Behavioral Training and Testing

Testing/Training Setups for Behavioral Task Behavioral training and testing for all tasks (cross-modal sensory selection task, basic auditory discrimination task, and cued noisy auditory discrimination task), took place in grid-floor mounted, custom-built enclosures made of acrylic plastic (maximum dimensions in cm: length: 15.2; width: 12.7; height: 24). All enclosures contained custom-designed operant ports, each of which was equipped with an IR LED/IR phaototransistor pair (Digikey, Thief River Falls, MN) for nose-poke detection. For all tasks, trial initiation was achieved through an initiation port mounted on the grid floor ∼6 cm away from the ‘response ports’ and ‘reward ports’ located at the front of the chamber. A pair of electrostatic speakers (Tucker Davis Technologies) producing the auditory stimuli were placed outside of the training apparatus and sound stimuli were conveyed via cylindrical tubes to apertures located at either side of the initiation port, allowing consistent delivery of stereotypical stimuli across trials. All stimuli and auditory cues across tasks were generated by a TDT Rx8 sound system (Tucker-Davis Technologies, Alachua, FL). Sound stimuli and auditory cues were recorded and assessed for intensity using a prepolarized icp array microphone (PCB Piezotronics, Depew, NY) after which frequency production was equalized using software-based calibration via SigCalRP (Tucker-Davis Technologies, Alachua FL). Visual stimuli for cross-modal sensory selection task were produced by two dimmable, white-light-emitting diodes (Mouser, El Cajon, CA) mounted on each side of the initiation port and controlled by an Arduino Mega microcontroller (Ivrea, Ital). Noise cues for noisy auditory discrimination task (see below) were produced by UV (320-380nm) or Green (495-510nm) light emitting diodes (Mouser, El Cajon, CA) mounted on the top of the enclosure and controlled by Arduino Mega microcontroller (Ivrea, Italy). For cross-modal sensory selection tasks, two response ports were mounted at the angled front wall 7.5 or 5 cm apart, respectively. Response ports were separated by 1 cm divider walls and each was capable of delivering a milk reward (10 μL evaporated milk delivered via a single-syringe pump (New Era Pump Systems, Farmingdale, NY) when a correct response was made. In the case of the auditory GO/NO GO task environment used for the basic and cued noisy auditory discrimination tasks, response and reward ports were stacked with the response port on top. The stacked ports were located centrally behind the initiation poke. Access to all response and reward ports was restricted by vertical sliding gates which were moved via a custom 3D printed rack and pinion gear system (MakerBot replicator, Brooklyn, NY) powered by a servo motor (Tower Hobbies, Champaign, IL). The TDT Rx8 sound production system (Tucker Davis Technologies, Alachua, FL) was controlled through MATLAB (MathWorks, Natick, MA), interfacing with a custom written software running on an Arduino Mega (Ivrea, Italy) for trial logic control. For all tasks, mice were food restricted to 85%–90% of their ad libitum body weight before training.

Cross-modal Sensory Selection Task Training and testing Schmitt et al., 2017 Schmitt L.I.

Wimmer R.D.

Nakajima M.

Happ M.

Mofakham S.

Halassa M.M. Thalamic amplification of cortical connectivity sustains attentional control. Wimmer et al., 2015 Wimmer R.D.

Schmitt L.I.

Davidson T.J.

Nakajima M.

Deisseroth K.

Halassa M.M. Thalamic control of sensory selection in divided attention. A total of 18 control and 6 Vgat Cre mice were trained on this task. No differences were observed in learning between these groups. Training was performed as previously described () and required ∼2 months of daily training for each mouse. Particular steps were taken throughout the training and testing periods to ensure that mice used the rules for sensory selection. Training was carried out in multiple stages. First, 10 μL of evaporated milk (reward) was delivered randomly to each reward port for shaping and reward habituation. Second, mice were trained to initiate individual trials and make association of side of reward poke with target stimuli (no conflict trials). Initially, mice had to briefly (50msec) break the infrared beam in the initiation port to trigger target stimulus presentation and render reward ports accessible. Mice were trained to hold their snouts for up to 700msec. Broadband white noise indicated trial availability, which prompted a mouse to initiate a trial. Upon successful initiation, the white noise was replaced by either brown (10-kHz low-pass-filtered white noise) or blue noise (11-kHz high-pass-filtered white noise) for 0.1sec to indicate whether to attend to vision or attend to audition. This was followed by a delay period (0.4-0.6 s) prior to target stimuli presentation. Target stimuli were presented in blocks of six trials consisting of single-modality stimulus presentation (no conflict). In attend to vision trials (brown noise), the location of the rewarded port was signaled by a white LED (visual target) mounted underneath it in order to establish an association between the location of the visual target and the location of the reward port. In attend audition trials (blue noise), mice learned the association between the auditory target, up-sweep (10-15kHz) or a down-sweep (16-12kHz) with right or left ports respectively. For symmetric task, a 0.1 s tone cloud consisting of a random set of overlapping pure tones (12.5 ms tone length with an overlap of between 2-8 tones at any given time) spanning a range of 4-46 kHz was played from the speaker on one side only. The same tone clode was used for right and left sides, and mice were trained to associate the location of sound and the location of the reward port. Rewards were available for 15sec following correct response, followed by a 5sec inter-trial interval (ITI). An incorrect response immediately renders the response ports inaccessible and was punished with a time-out, which consisted of a 30sec ITI. Third, conflict trials were introduced, in which auditory and visual targets were co-presented indicating reward at opposing locations and mice need to use trial cues (brown or blue noise) to match the target modality. Four different trial types were presented in repeating blocks: (1) three auditory-only trials; (2) three visual-only trials; (3) six conflict trials with auditory target; and (4) six conflict trials with visual target. Once mice performed successfully on conflict trials, single-modality trials were removed and block length was reduced to three trials. Fourth, during the final stage of training, all block structure was removed and trial type was randomized. For each mouse, training was continued until the animal’s performance level reached at least 65% for both trial cues, after which they were injected with viral vectors and implanted with optic fibers or microdrive (see relevant sections below). Following recovery, each animal was re-trained to the original performance criteria. For electrophysiological recordings and experiments with optical manipulation, testing conditions were equivalent to the final stage of training. To make sure mice did not have any biases toward one modality and that they were able to use trial cues to choose modalities, only sessions with balanced performance (both auditory and visual trial types above 65%) across target modalities in baseline trials (those without laser manipulations) were used for the further analysis.