea of heteromodal (i.e., transmodal) dispositions for proper naming in the left ATL. Copyright © 2015 the authors 0270-6474/15/351513-08$15.00/0.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 01/2015; 35(4):1513-20. DOI:10.1523/JNEUROSCI.3387-14.2015 · 6.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The present review aimed to check two proposals alternative to the original version of the 'semantic hub' hypothesis, based on Semantic Dementia (SD) data, which assumed that left and right anterior temporal lobes (ATLs) store in a unitary, amodal format all kinds of semantic representations. The first alternative proposal is that the right ATL might subsume non-verbal representations and the left ATL lexical-semantic representations and that only in the advanced stages of SD, when atrophy affects the ATLs bilaterally, the semantic impairment becomes 'multi-modal'. The second alternative suggestion is that right and left ATLs might underlie two different domains of knowledge, because general conceptual knowledge might be supported by the left ATL, and social cognition by the right ATL. Results of the review substantially support the first proposal, showing that the right ATL subsumes non-verbal representations and the left ATL lexical-semantic representations. They are less conclusive about the second suggestion, because the right ATL seems to play a more important role in behavioural and emotional functions than in higher level social cognition. Copyright © 2015. Published by Elsevier Ltd.
    Neuroscience & Biobehavioral Reviews 02/2015; 51. DOI:10.1016/j.neubiorev.2015.02.004 · 10.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report a lesion–symptom mapping analysis of visual speech production deficits in a large group (280) of stroke patients at the sub-acute stage (<120 days post-stroke). Performance on object naming was evaluated alongside three other tests of visual speech production, namely sentence production to a picture, sentence reading and nonword reading. A principal component analysis was performed on all these tests' scores and revealed a ‘shared’ component that loaded across all the visual speech production tasks and a ‘unique’ component that isolated object naming from the other three tasks. Regions for the shared component were observed in the left fronto-temporal cortices, fusiform gyrus and bilateral visual cortices. Lesions in these regions linked to both poor object naming and impairment in general visual–speech production. On the other hand, the unique naming component was potentially associated with the bilateral anterior temporal poles, hippocampus and cerebellar areas. This is in line with the models proposing that object naming relies on a left-lateralised language dominant system that interacts with a bilateral anterior temporal network. Neuropsychological deficits in object naming can reflect both the increased demands specific to the task and the more general difficulties in language processing.
    01/2015; 214. DOI:10.1016/j.nicl.2015.01.015


Available from