Article

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.

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    • "In contrast, evidence in support of the social knowledge hypothesis mostly relies on studies in which the person knowledge has been investigated only at a very specific level of representation (i.e., famous or familiar persons ). It is worth noting that specific level entities are also more demanding for the semantic system, and that some recent fMRI (Visser & Lambon Ralph, 2011) and TMS (Pobric, Jefferies and Lambon Ralph, 2007) studies showed that the ATL is also implicated in processing subordinate or basic level concepts. Thus, there are three possible hypotheses about the role plaid by ATL: it might only deal with the specific-level of processing (irrespective of the category), as suggested by Martin (2007), it might selectively process social knowledge (Skipper et al., 2011) or it might represent multimodal semantic concepts (Rogers et al., 2004). "
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    Cortex 07/2015; DOI:10.1016/j.cortex.2015.06.024 · 6.04 Impact Factor
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    • "These past studies concur that the anterior temporal lobes contribute to semantic representation (see also Gough et al., 2005; Pobric et al., 2007; Schwartz et al., 2009; Tranel et al., 1997; Woollams, 2012) necessary for accurate object naming. Putting this together with the results of left-lateralised lesions associated with the shared language component (discussed earlier), our findings are complementary to a proposed model of naming that suggests a left-localised phonological representation system which connects strongly to a bilaterally distributed conceptualisation network (Lambon Ralph et al., 2001; Schapiro et al., 2013). "
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    • "In the rTMS studies we found that, by using double-digit numbers, the resultant number judgement times were typically equivalent to, if not slightly slower than, decision times for the synonym judgement task. Accordingly, any activation observed for the semantic task when directly contrasted against that of the numerical task could not be due to differences in task difficulty (Pobric et al., 2007). "
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