Where Is the Semantic System? A Critical Review and Meta-Analysis of 120 Functional Neuroimaging Studies

Language Imaging Laboratory, Department of Neurology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Cerebral Cortex (Impact Factor: 8.67). 04/2009; 19(12):2767-96. DOI: 10.1093/cercor/bhp055
Source: PubMed


Semantic memory refers to knowledge about people, objects, actions, relations, self, and culture acquired through experience. The neural systems that store and retrieve this information have been studied for many years, but a consensus regarding their identity has not been reached. Using strict inclusion criteria, we analyzed 120 functional neuroimaging studies focusing on semantic processing. Reliable areas of activation in these studies were identified using the activation likelihood estimate (ALE) technique. These activations formed a distinct, left-lateralized network comprised of 7 regions: posterior inferior parietal lobe, middle temporal gyrus, fusiform and parahippocampal gyri, dorsomedial prefrontal cortex, inferior frontal gyrus, ventromedial prefrontal cortex, and posterior cingulate gyrus. Secondary analyses showed specific subregions of this network associated with knowledge of actions, manipulable artifacts, abstract concepts, and concrete concepts. The cortical regions involved in semantic processing can be grouped into 3 broad categories: posterior multimodal and heteromodal association cortex, heteromodal prefrontal cortex, and medial limbic regions. The expansion of these regions in the human relative to the nonhuman primate brain may explain uniquely human capacities to use language productively, plan, solve problems, and create cultural and technological artifacts, all of which depend on the fluid and efficient retrieval and manipulation of semantic knowledge.

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    • "Lexical and semantic information may be stored in semantic networks, including frontal (e.g. dorsomedial prefrontal cortex, inferior frontal gyrus, ventromedial prefrontal cortex) and M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPTBinder et al., 2009;Price, 2012). The greater activity seen in middle frontal, inferior parietal cortex and intraparietal sulcus during HI may reflect memory retrieval during perceptual reactivation. "
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    ABSTRACT: Sensory cortices can be activated without any external stimuli. Yet, it is still unclear how this perceptual reactivation occurs and which neural structures mediate this reconstruction process. In this study, we employed fMRI with mental imagery paradigms to investigate the neural networks involved in perceptual reactivation. Subjects performed two speech imagery tasks: articulation imagery (AI) and hearing imagery (HI). We found that AI induced greater activity in frontal-parietal sensorimotor systems, including sensorimotor cortex, subcentral (BA 43), middle frontal cortex (BA 46) and parietal operculum (PO), whereas HI showed stronger activation in regions that have been implicated in memory retrieval: middle frontal (BA 8), inferior parietal cortex and intraparietal sulcus. Moreover, posterior superior temporal sulcus (pSTS) and anterior superior temporal gyrus (aSTG) was activated more in AI compared with HI, suggesting that covert motor processes induced stronger perceptual reactivation in the auditory cortices. These results suggest that motor-to-perceptual transformation and memory retrieval act as two complementary mechanisms to internally reconstruct corresponding perceptual outcomes. These two mechanisms can serve as a neurocomputational foundation for predicting perceptual changes, either via a previously learned relationship between actions and their perceptual consequences or via stored perceptual experiences of stimulus and episodic or contextual regularity.
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    • "Functional connectivity analyses further showed that these prefrontal and more posterior regions were coupled together during the processing of event clusters. More specifically, the rostrolateral PFC was functionally connected to regions that have been associated with the controlled activation/selection and representation of semantic information (inferior frontal gyrus, lateral temporal cortex, inferior parietal cortex;Binder et al., 2009;Jefferies, 2013), as well as regions that might represent episodic details of specific events (hippocampus, retrosplenial cortex, precuneus, and visual cortex;Addis et al., 2004b;Daselaar et al., 2008;Martinelli et al., 2013). This functional coupling is consistent with the view that the rostrolateral PFC might support the joint consideration and integration of multiple sources of information to determine the relational dimensions that link events in clusters. "
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    ABSTRACT: When remembering the past or envisioning the future, events often come to mind in organized sequences or stories rather than in isolation from one another. The aim of the present fMRI study was to investigate the neural correlates of such event clusters. Participants were asked to consider pairs of specific past or future events: in one condition, the two events were part of the same event cluster (i.e., they were thematically and/or causally related to each other), whereas in another condition the two events only shared a surface feature (i.e., their location); a third condition was also included, in which the two events were unrelated to each other. The results showed that the processing of past and future events that were part of a same cluster was associated with higher activation in the medial prefrontal cortex (PFC), rostrolateral PFC, and left lateral temporal and parietal regions, compared to the two other conditions. Furthermore, functional connectivity analyses revealed an increased coupling between these cortical regions. These findings suggest that largely similar processes are involved in organizing events in clusters for the past and the future. The medial and rostrolateral PFC might play a pivotal role in mediating the integration of specific events with conceptual autobiographical knowledge 'stored' in more posterior regions. Through this integrative process, this set of brain regions might contribute to the attribution of an overarching meaning to representations of specific past and future events, by contextualizing them with respect to personal goals and general knowledge about one's life story.
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    • "Furthermore, the majority of studies demonstrated recruitment of the inhibitory control network (e.g., IFG and dACC) during strong interventions, suggesting that self-referential information was updated in a way that strengthened inhibitory control. Additionally, imaging results showed the involvement of regions involved in executive functioning (e.g., SFG) (Nee et al., 2013) and the semantic network, including MTG, STG, and IPL, involved in verbal and semantic processing (Binder et al., 2009;Rauschecker, 2011). Evidence for activation level changes in other regions, such as the insula and dlPFC, was limited and inconsistent. "
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    ABSTRACT: Neuroimaging provides a tool for investigating the neurobiological mechanisms of cognitive interventions in addiction. The aim of this review was to describe the brain circuits that are recruited during cognitive interventions, examining differences between various treatment modalities while highlighting core mechanisms, in drug addicted individuals. Based on a systematic Medline search we reviewed neuroimaging studies on cognitive behavioral therapy, cognitive inhibition of craving, motivational interventions, emotion regulation, mindfulness, and neurofeedback training in addiction. Across intervention modalities, common results included the normalization of aberrant activity in the brain's reward circuitry, and the recruitment and strengthening of the brain's inhibitory control network. Results suggest that different cognitive interventions act, at least partly, through recruitment of a common inhibitory control network as a core mechanism. This implies potential transfer effects between training modalities. Overall, results confirm that chronically hypoactive prefrontal regions implicated in cognitive control in addiction can be normalized through cognitive means.
    No preview · Chapter · Nov 2015
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