Semantic: association investigated with functional MRI and independent component analysis

Department of Neurology, University of Cincinnati, Cincinnati, OH 45267-0525, USA.
Epilepsy & Behavior (Impact Factor: 2.26). 02/2011; 20(4):613-22. DOI: 10.1016/j.yebeh.2010.11.010
Source: PubMed


Semantic association, an essential element of human language, enables discourse and inference. Neuroimaging studies have revealed localization and lateralization of semantic circuitry, making substantial contributions to cognitive neuroscience. However, because of methodological limitations, these investigations have only identified individual functional components rather than capturing the behavior of the entire network. To overcome these limitations, we have implemented group independent component analysis (ICA) to investigate the cognitive modules used by healthy adults performing the fMRI semantic decision task. When compared with the results of a standard general linear modeling (GLM) analysis, ICA detected several additional brain regions subserving semantic decision. Eight task-related group ICA maps were identified, including left inferior frontal gyrus (BA44/45), middle posterior temporal gyrus (BA39/22), angular gyrus/inferior parietal lobule (BA39/40), posterior cingulate (BA30), bilateral lingual gyrus (BA18/23), inferior frontal gyrus (L>R, BA47), hippocampus with parahippocampal gyrus (L>R, BA35/36), and anterior cingulate (BA32/24). Although most of the components were represented bilaterally, we found a single, highly left-lateralized component that included the inferior frontal gyrus and the medial and superior temporal gyri, the angular and supramarginal gyri, and the inferior parietal cortex. The presence of these spatially independent ICA components implies functional connectivity and can be equated with their modularity. These results are analyzed and presented in the framework of a biologically plausible theoretical model in preparation for similar analyses in patients with right- or left-hemispheric epilepsies.

Download full-text


Available from: Kwangki Kim
  • Source
    • "The first step in assessing the effects of disease states on cognitive networks is to build a robust model of the said network in healthy subjects so that these models can then be applied to testing and understanding of the cognitive deficits produced by the disease state. Recently, we have applied ICA to language fMRI data in order to build models for semantic decision, verb generation, and story processing [29]–[32], and we are currently testing the effects of stroke on such models. The aim of this study was to perform a comprehensive examination of the network for visual memory encoding using ICA and GCA of fMRI data to determine the directionality of the information flow and build a viable model of visual memory encoding that can serve as the basis for testing the effects of epilepsy (e.g., temporal vs. extra-temporal) on such a network. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Memory encoding engages multiple concurrent and sequential processes. While the individual processes involved in successful encoding have been examined in many studies, a sequence of events and the importance of modules associated with memory encoding has not been established. For this reason, we sought to perform a comprehensive examination of the network for memory encoding using data driven methods and to determine the directionality of the information flow in order to build a viable model of visual memory encoding. Forty healthy controls ages 19-59 performed a visual scene encoding task. FMRI data were preprocessed using SPM8 and then processed using independent component analysis (ICA) with the reliability of the identified components confirmed using ICASSO as implemented in GIFT. The directionality of the information flow was examined using Granger causality analyses (GCA). All participants performed the fMRI task well above the chance level (>90% correct on both active and control conditions) and the post-fMRI testing recall revealed correct memory encoding at 86.33±5.83%. ICA identified involvement of components of five different networks in the process of memory encoding, and the GCA allowed for the directionality of the information flow to be assessed, from visual cortex via ventral stream to the attention network and then to the default mode network (DMN). Two additional networks involved in this process were the cerebellar and the auditory-insular network. This study provides evidence that successful visual memory encoding is dependent on multiple modules that are part of other networks that are only indirectly related to the main process. This model may help to identify the node(s) of the network that are affected by a specific disease processes and explain the presence of memory encoding difficulties in patients in whom focal or global network dysfunction exists.
    Full-text · Article · Oct 2014 · PLoS ONE
  • Source
    • "Furthermore, no significant activation was found during “No Advice” trials at the within groups level, indicating that the absence of advice may not have produced a similar increase in cognitive effort to that was found in the “Expert” group. Rather when the experimenter’s advice was presented, regions involved in semantic processing [40] and adjustments made to optimize performance [43] were activated, suggesting more cognitive effort despite the presentation of advice. What is particularly interesting in the present study is that even though the “Expert” was not present, or ever seen, the importance given to advice from this source had a meaningful impact on brain activation and behavior. "
    [Show abstract] [Hide abstract]
    ABSTRACT: It is well recognized that individuals follow "Expert" advice, even when flawed and offers no advantage, and sometimes leads to disadvantages. The neurobiology underlying this is uncertain, and in particular there is an incomplete understanding of which brain regions are most involved when individuals chose to disobey an expert. To study this we examined functional magnetic resonance imaging (fMRI) differences during an investment game where subjects received differentially credible investment advice. Participants (n = 42; 32 males) played an investment game, in which they could Buy or Not Buy a sequence of stocks. The better they did, the more money they made. Participants received either "Expert" advice or "Peer" advice. Those receiving Expert advice were told the advice came from a certified financial "Expert". Those receiving Peer Advice were told the advice was that of the student administering the scans, who deliberately dressed and acted casually. Both streams of advice were predetermined and identical. The advice was scripted to be helpful initially, but progressively worse as the task continued, becoming 100% wrong by the end of the task. Subjects receiving Expert Advice followed the advice significantly longer on average, even though this was progressively worse advice. Thus, following Expert advice had poorer consequences for individuals, but this did not dissuade them from continuing to follow the advice. In contrast, when subjects disobeyed Expert advice they exhibited significant anterior cingulate cortex (ACC) and superior frontal gyrus activation relative to those disobeying Peer advice. These findings may suggest that in subjects who defy authority, or believe they are doing so (in this case by disobeying an "Expert") there is increased activation of these two brain regions. This may have relevance to several areas of behavior, and the potential role of these two brain regions in regard to disobedience behavior requires further study.
    Full-text · Article · Jan 2014 · PLoS ONE
  • Source
    • "To date, although the neural correlates of microlinguistic processing have been extensively studied (Vigneau et al., 2006), the investigation of the ability to organize the macrolinguistic aspects of message production have been much less explored. Recent neuropsychological , neuroimaging and fMRI studies have suggested that Broca's area and the adjacent portion of the left inferior frontal cortex may play a major role for the top-down controlled selection and/or retrieval of contextually adequate words from the mental lexicon (Loban, 1966; Wagner et al., 2001; Hagoort, 2005; Koechlin and Jubault, 2006; Lau et al., 2008; Kim et al., 2011; Whitney et al., 2011; Marini and Urgesi, 2012; Schuhmann et al., 2012). Once retrieved, this lexical information is unified into an overall representations that spans multi-word utterances "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we investigated the combined effect of transcranial direct current stimulation (tDCS) and an intensive Conversational therapy treatment on discourse skills in 12 persons with chronic aphasia. Six short video clips depicting everyday life contexts were prepared. Three videoclips were used to elicit spontaneous conversation during treatment. The remaining three were presented only before and after the therapy. Participants were prompted to talk about the contents of each videoclip while stimulated with tDCS (20 min 1 mA) over the left hemisphere in three conditions: anodic tDCS over the Broca's area, anodic tDCS over the Wernicke's area, and a sham condition. Each experimental condition was performed for 10 consecutive daily sessions with 14 days of intersession interval. After stimulation over Broca's area, the participants produced more Content Units, verbs and sentences than in the remaining two conditions. Importantly, this improvement was still detectable 1 month after the end of treatment and its effects were generalized also to the three videoclips that had been administered at the beginning and at the end of the therapy sessions. In conclusion, anodic tDCS applied over the left Broca's area together with an intensive "Conversational Therapy" treatment improves informative speech in persons with chronic aphasia. We believe that positive tDCS effects may be further extended to other language domains, such as the recovery of speech production.
    Full-text · Article · Sep 2013 · Frontiers in Human Neuroscience
Show more