Academic journal article Cognitive, Affective and Behavioral Neuroscience

Neurophysiology of Successful Encoding and Retrieval of Source Memory

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Neurophysiology of Successful Encoding and Retrieval of Source Memory

Article excerpt

Event-related potentials were recorded during encoding, to identify whether brain activity predicts subsequent retrieval of spatial source information, and during retrieval, to investigate the neural correlates of successful and unsuccessful spatial context recollection. The amplitude registered during encoding for study items that were later recognized and assigned a correct source judgment was more positive than the amplitude for recognized items given incorrect source judgments; this difference started 480 msec poststimulus, predominantly at central and anterior sites. During retrieval, the waveform was more positive from 250 to 1,600 msec poststimulus when the brain had retrieved episodic information successfully than when it had failed. These findings indicate that brain electrical activity recorded during the first presentation of an item within its context predicts the subsequent retrieval of the specific spatial context During retrieval, brain activity differed quantitatively at anterior sites and qualitatively at posterior sites according to the accuracy of source memory.

Shortly after the term "episodic memory" was introduced by Tulving (1972) to describe the memory that allows us to remember our own experiences, a dissociation began to be emphasized between two forms of retrieving episodic information-namely, that between "recollection" and "familiarity." These terms distinguish, respectively, episodic memory retrieved with or without the context information associated with the episode event when it was encoded. The phenomenological experience of remembering episodic information was introduced by Tulving (1985) when he described the "autonoetic" nature of episodic memory and provided empirical evidence via the "remember-know" paradigm. This procedure consists of asking subjects to express a "remember" response whenever they retrieve any contextual information referring to the study moment along with the item, and a "know" response when such contextual information is absent.

The remember-know procedure and other paradigms, such as those requiring recognition or retrieval of specific contextual information, have been extensively used to examine whether familiarity and recollection represent quantitatively or qualitatively different mnemonic processes (for a review, see Yonelinas, 2002). In addition to this question, increased research on episodic memory has provided evidence of different classes of retrieval processes. For example, Rugg and Wilding (2000) identified and described four retrieval processes, which they named "mode," "effort," "orientation," and "success" (see also Burgess & Shallice, 1996). The present study focuses on the "success" process, which occurs as a preretrieval event and consists of successfully recovering relevant episodic information when the brain is engaged in a retrieval attempt (Rugg & Henson, 2002).

Although several ERP studies have investigated memory for source information during encoding, most of these studies have compared the memory effects for correctly recognized items for which context was subsequently retrieved with those for items subsequently forgotten or missed (Duarte, Ranganath, Winward, Hayward, & Knight, 2004; Friedman & Trott, 2000; Mangels, Picton, & Craik, 2001; Senkfor & Van Petten, 1998; M. E. Smith, 1993), whereas in retrieval studies, items attracting correct source responses are usually compared with new items (Cycowicz & Friedman, 2003; Johansson, Stenberg, Lindgren, & Rosen, 2002; Johnson, Kounios, & Nolde, 1997; Leynes, Bink, Marsh, Alien, & May, 2003; Li, Morcom, & Rugg, 2004; Mark & Rugg, 1998; Rugg, Schloerscheidt, & Mark, 1998; Senkfor, Van Petten, & Kutas, 2002; A. P. R. Smith, Dolan, & Rugg, 2004; Trott, Friedman, Ritter, & Fabiani, 1997; Wegesin, Friedman, Varughese, & Stern, 2002; Wilding, 1999,2000; Wilding & Rugg, 1996, 1997). These approaches do not allow for an analysis of brain activity related to the successful encoding and retrieval of source information only, since both familiarity and recollection processes are combined when brain responses for correct source judgments are compared with those for either subsequently missed or correct new items. …

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