%0 Journal Article
%T Why Are the Right and Left Hemisphere Conceptual Representations Different?
%A Guido Gainotti
%J Behavioural Neurology
%D 2014
%R 10.1155/2014/603134
%X The present survey develops a previous position paper, in which I suggested that the multimodal semantic impairment observed in advanced stages of semantic dementia is due to the joint disruption of pictorial and verbal representations, subtended by the right and left anterior temporal lobes, rather than to the loss of a unitary, amodal semantic system. The main goals of the present review are (a) to survey a larger set of data, in order to confirm the differences in conceptual representations at the level of the right and left hemispheres, (b) to examine if language-mediated information plays a greater role in left hemisphere semantic knowledge than sensory-motor information in right hemisphere conceptual knowledge, and (c) to discuss the models that could explain both the differences in conceptual representations at the hemispheric level and the prevalence of the left hemisphere language-mediated semantic knowledge over the right hemisphere perceptually based conceptual representations. 1. Introduction The construct of ˇ°semantic hubˇ± has been proposed by Patterson et al. [1] and Lambon Ralph and Patterson [2] to identify a neural network, bilaterally supported by regions of the anterior temporal lobes (ATL), that should sustain the interactive activation of representations in all modalities and for all semantic categories. This construct was prompted by the observation of the selective loss of conceptual knowledge that can be observed in semantic dementia (SD) but has raised several empirical and theoretical objections. In a previous position paper [3], I have tried to evaluate if defects for items presented in every modality and across categories in SD necessarily point to an abstract-amodal format of the conceptual representations that are disrupted in this disease, or if alternative interpretations can be advanced. This problem is theoretically relevant, because the assumption of an abstract-amodal format of the conceptual representations is in keeping with cognitive models (e.g., [4¨C7]) that assume that semantic representations, accessed through structural descriptions, are stored in an abstract and propositional format. However, other models (e.g., [8¨C12]) refute the hypothesis of a unitary, abstract, and amodal semantic system and rather assume that conceptual knowledge is represented in the same format in which it has been constructed by the sensory-motor system. My conclusion, with respect to the abstract-amodal format of the conceptual representations disrupted in SD, counters a unitary system for two main reasons. The first was that the
%U http://www.hindawi.com/journals/bn/2014/603134/