The prefrontal cortex and hippocampus may support sequential working memory beyond episodic memory and spatial navigation. This stereoelectroencephalography (SEEG) study investigated how the dorsolateral prefrontal cortex (DLPFC) interacts with the hippocampus in the online processing of sequential information. Twenty patients with epilepsy (eight women, age 27.6 ± 8.2 years) completed a line ordering task with SEEG recordings over the DLPFC and the hippocampus. Participants showed longer thinking times and more recall errors when asked to arrange random lines clockwise (random trials) than to maintain ordered lines (ordered trials) before recalling the orientation of a particular line. First, the ordering-related increase in thinking time and recall error was associated with a transient theta power increase in the hippocampus and a sustained theta power increase in the DLPFC (3-10 Hz). In particular, the hippocampal theta power increase correlated with the memory precision of line orientation. Second, theta phase coherences between the DLPFC and hippocampus were enhanced for ordering, especially for more precisely memorized lines. Third, the theta band DLPFC → hippocampus influence was selectively enhanced for ordering, especially for more precisely memorized lines. This study suggests that theta oscillations may support DLPFC-hippocampal interactions in the online processing of sequential information.
Adult ; Female ; Humans ; Young Adult ; Epilepsy ; Hippocampus ; Memory, Short-Term ; Mental Recall ; Prefrontal Cortex ; Theta Rhythm ; Male

The hippocampus has been extensively implicated in spatial navigation in rodents and more recently in bats. Numerous studies have revealed that various kinds of spatial information are encoded across hippocampal regions. In contrast, investigations of spatial behavioral correlates in the primate hippocampus are scarce and have been mostly limited to head-restrained subjects during virtual navigation. However, recent advances made in freely-moving primates suggest marked differences in spatial representations from rodents, albeit some similarities. Here, we review empirical studies examining the neural correlates of spatial navigation in the primate (including human) hippocampus at the levels of local field potentials and single units. The lower frequency theta oscillations are often intermittent. Single neuron responses are highly mixed and task-dependent. We also discuss neuronal selectivity in the eye and head coordinates. Finally, we propose that future studies should focus on investigating both intrinsic and extrinsic population activity and examining spatial coding properties in large-scale hippocampal-neocortical networks across tasks.
Animals ; Humans ; Spatial Navigation/physiology* ; Hippocampus/physiology* ; Primates ; Neurons/physiology* ; Theta Rhythm/physiology*

Active exploratory behaviors have often been associated with theta oscillations in rodents, while theta oscillations during active exploration in non-human primates are still not well understood. We recorded neural activities in the frontal eye field (FEF) and V4 simultaneously when monkeys performed a free-gaze visual search task. Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials, and the phase-locking was dependent on saccade direction. The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response. V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases. Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing. Together, our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas, in addition to the theta phase locking caused by saccade-triggered responses.
Animals ; Frontal Lobe/physiology* ; Macaca mulatta ; Neurons/physiology* ; Saccades ; Theta Rhythm ; Visual Fields

Transcranial direct current stimulation (tDCS) has become a new method of post-stroke rehabilitation treatment and is gradually accepted by people. However, the neurophysiological mechanism of tDCS in the treatment of stroke still needs further study. In this study, we recruited 30 stroke patients with damage to the left side of the brain and randomly divided them into a real tDCS group (15 cases) and a sham tDCS group (15 cases). The resting EEG signals of the two groups of subjects before and after stimulation were collected, then the difference of power spectral density was analyzed and compared in the band of delta, theta, alpha and beta, and the delta/alpha power ratio (DAR) was calculated. The results showed that after real tDCS, delta band energy decreased significantly in the left temporal lobes, and the difference was statistically significant ( P < 0.05); alpha band energy enhanced significantly in the occipital lobes, and the difference was statistically significant ( P < 0.05); the difference of theta and beta band energy was not statistically significant in the whole brain region ( P > 0.05). Furthermore, the difference of delta, theta, alpha and beta band energy was not statistically significant after sham tDCS ( P > 0.05). On the other hand, the DAR value of stroke patients decreased significantly after real tDCS, and the difference was statistically significant ( P < 0.05), and there was no significant difference in sham tDCS ( P > 0.05). This study reveals to a certain extent the neurophysiological mechanism of tDCS in the treatment of stroke.
Brain/physiopathology* ; Brain Waves/physiology* ; Electroencephalography/methods* ; Humans ; Stroke/therapy* ; Stroke Rehabilitation/methods* ; Transcranial Direct Current Stimulation/methods*

Transcranial magneto-acoustic-electrical stimulation is a new non-invasive neuromodulation technology, in which the induced electric field generated by the coupling effect of ultrasound and static magnetic field are used to regulate the neural rhythm oscillation activity in the corresponding brain region. The purpose of this paper is to investigate the effects of transcranial magneto-acoustic-electrical stimulation on the information transfer and communication in neuronal clusters during memory. In the experiment, twenty healthy adult Wistar rats were randomly divided into a control group (five rats) and stimulation groups (fifteen rats). Transcranial magneto-acoustic-electrical stimulation of 0.05~0.15 T and 2.66~13.33 W/cm ² was applied to the rats in stimulation groups, and no stimulation was applied to the rats in the control group. The local field potentials signals in the prefrontal cortex of rats during the T-maze working memory tasks were acquired. Then the coupling differences between delta rhythm phase, theta rhythm phase and gamma rhythm amplitude of rats in different parameter stimulation groups and control group were compared. The experimental results showed that the coupling intensity of delta and gamma rhythm in stimulation groups was significantly lower than that in the control group ( P<0.05), while the coupling intensity of theta and gamma rhythm was significantly higher than that in the control group ( P<0.05). With the increase of stimulation parameters, the degree of coupling between delta and gamma rhythm showed a decreasing trend, while the degree of coupling between theta and gamma rhythm tended to increase. The preliminary results of this paper indicated that transcranial magneto-acoustic-electrical stimulation inhibited delta rhythmic neuronal activity and enhanced the oscillation of theta and gamma rhythm in the prefrontal cortex, thus promoted the exchange and transmission of information between neuronal clusters in different spatial scales. This lays the foundation for further exploring the mechanism of transcranial magneto-acoustic-electrical stimulation in regulating brain memory function.
Acoustics ; Animals ; Electric Stimulation ; Memory, Short-Term/physiology* ; Rats ; Rats, Wistar ; Theta Rhythm/physiology* ; Transcranial Direct Current Stimulation

The present study was aimed to explore the correlation between θ-γ neural oscillations phase-amplitude coupling (PAC) in hippocampal CA3 area and the changes of spatial identifying and cognitive ability before and after shock avoidance training in rats. According to the results of Y-type maze shock avoidance training, the rats were divided into two groups: the fast avoidance response group and the general avoidance response group. The local field potential (LFP) of hippocampal CA3 area was recorded by wireless telemetry before and after shock avoidance training. The variation of θ oscillation (3-7 Hz) and low-γ neural oscillation (30-60 Hz) PAC in hippocampal CA3 area was analyzed by MATLAB wavelet packet extraction technique. The results showed that, compared with the general avoidance response group, the fast avoidance response group exhibited higher θ-γ neural oscillation PAC in hippocampal CA3 area before training. θ-γ oscillation PAC in hippocampal CA3 area was increased in both groups after training. It was also noticed that θ-γ neural oscillation PAC of some frequency bands in the general avoidance response group were significantly higher than those in the fast avoidance response group. The results suggest that certain intensity of training can change the spatial identifying and cognitive ability of rats, and the mechanism may involve the increase of the synchrony of θ-γ neural oscillation, i.e., the enhancement of θ-γ phase-amplitude alternating frequency coupling in hippocampal neurons.
Animals ; Cognition ; Hippocampus ; Neurons ; Rats ; Theta Rhythm

The thalamostriatal pathway is implicated in Parkinson's disease (PD); however, PD-related changes in the relationship between oscillatory activity in the centromedian-parafascicular complex (CM/Pf, or the Pf in rodents) and the dorsal striatum (DS) remain unclear. Therefore, we simultaneously recorded local field potentials (LFPs) in both the Pf and DS of hemiparkinsonian and control rats during epochs of rest or treadmill walking. The dopamine-lesioned rats showed increased LFP power in the beta band (12 Hz-35 Hz) in the Pf and DS during both epochs, but decreased LFP power in the delta (0.5 Hz-3 Hz) band in the Pf during rest epochs and in the DS during both epochs, compared to control rats. In addition, exaggerated low gamma (35 Hz-70 Hz) oscillations after dopamine loss were restricted to the Pf regardless of the behavioral state. Furthermore, enhanced synchronization of LFP oscillations was found between the Pf and DS after the dopamine lesion. Significant increases occurred in the mean coherence in both theta (3 Hz-7 Hz) and beta bands, and a significant increase was also noted in the phase coherence in the beta band between the Pf and DS during rest epochs. During the treadmill walking epochs, significant increases were found in both the alpha (7 Hz-12 Hz) and beta bands for two coherence measures. Collectively, dramatic changes in the relative LFP power and coherence in the thalamostriatal pathway may underlie the dysfunction of the basal ganglia-thalamocortical network circuits in PD, contributing to some of the motor and non-motor symptoms of the disease.
Animals ; Brain Waves ; physiology ; Corpus Striatum ; physiopathology ; Cortical Synchronization ; physiology ; Dopaminergic Neurons ; physiology ; Electrocorticography ; Male ; Neural Pathways ; physiopathology ; Oxidopamine ; Parkinsonian Disorders ; physiopathology ; Rats, Wistar ; Thalamic Nuclei ; physiopathology ; Walking ; physiology

Stereo-electroencephalography (SEEG) is widely used to record the electrical activity of patients' brain in clinical. The SEEG-based epileptogenic network can better describe the origin and the spreading of seizures, which makes it an important measure to localize epileptogenic zone (EZ). SEEG data from six patients with refractory epilepsy are used in this study. Five of them are with temporal lobe epilepsy, and the other is with extratemporal lobe epilepsy. The node outflow (out-degree) and inflow (in-degree) of information are calculated in each node of epileptic network, and the overlay between selected nodes and resected nodes is analyzed. In this study, SEEG data is transformed to bipolar montage, and then the epileptic network is established by using independent effective coherence (iCoh) method. The SEEG segments at onset, middle and termination of seizures in Delta, Theta, Alpha, Beta, and Gamma rhythms are used respectively. Finally, the K-means clustering algorithm is applied on the node values of out-degree and in-degree respectively. The nodes in the cluster with high value are compared with the resected regions. The final results show that the accuracy of selected nodes in resected region in the Delta, Alpha and Beta rhythm are 0.90, 0.88 and 0.89 based on out-degree values in temporal lobe epilepsy patients respectively, while the in-degree values cannot differentiate them. In contrast, the out-degree values are higher outside the temporal lobe in the patient with extratemporal lobe epilepsy. Based on the out-degree feature in low-frequency epileptic network, this study provides a potential quantitative measure for identifying patients with temporal lobe epilepsy in clinical.
Brain Waves ; Electroencephalography ; Epilepsy, Temporal Lobe ; diagnosis ; Humans

OBJECTIVES: Insomnia is one of the most prevalent sleep disorders. Recent studies suggest that cognitive and physical arousal play an important role in the generation of primary insomnia. Studies have also shown that information processing disorders due to cortical hyperactivity might interfere with normal sleep onset and sleep continuity. Therefore, focusing on central nervous system arousal and normalizing the information process have become current topics of interest. It has been well known that neurofeedback can reduce the brain hyperarousal by modulating patients' brain waves during a sequence of behavior therapy. The purpose of this study was to investigate effects of neurofeedback therapy on electroencephalography (EEG) characteristics in patients with primary insomnia. METHODS: Thirteen subjects who met the criteria for an insomnia diagnosis and 14 control subjects who were matched on sex and age were included. Neurofeedback and sham treatments were performed in a random order for 30 minutes, respectively. EEG spectral power analyses were performed to quantify effects of the neurofeedback therapy on brain wave forms. RESULTS: In patients with primary insomnia, relative spectral theta and sigma power during a therapeutic neurofeedback session were significantly lower than during a sham session (13.9 ± 2.6 vs. 12.2 ± 3.8 and 3.6 ± 0.9 vs. 3.2 ± 1.0 in %, respectively; p < 0.05). There were no statistically significant changes in other EEG spectral bands. CONCLUSION: For the first time in Korea, EEG spectral power in the theta band was found to increase when a neurofeedback session was applied to patients with insomnia. This outcome might provide some insight into new interventions for improving sleep onset. However, the treatment response of insomniacs was not precisely evaluated due to limitations of the current pilot study, which requires follow-up studies with larger samples in the future.
Arousal ; Automatic Data Processing ; Behavior Therapy ; Brain ; Brain Waves ; Central Nervous System ; Diagnosis ; Electroencephalography ; Follow-Up Studies ; Humans ; Korea ; Neurofeedback ; Pilot Projects ; Sleep Initiation and Maintenance Disorders ; Sleep Wake Disorders

In 1924, Hans Berger, a German psychiatrist, recorded the brain waves from a human brain for the first time. Many advances have been made in this field since then. Currently, brain waves are generated by a variety of computer technologies, including brain computer interface technology, and robot or artificial intelligence technology has also made amazing progress. A mental health practitioner who deals with brain-related medicine has an obligation and responsibility to research and find clinical applications of brain waves because they contain a great deal of information hidden in the brain. Therefore, understanding the basics of electroencephalography will contribute to a determination and resolution of various clinical situations. This review discusses basic knowledge before dealing with brain waves. In addition to a visual inspection of general brain waves, quantitative analysis of brain waves is expected to become an important area of interest for mental health practitioners.
Artificial Intelligence ; Brain ; Brain Mapping ; Brain Waves ; Brain-Computer Interfaces ; Electroencephalography ; Humans ; Mental Health ; Psychiatry