Abstract
Emotion words constitute a special class of verbal stimuli which can quickly activate the limbic system outside the left-hemisphere language network. Such fast response to emotion words may arise independently of the left occipitotemporal area involved in visual word-form analysis and rely on a distinct amygdala-dependent emotion circuit involved in fearful face processing. Using a hemifield priming paradigm with fMRI, we explored how the left and right amygdala systems interact with the reading network during emotion word processing. On each trial, participants viewed a centrally presented target which was preceded by a masked prime flashed either to the left or right visual field. Primes and targets, each denoting negative or positive nouns, could be either affectively congruent or incongruent with each other. We observed that affective congruency produced parallel changes in neural priming between the left frontal and parietotemporal regions and the bilateral amygdala. However, we also found that the left, but not right, amygdala exhibited significant change in functional connectivity with the neural components of reading as a function of affective congruency. Collectively, these results suggest that emotion words activate the bilateral amygdala during early stages of emotion word processing, whereas only the left amygdala exerts a long-distance regulatory influence over the reading network via its strong within-hemisphere connectivity.
Highlights
Fluent reading begins with fast visual analysis of written words which in turn activates multiple neurocognitive systems involved in language processing
Since the whole-brain SPM identified the left inferior frontal gyrus (IFG), left anterior cingulate gyrus (ACG), left posterior parietal cortex (PPC), and left occipitotemporal cortex (OTC) as neural correlates of the valence x priming interaction, we examined functional connection strength with the amygdala in this left-hemisphere network involved in emotion word processing (p < 0.05 corrected for multiple comparisons)
The same valence-by-priming interaction was found in the left OTC (−40, −50, −18, Z = 4.56), bilateral ACG (−4, 20, 52, Z = 5.17), and left PPC (−38, −58, 66, Z = 4.30)
Summary
Fluent reading begins with fast visual analysis of written words which in turn activates multiple neurocognitive systems involved in language processing. In parallel with the cognitive models of reading, the occipitotemporal region is known to have structural and functional coupling with other left-hemisphere regions, including the lateral temporal area associated with meaning (Dehaene and Naccache, 2006), inferior parietal area involved in phonological conversion (Price, 2012), and frontotemporal. Amygdala Interactions During Reading junction area involved in pronunciation (Klein et al, 2015; Stevens et al, 2017). These neural structures form a mature reading network across variously different writing systems (Bolger et al, 2005; Nakamura et al, 2012a). The sensorimotor cortex outside the classical reading network is shown to play a role in semantic processing of nouns and verbs associated with body parts and their actions (Willems et al, 2010; Grisoni et al, 2016; Mollo et al, 2016)
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