Summing it up: Semantic activation processes in the two hemispheres as revealed by event-related potentials

Abstract

The coarse coding hypothesis suggests that semantic activation is broader in the right hemisphere, affording it an advantage over the left hemisphere for the activation of distantly related concepts or multiple meanings of lexically ambiguous words. Behavioral studies investigating coarse coding have yielded mixed results, perhaps in part because such measures sum across multiple processing stages. To more directly tap into the semantic activation processes that are the focus of the coarse coding hypothesis, the current study combined a visual half-field summation-priming paradigm with the measurement of event-related potentials (ERPs). Two primes converged onto a lateralized, unambiguous target (e.g., lion-stripes-tiger) or diverged onto different meanings of a lateralized, ambiguous target (e.g., kidney-piano-organ); in both cases, the primes were related to one another only through the target. In two experiments, participants either made lexical decisions to the targets or made a semantic-relatedness judgment between primes and target. Priming was measured as reductions in the amplitude of the N400, an ERP component that has been specifically linked to meaning activation and that showed semantic-level priming patterns in both of the tasks used in the present study. Counter to the predictions of the coarse coding hypothesis, equivalent N400 summation priming was observed for targets in the two visual fields, in both types of triplets and in both experiments. Thus, the current results fail to support the hypothesis that semantic activation patterns differ in the two hemispheres and point, instead, to other sources for observed asymmetries in verbal processing.

The language of arithmetic across the hemispheres: An event-related potential investigation

“…If the right hemisphere does this, it might explain some of its apparent difficulty in response selection, as seen in commissurotomized patients performing poorly in verification tasks for problems presented to the right hemisphere (e.g., Funnel et al, 2007). However, in the language domain, multiple direct tests of the coarse coding hypothesis have failed to find support for it (Kandhadai and Federmeier, 2007, 2008). Also problematic for this view is that one might have expected to see earlier effects of relatedness on the P300 in the right hemisphere, reflecting a lack of focus on the correct answer as a target item, which is not what we observed.…”

Individual differences in involvement of the visual object recognition system during visual word recognition

“…But more broadly, involvement of the RH in language comprehension is not only not maladaptive, it is normal and essential. Thus, as we consider hemispheric asymmetries in print specialization and how those interact with reading ability, it is important to note that RH involvement in reading is not always a sign of disorder -in fact the RH is clearly involved in many advanced reading functions in normal readers, such as integrating incoming text with sentence or discourse context (e.g., Federmeier, 2007;Federmeier & Kutas, 1999;Wlotko & Federmeier, 2007), resolving lexical and semantic ambiguities (Kandhadai & Federmeier, 2008, and interpreting non-literal language, as in jokes (Coulson & Williams, 2005). Further, in reading disorders besides dyslexia, such as alexia, RH compensation is associated with recovery (e.g., Cohen et al, 2003).…”

Differences of relevance in implicit and explicit memory tests: An ERP study

“…According to the total average ERPs in the lexical decision and the recognition test, we examined the source results of 300-900 ms and found the activation region was similar. Based on the previous literature [13][14][15] and the analysis of ERP component data, we chose relevance data at 400 ms and 600 ms in the lexical decision and the recognition test to make location analysis, shown in Figure 5. Table 3 displayed the Talairach coordinates of each source generator based on the low-resolution current density reconstruction.…”

“…ERP results in a large number of semantic researches revealed that the N400 effect was found [13][14][15] in the semantic processing of various words. For example, in a variety of experimental tasks on concrete and abstract words [13,15] , the experimenters found that N400 of concrete words was more negative than that of abstract words during 300-500 ms.…”