Developmental Changes of BOLD Signal Correlations with Global Human EEG Power and Synchronization during Working Memory

Abstract

In humans, theta band (5–7 Hz) power typically increases when performing cognitively demanding working memory (WM) tasks, and simultaneous EEG-fMRI recordings have revealed an inverse relationship between theta power and the BOLD (blood oxygen level dependent) signal in the default mode network during WM. However, synchronization also plays a fundamental role in cognitive processing, and the level of theta and higher frequency band synchronization is modulated during WM. Yet, little is known about the link between BOLD, EEG power, and EEG synchronization during WM, and how these measures develop with human brain maturation or relate to behavioral changes. We examined EEG-BOLD signal correlations from 18 young adults and 15 school-aged children for age-dependent effects during a load-modulated Sternberg WM task. Frontal load (in-)dependent EEG theta power was significantly enhanced in children compared to adults, while adults showed stronger fMRI load effects. Children demonstrated a stronger negative correlation between global theta power and the BOLD signal in the default mode network relative to adults. Therefore, we conclude that theta power mediates the suppression of a task-irrelevant network. We further conclude that children suppress this network even more than adults, probably from an increased level of task-preparedness to compensate for not fully mature cognitive functions, reflected in lower response accuracy and increased reaction time. In contrast to power, correlations between instantaneous theta global field synchronization and the BOLD signal were exclusively positive in both age groups but only significant in adults in the frontal-parietal and posterior cingulate cortices. Furthermore, theta synchronization was weaker in children and was –in contrast to EEG power– positively correlated with response accuracy in both age groups. In summary we conclude that theta EEG-BOLD signal correlations differ between spectral power and synchronization and that these opposite correlations with different distributions undergo similar and significant neuronal developments with brain maturation.

Beyond aphasia: Altered EEG connectivity in Broca’s patients during working memory task

“…In healthy controls, we found task-related increase in frontal theta power that was absent in patient group. Frontal theta power has been reported to correlate with WM load (Jensen & Tesche, 2002), but was also interpreted as an EEG index of Default Mode Network (Scheeringa et al, 2008) or suppression of WM-irrelevant networks (Michels, Lüchiner, Koenig, Martin, & Brandeis, 2012). If we were to consider task-related theta power changes in isolation, the results of our study could support any of these observations.…”

“…Indeed, the negative correlation between frontal theta power and Default Mode Network has been reported in resting state (Scheeringa et al, 2008). Specifically during WM task, increased theta power was related to the suppresion of the WM-irrelevant networks (Michels et al, 2012) or to the decreased activity in Default Mode Network (Scheeringa et al, 2009). Taking into account the concomitant task-related theta synchronization, desynchronization and power changes, the most plausible explanation for the lack of increase in frontal midline theta power in patient group would be an inefficient suppression of the WM-irrelevant or Default Mode Network.…”

Memory load effect in auditory–verbal short-term memory task: EEG fractal and spectral analysis

“…The most significant finding was the increase in FD with the increase in memory frequency is classically used to quantitatively measure the functional relationship between different brain regions involved in various cognitive processes, like STM. In general, synchronous oscillatory cortical electrical activity in the 4-7 Hz theta band and the 8-12 Hz alpha band was reported in numerous studies to be associated with STM (Michels et al 2012;Palomaki et al 2012;Rawle et al 2012;Toth et al 2012;White et al 2012;Hsieh and Ranganath 2014). Furthermore, changes in theta activity were found to be associated with changes in mental load (Jensen and Tesche 2002).…”

“…Based on findings of other studies which obtained differences between the first second of the retention period and the rest of it (Jensen and Tesche 2002;Michels et al 2012), we separated selected 5-s EEG trace into two. The first contained data from 0 to 1000 ms and the second contained data from 1000 to 5000 ms.…”

Transition dynamics of EEG-based network microstates during mental arithmetic and resting wakefulness reflects task-related modulations and developmental changes

“…Task-related oscillations associated with cognitive and perceptual processes have already been examined during different developmental stages (Yordanova and Kolev 1996;Uhlhaas et al 2009;Muller et al 2009). Several studies have shown the influence of maturation on the EEG signals in childhood based on spectral and synchronization analysis (e.g.…”