Objectives: Birds and mammals both possess two sleep states, slow-wave sleep (SWS) and rapid eye movement (REM) sleep. The chicken chick (Gallus gallus domesticus) embryo offers three key advantages relative to mammals for studying the relationship between brain development and the emergence of the sleep-waking cycle: (1) physiological independence of the embryo from its mother; (2) well-characterized brain development; and (3) easy accessibility for experimental manipulations at all stages of development. Our goal was to record chick embryo EEG and neck muscle EMG continuously during the final 5 days prior to hatching under the least invasive conditions possible in order to better understand how EEG patterns resembling sleep and waking states emerge developmentally. Methods: We utilized a miniature microprocessor-based wireless EEG/EMG recording system (6 channels of data with a maximum sampling frequency of 500 Hz and a resolution of 12 bits) attached to the egg shell. Eggs incubated for 16 days (hatching at day 21) were implanted with brain dura electrodes (affixed to the skull), consisting of 38-gauge gold-plated copper wires (MWS Wire Industries, Westlake Village, CA, USA) overlying the visual wulst of the dorsal pallium and the posterior-lateral part of the pallium of each hemisphere. The EMG was recorded with an electrode placed over the neck muscle. The egg was placed on a custom-made device for recording embryo movements from the egg shell, inside of a Faraday cage on top of a vibration-isolation table. The embryo was recorded continuously in a dark, heated and humidified chamber. Results: Continuous recording of embryos during their last five days prior to hatching revealed a gradual increase in EEG power between 1-10 Hz, with the emergence of cyclic variation in power correlated with variations in the self-similarity of the EEG waveform reminiscent of SWS-like and REM sleep-like activity appearing in the final period prior to hatching. Conclusions: The strength of the brain EEG signal emerges slowly and gradually over the final 30% of chick embryonic development, with cyclic variation reminiscent of SWS- and REM sleep-like brain states emerging towards the final stages of embryonic development.
Long-term EEG/EMG recordings from chick embryos
DI PASCOLI, STEFANO;
2012-01-01
Abstract
Objectives: Birds and mammals both possess two sleep states, slow-wave sleep (SWS) and rapid eye movement (REM) sleep. The chicken chick (Gallus gallus domesticus) embryo offers three key advantages relative to mammals for studying the relationship between brain development and the emergence of the sleep-waking cycle: (1) physiological independence of the embryo from its mother; (2) well-characterized brain development; and (3) easy accessibility for experimental manipulations at all stages of development. Our goal was to record chick embryo EEG and neck muscle EMG continuously during the final 5 days prior to hatching under the least invasive conditions possible in order to better understand how EEG patterns resembling sleep and waking states emerge developmentally. Methods: We utilized a miniature microprocessor-based wireless EEG/EMG recording system (6 channels of data with a maximum sampling frequency of 500 Hz and a resolution of 12 bits) attached to the egg shell. Eggs incubated for 16 days (hatching at day 21) were implanted with brain dura electrodes (affixed to the skull), consisting of 38-gauge gold-plated copper wires (MWS Wire Industries, Westlake Village, CA, USA) overlying the visual wulst of the dorsal pallium and the posterior-lateral part of the pallium of each hemisphere. The EMG was recorded with an electrode placed over the neck muscle. The egg was placed on a custom-made device for recording embryo movements from the egg shell, inside of a Faraday cage on top of a vibration-isolation table. The embryo was recorded continuously in a dark, heated and humidified chamber. Results: Continuous recording of embryos during their last five days prior to hatching revealed a gradual increase in EEG power between 1-10 Hz, with the emergence of cyclic variation in power correlated with variations in the self-similarity of the EEG waveform reminiscent of SWS-like and REM sleep-like activity appearing in the final period prior to hatching. Conclusions: The strength of the brain EEG signal emerges slowly and gradually over the final 30% of chick embryonic development, with cyclic variation reminiscent of SWS- and REM sleep-like brain states emerging towards the final stages of embryonic development.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
