Brain-Performance Correlates of Working Memory Retrieval in Schizophrenia: A Cognitive Modeling Approach

Abstract

Correlations of cognitive functioning with brain activation during a sternberg item recognition paradigm (SIRP) were investigated in patients with schizophrenia and in healthy controls studied at 8 sites. To measure memory scanning times, 4 response time models were fit to SIRP data. The best fitting model assumed exhaustive serial memory scanning followed by self-terminating memory search and involved one intercept parameter to represent SIRP processes not contributing directly to memory scanning. Patients displayed significantly longer response times with increasing memory load and differed on the memory scanning, memory search, and intercept parameters of the best fitting probability model. Groups differed in the correlation between the memory scanning parameter and linear brain response to increasing memory load within left inferior and left middle frontal gyrus, bilateral caudate, and right precuneus. The pattern of findings in these regions indicated that high scanning capacity was associated with high neural capacity among healthy subjects but that scanning speed was uncoupled from brain response to increasing memory load among schizophrenia patients. Group differences in correlation of the best fitting model's scanning parameter with a quadratic trend in brain response to increasing memory load suggested inefficient or disordered patterns of neural inhibition among individuals with schizophrenia, especially in the left perirhinal and entorhinal cortices. The results show at both cognitive and neural levels that disordered memory scanning contributes to deficient SIRP performance among schizophrenia patients.

P3 response during short-term memory retrieval revisited by a spatio-temporal analysis

“…Additionally, significantly shorter RTs were obtained for the positive probes compared with the negative probes. Faster RTs to positive than to negative probes were reported in several earlier working memory studies with Sternberg paradigm (Pelosi et al, 1995(Pelosi et al, , 1998Brown et al, 2009), while a study reported no RT difference between them (Pratt et al, 1989). Since the original study by Sternberg (1966), several cognitive models were proposed for search strategies on the basis of slopes of RTs to positive and negative probes, such as serialexhaustive search, serial-self terminating search or parallel search with limited capacity (Townsend and Fifić, 2004).…”

State-Space Analysis of Working Memory in Schizophrenia: An FBIRN Study

“…4) was composed of six blocks of memory items separated by fixation blocks (Brown et al, 2009). During a run, two memory sets for each memory set size were presented twice.…”

“…Although patients with schizophrenia (SZ) exhibit performance deficits in nearly all aspects of brain function, WM has been identified as one most severely affected functional domains (Bilder, 2009). The neural correlates of WM have been extensively studied using the psychometric and neuroimaging data gathered from healthy adults and from patients suffering from schizophrenia or schizoaffective disorder while performing a variant of the Sternberg Item Recognition Paradigm (SIRP) (Brown et al, 2009). The task involved the presentation of a memory set that included 1, 3, or 5 digits followed by 14 probe digits.…”

“…Participants responded manually to indicate whether or not a probe digit was included in the memory set just studied. Because it encompasses a large number of probe trials, the multi-probe, fixed-set design efficiently assesses the brains response to memory probe events under different memory load conditions (Brown et al, 2009). …”

“…I. Kim et al, 2009). Brown et al (2009) tested reaction times (RT) against four memory retrieval models and correlated the results with the fMRI time-series. Based on the decoupling of brain response to increasing memory load in patients and on group differences in the correlation of the best fitting models parameters to the brain’s response under increasing memory load, they suggested a hypothesis of inefficient or disordered patterns of neural inhibition among individuals with schizophrenia.…”