Relational Memory in the Early Stage of Psychosis: A 2-Year Follow-up Study

Abstract

Background: Relational memory, the ability to bind information into complex memories, is moderately impaired in early psychosis and severely impaired in chronic schizophrenia, suggesting relational memory may worsen throughout the course of illness.

Methods: We examined relational memory in 66 early psychosis patients and 64 healthy control subjects, with 59 patients and 52 control subjects assessed longitudinally at baseline and 2-year follow-up. Relational memory was assessed with 2 complementary tasks, to test how individuals learn relationships between items (face-scene binding task) and make inferences about trained relationships (associative inference task).

Results: The early psychosis group showed impaired relational memory in both tasks relative to the healthy control group. The ability to learn relationships between items remained impaired in early psychosis patients, while the ability to make inferences about trained relationships improved, although never reaching the level of healthy control performance. Early psychosis patients who did not progress to schizophrenia at follow-up had better relational memory than patients who did.

Conclusions: Relational memory impairments, some of which improve and are less severe in patients who do not progress to schizophrenia, are a target for intervention in early psychosis.

Keywords: hippocampus; longitudinal; memory; schizophrenia; schizophreniform.

Fig. 1.

Relational memory tasks. (A) Face-scene binding (FSB) task: subjects learned to associate a face with a background scene. During testing, participants were asked to find, with their eyes, the one face among 3 equally familiar faces that had been previously paired with the background scene while their eye movements were recorded. (B) Associative inference (AI) task: subjects learn 3 sets of paired associates: House with Face (H-F1), same House with new Face (H-F2), and 2 new Faces (F3-F4). In testing, memory for the trained pairs and a novel set of inferential face-face pairs (F1-F2), which could only be solved by overlapping associations with the house, were tested.

Fig. 2.

Flow diagram of study participants. All participants completed the associative inference (AI) task (right) at baseline and most participants also completed the face-scene binding (FSB) task (left).

Fig. 3.

Relational memory at baseline and follow-up. (A) The early psychosis group performed worse on the face-scene binding (FSB) task (smaller viewing slope) than the healthy control group and remained impaired at follow-up. (B) FSB task performance was similar across 16 schizophreniform disorder participants and 43 schizophrenia participants. (C) Associative inference (AI) performance (F1-F2 accuracy) improved over the 2 years, with better performance in the healthy control group than the early psychosis group. (D) AI performance at baseline and follow-up in schizophreniform disorder and schizophrenia. Schizophreniform disorder participants (N = 16) were more accurate than schizophrenia participants (N =43).

Fig. 4.

Individual relational memory performance in the schizophreniform disorder and schizophrenia groups. (A) Face-scene binding (FSB) performance was heterogeneous in both patient groups. (B) The majority of schizophreniform disorder participants showed good associative inference (AI) performance, while the schizophrenia group was more heterogeneous.