Why Are the Right and Left Hemisphere Conceptual Representations Different?

Abstract

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.

Impaired assessment of cumulative lifetime familiarity for object concepts after left anterior temporal-lobe resection that includes perirhinal cortex but spares the hippocampus

“…That these abnormalities were present even when object names were accompanied by picture cues is consistent with functional neuroimaging evidence showing that left PrC supports conceptual processing across multiple input modalities ( Bruffaerts et al, 2014;Clarke & Tyler, 2014). The pattern of results we observed is also in keeping with evidence from other lesion studies showing that unilateral left temporal lobe epilepsy, or left anterior temporal lobe resection for treatment of epilepsy, can lead to multi -modal impairments in conceptual processing (Lambon Ralph et al, 2012;Giovagnoli, Erbetta, Villani, & Avanzini, 2005;Antonucci, Beeson, Labiner, & Rapcsak, 2008; but see Gainotti, 2014).…”

“…Given that our task was designed to probe the familiarity of concepts that words refer to, rather than the familiarity of the words themselves, we also tested NB under conditions in which visual images of exemplars were provided in addition to concept names as cues (Experiment 3). This modification was introduced in order to explore whether any abnormalities would be limited to the input modality of verbal cues, or whether they might be multimodal and affect processing of object concepts based on picture cues as well (see Gainotti, 2014;Rice, Hoffman, & Lambon Ralph, 2015, for discussion). Finally, in Experiment 4, we sought evidence to establish some specificity with respect to the nature of MTL damage that cause behavioral abnormalities in judging cumulative lifetime familiarity.…”

Beyond the word and image: characteristics of a common meaning system for language and vision revealed by functional and structural imaging

“…In previous studies (Nielsen et al, 2013;Paivio, 1986;Stephan et al, 2003), it has been shown that while attention to external stimuli require more right parieto-frontal activation, attending to internal stimuli, narrative or self-reflection tend to recruit a left lateralized network including hubs in parieto-temporal and temporal cortex as well as the lateral and inferior prefrontal cortex. Thus, based on the overall literature observations (Gainotti, 2014;Nielsen et al, 2013;Paivio, 1986;Stephan et al, 2003) left dominant connections associated to language and perception of internal stimuli are in accordance with our findings and interpretation of a prime involvement of our common network in conceptualization rather than in sensory-motor processing. Thus based on the topography of the activated neural structures it seems unlikely that the shared neural system might be the result of either a purely linguistic computation or an attentional driven activity.…”

Reading words and other people: A comparison of exception word, familiar face and affect processing in the left and right temporal variants of primary progressive aphasia

“…However, such studies also demonstrate a differential sensitivity of the left rostral temporal lobe to language-mediated information (Marinkovic et al, 2003; Mion et al, 2010; Rice, Lambon Ralph, & Hoffman, 2015; Sharp, Scott, & Wise, 2004; Vandenberghe, Price, Wise, Josephs, & Frackowiak, 1996). This has been described as a significant challenge (see Gainotti, 2014) to assertions that the left and right rostral temporal lobes constitute a unitary, undifferentiated transmodal semantic system (Patterson, Nestor, & Rogers, 2007). However, they have more recently been characterized as a ‘graded transmodal representational hub’ in which the semantic function of rostral temporal sub-regions varies as a function of proximity and connectivity to different primary inputs (Binney, Parker, & Lambon Ralph, 2012; Lambon Ralph, 2014; Rice, Hoffman, & Lambon Ralph, 2015).…”