Impairments in Probabilistic Prediction and Bayesian Learning Can Explain Reduced Neural Semantic Priming in Schizophrenia

Abstract

It has been proposed that abnormalities in probabilistic prediction and dynamic belief updating explain the multiple features of schizophrenia. Here, we used electroencephalography (EEG) to ask whether these abnormalities can account for the well-established reduction in semantic priming observed in schizophrenia under nonautomatic conditions. We isolated predictive contributions to the neural semantic priming effect by manipulating the prime’s predictive validity and minimizing retroactive semantic matching mechanisms. We additionally examined the link between prediction and learning using a Bayesian model that probed dynamic belief updating as participants adapted to the increase in predictive validity. We found that patients were less likely than healthy controls to use the prime to predictively facilitate semantic processing on the target, resulting in a reduced N400 effect. Moreover, the trial-by-trial output of our Bayesian computational model explained between-group differences in trial-by-trial N400 amplitudes as participants transitioned from conditions of lower to higher predictive validity. These findings suggest that, compared with healthy controls, people with schizophrenia are less able to mobilize predictive mechanisms to facilitate processing at the earliest stages of accessing the meanings of incoming words. This deficit may be linked to a failure to adapt to changes in the broader environment. This reciprocal relationship between impairments in probabilistic prediction and Bayesian learning/adaptation may drive a vicious cycle that maintains cognitive disturbances in schizophrenia.

Transdiagnostic inflexible learning dynamics explain deficits in depression and schizophrenia

“…In patients diagnosed with schizophrenia, recent data showed that they are less able to mobilize predictive mechanisms to facilitate processing at the earliest stages of accessing the meanings of incoming words. 63 …”

Language Dysfunction in Schizophrenia: Assessing Neural Tracking to Characterize the Underlying Disorder(s)?

“…Word-level semantic processing in schizophrenia is most commonly investigated via priming paradigms. Yet, the literature is inconsistent in terms of whether the priming-N400 effects are enhanced or reduced in patients (Mathalon et al, 2002(Mathalon et al, , 2010Salisbury, 2008;Sharpe et al, 2020). This discrepancy may result from impairments at different levels of the linguistic hierarchy.…”

“…This discrepancy may result from impairments at different levels of the linguistic hierarchy. Patients may be impaired in lexical access (Kuperberg et al, 2019), may suffer from reduced or enhanced semantic activation (Titone et al, 2000;Mathalon et al, 2010), or may fail to derive predictions from the word context (Sharpe et al, 2020). Of note, the prediction failure account accords with results from sentence-level N400 studies: Whereas the N400 reflecting semantic retrieval and integration seems to be unaffected in schizophrenia (Kuperberg et al, 2006), converging evidence has shown that patients are unable to utilize contextual information to suppress irrelevant meanings of a target word, for example, when comprehending a homophone (Sitnikova et al, 2002).…”

Flexibility Retained: Unimpaired Updating of Expectations in Schizophrenia

“…This suggests that PSZ have difficulty updating their beliefs even in the face of disconfirmatory evidence compared to healthy control subjects (HCS) [15]. In addition to the perceptual level [15,16], similar deficits have also been observed at the level of higher-order processes that involve evidence gathering [17][18][19], probability learning [20][21][22], and language processing [23,24]. It is also worth noting that this deficit in prediction updating was found to be associated with the severity of delusional symptoms in PSZ, indicating the potential interplay between belief updating and delusion development in schizophrenia [15].…”