Citations of this article
Mendeley users who have this article in their library.
Get full text


The core clinical feature of semantic dementia is a progressive yet selective degradation of conceptual knowledge. Understanding the cognitive and neuroanatomical basis for this deficit is a key challenge for both clinical and basic science. Some researchers attribute the deficit to damage to pan-modal conceptual representations that are independent of any particular sensory-motor modality and are represented in the ventrolateral anterior temporal lobes. Others claim that damage to modality-specific visual feature representations in the occipitotemporal 'ventral stream' is responsible. In the present study, we tested the hypothesis that concept degradation in semantic dementia involves a combination of these pan-modal and modality-specific elements. We investigated factors influencing knowledge of object concepts by analysing 43 sets of picture-naming data from patients with semantic dementia. We found a strong influence of two pan-modal factors: highly familiar and typical items were named more accurately than less familiar/atypical items at all stages of the disorder. Items associated with rich sensory-motor information were also named more successfully at all stages, and this effect was present for sound/motion knowledge and tactile/action knowledge when these modalities were studied separately. However, there was no advantage for items rich in visual colour/form characteristics; instead, this factor had an increasingly negative impact in the later stages of the disorder. We propose that these results are best explained by a combination of (i) degradation of modality-independent conceptual representations, which is present throughout the disorder and is a consequence of atrophy focused on the ventrolateral anterior temporal lobes; and (ii) a later additional deficit for concepts that depend heavily on visual colour/form information, caused by the spreading of atrophy to posterior ventral temporal regions specialized for representing this information. This explanation is consistent with a graded hub-and-spoke model of conceptual knowledge, in which there is a gradual convergence of information along the temporal lobes, with visual attributes represented in the posterior cortex giving way to pan-modal representations in the anterior areas.




Hoffman, P., Jones, R. W., & Ralph, M. A. L. (2012). The degraded concept representation system in semantic dementia: Damage to pan-modal hub, then visual spoke. Brain, 135(12), 3770–3780. https://doi.org/10.1093/brain/aws282

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free