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Objective:To investigate the effects of 40 Hz and 70 Hz frequency flash stimulation on the ability of learning memory and autonomous exploratory in young rats.Methods:Twenty-seven SPF grade male SD rats aged 19-21 days were divided into control group (Ctr group), 40 Hz group and 70 Hz group with 9 in each group according to the random number table.The rats in Ctr group were not given flash stimulation, while rats in the 40 Hz and 70 Hz group were received 40 Hz, 70 Hz flash stimulation (1.5 h/d for 39 days), respectively.The Morris water maze experiment was used to assess the learning and memory ability of rats, and the open field experiment was used to evaluate the ability of autonomous exploratory of rats.Nissl staining was used to assess the morphology of Nissl bodies in the hippocampus CA1 region of the rats.The local field potentials (LFPs) collected from the primary visual cortex (V1 area) region by electrophysiological experiments was used to verify the synchronization of flash evoked neural oscillations.SPSS 23.0 software was used for statistical analysis.The repeated measures ANOVA and one-way ANOVA were used to analyze normal distribution measurement data, and LSD and Tamhane tests were used for further pairwise comparison.The Kruskal-Wallis test was used for non-normal distribution measurement data.Results:(1) The flash stimulation of 40 Hz and 70 Hz both can effectively caused synchronization of neural oscillations in the primary visual cortex of healthy young rats.(2) The results of repeated measures ANOVA analysis showed that there was no interaction effect of grouping and time in the escape latency of young rats in the Morris water maze positioning navigation phase( F=1.326, P>0.05 ). The escape latency had time main effect ( F=40.025, P<0.05), but no grouping main effect ( F=2.039, P>0.05). With the increase of learning days, the escape latency of young rats in each group decreased significantly.There was no interaction effect of grouping and time in the total distance of young rats ( F=2.029, P>0.079). It had time main effect ( F=32.052, P<0.05), but not grouping main effect ( F=2.390, P>0.05) on total distance.With the increase of learning days, the total distance of young rats in each group significantly shortened.On the 6th day of the Morris water maze experiment, there was no statistically significant difference among groups in terms of time in the target quadrant and the number of crossing platforms ( F=2.511, 0.802, both P>0.05). The results of the open field experiment showed that the total distance traveled in the center of young rats in each group was statistically significant ( H=8.935, P<0.05), the total distance traveled in the center in the 70 Hz group (3.80 (2.25, 6.93) m)was significantly longer than that in the 40 Hz group (0.80 (0.72, 1.46) m), P<0.05). The percentage of time spent in the center was statistically significant in the three groups ( H=11.050, P<0.05). Young rats in the 70 Hz group spent significantly higher percentage of time in the center(3.20(2.43, 8.30)) than those in the 40 Hz group (0.95 (0.37, 1.06 ), P<0.05 ). (3) Nissl staining results showed that Nissl bodies in the hippocampal CA1 area of young rats in Ctr, 40 Hz and 70 Hz group were all arranged neatly and tightly, no edema was found in the surrounding stroma, and no obvious inflammatory cell infiltration was found. Conclusion:70 Hz frequency flash stimulation may promote the ability of learning memory and autonomous exploratory of young rats.
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Objective:To investigate the synchronized feature patterns of local field potentials in the hippocampus (HPC) and prefrontal cortex (PFC) during working memory based on time-varying spectral coherence so as to support the study of information processing mechanisms in working memory.Methods:The local field potentials (LFPs) signals of the ventral hippocampus (vHPC) and medial prefrontal cortex (mPFC) were collected from six SD rats during the performance of a spatial working memory task in the Y-maze, and the time-frequency distributions of vHPC and mPFC LFPs were calculated by applying the short-time Fourier transform (STFT) to determine the characteristic frequency bands of the working memory and then to investigate the synchronized patterns of vHPC and mPFC LFPs based on the coherent of the time-varying frequency spectrum. Finally, support vector machines were applied to explore the feasibility of applying spectral coherence values to predict working memory.Results:When rats performed working memory tasks correctly, the energy of the theta band (4 - 12 Hz) of the HPC and PFC increased (all P < 0.01), and the spectral coherence value of the theta band of the HPC-PFC increased ( P < 0.05). Support vector machine training and prediction using the average peak spectral coherence and the difference between the peak and the onset when correctly and incorrectly executing the working memory as features resulted in 89% accuracy, 90% precision, 88% recall, and 88% F1 scores, all of which were statistically significant differences compared to the results of the randomly disrupted labeled data rearranging (all P < 0.05). Conclusions:Synchronized synergy in the HPC-PFC theta band is one of the potential mechanisms for correctly performing information processing in working memory.
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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.
Subject(s)
Animals , Rats , Acoustics , Electric Stimulation , Memory, Short-Term/physiology , Rats, Wistar , Theta Rhythm/physiology , Transcranial Direct Current StimulationABSTRACT
Objective:To investigate the effects of high frequency repetitive transcranial magnetic stimulation (rTMS) on learning memory and neuroelectric activity in rats. Methods:Eight Wistar rats were randomly divided into control group (n = 4) and rTMS group (n = 4). rTMS group was stimulated 14 days by rTMS with the frequency of 5 Hz, and the stimulation intensity was 100% motor threshold. The control group did not accepted rTMS. Then, the 16 channel local field potentials (LFPs) and spikes were recorded from their prefrontal cortex (PFC) in each group during the working memory tasks. The time-frequency analysis based on the short-time Fourier transform was performed on the LFPs, and the spike was analyzed by the release rate method. Multitaper Spectral Coherence was used to analyze the Synchronization Degree of LFPs-spike. Results:In the working memory experiment, rTMS group needed less days than the control group to reach the task correction criterion (t = 2.51, P = 0.046). The energy intensity of the θ-band and γ-band of the LFPs was significantly higher in rTMS group than in the control group (t > 12.49, P < 0.001), θ-band and γ-band LFPs-spike were more synchronized (t > 8.82, P < 0.001), but there was no significant difference in the average rate of spike between groups (t = 1.73, P = 0.067). Conclusion:High frequency rTMS could increase the LFPs energy in working memory experiment, enhance cooperative coding process for LFPs and spike, and improve the working memory ability of the rats.
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Repetitive transcranial magnetic stimulation(rTMS) is a painless and non-invasive method for stimulation and modulation in the field of cognitive neuroscience research and clinical neurological regulation. In this paper, adult Wistar rats were divided into the rTMS group and control group randomly. Rats in the rTMS group were stimulated with 5 Hz rTMS for 14 days, while the rats in the control group did not accept any stimulation. Then, the behavior and local field potentials (LFPs) were recorded synchronously when the rats perform a working memory (WM) task with T-maze. Finally, the time-frequency distribution and coherence characteristics of the LFPs signal in the prefrontal cortex (PFC) during working memory task were analyzed. The results showed that the rats in the rTMS group needed less training days to reach the task correction criterion than the control group (
Subject(s)
Animals , Rats , Memory, Short-Term , Neurons , Prefrontal Cortex , Rats, Wistar , Transcranial Magnetic StimulationABSTRACT
Motor timing is an important part of sensorimotor control. Previous studies have shown that beta oscillations embody the process of temporal perception in explicit timing tasks. In contrast, studies focusing on beta oscillations in implicit timing tasks are lacking. In this study, we set up an implicit motor timing task and found a modulation pattern of beta oscillations with temporal perception during movement preparation. We trained two macaques in a repetitive visually-guided reach-to-grasp task with different holding intervals. Spikes and local field potentials were recorded from microelectrode arrays in the primary motor cortex, primary somatosensory cortex, and posterior parietal cortex. We analyzed the association between beta oscillations and temporal interval in fixed-duration experiments (500 ms as the Short Group and 1500 ms as the Long Group) and random-duration experiments (500 ms to 1500 ms). The results showed that the peak beta frequencies in both experiments ranged from 15 Hz to 25 Hz. The beta power was higher during the hold period than the movement (reach and grasp) period. Further, in the fixed-duration experiments, the mean power as well as the maximum rate of change of beta power in the first 300 ms were higher in the Short Group than in the Long Group when aligned with the Center Hit event. In contrast, in the random-duration experiments, the corresponding values showed no statistical differences among groups. The peak latency of beta power was shorter in the Short Group than in the Long Group in the fixed-duration experiments, while no consistent modulation pattern was found in the random-duration experiments. These results indicate that beta oscillations can modulate with temporal interval in their power mode. The synchronization period of beta power could reflect the cognitive set maintaining working memory of the temporal structure and attention.
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The possible influence of electromagnetic field (EMF) on the function of neural systems has been widely concerned. In this article, we intend to investigate the effects of long term power frequency EMF exposure on brain cognitive functions and it's mechanism. The Sprague-Dawley (SD) rats were randomly divided into 3 groups: the rats in EMF Ⅰ group were placed in the 2 mT power frequency EMF for 24 days. The rats in EMF Ⅱ group were placed in the 2 mT power frequency EMF for 48 days. The rats in control group were not exposed to the EMF. Then, the 16 channel local field potentials (LFPs) were recorded from rats' prefrontal cortex (PFC) in each group during the working memory (WM) tasks. The causal networks of LFPs were also established by applying the directed transfer function (DTF). Based on that, the differences of behavior and the LFPs network connection patterns between different groups were compared in order to investigate the influence of long term power frequency EMF exposure on working memory. The results showed the rats in the EMF Ⅱ group needed more training to reach the task correction criterion (over 80%). Moreover, the causal network connection strength and the global efficiency of the rats in EMF Ⅰ and EMF Ⅱ groups were significantly lower than the corresponding values of the control group. Meanwhile, significant differences of causal density values were found between EMF Ⅱ group and the other two groups. These results indicate that long term exposure to 2 mT power frequency EMF will reduce the connection strength and the information transfer efficiency of the LFPs causal network in the PFC, as well as the behavior performance of the rats. These results may explain the effect of EMF exposure on working memory from the view of neural network connectivity and provide a support for further studies on the mechanism of the effect of EMF on cognition.
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Objective Toinvestigatetheentropyoflocalfieldpotentials(LFPs)recordedinratmedialprefrontal cortex during a Y-maze working memory (WM) task, to provide computing support for neural coding mechanism.Methods Sixteen-channel LFPs were recorded from SD rats while they performed a Y-maze WM task.The data came from 4 rats, 20 trials (10 correct trials and 10 incorrect trials) per rat provided by laboratory of neurobiology in medicine,Tianjin Medical University.Original LFPs were preprocessed to remove 50 Hz power line noise and baseline drift.Multi-taper Fourier transform was applied to calculate spatial distributions of LFPs and band pass filter were used to extract characteristic signal.The entroy coding of 16 channel LFPs was as follows: the physiological window was set to be 500 ms, the step length of physiological window was set to be 125 ms, windows were added to LFPs data, and then LFPs entropy of each sliding window was computed and averaged to get the trend of multichannel entropy values duringthe WM task.Results The power of θ band (4-12 Hz) in LFPs increased.The averaged entropy value ofmultichannel θ band LFPs in correct trials was 0.939±-0.020, which were larger than those in the resting state, 0.795±0.031 (P＜0.05).Those during wrong WM task had no significant difference, which didn't encode the WM task.Conclusions The principal frequency band related to WM is the θ band and LFPs entropy encodes the WM effectively.
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Objective This paper aimed to investigate the collaborative coding of two different modes of neural signals including local field potentials and spiking activity (multi-unit activity) which recorded in medial prefrontal cortex of sprague-dawley (SD) rats in Y maze working memory (WM) task,to provide computing support for neural coding mechanism of WM.Methods 1.Experiment data was multi-channel neural signals (local field potentials (LFPs)-Spikes) recorded from prefrontal cortex of 4 SD rats during WM process and resting state,provided by the lab of Neuro-engineering,Tianjin Medical University.2.LFPs preprocessing included baseline drift removing and power-line noise eliminating.3.Physiology window width 500 ms,step 125 ms were selected and average rate per channel was calculated to turn the discrete point signal spikes to continuous signal.4.LFPs characteristic frequency band was obtained by using short time Fourier transform and signals of the characteristic frequency band were extracted by band pass filter.5.Mutual information (MI) of LFPs-spikes was computed to get the distribution of multi-channel MI values.Results 1.LFPs distribution demonstrated that the power focused at θ band (4-12 Hz)during the WM tasks.2.The average MI value of θ band LFPs and spikes (4 rats,over 10 trials) were 0.49±0.04,0.39±0.03,0.41±0.03,0.48±0.02,respectively,which were significantly larger than those in the resting state (t test,P＜0.05).Conclusions These findings indicate that θ band LFPs represents behavior correlated to WM and its synergy with spiking activity plays an important role in encoding WM task.
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Central Nervous System (CNS) regeneration and repair mechanism are two important aspects of functional recovery in the adult central nervous system following brain and spinal cord injury. Following olfactory tract transection in neonatal rats, functional connectivity between the olfactory bulb and the piriform cortex gets re-established by 120 days. The recovery of the dendritic morphology was associated with the synchronized oscillatory activity between olfactory bulb and piriform cortex. Mitral cells which were regenerated after the transection showed profuse branching, indicative of their undifferentiated state. However, normal dendritic morphology could be seen by 120 days after olfactory tract transection. These results thus provide a supportive evidence for the restoration of the functional connections between the olfactory bulb and the piriform cortex at 120 days.
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Objective To investigate how the independent components(ICs)energies of multichannel local field potentials(LFPs) code event base on the analysis of ICA of the cortical LFPs of rats. Methods Taking the event point as the zero point, 15-channel LFPs between the span of ±500ms recorded from the prefrontal cortex of rats were decomposed into 15 ICs. The energies of the ICs were computed in a 50-ms window. By sliding the window with step of 25 ms, a dynamic distribution mapping of the 15 ICs' energies was established. ICs with distinctly increased energies during the span of ±200 ms, which indicating that these ICs energies coded event,were selected as the targets. The corresponding channels of these ICs were determined consequently via the inverse transformation of ICA. Results Considering each trail of the repetitious analysis for the same segment of data, the spatial localization of the dominate function region(s) turned out to be relatively stable in spite of the uncertainty of the number and sequence of the target IC(s) due to the ambiguities of the decomposition of ICA.Meanwhile, the analysis results of a series of data segments showed satisfactory correspondence between data segments and dominate function regions. Conclusion The ICs' energies of multichannel LFPs are able to code events in working memories; It is valid for ICA to identify the coding patterns of multichannel LFPs to events; ICA is capable to localize the dominate function regions of event coding with satisfactory robustness.