Neuroscan synamps2 system

Recording and offline analysis of EEG and EOG data was done with Neuroscan Synamps 2 system and Scan 4.5 software (Compumedics, Melbourne, Australia). During the task(s), EEG activity was recorded continuously from 64 scalp electrodes placed according to the international 10–10 system (EASYCAP GmbH, Herrsching, Germany), referenced to the left earlobe. Horizontal and vertical EOG was recorded from electrodes placed above and below the left eye (vEOG) and beside the outer canthi of both eyes (hEOG). Impedances were kept below 35kΩ. EEG and EOG were amplified, band-pass filtered at 0.05–100 Hz, and digitised at 2000 Hz.

In one group of rats, scalp electrodes were used to monitor EEG changes during the experiments. To avoid possible stress effects following invasive surgical implantation, we recorded the EEG from 9 mm stainless steel EEG needle electrodes inserted into the scalp during anesthesia so that they were touching the outer table of the skull. This technique is used for EEG monitoring intraoperatively in humans. After rats were anesthetized with 2% isoflurane and IV catheter insertion, two scalp electrodes [Astro-Med/ Grass Technologies] were placed, as shown in Fig 2. We drew a line between the anterior edge of bilateral ears, likely between Bregma and Lambda [25 (link)]. From the midpoint, one electrode was placed anteriorly perpendicular to the line and the other one was placed posteriorly perpendicular to the line. Two EEG channels were recorded, the first one from an electrode placed over the anterior portion of the brain, and a second electrode placed over the posterior portion of the brain. The EMG was obtained from an electrode placed over the left shoulder, all referenced to an electrode placed near the snout. A ground electrode was placed on the dorsal neck. These three channels were recorded with an A/D rate of 500 Hz/channel, with a 0.05–100 Hz bandpass and 12 dB/octave roll-off. Potentials were amplified with a Neuroscan SYNAMPS 2 system (Compumedics, Inc., Charlotte, NC).

EEG data were recorded using a 64-channel Neuroscan Synamps2 system (Compumedics Neuroscan). The EEG signals were filtered from 0.05 to 100 Hz and digitized at 1,000 Hz. A 64-channel Ag-AgCl electrode cap was used. All electrodes were referenced to a REF electrode between Cz and CPz. Impedances were kept below 5 kΩ. Markers corresponding to the onset of the adapters were co-registered with the EEG signal. Electrodes placed above and below the left eye and the external ocular canthi of both eyes were used to record vertical electrooculogram (vEOG) and horizontal electrooculogram (hEOG).

Continuous EEG was sampled at a rate of 500 Hz from 64 Ag/AgCl electrodes placed according to the international 10–10 system (EASYCAP GmbH, Herrsching, Germany). Online, the signal was referenced to the left earlobe with impedances kept below 10 kΩ. Signals from the right earlobe were also recorded. Bipolar channels recorded vertical (VEOG) and horizontal (HEOG) electro-oculogram from above and below the midpoint of the right eye and beside the outer canthi of both eyes. Recording and offline analysis of EEG and EOG data was conducted with Neuroscan Synamps2 system and SCAN 4.5 software (Compumedics, Melbourne, Australia).
Offline, EEG and EOG signal were digitally filtered using a 30-Hz lowpass filter with 24 dB slope, then re-referenced to the average of the left and right earlobes.

EEG recordings were carried out using a 64-channel cap with the Neuroscan Synamps2 system (Compumedics), in accordance with the international 10/10 system. Vertical and horizontal electrooculograms (EOGs) were monitored and recorded as well: two electrodes were placed over and below the dominant eye for the vertical eye movements, and two electrodes were placed at the outer canthi of the eyes for the horizontal movements. The electrode impedance was kept under 10 kΩ. EEG data were digitized at 500 Hz, with an online bandpass filter from 0.05 to 100 Hz applied. An average mastoid reference was used.