Changes in brain electrical activity during extended continuous word recognition

Abstract

Twenty healthy subjects (10 men, 10 women) participated in an EEG study with an extended continuous recognition memory task, in which each of 30 words was randomly shown 10 times and subjects were required to make old vs. new decisions. Both event-related brain potentials (ERPs) and induced band power (IBP) were investigated. We hypothesized that repeated presentations affect recollection rather than familiarity.For the 300-to 500-ms time window, an dold/newT ERP effect was found for the first vs. second word presentations. The correct recognition of an doldT word was associated with a more positive waveform than the correct identification of a new word. The old/new effect was most pronounced at and around the midline parietal electrode position. For the 500-to 800-ms time window, a linear repetition effect was found for multiple word repetitions. Correct recognition after an increasing number of repetitions was associated with increasing positivity. The multiple repetitions effect was most pronounced at the midline central (Cz) and fronto-central (FCz) electrode positions and reflects a graded recollection process: the stronger the memory trace grows, the more positive the ERP in the 500-to 800-ms time window. The ERP results support a dual-processing model, with familiarity being discernable from a more graded recollection state that depends on memory strengths.For IBP, we found dold/newT effects for the lower-2 alpha, theta, and delta bands, with higher bandpower during doldT words. The lower-2 alpha dold/newT effect most probably reflects attentional processes, whereas the theta and delta effects reflect encoding and retrieval processes. Upon repeated word presentations, the magnitude of induced delta power in the 375-to 750-ms time window diminished linearly. Correlation analysis suggests that decreased delta power is moderately associated with faster decision speed and higher accuracy. D

From N400 to N300: Variations in the timing of semantic processing with repetition

“…In accord with a number of previous studies, N400 amplitude did not significantly vary with the number of presentations after this initial repetition effect (Besson et al, 1992;Kazmerski and Friedman, 1997;Kounios and Holcomb, 1992;Van Strien et al, 2005;Young and Rugg, 1992). In contrast, the amplitude of LPC increased linearly with repetition and thus gave a graded reflection of the number of presentations.…”

“…In contrast, the amplitude of LPC increased linearly with repetition and thus gave a graded reflection of the number of presentations. Previous studies reporting similar effects had used explicit memory tasks (i.e., recognition memory) and lower rates of repetitions (Johnson et al, 1985;Segalowitz et al, 1997;Van Strien et al, 2005). The fact that similar modulations of LPC with repetition were observed in a semantic task and with unchanged context may indicate that the encoding of unique aspects of events (i.e., different presentations) may be an automatic process.…”

“…This ERP is often associated with episodic recollection (Friedman and Johnson, 2000;Mecklinger, 2000;Paller and Kutas, 1992;Rugg and Curran, 2007). In continuous recognition paradigms in which multiple presentations were included, it was shown that LPC amplitude could provide a graded reflection of the number of stimulus repetitions (Segalowitz et al, 1997;Van Strien et al, 2005). In contrast, no latency modulations were reported in these studies.…”

“…In the semantic categorization task of Renoult and Debruille (2011), trials were divided into five levels of repetitions (0-20, 20-40, 40-60, 60-80, and 80-100) and a progressive reduction in RTs was found until a floor of about 800 ms post-target onset was reached. Note that this floor is certainly task specific, since in non-semantic tasks, such as recognition memory, mean RTs to repeated words can be as short as 600 ms post-target onset (Van Strien et al, 2005). However, the chronological information that RTs offer does not only reflect the process of interest, such as semantic processing, but also evaluative and decision processes.…”

Context-dependent repetition effects on recognition memory

“…A common finding of many studies of recognition is a memory improvement when information is repeatedly presented for studying (Baddeley, Vargha-Khadem, & Mishkin, 2001;Curran, Tepe, & Piatt, 2006;van Strien, Hagenbeek, Stam, Rombouts, & Barkhof, 2005). As an example, using a continuous recognition paradigm van Strien et al (2005) Consequently, a scalar signal is provided that tracks the global similarity between the test probe and the studied items (Hintzman, 2001).…”