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.

  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    ABSTRACT: A person can be appraised as an individual or as a member of a social group. In the present study we tested whether the knowledge about social groups is represented independently of the living and non-living things. Patients with frontal and temporal lobe tumors involving either the left or the right hemisphere performed three tasks - picture naming, word-to-picture matching and picture sorting - tapping the lexical semantic knowledge of living things, non-living things and social groups. Both behavioral and voxel-based lesion-symptom mapping (VLSM) analyses suggested that social groups might be represented differently from other categories. VLSM analysis carried out on naming errors revealed that left-lateralized lesions in the inferior frontal gyrus, amygdala, insula and basal ganglia were associated with the lexical-semantic processing of social groups. These findings indicate that the social group representation may rely on areas associated with affective processing. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Cortex 07/2015; DOI:10.1016/j.cortex.2015.06.024 · 6.04 Impact Factor
  • Source
    • "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). "
    [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
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    ABSTRACT: By developing and applying a method which combines fMRI and rTMS to explore semantic cognition, we identified both intrinsic (related to automatic changes in task/stimulus-related processing) and induced (i.e., associated with the effect of TMS) activation changes in the core, functionally-coupled network elements. Low-frequency rTMS applied to the human anterior temporal lobe (ATL) induced: (a) a local suppression at the site of stimulation; (b) remote suppression in three other ipsilateral semantic regions; and (c) a compensatory up-regulation in the contralateral ATL. Further examination of activity over time revealed that the compensatory changes appear to be a modulation of intrinsic variations that occur within the unperturbed network. As well as providing insights into the dynamic collaboration between core regions, the ability to observe intrinsic and induced changes in vivo may provide an important opportunity to understand the key mechanisms that underpin recovery of function in neurological pa-tient groups. & 2014 Published by Elsevier Ltd.
    Neuropsychologia 11/2014; 18. DOI:10.1016/j.neuropsychologia.2014.11.009 · 3.45 Impact Factor
Show more


Available from