Abstract
Contextual information is used to support and organize episodic memory. Prior research has reliably shown memory deficits in psychosis; however, little research has characterized how this population uses contextual information during memory recall. We employed an approach founded in a computational framework of free recall to quantify how individuals with first episode of psychosis (FEP, N = 97) and controls (CON, N = 55) use temporal and semantic context to organize memory recall. Free recall was characterized using the Hopkins Verbal Learning Test-Revised (HVLT-R). We compared FEP and CON on three measures of free recall: proportion recalled, temporal clustering, and semantic clustering. Measures of temporal/semantic clustering quantified how individuals use contextual information to organize memory recall. We also assessed to what extent these measures relate to antipsychotic use and differentiated between different types of psychosis. We also explored the relationship between these measures and intelligence. In comparison to CON, FEP had reduced recall and less temporal clustering during free recall (p < 0.05, Bonferroni-corrected), and showed a trend towards greater semantic clustering (p = 0.10, Bonferroni-corrected). Within FEP, antipsychotic use and diagnoses did not differentiate between free recall accuracy or contextual organization of memory. IQ was related to free recall accuracy, but not the use of contextual information during recall in either group (p < 0.05, Bonferroni-corrected). These results show that in addition to deficits in memory recall, FEP differed in how they organize memories compared to CON.
Highlights
Impairments in episodic memory, the ability to encode and retrieve details of past experiences, are a core feature of psychosis
first episode of psychosis (FEP) tended to show greater semantic clustering compared to CON, these results were only trend level when correcting for multiple comparisons (p = 0.03, uncorrected; p = 0.10; corrected; Fig. 1, Right; Table 1)
When analyzing all three trials of learning, there was a main effect of group such that FEP used semantic clustering more often CON (p = 0.05, Supplementary Table 1), there was no interaction between group and trial number (p = 0.37, Supplementary Table 1)
Summary
Impairments in episodic memory, the ability to encode and retrieve details of past experiences, are a core feature of psychosis. The context maintenance and retrieval model (CMR) is a computational model that provides quantification of how individuals may use different types of contextual information to guide free recall.[10] This modeling approach provides insight into distinct processes underlying free recall performance and lets us quantify an individual’s organizational structure of memory to quantify systematic differences across populations. It provides insight into the neural mechanisms underlying free recall, as the use of temporal and semantic context during free recall is associated with the hippocampus and anterior temporal lobe, respectively.[11,12]. # of Items recalled Constant FEP vs. CON Age Sex PSES Education (yrs) Temporal clustering Constant
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