On the Role of Bilateral Brain Hypofunction and Abnormal Lateralization of Cortical Information Flow as Neural Underpinnings of Conventional Metaphor Processing Impairment in Schizophrenia: An fMRI and EEG Study

Abstract

Figurative language processing (e.g. metaphors) is commonly impaired in schizophrenia. In the present study, we investigated the neural activity and propagation of information within neural circuits related to the figurative speech, as a neural substrate of impaired conventional metaphor processing in schizophrenia. The study included 30 schizophrenia outpatients and 30 healthy controls, all of whom were assessed with a functional Magnetic Resonance Imaging (fMRI) and electroencephalography (EEG) punchline-based metaphor comprehension task including literal (neutral), figurative (metaphorical) and nonsense (absurd) endings. The blood oxygenation level-dependent signal was recorded with 3T MRI scanner and direction and strength of cortical information flow in the time course of task processing was estimated with a 64-channel EEG input for directed transfer function. The presented results revealed that the behavioral manifestation of impaired figurative language in schizophrenia is related to the hypofunction in the bilateral fronto-temporo-parietal brain regions (fMRI) and various differences in effective connectivity in the fronto-temporo-parietal circuit (EEG). Schizophrenia outpatients showed an abnormal pattern of connectivity during metaphor processing which was related to bilateral (but more pronounced at the left hemisphere) hypoactivation of the brain. Moreover, we found reversed lateralization patterns, i.e. a rightward-shifted pattern during metaphor processing in schizophrenia compared to the control group. In conclusion, the presented findings revealed that the impairment of the conventional metaphor processing in schizophrenia is related to the bilateral brain hypofunction, which supports the evidence on reversed lateralization of the language neural network and the existence of compensatory recruitment of alternative neural circuits in schizophrenia.

On the specificity of figurative language comprehension impairment in schizophrenia and its relation to cognitive skills but not psychopathological symptoms - Study on metaphor, humor and irony

“…Secondly, the specificity of subdomain-related levels of impairment has been proved chiefly in the case of conventional and novel metaphors, and such an effect has been found both in CON and SCH groups, i.e., conventional metaphors are more easily recognised than novel metaphors. In line with the presented results, recent research on metaphor comprehension differentiated between conventional and non-conventional metaphors, although both were impaired in schizophrenia ( Adamczyk et al, 2021 ; Mossaheb et al, 2014 ; Rapp et al, 2018 ). Conventional metaphors include culture-based expressions in which fixed meanings are integrated into everyday language and thus are easier to comprehend than de novo-created meanings of novel metaphors.…”

“…The experimental stimuli for the figurative language comprehension task (FLC) were based on the previous experimental materials to assess comprehension of humor ( Adamczyk et al, 2019 ), metaphor ( Adamczyk et al, 2021 ; Mashal et al, 2014 ; Rapp et al, 2018 ), irony ( Del Goleto et al, 2016 ; Rapp et al, 2010 , Rapp et al, 2014 ; Varga et al, 2013 ) and sarcasm ( Filik et al, 2019 ). The experimental stimuli were written 7-line stories containing a description of the social/situational context and the dialogue between two protagonists (i.e.…”

“…Recent research showed that ToM deficits in schizophrenia may affect language comprehension at the semantic-pragmatic processing level, regardless of the IQ level ( Gavilán and García-Albea, 2011 ). Patients with schizophrenia often show a tendency to be overly concrete and to prefer literal meaning, as indicated by studies on the understanding of pragmatic aspects of language, i.e., proverbs, metaphors, humor, and irony ( Adamczyk et al, 2016 , Adamczyk et al, 2017 , Adamczyk et al, 2021 ; Rossetti et al, 2018 ; Kircher et al, 2007 ; Langdon et al, 2002 ; Rapp et al, 2013 ; Varga et al, 2013 ). In general, the reported tendency to use literal language and difficulties in understanding figurative meanings in schizophrenia seem to be mainly related to impaired cognition, i.e., deficiencies in set-shifting and abnormal semantic associations in a given linguistic context ( Kuperberg and Caplan, 2003 ; Polimeni et al, 2010 ).…”

Disturbances in theta-beta band oscillations in precuneus and aberrant effective connectivity within default mode network as potential biomarkers of chronic schizophrenia: an EEG resting-state study

“…Particularly, we showed that left frontal sources of DMN (mPFC/IFG) in schizophrenia present widespread connectivity to PREC/PCC and bilateral parietal cortices (ANG), while in the CON group, mPFC/IFG serves as major receivers of left PREC/PCC stimulation, but in higher oscillations, i.e., beta band. Such reversed effective connectivity pattern observed during the RS, i.e., opposite directional information ow, has been previously observed in task-related studies in schizophrenia (Adamczyk et al, 2019(Adamczyk et al, , 2021. This phenomenon may be considered a nominal effective connectivity-related schizophrenia biomarker.…”

Dysconnectivity of the cerebellum and somatomotor network correlates with the severity of alogia in chronic schizophrenia

“…The study involved two groups: 30 chronic schizophrenia patients (SCH) and 30 controls (CON) matched with respect to age and sex (Table I; the sample is described in detail elsewhere, Adamczyk et al, 2021). All participants signed the informed consent for the participation in the study.…”