Figure 5. Optogenetic inactivation of the POm during an active goal-directed task.

(A) Left, experimental design. The inhibitory opsin, archaerhodopsin (ArchT) was unilaterally injected into the POm and a fiber-optic cannula was chronically inserted into the brain. Right, localized ArchT spread in POm and fiber-optic track (dotted line), bar = 1 mm. POm was photoinactivated (590 nm, 5 mW, 2 s) either 500 ms prior to, and during the stimulus (S) and response (Rs) epochs (Stim/Resp), or during the reward epoch (Rw) in expert mice performing the ‘action’ goal-directed task. (B) Behavioral performance (d prime) for LED OFF vs LED ON during the stim/response epoch (n = 9 mice). Wilcoxon matched-pairs signed rank test. (C) z-Score during (left) HIT and (right) false alarm for LED OFF vs LED ON during the stim/response epoch (n = 9 mice). Wilcoxon matched-pairs signed rank test. (D) Latency to the first response lick in LED OFF vs LED ON during the stim/response epoch. Wilcoxon matched-pairs signed rank test. (E) Behavioral performance (d prime) during LED OFF and LED ON during the reward epoch in expert mice performing the ‘action’ goal-directed task (n = 5 mice). Wilcoxon matched-pairs signed rank test. (F) Normalized latency to the first response lick during LED ON in the stim/response epoch (solid) and reward (empty) epoch (normalized to the latency to the first lick during LED OFF). Line, median. Mann–Whitney test. Individual values are shown. *p < 0.05.

Figure 5—figure supplement 1. POm neurons are partially photoinhibited by 590 nm LED.

(A) The inhibitory opsin, archaerhodopsin (ArchT) was unilaterally injected into the POm and after 10–14 days, the brain was sectioned into 300-μm thick slices. Whole-cell patch clamp voltage recordings were then performed in POm neurons expressing ArchT. (B) Voltage recording during 590 nm light exposure from an example POm neuron (top) at rest and (bottom) during a current step injection (30 pA; 2 s). (C) Photoinhibition caused a decrease in evoked action potentials during different current steps (20, 30, and 60 pA) for example in (B). Control (Ctrl) firing was determined during current step injection in the absence of LED. (D) Action potential firing evoked during current step injections (0–100, 100–200, and 200–300 pA) was partially inhibited during LED (0–100 pA, p = 0.031; 100–200 pA, p = 0.016; 200–300 pA, p = 0.004; Wilcoxon matched-pairs signed rank test). (E) Voltage response at rest at the start of the LED pulse (300 ms, light orange) normalized to the steady-state ‘end’ voltage (300 ms prior to end of pulse; p = 0.031; Wilcoxon matched-pairs signed rank test). Note, photosuppression would be less effective in vivo than in vitro due to different light penetration and scattering.

Figure 5—figure supplement 2. LED in POm does not alter goal-directed behavior.

(A) Behavioral task design. Mice were either injected with the inhibitory opsin, AAV-ArchT or the Green Fluorescent Protein control, AAV-GFP. Mice were then habituated to head-restraint and trained to report the detection of a tactile stimulus (200 Hz, 500 ms) by licking a reward port. Correct responses were rewarded with sucrose water reward (10 μl, 10% sucrose). Incorrect responses were punished with a timeout. (B) The number of training sessions required to reach expert performance (>80% correct) in the tactile goal-directed task in mice previously injected with AAV-ArchT (orange) or AAV-GFP (green). (C) Performance, measured as percent correct, in expert mice (p = 0.15; unpaired t-test). (D) Behavioral performance (d prime) for LED OFF vs ON trials (n = 9 mice) in mice previously injected with AAV-GFP (green). (E) Hit rate in expert mice (p = 0.11; unpaired t-test). (F) False alarm (FA) rate in expert mice (p = 0.21; unpaired t-test). Mice are considered expert when >80% correct performance in the tactile goal-directed task. AAV-ArchT, orange, n = 9 mice; AAV-GFP, green, n = 9 mice. All data passed normality test (Shapiro–Wilk test).