Language abnormalities in schizophrenia: binding core symptoms through contemporary empirical evidence

Abstract

Both the ability to speak and to infer complex linguistic messages from sounds have been claimed as uniquely human phenomena. In schizophrenia, formal thought disorder (FTD) and auditory verbal hallucinations (AVHs) are manifestations respectively relating to concrete disruptions of those abilities. From an evolutionary perspective, Crow (1997) proposed that “schizophrenia is the price that Homo sapiens pays for the faculty of language”. Epidemiological and experimental evidence points to an overlap between FTD and AVHs, yet a thorough investigation examining their shared neural mechanism in schizophrenia is lacking. In this review, we synthesize observations from three key domains. First, neuroanatomical evidence indicates substantial shared abnormalities in language-processing regions between FTD and AVHs, even in the early phases of schizophrenia. Second, neurochemical studies point to a glutamate-related dysfunction in these language-processing brain regions, contributing to verbal production deficits. Third, genetic findings further show how genes that overlap between schizophrenia and language disorders influence neurodevelopment and neurotransmission. We argue that these observations converge into the possibility that a glutamatergic dysfunction in language-processing brain regions might be a shared neural basis of both FTD and AVHs. Investigations of language pathology in schizophrenia could facilitate the development of diagnostic tools and treatments, so we call for multilevel confirmatory analyses focused on modulations of the language network as a therapeutic goal in schizophrenia.

Neuroimaging epicenters as potential sites of onset of the neuroanatomical pathology in schizophrenia

“…First, we found that the epicenter distribution of schizophrenia is spatially correlated with a low-dimensional representation of cognitive processes, to which the greatest positive contributions are enriched at language processes. This is in line with our observation that the language region as the possible origin of neurophysiological pathology, supporting language hypothesis in schizophrenia ( 57 , 58 ). Second, we found a robust spatial concordance between the epicenter distribution of schizophrenia and gene expression profiles of cerebral cortex.…”

Grammatical impairment in schizophrenia: An exploratory study of the pronominal and sentential domains

“…The general idea is that Grammar in the face of SZ has a specific linguistic profile, which differs from neurotypicals' profile. Moreover, the link between SZ and language dysfunctions is supported by current findings indicating associations between FTD and structural and functional anomalies in language areas of the brain [16,17], as well as an overlap between FTD and AVH, even in early stages of SZ, with substantial shared anomalies in language areas of the brain, and gene overlap between language dysfunctions and SZ [18,19].…”

Automated analysis of speech as a marker of sub-clinical psychotic experiences

“…These symptoms can manifest in vocal features like a slower rate of speech with shorter utterances, more pauses, reduced variation in frequency or in language use, like in decreased density of ideas ( 15 ). In addition to these speech alterations, individuals with psychosis may exhibit other speech-related phenomena such as perseveration (continual involuntary repetition of a thought), neologisms (the coining or use of new words), clang associations (groupings of words that are based on similar-sounding sounds, even though the words themselves do not have any logical reason to be grouped together), and echolalia (the unsolicited repetition of utterances made by others) ( 12 , 16 ) ( Table 2 ).…”