Down-regulation of theta amplitude through neurofeedback improves executive control network efficiency in healthy children.

Despite extensive clinical research on neurofeedback (NF) in attention-deficit/hyperactivity disorder (ADHD), few studies targeted the optimization of attention performance in healthy children. As a crucial component of attention networks, the executive control network, involved in resolving response conflicts and allocating cognitive resources, is closely linked to theta activity. Here, we aimed to answer whether theta down-regulating NF can enhance healthy children's attention performance, especially the executive control network. Sixty children aged 6-12 years were randomly assigned to the NF and waitlist control groups. The NF group received theta down-regulation NF training for five days (a total of 100 mins), and the attention performance of both groups was measured by the attention network test (ANT) in the pre, post-NF, and 7-day follow-up. The electroencephalographic (EEG) results demonstrated a significant decrease in resting-state theta amplitude within sessions. For the behavioral results, the NF group exhibited significant improvements in overall attention performance and the efficiency of the executive control network relative to the control group in the post-NF and follow-up assessment, whereas the alerting and orienting networks remained unchanged. These findings proved the feasibility of theta down-regulating NF and its positive effect on attention in the healthy children population. In particular, the facilitation of the efficiency of the executive control network and the unaltered performance of the other two attention networks in the NF group may support the causality between theta rhythm and the executive control network.

Mindfulness-Based Cognitive Therapy in Recurrent MDD Patients With Residual Symptoms: Alterations in Resting-State Theta Oscillation Dynamics Associated With Changes in Depression and Rumination.

Many patients with major depressive disorder (MDD) suffer from residual symptoms. Rumination is a specific known risk factor for the onset, severity, prolongation, and relapse of MDD. This study aimed to examine the efficacy and EEG substrates of mindfulness-based cognitive therapy (MBCT) in alleviating depression and rumination in an MDD population with residual symptoms. We recruited 26 recurrent MDD individuals who had residual symptoms with their current antidepressants to participate in the 8-week MBCT intervention. We evaluated the efficacy and changes in the dynamics of resting-state theta rhythm after the intervention, as well as the associations between theta alterations and improvements in depression and rumination. The participants showed reduced depression, enhanced adaptive reflective rumination, and increased theta power and phase synchronization after MBCT. The increased theta-band phase synchronizations between the right occipital regions and the right prefrontal, central, and parietal regions were associated with reduced depression, while the increase in theta power in the left parietal region was associated with improvements in reflective rumination. MBCT could alleviate depression and enhance adaptive, reflective rumination in recurrent MDD individuals with residual symptoms through the modulation of theta dynamics in specific brain regions.

Rehabilitating the brain through meditation and electrical stimulation.

This paper is a review of our recent studies and ideas related to the neuropsychological issues that Robert Rafal and I worked together to understand attention and hopefully improve it in a variety of patients. Rehabilitation is also a goal of my current research to determine if non invasive stimuli can improve white matter in humans. We have found that fractional anisotropy (FA) is improved in pathways surrounding the anterior cingulate cortex (ACC) following two week to four weeks of meditation training. We hypothesized that the frontal theta increased following meditation training might be a cause of the improved connectivity. This was confirmed by a mouse study using optogenetics to impose theta rhythms in the ACC. We have evidence that electrical stimulation while performing a task that activates the ACC can also increase theta. We plan studies to determine whether two to four weeks of stimulation can improve FA in pathways surrounding the anterior cingulate.

A Corticothalamic Circuit for Dynamic Switching between Feature Detection and Discrimination.

Sensory processing must be sensitive enough to encode faint signals near the noise floor but selective enough to differentiate between similar stimuli. Here we describe a layer 6 corticothalamic (L6 CT) circuit in the mouse auditory forebrain that alternately biases sound processing toward hypersensitivity and improved behavioral sound detection or dampened excitability and enhanced sound discrimination. Optogenetic activation of L6 CT neurons could increase or decrease the gain and tuning precision in the thalamus and all layers of the cortical column, depending on the timing between L6 CT activation and sensory stimulation. The direction of neural and perceptual modulation - enhanced detection at the expense of discrimination or vice versa - arose from the interaction of L6 CT neurons and subnetworks of fast-spiking inhibitory neurons that reset the phase of low-frequency cortical rhythms. These findings suggest that L6 CT neurons contribute to the resolution of the competing demands of detection and discrimination.

Mechanisms of white matter change induced by meditation training.

Training can induce changes in specific brain networks and changes in brain state. In both cases it has been found that the efficiency of white matter as measured by diffusion tensor imaging is increased, often after only a few hours of training. In this paper we consider a plausible molecular mechanism for how state change produced by meditation might lead to white matter change. According to this hypothesis frontal theta induced by meditation produces a molecular cascade that increases myelin and improves connectivity.

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 (1000Hz pure tone), novel (familiar environmental sounds such as dog bark, buzz, car crashing sound and so on), and standard sounds (950Hz 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.

Theta oscillations orchestrate medial temporal lobe and neocortex in remembering autobiographical memories.

Remembering autobiographical events can be associated with detailed visual imagery. The medial temporal lobe (MTL), precuneus and prefrontal cortex are held to jointly enable such vivid retrieval, but how these regions are orchestrated remains unclear. An influential prediction from animal physiology is that neural oscillations in theta frequency may be important. In this experiment, participants prospectively collected audio recordings describing personal autobiographical episodes or semantic knowledge over 2 to 7 months. These were replayed as memory retrieval cues while recording brain activity with magnetoencephalography (MEG). We identified a peak of theta power within a left MTL region of interest during both autobiographical and General Semantic retrieval. This MTL region was selectively phase-synchronized with theta oscillations in precuneus and medial prefrontal cortex, and this synchrony was higher during autobiographical as compared to General Semantic knowledge retrieval. Higher synchrony also predicted more detailed visual imagery during retrieval. Thus, theta phase-synchrony orchestrates in humans the MTL with a distributed neocortical memory network when vividly remembering autobiographical experiences.

Alterations in the sense of time, space, and body in the mindfulness-trained brain: a neurophenomenologically-guided MEG study.

Meditation practice can lead to what have been referred to as "altered states of consciousness."One of the phenomenological characteristics of these states is a joint alteration in the sense of time, space, and body. Here, we set out to study the unique experiences of alteration in the sense of time and space by collaborating with a select group of 12 long-term mindfulness meditation (MM) practitioners in a neurophenomenological setup, utilizing first-person data to guide the neural analyses. We hypothesized that the underlying neural activity accompanying alterations in the sense of time and space would be related to alterations in bodily processing. The participants were asked to volitionally bring about distinct states of "Timelessness" (outside time) and "Spacelessness" (outside space) while their brain activity was recorded by MEG. In order to rule out the involvement of attention, memory, or imagination, we used control states of "Then" (past) and "There" (another place). MEG sensors evidencing alterations in power values were identified, and the brain regions underlying these changes were estimated via spatial filtering (beamforming). Particularly, we searched for similar neural activity hypothesized to underlie both the state of "Timelessness" and "Spacelessness." The results were mostly confined to the theta band, and showed that: (1) the "Then"/"There" overlap yielded activity in regions related to autobiographic memory and imagery (right posterior parietal lobule (PPL), right precentral/middle frontal gyrus (MFG), bilateral precuneus); (2) "Timelessness"/"Spacelessness" conditions overlapped in a different network, related to alterations in the sense of the body (posterior cingulate, right temporoparietal junction (TPJ), cerebellum); and (3) phenomenologically-guided neural analyses enabled us to dissociate different levels of alterations in the sense of the body. This study illustrates the utility of employing experienced contemplative practitioners within a neurophenomenological setup for scientifically characterizing a self-induced altered sense of time, space and body, as well as the importance of theta activity in relation with these altered states.

The topographical N170: electrophysiological evidence of a neural mechanism for human spatial navigation.

We recently demonstrated that the latency of a component of the event-related brain potential, the topographical N170 (NT170), is sensitive to the spatial location of reward-related stimuli in a virtual maze environment, occurring earlier for rewards found following rightward turns compared to leftward turns. We suggested that this NT170 latency effect may result from phase reset of an ongoing theta rhythm by a parahippocampal system for spatial navigation. Here we tested several predictions that follow from this proposal, namely, that the effect is observed only when the rewards are presented in a spatial environment, that it is sensitive to individual differences in spatial ability, that it is localizable to the right parahippocampal region, and that it is consistent with partial phase resetting of an ongoing theta rhythm. These results hold promise for integrating ERP measures of spatial navigation with extensive animal, human, and computational literatures on parahippocampal function.