Abstract
Deficits in cognitive functions are frequent in schizophrenia and are often conceptualized as stable characteristics of this disorder. However, cognitive capacities may fluctuate over the course of a day and it is unknown if such variation may be linked to the dynamic expression of psychotic symptoms. This investigation used Ecological Momentary Assessment (EMA) to provide mobile tests of cognitive functions and positive symptoms in real time. Thirty-three individuals with schizophrenia completed five EMA assessments per day for a one-week period that included real-time assessments of cognitive performance and psychotic symptoms. A subsample of patients and 31 healthy controls also completed a functional MRI examination. Relative to each individual’s average score, moments of worsened cognitive performance on the mobile tests were associated with an increased probability of positive symptom occurrence over subsequent hours of the day (coef = 0.06, p < 0.05), adjusting for the presence of psychotic symptoms at the moment of mobile test administration. These prospective associations varied as a function of graph theory indices in MRI analyses. These findings demonstrate that cognitive performance is prospectively linked to psychotic symptom expression in daily life, and that underlying brain markers may be observed in the Executive Control Network. While the potential causal nature of this association remains to be investigated, our results offer promising prospects for a better understanding of the underlying mechanisms of symptom expression in schizophrenia.
Highlights
Despite an extensive literature documenting cognitive deficits in schizophrenia, investigations to date have reported no or only a weak associations between cognitive performance1 3 Vol.:(0123456789)European Archives of Psychiatry and Clinical Neuroscience momentary fluctuations in cognitive performance are linked to the experience of positive symptoms in daily life.Despite the development of multimodal neuroimaging techniques, the relationship between brain-based biomarkers of schizophrenia and symptom expression is still poorly understood
Resting-state Functional magnetic resonance imaging (fMRI) measures the spontaneous brain activity based on low-frequency fluctuations in Blood Oxygen Level-Dependent (BOLD) signals during resting conditions [21], and resting-state Functional Connectivity refers to the co-variation of BOLD signals between brain regions that is considered to reflect brain’s intrinsic and stable functional organization [22]
The fronto-parietal network is known to be involved in cognitive performance, and in executive functioning [23, 24], that may play an important role in the pathophysiology of this disorder
Summary
Despite an extensive literature documenting cognitive deficits in schizophrenia, investigations to date have reported no or only a weak associations between cognitive performance1 3 Vol.:(0123456789)European Archives of Psychiatry and Clinical Neuroscience momentary fluctuations in cognitive performance are linked to the experience of positive symptoms in daily life.Despite the development of multimodal neuroimaging techniques, the relationship between brain-based biomarkers of schizophrenia and symptom expression is still poorly understood. Mathematical Theory of graphs has emerged as a powerful framework to investigate intrinsic brain networks overall organization or topology based on rs-fMRI data [25, 26] This framework defines the brain as a graph consisting of nodes (brain regions) linked by edges (functional interconnections). Through the calculation of mathematical indices called “metrics”, graph theory makes it possible to evaluate properties of brain networks that reflect their capacity to transmit information Some of these metrics are related to the concept of functional segregation (i.e. the existence of functionally specialized regions) and others to the concept of functional integration (i.e. the fact that these specialized regions are organized in interacting functional networks). The combination of graph theory analyses with EMA data concerning the dynamic within-person association of cognitive fluctuations and symptom expression would provide valuable insight into the complex brain-daily life experience in schizophrenia
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