The role of midfrontal theta oscillations across the development of cognitive control in preschoolers and school‐age children

The development of cognitive control enables children to better resist acting based on distracting information that interferes with the current action. Cognitive control improvement serves different functions that differ in part by the type of interference to resolve. Indeed, resisting to interference at the task‐set level or at the response‐preparation level is, respectively, associated with cognitive flexibility and inhibition. It is, however, unknown whether the same neural mechanism underlies these two functions across development. Studies in adults have revealed the contribution of midfrontal theta (MFT) oscillations in interference resolution. This study investigated whether MFT is involved in the resolution of different types of interference in two age groups identified as corresponding to different latent structures of executive functions. Preschool (4–6 years) and school children (6–8 years) were tested with a task involving interference at the response level and/or the task‐set level while (electroencephalogram) EEG was recorded. Behaviorally, response time and accuracy were affected by task‐set. Both age groups were less accurate when the interference occurred at the task‐set level and only the younger group showed decreased accuracy when interference was presented at the response‐preparation level. Furthermore, MFT power was increased, relative to the baseline, during the resolution of both types of interference and in both age groups. These findings suggest that MFT is involved in immature cognitive control (i.e., preschool and school‐ages), by orchestrating its different cognitive processes, irrespective of the interference to resolve and of the level of cognitive control development (i.e., the degree of differentiation of executive functions).     

Electrophysiological spatiotemporal dynamics during implicit visual threat processing

Numerous studies have found evidence for corticolimbic theta band electroencephalographic (EEG) oscillations in the neural processing of visual stimuli perceived as threatening. However, varying temporal and topographical patterns have emerged, possibly due to varying arousal levels of the stimuli. In addition, recent studies suggest neural oscillations in delta, theta, alpha, and beta-band frequencies play a functional role in information processing in the brain. This study implemented a data-driven PCA based analysis investigating the spatiotemporal dynamics of electroencephalographic delta, theta, alpha, and beta-band frequencies during an implicit visual threat processing task. While controlling for the arousal dimension (the intensity of emotional activation), we found several spatial and temporal differences for threatening compared to nonthreatening visual images. We detected an early posterior increase in theta power followed by a later frontal increase in theta power, greatest for the threatening condition. There was also a consistent left lateralized beta desynchronization for the threatening condition. Our results provide support for a dynamic corticolimbic network, with theta and beta band activity indexing processes pivotal in visual threat processing.     

Sleep EEG changes during adolescence: An index of a fundamental brain reorganization

Delta (1–4 Hz) EEG power in non-rapid eye movement (NREM) sleep declines massively during adolescence. This observation stimulated the hypothesis that during adolescence the human brain undergoes an extensive reorganization driven by synaptic elimination. The parallel declines in synaptic density, delta wave amplitude and cortical metabolic rate during adolescence further support this model. These late brain changes probably represent the final ontogenetic manifestation of nature’s strategy for constructing nervous systems: an initial overproduction of neural elements followed by elimination. Errors in adolescent brain reorganization may cause mental illness; this could explain the typical age of onset of schizophrenia. Longitudinal studies of sleep EEG are enhancing our knowledge of adolescent brain maturation. Our longitudinal study of sleep EEG changes in adolescence showed that delta power, which may reflect frontal cortex maturation, begins its decline between ages 11 and 12 years and falls by 65% by age 17 years. In contrast, NREM theta power begins its decline much earlier. Delta and theta EEG frequencies are important to sleep theory because they behave homeostatically. Surprisingly, these brain changes are unrelated to pubertal maturation but are strongly linked to age. In addition to these (and other) maturational EEG changes, sleep schedules in adolescence change in response to a complex interaction of circadian, social and other influences. Our data demonstrate that the daytime sleepiness that emerges in adolescence is related to the decline in NREM delta as well as to altered sleep schedules. These longitudinal sleep data provide guideposts for studying cognitive and behavioral correlates of adolescent brain reorganization.     

Regional and inter-regional theta oscillation during episodic novelty processing

Recent event-related potential (ERP) and functional magnetic resonance imaging (fMRI) studies suggest that novelty processing may be involved in processes that recognize the meaning of a novel sound, during which widespread cortical regions including the right prefrontal cortex are engaged. However, it remains unclear how those cortical regions are functionally integrated during novelty processing. Because theta oscillation has been assumed to have a crucial role in memory operations, we examined local and inter-regional neural synchrony of theta band activity during novelty processing. Fifteen right-handed healthy university students participated in this study. Subjects performed an auditory novelty oddball task that consisted of the random sequence of three types of stimuli such as a target (1000 Hz pure tone), novel (familiar environmental sounds such as dog bark, buzz, car crashing sound and so on), and standard sounds (950 Hz pure tone). Event-related spectra perturbation (ERSP) and the phase-locking value (PLV) were measured from human scalp EEG during task. Non-parametric statistical tests were applied to test for significant differences between stimulus novelty and stimulus targets in ERSP and PLV. The novelty P3 showed significant higher amplitude and shorter latency compared with target P3 in frontocentral regions. Overall, theta activity was significantly higher in the novel stimuli compared with the target stimuli. Specifically, the difference in theta power between novel and target stimuli was most significant in the right frontal region. This right frontal theta activity was accompanied by phase synchronization with the left temporal region. Our results imply that theta phase synchronization between right frontal and left temporal regions underlie the retrieval of memory traces for unexpected but familiar sounds from long term memory in addition to working memory retrieval or novelty encoding.     

Midline theta dissociates agentic extraversion and anhedonic depression

The agency facet of extraversion is related to individual differences in reward anticipation and has been linked to the neurotransmitter dopamine. Dopamine has also been associated with components of anhedonia, which is one of the cardinal symptoms of depression and refers to lack of responsiveness to pleasurable stimuli. This raises the question whether low agency is associated with anhedonia symptoms in depression and if agency and anhedonia are characterized by similar neurobiological mechanisms. To address this hypothesis, we tested whether questionnaire measures of agency and anhedonia are correlated within depressed (n = 20) and non-depressed (n = 22) participants. Further, we investigated whether dopamine-related signatures in the EEG recorded during a gambling task (feedback-evoked theta activity, and frontal versus posterior theta activity) similarly relate to agency and anhedonia. Results indicated that anhedonia was significantly elevated in the depression group, and negatively correlated with agency. However, while theta activity evoked by negative vs. positive feedback was sensitive to anhedonia and depression status but unrelated to agency, frontal versus parietal theta activity predicted agency, but was unrelated to anhedonia and depression. Together, this double dissociation suggests that in spite of considerable phenotypical overlap, anhedonia and agency may be linked to partially distinct neurobiological markers.     

Input-specific long-term potentiation in the rat lateral amygdala of horizontal slices

Long-term potentiation (LTP) at input synapses to the lateral nucleus of the amygdala (LA) is a candidate mechanism for memory storage during fear learning. Cellular mechanisms of LTP have been nearly exclusively investigated in coronal brain slices. In our experiments, we used a horizontal brain slice preparation of rats that preserved most of the connections to cortical areas and the hippocampus. The stimulation electrodes were located either within the external capsule (EC) or the LA. The aim of the present study was to investigate the mechanisms of LTP induced either by weak theta burst stimulation (TBS) or strong high frequency stimulation (HFS) using the two different stimulation sites. Whereas both TBS and HFS of afferences running through the LA induced stable LTP, TBS failed to induce LTP of EC-inputs to the LA. The present findings also show that LTP in the LA exhibits vulnerability at different time windows after induction. The time window was dependent on the kind of stimulated afferences. Later LTP becomes resistant to disruption by low frequency stimulation. We could show that both used inputs depended on NMDA receptors for LTP-induction. LTP induced by stimulation of fibers within the LA was not altered by nifedipine (10 microM). In contrast, EC-induced LTP was dependent on L-type voltage-gated calcium channels (VGCC). Finally, we found a higher magnitude of LTP in females using TBS, whereas HFS did not cause gender-specific differences. Our study supports the conclusion that the form of LA-LTP depend on which afferences are activated and what pattern of stimulation is used to induce LTP.     

Danger and usefulness are detected early in auditory lexical processing: evidence from electroencephalography

Visual emotionally charged stimuli have been shown to elicit early electrophysiological responses (e.g., [Ihssen et al., 2007], [Schupp et al., 2003] and [Stolarova et al., 2006]). We presented isolated words to listeners, and observed, using generalized additive modeling, oscillations in the upper part of the delta range, the theta range (Bastiaansen & Hagoort, 2003), and the lower part of the alpha range related to degree of (rated) danger and usefulness (Wurm, 2007) starting around 150 ms and continuing to 350 ms post stimulus onset. A negative deflection in the oscillations tied to danger around 250-300 ms fits well with a similar negativity observed in the same time interval for visual emotion processing. Frequency and competitor effects emerged or reached maximal amplitude later, around or following the uniqueness point. The early effect of danger, long before the words’ uniqueness points, is interpreted as evidence for the dual pathway theory of LeDoux (1996).     

Shadows of music-language interaction on low frequency brain oscillatory patterns

Electrophysiological studies investigating similarities between music and language perception have relied exclusively on the signal averaging technique, which does not adequately represent oscillatory aspects of electrical brain activity that are relevant for higher cognition. The current study investigated the patterns of brain oscillations during simultaneous processing of music and language using visually presented sentences and auditorily presented chord sequences. Music-syntactically regular or irregular chord functions were presented in sync with syntactically or semantically correct or incorrect words. Irregular chord functions (presented simultaneously with a syntactically correct word) produced an early (150-250 ms) spectral power decrease over anterior frontal regions in the theta band (5-7 Hz) and a late (350-700 ms) power increase in both the delta and the theta band (2-7 Hz) over parietal regions. Syntactically incorrect words (presented simultaneously with a regular chord) elicited a similar late power increase in delta-theta band over parietal sites, but no early effect. Interestingly, the late effect was significantly diminished when the language-syntactic and music-syntactic irregularities occurred at the same time. Further, the presence of a semantic violation occurring simultaneously with regular chords produced a significant increase in later delta-theta power at posterior regions; this effect was marginally decreased when the identical semantic violation occurred simultaneously with a music syntactical violation. Altogether, these results show that low frequency oscillatory networks get activated during the syntactic processing of both music and language, and further, these networks may possibly be shared.     

Reward feedback processing in children and adolescents: Medial frontal theta oscillations

We examined event-related electroencephalography (EEG) oscillations, including event-related spectral perturbations (ERSP) and intertrial coherence (ITC), to compare feedback processing during a chance-based reward vs. non-reward task in groups of 10–12-year-old (n = 42), 13–14-year-old (n = 34) and 15–17-year-olds (n = 32). Because few, if any studies have applied these analytic methods to examine feedback processing in children or adolescents, we used a fine-grained approach that explored one half hertz by 16 ms increments during feedback (no win vs. win events) in the theta (4–8 Hz) frequency band. Complex wavelet frequency decomposition revealed that no win feedback was associated with enhanced theta power and phase coherence. We observed condition and age-based differences for both ERSP and ITC, with stronger effects for ITC. The transition from childhood to early adolescence (13–14 yrs.) was a point of increased differentiation of ITC favoring no win vs. wins feedback and also compared to children or older adolescents, a point of heightened ITC for no win feedback (quadratic effect).