This protocol is significant because it enables users to develop customizable multitaper spectrograms without prior signal processing knowledge. The main technical advantage of the program is the program's user-friendly design and the ability to create multitaper spectrograms using computers without MATLAB licensing. Seven to 10 days after the electrode implantation surgery, configure the data acquisition system to record all of the signals in millivolts, and obtain EEG recordings for the desired experimental duration.
Amplify and digitize the unfiltered EEG signals using the appropriate data acquisition instrumentation and software. Then have two different individuals independently score each 10-second bin of the digital EEG, blue trace, and EMG, black trace, recordings as wakefulness, REM sleep, or non-REM sleep in an appropriate sleep scoring software program. Download the compiled Multitaper Spectrogram Program.
For spectrogram computation, obtain raw, unprocessed EEG data in either EDF or CSV file format, and place the file into the same location as the compiled program file, and launch the Spectrogram Program. Follow the pop-up prompts, and select the appropriate file format. Enter the entire EEG file name, and select the parameters for the spectrogram calculation.
Enter titles for both the spectrogram and EEG. Then, click File and Save to save the resulting spectrogram and EEG trace in the desired file format. This figure shows representative similarities and differences in the cortical EEG during wakefulness, non-REM sleep, and REM sleep.
This hypnogram was used to plot the temporal organization of the states of sleep and wakefulness based on assessments of the EEG and EMG recordings. In contrast to the discretized hypnogram, a spectrogram can be used to illustrate highly dynamic changes in EEG frequency and power as a function of time and to highlight the similarities between the cortical EEG signal during wakefulness and REM sleep. These multitaper spectrograms each summarize four hours of EEG recordings after systemic administration of saline, morphine, buprenorphine, or fentanyl.
This figure shows the use of spectrograms to visualize the effects of different opiates on cortical EEG power. The slow-wave activity present in the saline condition is eliminated by morphine and buprenorphine. After fentanyl administration, slow-wave delta power can be observed.
EEG changes illustrated by the spectrograms can be further quantified and expressed as the average dominate spectral power of each half frequency. For example, as illustrated in this graph, averaging the spectral power within specific EEG frequency bands revealed that in the 0.5 to four hertz frequency range, the EEG power was much higher with saline treatment than with buprenorphine. Mice with chronically implanted EEG and EMG electrodes remain healthy for many months, enabling novel studies of drug-drug interactions and chronic drug administration.
Additionally, these techniques can provide new insights into efforts to develop chemical countermeasures to opiate-induced respiratory depression.
