FIGURE 4: Auditory cortical sound responses encode predicted time to reward.

A. Left: An illustration of the electrodes implanted in right AC. Right: Histological verification of electrode position in AC of the right hemisphere. The brain slice acquired from an example animal is overlaid with the corresponding coronal section from the Allen Mouse Brain Atlas (see Methods). The electrode track is indicated by the green dotted line on the brain slice and the markers on the right indicate the depth at which the electrode was implanted in the right hemisphere. Scale bar: 500μm

B. Average peri-sound lick rate response curves (solid line denotes mean, shaded area represents SEM across trials) of an example animal trained to perform on the four different sound-reward intervals represented by different colors. Left: Rewarded trials; Right: Catch trials. Shaded pink region represents the 1.5s long sound period. Solid and dotted lines represent when reward was given in rewarded trials and expected in catch trials for each of the sound-reward interval.

C. Average estimated slope of predictive licking response curves for each of the four sound-reward intervals across all animals (N = 8) for rewarded trials (left,***p=0.000054, Kruskal-Wallis test) and for catch trials (right, ***p =0.00012, Kruskal-Wallis test). Error bars represent mean ± SEM across animals.

D. Normalized average AC LFP responses to the sound onset from an example animal trained on the four different sound-reward intervals represented by the different colors (solid line denotes mean, shaded area represents SEM across no-lick trials). The shaded pink region represents the period from sound onset as shown in the illustration above.

E. Average onset response magnitude computed across animals (N = 8) for each of the sound-reward intervals. Error bars represent mean ± SEM across animals. Comparison across sound-reward intervals yields ***p = 1.9×10⁻³⁵ (Kruskal-Wallis test).

F. Normalized average AC LFP responses to the sound offset from an example animal trained on the four different sound-reward intervals represented by the different colors (solid line denotes mean, shaded area represents SEM across no-lick trials). The shaded yellow region represents the period from sound onset as shown in the illustration above.

G. Average offset response magnitude computed across animals (N = 8) for each of the sound-reward intervals. Error bars represent mean ± SEM across animals. Comparison across sound-reward intervals yields p = 0.263 (Kruskal-Wallis test).