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: 9.67). 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.

Download full-text

Full-text

Available from: Elizabeth Jefferies, Sep 16, 2015
    • "A similar method of ATL disruption was used very recently by Jackson, Lambon Ralph, and Pobric (2015). Other authors (Pobric et al., 2007, 2009 and 2010; Chiou, Sowman, Etchell, & Rich, 2014; Lambon Ralph et al., 2009) previously used rTMS of the right and left TP to obtain novel evidence supporting the 'semantic hub' hypothesis with an ''offline'' approach, i.e. comparing the performance obtained during the temporary refractory period with that obtained on the same task outside this refractory window. Here we aimed to obtain a time-locked disruption of the neural activity of the right or left TP in concomitance with the presentation of each face and name whose familiarity had to be assessed. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The aims of the present experiment was to investigate: (a) if transient disruption of neural activity in the right (RTP) or left temporal pole (LTP) can interfere with the development of a familiarity feeling to the presentation of faces/written names of famous/unknown people; and (b) if this interference specifically affects the familiarity for faces after inhibition of the RTP and for names after inhibition of the LTP. Twenty healthy volunteers took part in the study. Repetitive transcranial magnetic stimulation (rTMS) was administered online; it disrupted the neural activity of the right or left TP in concomitance with the presentation of each face and name whose familiarity had to be assessed. Furthermore, in a control group, each participant was submitted to a single experimental session in which rTMS was delivered to the vertex in association with the presentation of faces and written names. Since previous rTMS studies have shown that the temporary inactivation of the right and left TP influences the response latencies, but not the number of correct responses, in this study we took into account both the number of correct responses obtained in different experimental conditions and the corresponding response latencies. A three-way factorial ANOVA carried out on the Response Scores showed only a general effect of the Type of Stimuli, due to better performances on names than on faces. This greater familiarity of names is consistent with previous data reported in the literature. In the three-way factorial ANOVA carried out on the Latency Scores, post-hoc analyses showed an increased latency of responses to faces after right stimulation in Latency Total, Latency on Correct responses and Latency on Unfamiliar faces. None of these results were obtained in the control group. These data suggest that rTMS at the level of the RTP preferentially affects the development of familiarity feelings to the presentation of faces of famous people.
    No preview · Article · Sep 2015 · Neurobiology of Learning and Memory
  • 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.
    Full-text · Article · Jul 2015 · Cortex
  • Source
    • "e l s e v i e r . c o m / l o c a t e / p h b conceptual processing ([29]; [40] [47]) whereas perceptual processing is thought to involve more posterior regions [3] [42]. These different types of memory have been examined in Alzheimer's disease (AD), normal aging and amnesic patients but not yet in ESRD [2]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Possible impairments of memory in end-stage renal disease (ESRD) were investigated in two experiments. In Experiment 1, in which stimulus words were presented visually, participants were tested on conceptual or perceptual memory tasks, with retrieval being either explicit or implicit. Compared with healthy controls, ESRD patients were impaired when memory required conceptual but not when it required perceptual processing, regardless of whether retrieval was explicit or implicit. An impairment of conceptual implicit memory (priming) in the ESRD group represented a previously unreported deficit compared to healthy aging. There were no significant differences between pre- and immediate post-dialysis memory performance in ESRD patients on any of the tasks. In Experiment 2, in which presentation was auditory, patients again performed worse than controls on an explicit conceptual memory task. We conclude that the type of processing required by the task (conceptual vs. perceptual) is more important than the type of retrieval (explicit vs. implicit) in memory failures in ESRD patients, perhaps because temporal brain regions are more susceptible to the effects of the illness than are posterior regions. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · May 2015 · Physiology & Behavior
Show more