Intentional inhibition in memory and hallucinations: Directed forgetting and updating.

Abstract

Hallucinations have been recently associated with inhibitory deficits in memory. In this study, the authors investigated whether hallucinations were related to difficulties to inhibit irrelevant information from episodic memory (Experiment 1) and working memory (Experiment 2). In Experiment 1, a directed forgetting task was used. This task measures participants' ability to intentionally forget some recently learned material, when instructions indicate that it is no longer relevant. In Experiment 2, an updating task was used. This task requires participants to intentionally suppress irrelevant information from working memory. Results showed that patients with schizophrenia with hallucinations presented inhibitory deficits in the directed forgetting task and an increase in the number of intrusions in the updating task, compared to patients without hallucinations and healthy controls. No correlations were found between indices of inhibition and other general, negative or positive symptoms. These findings support the existence of an association between intentional inhibition in memory and hallucinations, and they suggest that problems to suppress memory representations can underlie hallucinations in schizophrenia.

Inhibitory deterioration may contribute to hallucinations in Alzheimer's disease

“…This consideration fits with empirical data showing significant correlations between the ability to suppress mental representations from episodic memory and severity of hallucinations in schizophrenia (Waters, Badcock, Maybery, & Michie, 2003). Consistent with these findings, individuals with schizophrenia with hallucinations have been found to show more impairment in intentional suppression of previously learned material compared to individuals with no hallucinations (Badcock, Waters, & Maybery, 2007;Soriano, Jiménez, Román, & Bajo, 2009). Taken together, the literature suggests that difficulties in intentionally inhibiting irrelevant thoughts or representations may underlie hallucinations.…”

Clinical and neurocognitive aspects of hallucinations in Alzheimer’s disease

“…This assumption can be supported by empirical studies showing that difficulties in intentionally inhibiting irrelevant thoughts or representations may be associated with hallucinations in Schizophrenia [66], obsessive-compulsive disorder [56], as well as in individuals prone to hallucinations [57, 61]. More specifically, the memory suppression compromise model emphasizes both inhibitory decline and memory impairment in AD and fits with the model of Hemsley [52] who have proposed an interplay between inhibitory processing and memory impairment to account for the presence of hallucinations in schizophrenia (see also [53]).…”

“…The directed forgetting task has been used to demonstrate relationships between deficits in memory suppression and hallucinations in schizophrenia. A study assessed the directed forgetting list task in schizophrenia participants with and without hallucinations and found that, relatively to those without hallucinations, participants with hallucinations presented inhibitory deficits on this task (i.e., they have difficulties to suppress the List 1 items) [61]. According to Soriano, Jimenez [61], difficulties in suppressing memory representations could underlie hallucinations in schizophrenia.…”

Hallucinations in Healthy Older Adults: An Overview of the Literature and Perspectives for Future Research

“…In support, the ability to suppress mental representation from episodic memory has been associated with the severity of hallucinations (but not delusions) in schizophrenia (Waters et al, 2003; Badcock et al, 2005; Hemsley, 2005). Similarly, Soriano et al (2009) compared directed forgetting performance in schizophrenia patients with and without hallucination and found that patients with hallucinations presented inhibitory deficits compared to patients without hallucinations (Soriano et al, 2009). Interestingly, similar (though milder) difficulties with intentional inhibition have also been found in healthy young adults prone to hallucinations (Paulik et al, 2007, 2008), leading some authors to suggest that what may differ between clinical and non-clinical hallucinators is how they cope with and/or interpret the experience (Morrison, 2005).…”