Abstract
Working memory (WM) refers to the temporary retention and manipulation of information, and its capacity is highly susceptible to training. Yet, the neural mechanisms that allow for increased performance under demanding conditions are not fully understood. We expected that post-training efficiency in WM performance modulates neural processing during high load tasks. We tested this hypothesis, using electroencephalography (EEG) (N = 39), by comparing source space spectral power of healthy adults performing low and high load auditory WM tasks. Prior to the assessment, participants either underwent a modality-specific auditory WM training, or a modality-irrelevant tactile WM training, or were not trained (active control). After a modality-specific training participants showed higher behavioral performance, compared to the control. EEG data analysis revealed general effects of WM load, across all training groups, in the theta-, alpha-, and beta-frequency bands. With increased load theta-band power increased over frontal, and decreased over parietal areas. Centro-parietal alpha-band power and central beta-band power decreased with load. Interestingly, in the high load condition a tendency toward reduced beta-band power in the right medial temporal lobe was observed in the modality-specific WM training group compared to the modality-irrelevant and active control groups. Our finding that WM processing during the high load condition changed after modality-specific WM training, showing reduced beta-band activity in voice-selective regions, possibly indicates a more efficient maintenance of task-relevant stimuli. The general load effects suggest that WM performance at high load demands involves complementary mechanisms, combining a strengthening of task-relevant and a suppression of task-irrelevant processing.
Highlights
Working memory (WM) has been defined as the ability to temporary maintain and manipulate stored information (Baddeley, 2003; D’Esposito, 2007; Jonides et al, 2008)
We focused on whether load-related changes in neuronal power differ between training groups, since we were interested in whether the neural correlates of WM processing at high load demands differ as a function of post-training performance efficiency
In order to test the effects of load on WM performance, accuracy rates were compared with a GLMM, including the predicting variables WM load and group (AG, training group (TG), control group (CG)) as fixed effects
Summary
Working memory (WM) has been defined as the ability to temporary maintain and manipulate stored information (Baddeley, 2003; D’Esposito, 2007; Jonides et al, 2008). Language processing highly relies on WM processes, as information needs to be maintained and integrated over time, for example during phrasal or sentence level processing (Montgomery, 2000; Emmorey et al, 2017). Verbal WM is crucial for speech comprehension (Buchsbaum and D’Esposito, 2019), but speech comprehension requires the processing of extralinguistic cues, such as voice features and prosody (Larrouy-Maestri et al, 2013; Hellbernd and Sammler, 2016). Language learning can benefit from prosodic cues, suggesting interactions of verbal and extralinguistic memory (Schon et al, 2008; de Diego-Balaguer et al, 2015). In a voice recognition task, we focus on auditory WM of extralinguistic cues. The present study investigated the neural mechanisms that allow enhanced auditory WM performance at high difficulty levels following WM training
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