Synchronized brain activity during rehearsal and short-term memory disruption by irrelevant speech is affected by recall mode

Abstract

EEG coherence as a measure of synchronization of brain activity was used to investigate effects of irrelevant speech. In a delayed serial recall paradigm 21 healthy participants retained verbal items over a 10-s delay with and without interfering irrelevant speech. Recall after the delay was varied in two modes (spoken vs. written). Behavioral data showed the classic irrelevant speech effect and a superiority of written over spoken recall mode. Coherence, however, was more sensitive to processing characteristics and showed interactions between the irrelevant speech effect and recall mode during the rehearsal delay in theta (4–7.5 Hz), alpha (8–12 Hz), beta (13–20 Hz), and gamma (35–47 Hz) frequency bands. For gamma, a rehearsal-related decrease of the duration of high coherence due to presentation of irrelevant speech was found in a left-lateralized fronto-central and centro-temporal network only in spoken but not in written recall. In theta, coherence at predominantly fronto-parietal electrode combinations was indicative for memory demands and varied with individual working memory capacity assessed by digit span. Alpha coherence revealed similar results and patterns as theta coherence. In beta, a left-hemispheric network showed longer high synchronizations due to irrelevant speech only in written recall mode. EEG results suggest that mode of recall is critical for processing already during the retention period of a delayed serial recall task. Moreover, the finding that different networks are engaged with different recall modes shows that the disrupting effect of irrelevant speech is not a unitary mechanism

Fronto-parietal and fronto-temporal theta phase synchronization for visual and auditory-verbal working memory

“…Previous EEG studies in human have shown that theta phase synchronization between frontal and temporal regions is observed during several WM tasks including encoding, maintenance, and retrieval processes (Sarnthein et al, 1998; Sauseng et al, 2004; Serrien et al, 2004). Moreover, fronto-parietal theta synchronization is enhanced under WM tasks which required high WM load and complex manipulation (Sauseng et al, 2005; Kopp et al, 2006; Payne and Kounios, 2009). The present study also supports the hypothesis that theta synchronization is a requirement of executive function.…”

Oscillatory mechanisms of process binding in memory

“…It was also shown that coherent theta activity plays an important role for the successful encoding of episodic information (Fell et al, 2001(Fell et al, , 2003Sumerfield and Mangels, 2005;Weiss and Rappelsberger, 2000) and memory span (Kopp et al, 2006).…”

For whom the bell tolls: periodic reactivation of sensory cortex in the gamma band as a substrate of visual working memory maintenance

“…Even recently, Salazar et al (2012) found clear evidence for item-specific increases in fronto-parietal 14–30 Hz beta oscillatory coherence during WM maintenance. Several other studies have shown that lower-frequency oscillatory synchronization between prefrontal and temporal lobes (Von Stein et al, 1999; Serrien et al, 2004) and between prefrontal and parietal lobes (Lutzenberger et al, 2002; Babiloni et al, 2004; Kopp et al, 2006; Payne and Kounios, 2009) are associated with the maintenance of information during WM tasks. Some of these effects are also dependent on the number of items that participants have to maintain (see Fell and Axmacher, 2011, for a discussion).…”