Fig 1.
(A) A stimulating and recording microdrive. One 12-pin connector array (for recording electrodes) and one 2-pin header (for stimulating electrode) are glued to the base of a microdrive. Each bundle of two pieces (for one tetrode and one stimulating electrode, or for two tetrodes) of polyimide tubing is glued to an independently movable screw nut on the microdrive base. The free ends of electrode wires are wrapped around to adjacent connection pins. Twelve channels are formatted with three tetrodes. The diameter of the recording electrodes is 13 μm, and the diameter of the stimulating electrode is 50 μm. (B) Histology of one brain slice after kindling and the corresponding atlas (modified from the mouse brain atlas of Franklin and Paxinos [25], Bregma -1.2 mm). The brain slice was stained with Nissl staining (cresyl violet). The stimulating bipolar electrode and one recording tetrode were implanted into the right BLA, and the other two tetrodes were implanted into the right CA1 and the right MDT. Red stars marked the corresponding stimulating and recording sites. (C) A representative recording of the ADs recorded from BLA. The current stimulus train consisted of 1-ms (rectangular square wave) pluses at 60 Hz, and the duration of the stimulus was 1 s. The stimulus artifact resulted from the stimulus train.
Fig 2.
Example of discharges evoked by electrical stimulation.
(A) Raw signals recorded in MDT by one tetrode, and the bold blue vertical line indicated the electrical stimulation. (B) The expanded view of signals before stimulation (left column, a), during seizure (middle column, b) and after seizure termination (right column, c). (C) LFPs of corresponding signals by band-pass filtering (0.5–80Hz). (D) MUA of corresponding signals by high-pass filtering (>250Hz). (E) The enlarged view of corresponding MUA in D. It shows that during seizure, the frequency of MUA was higher than that before the stimulation and that after the seizure termination. The variation of the amplitude of MUA showed the same phenomenon.
Fig 3.
Dynamics of AD during epileptogenesis.
(A) The average stimulus number for each stage. (B) Durations of ADs in different stages of epileptogenesis. The durations were positively related to the seizure intensity. Values are expressed as the mean ± SE. (two-way ANOVA, n = 7, ** P < 0.01). LFPs and the corresponding power spectrum of an example mouse are shown in C and D. (C) LFPs were recorded from three tetrodes in the CA1, MDT, and BLA during SCS (a), PS (b), and SGS (c). All data were filtered at 0.5~80 Hz. The seizure onset time is marked by the black line, and the seizure termination time is marked by the red line. ADs occurred only in BLA during SCS (a). During PS (b) and SGS (c), ADs in CA1 and MDT, as well as BLA, appeared almost simultaneously, and the waveforms were similar. (D) Power spectrum of LFPs shown in (A). The color bar presented on the right shows the corresponding power per frequency (dB/Hz). There was no significant change in the power spectrum during SCS except for those in BLA (a), where the power mainly increased in the delta and theta bands. During PS (b) and SGS (c), the power increased in the delta, theta, alpha, beta, gamma and even ripple bands, and the power decreased across all frequencies after the seizure termination. The temporal dynamics of power were similar in all three regions. Because of the 60-Hz stimulation, the high power was found at 60 Hz, and its harmonics, at higher frequencies (120 Hz, 180 Hz), during the 1-s stimulation.
Fig 4.
Dynamics of PLV during epileptogenesis in an example mouse.
The raw LFPs at different stages of seizures recorded in BLA are shown in (A), whereas (B), (C), and (D) present the corresponding PLVs between CA1 & MDT, BLA & MDT, and BLA & CA1, respectively. The color bar presented on the right shows the corresponding PLVs. The time point 0 represents the seizure onset time and is marked by the black line. The seizure termination time is marked by the red line. During seizures at each stage, the dynamics of the PLVs between LFPs from CA1 & MDT (B) were similar to those from BLA & MDT (C). The PLVs were relatively low and remained approximately unchanged during the entire period of SCS. The PLVs remained at a relatively low level during PS but increased dramatically shortly after the seizure termination across almost all frequency bands and then reached their maximum value. During the initial period of SGS, the PLVs remained at a relatively low level but increased dramatically before the seizure termination across almost all frequencies before reaching their maximum value. The PLVs of the LFPs between BLA & CA1 (D) were maintained at a relatively higher level than those between the other regions during the entire period of the seizure across the three stages.
Fig 5.
Statistical analysis results of PLVs.
(A) Period’s definition. The AD period is the period between seizure onset and termination, and the middle third of the AD period (AD2) was chosen as the representation of AD period. The PreAD period is before the stimulation and was 10-s long. The PostAD period denotes the period after the AD termination and was 10-s long. Statistical analysis results of PLVs between the LFPs from CA1 & MDT are shown in (B), and those from BLA & MDT were shown in (C). During PS, the PLVs of the PostAD were significantly higher than the PLVs of the AD and PreAD (B, C). These results were the same during SGS (B, C). The PLVs of the PostAD between CA1 & MDT during PS and SGS were significant higher than those during SCS (B). Values are expressed as the mean ± SE. (two-way ANOVA, n = 7, * P< 0.05, ** P< 0.01).
Fig 6.
PLVs in different frequency sub-bands between different regions during seizures.
Statistical analysis results of the PLVs in the theta (A-B), alpha (C-D), beta (E-F) and gamma (G-H) frequency bands between CA1 & MDT (A, C, E, G), and between BLA & MDT (B, D, F, H). During PS, the PLVs of the PostAD were significantly higher than the PLVs of the PreAD in all sub-bands (A~C, E~H) except in the alpha band between BLA & MDT (D). The PLVs of the PostAD were significantly higher than the PLVs of the AD in all sub-bands (A~B, F~H); except in the alpha and beta bands between CA1 & MDT (C, E), and in the alpha band between BLA & MDT (D). During SGS, the PLVs of the PostAD were significantly higher than the PLVs of the PreAD in all sub-bands (A~C, E, G~H) except in the alpha and beta bands between BLA & MDT (D, F); the PLVs of the PostAD were significantly higher than the PLVs of the AD in theta, alpha and gamma bands between CA1 & MDT (A, C, G), and in the theta and gamma bands between BLA & MDT (B, H).The PLVs of the PostAD during PS and SGS were significantly higher than those during SCS in all sub-bands between CA1 & MDT (A, C, E, G) and in the alpha band between BLA & MDT (B). In the theta band, the PLVs of the PostAD during SGS were significantly higher than those during PS (A~B). The values are expressed as the mean ± SE. (two-way ANOVA, n = 7, * P < 0.05, ** P< 0.01).