Neurophysiological Verbal Working Memory Patterns in Children: Searching for a Benchmark of Modality Differences in Audio/Video Stimuli Processing

Abstract

Exploration of specific brain areas involved in verbal working memory (VWM) is a powerful but not widely used tool for the study of different sensory modalities, especially in children. In this study, for the first time, we used electroencephalography (EEG) to investigate neurophysiological similarities and differences in response to the same verbal stimuli, expressed in the auditory and visual modality during the n-back task with varying memory load in children. Since VWM plays an important role in learning ability, we wanted to investigate whether children elaborated the verbal input from auditory and visual stimuli through the same neural patterns and if performance varies depending on the sensory modality. Performance in terms of reaction times was better in visual than auditory modality ( p = 0.008) and worse as memory load increased regardless of the modality ( p < 0.001). EEG activation was proportionally influenced by task level and was evidenced in theta band over the prefrontal cortex ( p = 0.021), along the midline ( p = 0.003), and on the left hemisphere ( p = 0.003). Differences in the effects of the two modalities were seen only in gamma band in the parietal cortices ( p = 0.009). The values of a brainwave-based engagement index, innovatively used here to test children in a dual-modality VWM paradigm, varied depending on n-back task level ( p = 0.001) and negatively correlated ( p = 0.002) with performance, suggesting its computational effectiveness in detecting changes in mental state during memory tasks involving children. Overall, our findings suggest that auditory and visual VWM involved the same brain cortical areas (frontal, parietal, occipital, and midline) and that the significant differences in cortical activation in theta band were more related to memory load than sensory modality, suggesting that VWM function in the child’s brain involves a cross-modal processing pattern.

Gamma-Band Modulation in Parietal Area as the Electroencephalographic Signature for Performance in Auditory–Verbal Working Memory: An Exploratory Pilot Study in Hearing and Unilateral Cochlear Implant Children

“…Moreover, in our data, the absence of differences in the activation of the auditory and visual area between HC and UCI argues for the lack of audio-visual cross modalities in CI users, suggesting that earlier and longer CI use would inhibit the cross-modal reorganization of auditory regions in early deafness as hypothesized by Ding and colleagues [ 39 ]. Furthermore, the comparison between HC and UCI concerning gamma activation in the left hemisphere would show that verbal WM is stronger characterized by gamma left hemisphere activation only in HC (in line with our previous work, see [ 28 ]). In fact, there were no significant differences in the other EEG frequencies in the left hemisphere between groups and within the UCI, which seem to be deficient in gamma activation during the n-back task, whereas less gamma pattern of activity is considered indicative of (inefficient) neural resource management to achieve proper cognitive performance [ 117 ].…”

“…Moreover, both HC and UCI groups have higher IES values in the audio conditions, especially for 2-back, which seems to be the most challenging task condition [ 84 ] regardless of the group ( Figure 3 ). Longer IES values for the auditory task are in line with previous studies on HC children and adults [ 28 , 85 , 86 , 87 ], and contradict the hypothesis that auditory stimuli enhance performance by having longer-lasting representation [ 88 , 89 ] and more durable stimuli binding [ 90 ]. This result seems particularly interesting regarding the clinical group, given that the model of Pisoni and colleagues [ 23 ] proposes that poor performance on VWM tasks in CI users could be partly due to fragile, underspecified phonological representations of letters in short-term memory.…”

“…Methods for recording and analysis in the current study follow those described in previous publications from our group [ 28 , 45 ]. An abbreviated version of these methods is provided below.…”

“…However, a comprehensive understanding of how these factors interact and the neural mechanisms underlying these interactions are unknown. In fact, most studies have addressed working memory (WM) deficits in children with cochlear implants by assessing outcomes with psychometric scales and speech tests [ 26 , 27 ], especially in Verbal WM, and investigation of the neural correlates of this crucial executive function in children is rare, particularly in clinical children’s samples [ 28 ].…”

Bridging the Gap between Psychophysiological and Audiological Factors in the Assessment of Tinnitus: An EEG Investigation in the Beta Band

“…The stimulus was delivered by 2 audio speakers placed 1 m in front of the participants at face height, as in previous auditory neuroscience clinical studies [ 107 ]. Total auditory stimulation was set at 65 dB [ 56 ].…”