Semantic association investigated with functional MRI and independent component analysis

Abstract

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, due to 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 fMRI semantic decision task. When compared to the results of a standard GLM analysis, ICA detected several additional brain regions subserving semantic decision. Eight taskrelated 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). While most of the components were represented bilaterally, we found a single, highly leftlateralized 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 lefthemispheric epilepsies.

Please Get to the Point! A Cortical Correlate of Linguistic Informativeness

“…Therefore, we may interpret this as a strategy to cope with the increased perception of difficulties in selecting the right concepts. Interestingly, this interpretation is coherent with recent reports where anterior and posterior portions of the left inferior frontal cortex have been postulated to be important for the top-down controlled retrieval of concepts and the subsequent selection of highly activated candidates, respectively (Schuhmann, Schiller, Goebel, & Sack, 2012;Kim, Karunanayaka, Privitera, Holland, & Szaflarski, 2011;Lau, Phillips, & Poeppel, 2008).…”

The effect of lexical deficits on narrative disturbances in fluent aphasia

“…Recent neuropsychological and neuroimaging evidence highlights the possibility that difficulties in the process of lexical selection might not only affect grammatical processing but even impair the patients' ability to produce a well-formed narrative discourse at the macrolinguistic level. For example, it has been shown that the top-down controlled selection and/or retrieval of contextually adequate words from the mental lexicon (likely implemented in a set of cortical and subcortical areas including but not limited to the left inferior frontal cortex; Hagoort, 2005;Kim, Karunanayaka, Privitera, Holland, & Szaflarski, 2011;Lau, Phillips, & Poeppel, 2008;Whitney, Kirk, OʼSullivan, Lambon Ralph, & Jefferies, 2011) triggers the unification of lexical information into an overall representation that spans multiword utterances. Similarly, in Marini and Urgesi (2012), repetitive Transcranial Magnetic Stimulation applied over the dorsal portion of the anterior left inferior frontal gyrus reduced the levels of lexical informativeness of narratives produced by a group of healthy individuals that, in turn, caused the production of errors of global coherence.…”

Why Mental Arithmetic Counts: Brain Activation during Single Digit Arithmetic Predicts High School Math Scores

“…Such findings could suggest a role for the left SMG in the processing of rhythmic, phonologically encoded arithmetic facts in memory (i.e., processing deeply encoded arithmetic facts as a type of rhyme). However, other studies point to a role for the SMG in the processing of semantic associations, both in the context of arithmetic (Grabner et al, 2012) and linguistic processing (Kim et al, 2011), suggesting a more complex and abstract function underlying SMG activity. Thus, SMG's involvement in arithmetic fact retrieval may represent a more "mature" calculation mechanism comprising semantic memory search processes that rely on phonological, timing, and semantic processing mechanisms.…”