Acute ethanol enhances septohippocampal coordination but disrupts intrinsic hippocampal theta dynamics during foraging.

Propagation of infra-slow and slow brain activities in electroencephalogram related to behavioral information processing.

Modulation of motor cortical theta and gamma oscillations using phase-targeted, closed-loop optogenetic stimulation of local excitatory and inhibitory neurons.

The flexible handling of perception-action representations is crucial for cognitive control such as response inhibition, which depends on the catecholaminergic system. However, how cross-frequency interactions support perception-action integration during response inhibition, and how they are modulated by catecholamines, remains unknown. In this placebo-controlled study employing methylphenidate, using electroencephalography (EEG) and a modified Go/Nogo task, we investigate phase-amplitude coupling (PAC) between theta (θ), alpha (α), beta (β), and gamma (γ) oscillations. We demonstrate that these interactions are hierarchically organized, with early α-β PAC supporting perceptual-motor representation, and subsequent β-γ coupling refining downstream processing. Transfer entropy analyses indicate a feed-forward α-β to β-γ influence, suggesting that slower oscillations gate updates in faster bands. Crucially, methylphenidate selectively enhances late β-γ coupling, supporting a functional specialization where α-β rhythms enable access and reconfiguration, while β-γ rhythms mediate local control. These findings suggest a temporally structured mechanism where the catecholaminergic system modulates flexible perception-action integration during response inhibition.

There is growing interest in non-invasive brain stimulation (NIBS) as a safe and practical method to support cognitive function during ageing. NIBS using rhythmic sensory stimuli entrains brain oscillations and synchronizes functional networks, but the choice of NIBS frequency to enhance performance in cognitive tasks remains unclear. We adopt a network neuroscience approach to NIBS, linking network connectivity, EEG oscillatory frequencies and behavioural performance to test the effects of personalized rhythmic auditory stimulation (RAS) on an inhibitory control task (Simon task) in older adults aged 60-75 years. Simon task trials were preceded by ≈1.7-3.2 s of personalized RAS (clicks) at each individual's theta oscillation frequency (fθ), a slightly faster variant (fθ+), a fixed low-frequency control at 2 Hz (f2Hz) or a non-rhythmic control (NR). Reaction times (RTs) after personalized stimulation were faster than f2Hz and NR, with stronger brain entrainment to rhythmic stimulation linked to faster RTs. Task-related EEG signals showed enhanced attentional processes and more efficient cortical responses following the personalized stimulation. Individuals with lower baseline performance had the greatest benefits. The findings suggest personalized RAS enhances cognitive performance in ageing and provides a cost-effective neurorehabilitation approach to mitigate age-related cognitive decline.

Prior EEG research has shown that during working memory, alpha (8 to 14 Hz) and theta (4 to 8 Hz) oscillations tend to form a 2:1 frequency ratio. According to the Binary Hierarchy Brain Body Oscillation Theory (BHBBOT), a recent model grounded in mathematical analysis, this cross-frequency configuration reflects enhanced connectivity between brain regions generating these rhythms. However, this prediction has not yet been empirically tested. In this study, we leveraged high density EEG, source localization and connectivity metrics derived from Information Theory (IT) and the Theory of Weakly Coupled Oscillators (TWCO) to examine whether the previously observed alpha-theta cross-frequency dynamics during working memory are accompanied by changes in connectivity. Our results show that a significant increase in the proportion of 2:1 ratios between regions generating frontal theta and parietal alpha rhythms was accompanied by relative decreases in connectivity, as revealed by both IT and TWCO metrics. Furthermore, phase synchrony between these two regions was significantly reduced during working memory and correlated negatively with behavioral performance. In conclusion, our results show that the increased occurrence of 2:1 alpha:theta cross-frequency ratios during working memory reflects functional segregation (rather than integration) and therefore directly challenges some of the predictions of the BHBBOT.

Frontal midline theta oscillations are key neural markers for learning, set-shifting, and adaptive behavior, signaling cognitive control and the reorganization of neural representations. The present study explored how these oscillations mediate the extraction and updating of statistical regularities. We delivered 6-Hz in-phase or sham transcranial alternating current stimulation, synchronizing frontal midline theta during an eye-tracking probabilistic sequence learning task designed to test cognitive flexibility and assess changes in pre-stimulus gaze direction. A novel probabilistic sequence with a partially overlapping structure was introduced that allowed us to distinguish between the retention of old sequences and the acquisition of new ones. Following comparable statistical learning in both groups during the stimulation session, our results showed that frontal midline theta synchronization enhances the adaptation of predictive processes shown by the reduction of erroneous anticipations of previously learned regularities and more flexible anticipation of novel regularities. These results suggest a role of frontal midline theta in the flexible rewiring of the mental representations of prior probabilistic structures and in making predictions more accurate.

Flow is a psychological state of deep immersion and engagement associated with enhanced performance and well-being, yet its neural correlates remain poorly understood. Here, we investigated whether flow is experienced during Memphis Jookin’, a street dance style originating in Memphis, Tennessee, and examined its behavioral and neurophysiological signatures. Professional Memphis Jookers (N = 6) completed validated self-report measures assessing flow, interoceptive awareness, and embodied responses to movement. Two participants wore 32-electrode electroencephalography (EEG) systems while engaging in choreographed and improvised dance, observing other dancers, and resting state. Independent components were localized using dipole modeling for one participant, with spectral parameterization and functional connectivity assessed. Dancers reported high levels of trait and state flow and demonstrated elevated interoceptive awareness compared to individuals trained in other mind–body practices. Theta-band activity was prominent during dance across regions including the posterior cingulate gyri, inferior temporal gyrus, middle occipital gyrus, paracentral lobule, supplementary motor area, and Rolandic operculum. Resting-state functional connectivity increased after dance across theta, alpha, beta, and gamma frequency bands. Together, these findings suggest that street dance elicits robust flow states accompanied by distinct patterns of large-scale brain activity and connectivity, highlighting dance as an embodied practice with translational relevance for health and well-being.

The enjoyment of music involves a complex interplay between brain perceptual areas and the reward network. While previous studies have shown that musical liking is related to an enhancement of synchronization between the right temporal and frontal brain regions via theta frequency band oscillations, the underlying mechanisms of this interaction remain elusive. Specifically, a causal relationship between theta oscillations and musical pleasure has yet to be shown. In the present study, we address this question by using transcranial alternating current stimulation (tACS). Twenty-four participants underwent three different sessions where they received tACS over the right auditory cortex before listening to and rating a set of melodies selected to vary in familiarity and complexity. In the target session, participants received theta stimulation, while in the other two sessions, they received beta and sham stimulation, serving as controls. We recorded brain activity using EEG during task performance to confirm the effects of tACS on oscillatory activity. Results revealed that compared with sham, theta, but not beta, stimulation resulted in higher liking ratings specifically for unfamiliar music with low complexity. In addition, we found increased theta connectivity between the right temporal and frontal electrodes for these stimuli when they were most liked after theta stimulation but not after beta stimulation. These findings support a causal and frequency-specific relationship between music hedonic judgments and theta oscillatory mechanisms that synchronize the right temporal and frontal areas. These mechanisms play a crucial role in different cognitive processes supported by frontotemporal loops, such as auditory working memory and predictive processing, which are fundamental to music reward processing.

Neural reinstatement and sequential reactivation of navigational episodic memory and its age-related decline.

Theta-paced stimulation of the thalamic nucleus reuniens entrains mPFC-HPC oscillations and facilitates the acquisition of extinction memories.

Now you recall it, now you don't: Working memory performance fluctuates with a theta rhythm.

Behavioral theta oscillations in cross-modal stimulus conflict and response conflict processing

The current randomized controlled trial (RCT) examined both immediate and long-term effects of five consecutive bifrontal tACS sessions on verbal WM functioning in 30 healthy adult participants. WM performance and event-related quantitative electroencephalography (qEEG) parameters (mean power of frontal theta oscillations during three different WM events) were noted at baseline, immediately after tACS intervention, and at four-week post intervention. In comparison to the sham-tACS group, WM performance in active tACS group was improved following a four-week post-intervention period across all WM events, but not immediately after tACS intervention. Left prefrontal theta power in the active group decreased immediately after the intervention (in comparison to baseline) and remained low at four weeks, while the sham group returned to high theta-power baseline levels. Additionally, at four weeks post-intervention, participants in the active group demonstrated higher episodic memory accuracy compared to the sham group, which was associated with lower frontal theta power during WM encoding events. These findings are consistent with the hypothesized long-term plasticity effects. The current results highlight the role of event-related prefrontal theta power modulation in enhancing verbal WM and episodic memory retrieval in humans acutely, and over time.

BackgroundHealthy aging and cognitive decline in Alzheimer's Disease (AD) and its precursor, Mild Cognitive Impairment (MCI), are linked to changes in resting‐state EEG power spectral density (PSD). Theta band (3‐7 Hz) power decreases with normal aging but increases with cognitive decline. However, frequency content does not always indicate true oscillatory activity. Oscillations reflect power concentration at a specific frequency, appearing as peaks in the frequency domain and visible rhythms in the time domain. Rhythmicity analysis quantifies oscillation persistence (percentage of time observed) independently of power. This study examined Theta power and Theta rhythms in healthy controls (HC) versus individuals with MCI/AD.MethodParticipants included 32 AD, 88 MCI, and 115 and age‐ matched HC, who completed 5‐minutes of resting‐state eyes‐closed EEG at their baseline visit. PSD was computed for one‐second epochs. Relative Theta power was defined as the proportion of total power in the Theta band, averaging across epochs. Theta rhythm duration was defined as the percentage of epochs with Theta oscillations. Baseline differences and longitudinal changes were analyzed for a subset of participants: 28 MCI and 5 AD with at least one follow‐up visit, and 25 HC with at least two follow‐ups.ResultAt baseline, the MCI/AD group exhibited significantly higher relative Theta power (p <0.01, df=233, ES=0.35 at T6) and a greater Theta rhythm duration (p <0.01, df=231, ES=0.41 at T6) compared to HC. Longitudinally, HC exhibited a significant reduction in Theta power by the second follow‐up (p <0.05, df=24, ES=0.51 at Cz), with no significant changes in Theta rhythms duration. In contrast, MCI/AD showed a significant increase in Theta rhythm duration (and not power) at first follow‐up visit (p < 0.05, df =32, ES=0.30 at T3).ConclusionTheta power and Theta rhythm duration are both linked to cognitive decline in MCI and AD but differ from healthy aging patterns. While Theta power reflects age‐related changes, Theta rhythms duration may serve as a specific biomarker for disease progression in MCI and AD. These findings support the value of Rhythmicity analysis in EEG‐based biomarkers of cognitive decline.

40 Hz light flicker stimulation is deemed to hold considerable promise in the treatment of Alzheimer's disease (AD). However, whether its long-term effect can improve working memory and its related mechanisms remains to be further explored. In this study, 21 adult Wistar rats were randomly divided into the AD light-stimulation group, the AD group and the control group. AD models were established in the first two of these groups, with the light-stimulation group receiving long-term 40 Hz light flicker stimulation. Working memory performance across groups was subsequently evaluated using the T-maze task. To investigate the potential neural mechanisms underlying the effects of 40 Hz light stimulation on working memory, we examined changes in neuronal excitability within the hippocampus (HPC) and medial prefrontal cortex (mPFC), as well as alterations in inter-regional synchronization of neural activity. The findings demonstrated that prolonged 40 Hz light stimulation significantly improved working memory performance in AD model rats. Furthermore, the intervention enhanced the synchronization of neural activity between the hippocampus (HPC) and medial prefrontal cortex (mPFC), as well as the efficiency of information transfer, primarily mediated by theta and low-frequency gamma oscillations. This study provides theoretical support for exploring the mechanisms of 40 Hz light flicker stimulation and its further clinical application in the prevention and treatment of Alzheimer's disease.

Significant cognitive impairment follows cardiac arrest, yet few interventions restore memory. We previously demonstrated that physical exercise (PE) after asphyxial cardiac arrest (ACA) mitigates memory deficits and cell loss in the septal nuclei, but not in the hippocampus in rats. Given the critical role of the septum in modulating hippocampal theta oscillations, essential for memory, we hypothesize that PE preserves memory by safeguarding septal pacemaker neurons and septo-hippocampal theta activity. Adult male and female rats underwent 8 minutes of ACA or sham surgery and were randomly assigned to 5 days of treadmill running (PE) or sedentary conditions. Long- and short-term memory were assessed using fear conditioning and Y-maze tests. Immunohistochemistry quantified septal cholinergic and gamma-aminobutyric acid-ergic neurons. Local field potential recordings evaluated oscillatory activity across the septo-hippocampal network. ACA induced persistent deficits in memory and disrupted theta oscillations throughout the septum and CA1 laminae. These changes were accompanied by selective loss of cholinergic and gamma-aminobutyric acid-ergic septal neurons. PE markedly improved cognitive performance and restored theta power across the septo-hippocampal axis. Only cholinergic, not gamma-aminobutyric acid-ergic, neurons were preserved after PE. All effects were consistent across sexes. Importantly, enhancements in CA1 theta power closely tracked behavioral recovery, implying that reestablishment of cholinergic-driven network dynamics plays a central role in memory restoration. This study is the first to directly implicate PE-induced cholinergic neuron preservation in the reengagement of septo-hippocampal circuitry and cognitive recovery postcardiac arrest. Rather than relying on hippocampal cell survival, the observed memory improvements appear to stem from reinstated interregional theta synchrony. These findings define a novel mechanistic pathway for promoting functional recovery via targeted circuit-level rehabilitation after ischemic brain injury.

ABSTRACTAfter fear conditioning, repeated presentation of the conditioned stimulus (CS) alone produces a context‐dependent extinction of learned fear. The hippocampus has a critical role in this process, but the mechanism by which contextual information encoded by the hippocampus leads to fear suppression is unknown. We hypothesize that contextual information encoded by the dorsal hippocampus supports the recall of extinction memory by the medial prefrontal cortex (mPFC). To test this hypothesis, we evaluated the oscillatory coherence and directional coupling of the hippocampus and mPFC during context‐dependent extinction retrieval in a previously published experiment. In this experiment, male and female rats were subjected to auditory fear conditioning followed by fear extinction and extinction retrieval procedures. Previous analyses focused on oscillatory coupling during the CS; here, we performed new analyses to assess hippocampal‐prefrontal coupling in the context in which extinction occurred. We found that, after extinction, re‐exposing the animals to the extinction context produces a marked increase in dorsal hippocampal theta (6–8 Hz) oscillations. This increase was associated with enhanced coherence between the dHPC and the prelimbic (PL), but not the infralimbic (IL), division of the mPFC. Moreover, Granger causality analyses revealed that hippocampal theta oscillations preceded theta in the PL throughout the extinction retrieval session. This effect emerged during exposure to the extinction context and persisted during the presentation of the CSs and the expression of freezing behavior. Interestingly, this pattern of coherence was not observed between the dHPC and the IL. These results suggest that oscillatory coupling between the dorsal hippocampus and PL facilitates the context‐dependent retrieval of the extinguished fear memory.

Effects of theta tACS on tactile texture memory consolidation.

Longitudinal brain-wide recordings reveal early neurophysiological alterations in memory-impaired mice.