Body temperature was continuously monitored by a rectal thermometer and maintained at 37°C ± 0.5°C by placing the animal on a heating pad. For experiments on head-fixed, fully awake rats, animals were remounted in a second frame above a spherical treadmill (air-supported polystyrol ball with 300 mm diameter; Jetball, PhenoSys; see Dombeck et al., 2007). In this system, animals were able to groom, rest, or run, with maximal linear velocities of 40 cm s−1.

Rats were allowed to recover from anesthesia and adapt to the recording device for at least 3 hr. The insertion PARP assay of the recording electrodes was performed under a light and brief inhalation anesthesia, applying 0.2%–0.4% isoflurane (Forane; Abbott) via a ventilation

mask for <5 min. Anesthesia was terminated immediately after the WC configuration was established, and data acquisition was started ∼10 min later. Panobinostat Analgesia was ensured by i.p. application of 50 mg/kg metamizole (Sanofi-Aventis; in strict accordance with animal regulations). In awake animals, all sensors were removed to minimize stress. Vigilance of animals was judged by high muscle tone, movement of whiskers, tail, and limbs, the presence of postural reactions, and locomotor patterns. Animals were able to move on the spherical treadmill freely but characteristically from showed a low level of motor activity under our conditions, with long periods of immobility/lingering and short periods of movement, as expected during exploration of a relatively new environment (Whishaw and Kolb, 2005). The total recording time was 5–30 min (including periods of both immobility

and moderate motor activity). Robust theta and gamma activity was recorded in the LFP under these behavioral conditions. However, our theta peak frequency corresponded to the lower part of the previously defined theta frequency range, presumably due to the inclusion of both immobility and moderate motor activity periods in our analysis (Bland, 1986 and Buzsáki, 2002). Pipettes for both WC and LFP recording were fabricated with a Brown-Flaming micropipette puller (either P-97 or P-1000; Sutter Instrument), using 1 mm outer diameter and 0.5 mm inner diameter borosilicate glass capillaries (Hilgenberg). Pipettes used for patch-clamp recording had tip resistances of 4–7 MΩ. For current-clamp experiments, pipette solution contained 134 mM K-gluconate, 2 mM KCl, 10 mM EGTA, 2 mM MgCl2, 2 mM Na2ATP, 10 mM HEPES, and 3 mg ml−1 biocytin (pH adjusted to 7.28 with KOH). For voltage-clamp experiments with EPSCs, a pipette solution containing 134 mM K-methanesulfonate, 2 mM KCl, 10 mM EGTA, 2 mM MgCl2, 2 mM Na2ATP, 10 mM HEPES, 3 mg ml−1 biocytin, and 5 mM QX-314 was used.