Figure 1.
Marmoset chair and behavior setup.
A. Marmoset chair with feeding tube, infrared lick detector, and optional head restraint mechanism for single-unit recording. The neck plate slides out to allow a marmoset to enter the chair from below. After securing neck plate, the feeding tube can be adjusted to create a comfortable reach for each monkey. B. Schematic of task setup. Sounds are played from free field speakers while marmosets lick to target sounds for a reward which is delivered by a syringe pump via a feeding tube. Lick responses are recorded when the infrared beam is broken by the animal’s face or tongue. Behavior apparatus are controlled by a personal computer and powered by a custom built power supply and electrical isolation module.
Figure 2.
After a variable number of background stimuli (or silent periods, for the detection task described here), targets begin alternating with the background stimuli/silent periods. If a lick is registered within the preset number of alternations, a food reward is given. After the animal has finished consuming the reward (as measured via the lick detector), the next inter-target interval begins with background stimuli or silent intervals. A lick outside of a target interval results in a timeout.
Figure 3.
A–E. Learning curves for 5 naive marmosets performing an auditory detection task with broad band noise or pure tone stimuli. Data represent training Phase 2 (see Response Shaping). Training is considered complete when 4 of 5 consecutive sessions have been completed with at least 80% hit rate and less than 25% false positives. Average time to train across all animals was 12 sessions with a standard deviation of 6 sessions. F. Average hit rate and false positive rate over all training sessions. Later sessions had fewer data points averaged due to some animals completing training more quickly than others.
Figure 4.
A. Example of a licking response to a target trial along with reward and feeding behavior to target trials for a representative behavior session. B and C. Distribution of response latencies within the same session (B), measured as the elapsed time from the onset of the first target stimulus to the first lick, and lick durations (C), measured as the time from the first lick to the offset of the last lick. D. Example sham trial with an error response. Sessions consisted of 80 to 100 trials of which 30% were sham trials.
Figure 5.
Single unit recording during behavior.
Example of voltage signal, high pass filtered for spike sorting, from a high impedance microelectrode recording single unit activity in marmoset auditory cortex during task performance. Time is referenced to pre-stimulus delivery interval. The licking behavior can be performed without compromising recording stability (meaning that units can be held reliably) or signal quality. Note that spikes can be easily discerned both before and after a lick is detected.