Spatial and temporal features of superordinate semantic processing studied with fMRI and EEG

Abstract

The relationships between the anatomical representation of semantic knowledge in the human brain and the timing of neurophysiological mechanisms involved in manipulating such information remain unclear. This is the case for superordinate semantic categorization—the extraction of general features shared by broad classes of exemplars (e.g., living vs. non-living semantic categories). We proposed that, because of the abstract nature of this information, input from diverse input modalities (visual or auditory, lexical or non-lexical) should converge and be processed in the same regions of the brain, at similar time scales during superordinate categorization—specifically in a network of heteromodal regions, and late in the course of the categorization process. In order to test this hypothesis, we utilized electroencephalography and event related potentials (EEG/ERP) with functional magnetic resonance imaging (fMRI) to characterize subjects' responses as they made superordinate categorical decisions (living vs. non-living) about objects presented as visual pictures or auditory words. Our results reveal that, consistent with our hypothesis, during the course of superordinate categorization, information provided by these diverse inputs appears to converge in both time and space: fMRI showed that heteromodal areas of the parietal and temporal cortices are active during categorization of both classes of stimuli. The ERP results suggest that superordinate categorization is reflected as a late positive component (LPC) with a parietal distribution and long latencies for both stimulus types. Within the areas and times in which modality independent responses were identified, some differences between living and non-living categories were observed, with a more widespread spatial extent and longer latency responses for categorization of non-living items.

Emotional Granularity Effects on Event-Related Brain Potentials during Affective Picture Processing

“…In general, participants showed an early positive peak near 150 ms (P1), a negative peak near 180 ms (N1), a middle positive peak near 240 ms (P2), a negative peak near 300 ms (N2), a positive peak near 350 ms (P3), a negative peak near 400 ms (N400), and a late positive peak near 510 ms (LPP). The amplitude greatly decreased to a negative amplitude after the late positive peak, resembling ERP waveforms reported in other studies (e.g., Costanzo and McArdle, 2013). The main effect of granularity was significant between 60–90 ms (β = 2.01, F = 10.03, p = 0.0016), 270–300 ms (β = -3.86, F = 20.43, p < 0.0001), and 540–570 ms (β = 3.29, F = 10.72; p = 0.0011), when we used alpha level 0.0025 (Bonferroni correction for 20 time bins).…”

Time to wave good-bye to phase scrambling: Creating controlled scrambled images using diffeomorphic transformations

“…The images were divided into 13 categories: sporting equipment, shoes, electronics, kitchen supplies, office supplies, instruments, tools, clothing, faces, mammals, birds, bikes, and fruit. The categories could also be divided into subsets thought to be important in human semantic representation, such as living versus nonliving (Costanzo et al, 2013) or mobile versus stationary (Kriegeskorte et al, 2008). We compared our ''diffeomorphed'' images to three other image scrambling methods prevalent in the perception literature.…”

Electrophysiological Correlates of Emotional Content and Volume Level in Spoken Word Processing

“…Next to the EPN-counterpart in response to auditory emotional stimuli, evidence also suggests the existence of an equivalent to the late positive complex (LPC), which has reliably been shown to reflect sustained elaborate processing of emotional stimuli in the visual modality. An auditory LPC was reported for spoken words with emotional connotation (Ofek et al, 2013 ; Hatzidaki et al, 2015 ) and emotionally uttered words and sentences (Costanzo et al, 2013 ; Paulmann et al, 2013 ). Although there is evidence for some similarities between emotion-related ERP effects in the visual and auditory modality, it is noteworthy that these effects show pronounced differences in their temporal dynamics.…”