Transitive inference deficits in unaffected biological relatives of schizophrenia patients

Episodic Memory and Schizophrenia: From Characterization of Relational Memory Impairments to Neuroimaging Biomarkers

Episodic memory research in schizophrenia has a long history already which has clearly established significant impairments and strong associations with brain measures and functional outcome. The purpose of this chapter is not to make an exhaustive review of the recent literature but to highlight some relatively recent developments in the cognitive neuroscience field of episodic memory and schizophrenia. Hence, we present a contemporary view focusing specifically of relational memory which represents a form of episodic memory that refers to associations or binding among items or elements presented together. We describe the major tasks used and illustrate how their combination with brain imaging has: (1) favored the use of experimental memory tasks to isolate specific processes with specific neural correlates, (2) led to a distributed view of the neural correlates of memory impairments in schizophrenia where multiple regions are contributing, and (3) made possible the identification of fMRI biomarkers specific to episodic memory. We then briefly propose what we see as the next steps for memory research in schizophrenia so that the impact of this work can be maximized.

Impaired theta phase coupling underlies frontotemporal dysconnectivity in schizophrenia

Frontotemporal dysconnectivity is a key pathology in schizophrenia. The specific nature of this dysconnectivity is unknown, but animal models imply dysfunctional theta phase coupling between hippocampus and medial prefrontal cortex (mPFC). We tested this hypothesis by examining neural dynamics in 18 participants with a schizophrenia diagnosis, both medicated and unmedicated; and 26 age, sex and IQ matched control subjects. All participants completed two tasks known to elicit hippocampal-prefrontal theta coupling: a spatial memory task (during magnetoencephalography) and a memory integration task. In addition, an overlapping group of 33 schizophrenia and 29 control subjects underwent PET to measure the availability of GABAARs expressing the α5 subunit (concentrated on hippocampal somatostatin interneurons). We demonstrate-in the spatial memory task, during memory recall-that theta power increases in left medial temporal lobe (mTL) are impaired in schizophrenia, as is theta phase coupling between mPFC and mTL. Importantly, the latter cannot be explained by theta power changes, head movement, antipsychotics, cannabis use, or IQ, and is not found in other frequency bands. Moreover, mPFC-mTL theta coupling correlated strongly with performance in controls, but not in subjects with schizophrenia, who were mildly impaired at the spatial memory task and no better than chance on the memory integration task. Finally, mTL regions showing reduced phase coupling in schizophrenia magnetoencephalography participants overlapped substantially with areas of diminished α5-GABAAR availability in the wider schizophrenia PET sample. These results indicate that mPFC-mTL dysconnectivity in schizophrenia is due to a loss of theta phase coupling, and imply α5-GABAARs (and the cells that express them) have a role in this process.

Related to Anxiety: Arbitrarily Applicable Relational Responding and Experimental Psychopathology Research on Fear and Avoidance

Humans have an unparalleled ability to engage in arbitrarily applicable relational responding (AARR). One of the consequences of this ability to spontaneously combine and relate events from the past, present, and future may, in fact, be a propensity to suffer. For instance, maladaptive fear and avoidance of remote or derived threats may actually perpetuate anxiety. In this narrative review, we consider contemporary AARR research on fear and avoidance as it relates to anxiety. We first describe laboratory-based research on the emergent spread of fear- and avoidance-eliciting functions in humans. Next, we consider the validity of AARR research on fear and avoidance and address the therapeutic implications of the work. Finally, we outline challenges and opportunities for a greater synthesis between behavior analysis research on AARR and experimental psychopathology.

Impulsivity in unaffected adolescent biological relatives of schizophrenia patients

OBJECTIVE

Although schizophrenia is not a prototypic impulse-control disorder, patients report more impulsive behaviors, have higher rates of substance use, and show dysfunction in brain circuits that underlie impulsivity. We investigate impulsivity in unaffected biological relatives of schizophrenia patients to further understand the relationships between schizophrenia risk and impulse control during adolescence.

METHOD

Group differences in impulsivity (UPPS-P Impulsive Behavior Scale and delay discounting) were tested in 210 adolescents contrasting 39 first- and 53 second-degree biological relatives of schizophrenia patients, and 118 subjects with no schizophrenia family history (NSFH).

RESULTS

Compared to NSFH adolescents and to second-degree relatives, first-degree relatives of schizophrenia patients had increased impulsivity-related behaviors (higher UPPS-P Perseverance, Positive Urgency and Premeditation subscale scores) and greater preference for immediate rewards (smaller AUC and larger discounting constant). Second-degree relatives did not differ significantly from NSFH adolescents on self-report impulsive behaviors or on measures of impulsive decision-making. These group differences remained even after careful consideration of potential confounding factors.

CONCLUSION

Impulsivity is associated with schizophrenia risk, and its severity increases with greater familial relatedness to the schizophrenia proband. Additional studies are needed to understand the role impulsivity may play in mediating schizophrenia susceptibility during adolescence.

Schizotypal traits and cognitive performance in siblings of patients with psychosis

INTRODUCTION

Schizotypy has been proposed to be the expression of genetic vulnerability to schizophrenia. The available literature shows cognitive similarities between schizotypy and schizophrenia, with mildly impaired performance being associated with schizotypy. This study aims to determine the relationship between schizotypy and cognitive performance in siblings of patients with psychosis.

METHODS

Schizotypal features and cognitive performance on a neuropsychological battery were compared between 48 siblings of patients with psychosis and 44 healthy controls. The relationships between schizotypy and cognitive performance were analysed by controlling the condition of being a sibling.

RESULTS

Siblings showed poorer performance on vigilance/sustained attention (M = 37.6; SD = 7.1) and selective attention/interference control/working memory (M = 23.28; SD = 2.7) tasks. The variance in vigilance/sustained attention performance was explained, at 30%, by the interpersonal factor of schizotypy on the suspiciousness dimension and the condition of being a sibling.

CONCLUSIONS

Interpersonal features of schizotypy in siblings of patients with psychosis are associated with deficits in vigilance/sustained attention performance.