ABSTRACT
Objective To study the feature of theta oscillation during working memory (WM) dysfunction in patients with mild cognitive impairment (MCI). Methods Fifteen MCI patients (MCI group) and 15 healthy subjects for checkup (control group) in Tianjin Medical University General Hospital from January to November 2016 were recruited. The differences of behavioral results in visual WM tasks were compared between the two groups. Thirty four-channel electroencephalogram (EEG) signals were recorded simultaneously. Short-Time Fourier transform was used to calculate spatial and time-frequency distribution of power and spectral coherence of multi-channel EEGs. Results Compared with control group, MCI group showed significantly longer reaction time and lower accuracy in WM tasks (P<0.01). The analysis of EEGs revealed that the power of Fz channel was the biggest at frontal midline in both groups. And the power density of theta oscillation was lower at frontal electrode sites in MCI group than that of control group ( P<0.01), and theta coherence was significantly decreased in frontal region and between frontal-posterior regions ( P<0.05). Conclusion The absence of theta oscillaton in frontal region may be one of the important reasons of working memory dysfunction for MCI.
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Objective To investigate the characteristic of theta oscillation in patients with frontal lobe epilepsy (FLE) by the analysis of multi-channel electroencephalographs (EEGs) during rest state and working memory(WM) maintenance. Methods The 19 FLE patients and 17 healthy subjects underwent EEG recording with 34-channel EEG machine during visual working memory task performance. The differences of behavioral results were analyzed between FLE group and controls. Short-time Fourier transform was used to calculate the power spectral density of different frequency bands in 34 channels. The theta power values during the retention period of working memory and rest state were compared between two groups. Results Compared with controls, reaction time of FLE increased significantly (P<0.01) and accuracy decreased (P<0.05). The power spectral density of theta band for FLE increased both in Fz and frontal region during rest state (P<0.01). Compared with controls, the power spectral density of theta oscillation decreased significantly in the frontal region for FLE during WM maintenance. Conclusion Our results suggest that working memory in patients with FLE was impaired. The absence of theta oscillation during the WM delayde period may provide a possible neural mechanism for the working memory dysfunction in FLE.
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Objective To observe changes in hippocampal network electrical activities in electroacupuncture regulation of abnormal cardiovascular activities and explore the central mechanism of the regulation. Method Experimental rats were randomized into three groups: normal urethane anesthesia without electroacupuncture (n=15), urethane enhanced deep anesthesia (n=9) and normal anesthesia plus anal canal pressurization (n=15). Femoral arterial pressure, cardiac electricity, hippocampal field potentials and cellular discharge were recorded in the three groups. The normal anesthesia group did not receive intervention measures. The other two groups received acupuncture intervention after successful induction of abnormal blood pressure. Result In rats with normal urethane anesthesia, sleep-like periodic hippocampal electrical activity occurred with periodic cardiovascular activities and theta oscillations was corresponding to increased heart rates. In rats with deep anesthesia and hypotension, theta oscillations appeared in hippocampal network with increased blood pressure and heart rates after electroacupuncture (P<0.001). Anal canal pressurization induced increases in blood pressure and heart rates and caused theta oscillations in hippocampal network. During that time, electroacupuncture could still activate theta-related cells, reduce blood pressure and decrease heart rates (P<0.001). Conclusion Theta oscillations in hippocampal network are involved in the bidirectional regulating effect of electroacupuncture on abnormal cardiovascular activities.
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Objective To study the effects of acute weak vagus nerve stimulation on hippocampal CA1 unit discharges and field potentials of normal and epileptiform discharging rats.Methods The experiments were performed with 55 male Sprague-Dawley rats weighing 180～250 g,SPF grade.Animals were divided into normal(n=45)and regularly epileptiform discharging(n=10)groups.The normal rat group:Separate the left neck vagus nerve and ligate the peripheral end.Acute weak electrical stimulation(10 Hz,0.5 ms,1.5～5.0 V,15～20 unit /train)were administered to the left neck vagus nerve central end.20 trains were performed with a regular interval of 5 min.Record the unit discharges of right hippocampal CA1 and field potentials of bilateral hippocampal CA1.The epileptiform discharging group:Gelatin spongia was put onto the left cortex to induce epileptiform discharges.After 30 min stable regularly discharging,continue the procedure in the first group.Results Cyclical theta oscillation(about 3～6.5 Hz)appeared in bilateral hippocampal CA1 of normal rats after the stimulation(strain m=5～7,38/45,84.4%).With oscillation,there is unit discharging.It has two kinds:theta-on(n=30)and theta-off(n=5).The sharp wave amplitude was inhibited while the sharp wave interval increased following the acute weak vagus nerve stimulation(n=10)in epileptiform discharging rats.Theta oscillation was induced during the sharp wave.With oscillation,there is tonic unit discharging(n=10).The number of action potential spikes positively correlate with the sharp wave intervals(P