An ERP study of hemispheric differences in perceptual representations of language reveals meaning attribution in the right hemisphere and constituents of the N400-effect.

Recent findings have revealed that the right hemisphere (RH) is uniquely involved in integrating perceptual information from linguistic input to simulate a mental model of that input. We extend on these findings by testing whether meaning is generated from such models. Participants (N = 37) heard auditory passages describing the visuospatial arrangement of elements into a perceptual representation of a familiar object, then judged whether a laterally-presented target word matched the object. We found a central N400-effect for left visual-field targets, suggesting that meaning was also accessible to the RH. There was no statistical difference for right visual-field targets. Principle component analysis of the data revealed that the N400-effect was driven by positive components. Consequently, the results suggest that i) RH contributions to language comprehension include integrative and perceptual processes that enable overall meaning to be generated from representations of discourse, and ii) positive ERP components may produce N400-effects.

A randomized controlled trial examining the impact of individual trauma-focused therapy for individuals receiving group treatment for depression.

OBJECTIVES: Adverse life events are associated with increased likelihood of depression and poorer prognosis. Trauma-focused treatments (TFT) appear to be effective in decreasing comorbid depressive symptoms. Accordingly, the aim of this study was to evaluate the effectiveness of a TFT on the memories of aversive events for individuals with a primary diagnosis of depression. METHODS: A randomized controlled trial was conducted with 49 participants recruited from a 10-day outpatient group programme. All participants showed symptoms of depression with a subgroup (80%) meeting the DSM-5 criteria for a major depressive episode. Participants received treatment as usual (TAU); three additional individual trauma-focused sessions; or three additional individual assertiveness training sessions. Participants were assessed with regards to depression diagnosis and related symptoms. RESULTS: For participants with a major depressive episode, the addition of trauma-focused sessions significantly increased the likelihood of remission when compared to TAU, or additional assertiveness training. While no significant treatment difference was noted in depressive symptom change post-treatment, six weeks after treatment those who received an adjunct treatment were more likely to maintain treatment gains than those who received TAU. Furthermore, at 12-week follow-up, participants who received a TFT reported significantly fewer depressive symptoms than those who received assertiveness training. CONCLUSIONS: While differences in outcomes were minimal immediately post-treatment, differences among treatment groups increased over time. Thus, as few as three additional TFT sessions may impact positively on symptom change for people completing a group programme for the treatment of depression. PRACTITIONER POINTS: Depression is the greatest cause of disability worldwide. Adverse experiences are linked with an increased likelihood of depression, more severe symptoms and poor treatment outcomes following evidence-based interventions. As few as three trauma-focused sessions can improve treatment outcomes in terms of depression diagnosis and related symptoms for individuals receiving group cognitive behavioural therapy.

Perceptual elaboration paradigm (PEP): A new approach for investigating mental representations of language.

To examine hemispheric differences in accessing a mental representation that embodies perceptual elements and their spatial relationships (i.e., perceptual elaboration and integration), we developed a cross-modal perceptual elaboration paradigm (PEP) in which an imagined percept, rather than a propositional concept, determined congruency. Three target image conditions allow researchers to test which mental representation is primarily accessed when the target is laterally presented. For example, the "Integrated" condition is congruent with either propositional or perceptual mental representations; therefore, results from both hemifield conditions (RVF/LH vs. LVF/RH) should be comparable. Similarly, the "Unrelated" condition is incongruent with either propositional or perceptual mental representations; therefore, results from both hemifield conditions should be comparable as well. However, the "Unintegrated" condition is congruent with the propositional mental representation but not the perceptual mental representation. Should either hemisphere access one representation initially, differences will be revealed in either behavioural or electroencephalography results. This paradigm:•is distinct from existing paired paradigms that emphasize semantic associations.•is important given increasing evidence that discourse comprehension involves accessing perceptual information.•allows researchers to examine the extent to which a mental representation of discourse can embody perceptual elaboration and integration.

Hemispheric differences in perceptual integration during language comprehension: An ERP study.

The left hemisphere (LH) is responsible for many fundamental aspects of language; however, converging evidence suggests the right hemisphere (RH) is critically involved in higher-level language comprehension. We examined the extent of each hemispheres' access to a meaningful mental representation of language by recording electroencephalography while participants (N = 44) completed a computer-based task where auditory sentences described individual elements of an image. If integrated successfully, this allowed the construction of a meaningful mental representation. If unsuccessful, the individual elements were in themselves meaningless. Participants saw a lateralised image that was either an integrated representation of the object described in the previous auditory passage ("integrated"), an unintegrated representation of each of the individual elements ("unintegrated"), or an integrated representation of an object that did not match the previous passage ("unrelated"). Evidenced by the trend in N300 amplitudes, we found that both hemispheres accessed a mental representation that embodied the elements described in the preceding passage. However, only the RH distinguished integrated versus unintegrated targets, suggesting that the RH accessed a mental representation that embodied the correct spatial relationships between elements (i.e., perceptual integration) as well as the individual imagined elements (i.e., perceptual elaboration). These results provide evidence of a clear RH contribution to the integration of perceptual information during language comprehension.

Hemispheric differences in the processing of contextual information during language comprehension.

This study investigated the proposition that the right hemisphere (RH) processes language in a global, integrative manner that maintains access to earlier contextual information, whereas the left hemisphere (LH) processes in a local fashion and only keeps active the most recent concept. Thirty-four right-handed participants completed a lexical decision task using a split visual-field paradigm, with reaction time and error rates recorded. Three sentences were presented, where an inference was required in order to produce coherence between the first and second sentences. The third sentence was not directly related to the inference generation, but was consistent with the scenario set out in the prior context. Targets were either "Global", where the target reflected the meaning of the inference generated in order for coherence to have been created; or "Local", where the target reflected the meaning of only the third sentence and therefore did not require integration of previous context. Significantly greater facilitation was observed for the RH/left visual field than LH/right visual field for "Global" targets, while no hemispheric differences were observed for "Local" targets. This study provides evidence for the distillation of current models of hemispheric language comprehension into underlying local and global processes.

Integration and coarse coding: right hemisphere processing of message-level contextual information.

A number of different models have been proposed in order to explain the underlying processing mechanisms of each hemisphere for contextual information in sentences. While the coarse-coding hypothesis (Beeman, 1998) remains prominent in the literature, it is inconsistent in its current form with strong evidence suggesting that the RH has a capacity for comprehension that extends beyond word-level processing. Experiment 1 set out to investigate the proposed special role of the RH for integrating broad concepts by centrally presenting one, two, or three sentences followed by an associated word or nonword target to either the left or right visual field. Each sentence, in itself, provided only minimal cues to the nature of the target, but in combination with others created a much more powerful context. A total of 32 right-handed undergraduate psychology students participated in a computer-based lexical decision task where reaction time and error rates were recorded. In contrast to expectations based on the coarse-coding hypothesis, targets presented to the RVF/LH were as strongly facilitated as targets presented to the LVF/RH at all levels of contextual support. Due to some ambiguity in the results as to the level of processing of each hemisphere, an additional experiment was conducted which aimed to resolve this difficulty through a modification to the scrambled sentence condition. Experiment 2 provided a clear demonstration that the equality of facilitation observed in both experiments occurred as a result of message-level processing. This finding indicates that the coarse/fine-coding distinction between left and right hemisphere processing cannot be applied to message-level processing.

The sensitivity of the right hemisphere to contextual information in sentences.

One explanation for the inconsistencies in research examining the sentence comprehension abilities of the right hemisphere (RH) is the presence of confounding variables that have generally served to disadvantage the processing capacities of the RH. As such, the present study aimed to investigate hemispheric differences in the use of message-level sentential information by removing some of the factors known to be inherently disadvantageous for RH comprehension. Thirty-two right-handed undergraduate university students participated in a computer-based lexical decision task where RT and error rates were recorded. The sensitivity of each hemisphere to the message-level contextual information contained in short versus long sentences was compared, as well as the effect of stimulus modality (visual compared to auditory). The results showed that the RH benefited from increased levels of context to at least the same extent as the LH and that, more importantly, this could not be explained by word-level processes alone. This finding, unusual in behavioral research on normal individuals but consistent with neuropsychological, electrophysiological, and neuroimaging approaches, suggests that the RH plays an important role in sentence comprehension, at least in relation to sentences that conform to a relatively simple structure.

Message-level processing of contextual information in the right cerebral hemisphere.

Recent research into right hemisphere (RH) sentence comprehension has produced a number of inconsistent results, particularly in relation to the types of processing used. The present study investigated whether the RH utilizes message-level mechanisms during sentence comprehension and whether it benefits from additional contextual information that is not the result of simple word-level associations. Thirty-six right-handed Murdoch University undergraduate psychology students participated in a computer-based lexical decision task where reaction time and error rates were recorded. Normal and scrambled versions of sentences with high, low, and neutral levels of constraint were presented centrally, with the sentence-final word presented to either the left or right visual field. The results demonstrated that the RH was facilitated by increases in context to at least the same extent as the left hemisphere (LH) and, furthermore, that this was not simply due to increased word-level associations. These findings are in contrast to previous behavioral research that suggests the RH is less sensitive to message-level processing than the LH.