Methods

Chronic recordings were performed in the Langone Medical Center of the New York University and the Department of Physiology of the School of Medicine of the University of Szeged. All experiments were performed in accordance with European Union guidelines

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Methods

2.1

Experimental Procedures

Chronic recordings were performed in the Langone Medical Center of the New York University and the Department of Physiology of the School of Medicine of the University of Szeged. All experiments were performed in accordance with European Union guidelines (2003/65/CE) and the National Institutes of Health Guidelines for the Care and Use of Animals for Experimental Procedures. The experimental protocols were approved by the Animal Care and Use Committee of New York University Medical Center and the Ethical Committee for Animal Research at the Albert Szent-György Medical and Pharmaceutical Center of the University of Szeged respectively. Animals were anesthetized with isoflurane anesthesia and one or several craniotomies were performed with stereotaxical guidance. One or more silicon probes were mounted in custom-made micro-drives to allow their precise vertical movement after implantation. The probes were inserted over the target region and the micro-drives attached to the skull with dental cement. The craniotomies were sealed with sterile wax. Two stainless steel screws were drilled over the cerebellum and serve as ground and reference for the recordings. Several additional screws were drilled into the skull and covered with dental cement to strengthen the implant. Finally, a copper mesh was attached to the skull with dental cement and connected to the ground screw to act as a Faraday cage and prevent the recording from the environmental electric noise (Fig. 2.1a. For more details, see Vandecasteele et al. [45]). After recovery, the probe is moved gradually in 70–150 µm steps until the desired target is reached. The operated animals were housed in individual cages. To record neuronal activity during sleep or waking behaviors the probes were connected to a pre-amplifier headstage attached to a long cable pending from the room ceiling that allow full movement to the animal (Fig. 2.1b). The rats’ positions during behavioral sessions were estimated using video tracking of two LEDs fixed

© Springer International Publishing Switzerland 2016 A. Fernández-Ruiz, Extracellular Potentials in the Hippocampus, Springer Theses, DOI 10.1007/978-3-319-41039-5_2

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2 Methods

Fig. 2.1 a Implantation of a 256 channels silicon probe (NeuroNeuxus) in the hippocampus of a Long Evans rats. Observe the multiplexed pre-amplifier PCB and the microdrive where the probe is mounted. b An animal being recorded during exploration for food reward (cookies) in an open field. Two LEDs mounted in the headstage are used for position tracking

to the headstage. The wide-band signal was low-pass filtered and down sampled to 1250 Hz to generate the LFP and was high-pass filtered (>0.8; 20 kHz) for spike detection. Following the termination of the experiments, the animals were deeply anesthetized, and transcardially perfused first with 0.9 % saline solution followed by 4 % formaldehyde solution. The brains were sectioned by a Vibratome (Leica) at 70 µm sections, parallel with the plane of the implanted silicon prob

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