بررسی پتانسیل مربوط به رویداد اثر همگرایی معنایی در بیماران مبتلا به اسکیزوفرنیا An Event Related Potentials Study of Semantic Coherence Effect during Episodic Encoding in Schizophrenia Patients

1. Introduction Cognitive dysfunctioning is a core feature in schizophrenia [1], with episodic memory being one of the most impaired cognitive areas in this pathology [2, 3]. In the context of dual process models, familiarity and recollection are two distinct processes within episodic memory [4–6]. Familiarity refers to the judgment of prior occurrence, while recollection is accompanied by contextual or associative information related to the stimulus. Both processes are altered in schizophrenia [7–9]. In spite of this alteration, schizophrenia patients benefit from explicit semantic strategies provided at encoding which promote successful memory performance during test [10, 11]. However, studies show that while, in healthy controls, episodic memory enhancement can be related to an increase in both familiarity and recollection estimates [5, 12–14], in schizophrenia patients, this enhancement is linked to an increase in familiarity, alone [15–17]. For example, in a recent behavioral study [17], we designed an associative recognition memory task to test the effect of semantic coherence between a category name and a word pair on familiarity and recollection processes in schizophrenia. We used the process dissociation procedure (PDP, [4]) to calculate the respective parts of these processes contributing to the overall recognition performance. During the study phase, pairs of words either semantically related or unrelated to a given category name were deeply encoded [18]. During the test, the results indicated an enhancement of episodic memory performance for semantically related word pairs compared to semantically unrelated ones in both healthy controls and schizophrenia patients. In healthy controls, this enhancement was linked to an increase in recollection estimates, whereas, in schizophrenia patients, semantic coherence led to increased familiarity. Thereby, this pattern of the results obtained during the test must be in relation to different strategies employed during encoding by the two groups of participants. In other words, even under the same explicit encoding instructions and having similar categorization performances during the study, schizophrenia patients should have used different encoding strategies compared to the ones employed by healthy individuals, which in turn should have led to an increase in familiarity estimates alone in this group. Literature indicates that, in associative recognition memory tasks, interitem binding mechanisms can lead to successful recollection process [19].