Tubes for fluid were constructed from 18G stainless steel tubing that was bent to follow the curve of the objective. Sensors and actuators in the behavioral training chamber were controlled Selleckchem 3 MA by the freely available, open-source software platform Bcontrol (Erlich et al., 2011). Bcontrol consists of an enhanced finite state machine, instantiated on a linux computer running a real-time operating system (RTLinux), and capable of state transitions at a rate of 6 kHz, plus a second computer, running custom software written in MATLAB. The state machine contained a multifunction data acquisition card (PCI-6025E, National Instruments), which was connected to the sensors and actuators in the behavioral chamber via a powered
breakout box (Island Motion). Each behavioral trial consisted of a sequence of states in which different actuators—for
example, opening of a solenoid valve for water reward—could be triggered. Transitions between the states were either governed by elapsed times (e.g., 40 ms PFI-2 datasheet for water reward) or by the animal’s actions, which caused changes to the voltage output of a sensor in the chamber (e.g., the headplate contacting the miniature snap action switches). Sensors included infrared LED sensors (Island Motion) and miniature snap action switches. Actuators included speakers (Island Motion), visible LEDs (Island Motion), solenoid valves for water reward (Island Motion), and solenoid valves for the air, which drove the pneumatic linear actuators. Solenoid valves controlled by Bcontrol also were used to apply and remove the immersion fluid for the microscope objective. Output signals from the state machine were also used to trigger actions in downstream devices, such as the imaging acquisition computer. Animal use procedures were approved by the Princeton University Institutional Animal Care and Use Committee and carried out in accordance with National Institutes Carnitine palmitoyltransferase II of Health standards. All
subjects were adult male Long-Evans rats (Taconic) weighing between 200 g and 400 g. Rats were placed on a water schedule in which fluids are provided during behavioral training and an additional period lasting 0–1 hr. To implant the headplate, we anesthetized animals with isoflurane in oxygen and gave Buprenorphine as an analgesic. Animals also received an injection of dexamethasone the day of and the day after surgery. Once anesthetized, the scalp and periosteum were retracted, exposing the skull. Dental cement (Metabond) was used to bond the headplate to the skull. After a 1-week recovery period, implanted animals began training in voluntary head restraint. We found two aspects of the headplate implantation surgery to be critical for the integrity of the junction between the skull and the headplate over a long period of time. First, sterile technique was critical to prevent infection of the bone, which can lead to a softening of the skull and loss of headplates.