DOI: 10.5068/d1109s
title: A bidirectional corticoamygdala circuit for the encoding and retrieval of detailed reward memories

description: Adaptive reward-related decision making often requires accurate and
 detailed representation of potential available rewards. Environmental
 reward-predictive stimuli can facilitate these representations, allowing
 one to infer which specific rewards might be available and choose
 accordingly. This process relies on encoded relationships between the cues
 and the sensory-specific details of the reward they predict. Here we
 interrogated the function of the basolateral amygdala (BLA) and its
 interaction with the lateral orbitofrontal cortex (lOFC) in the ability to
 learn such stimulus-outcome associations and use these memories to guide
 decision making. Using optical recording and inhibition approaches,
 Pavlovian cue-reward conditioning, and the outcome-selective
 Pavlovian-to-instrumental transfer (PIT) test in male rats, we found that
 the BLA is robustly activated at the time of stimulus-outcome learning and
 that this activity is necessary for sensory-specific stimulus-outcome
 memories to be encoded, so they can subsequently influence reward choices.
 Direct input from the lOFC was found to support the BLA in this function.
 Based on prior work, activity in BLA projections back to the lOFC was
 known to support the use of stimulus-outcome memories to influence
 decision making. By multiplexing optogenetic and chemogenetic inhibition
 we performed a serial circuit disconnection and found that the lOFCàBLA
 and BLAàlOFC pathways form a functional circuit regulating the encoding
 (lOFCàBLA) and subsequent use (BLAàlOFC) of the stimulus-dependent,
 sensory-specific reward memories that are critical for adaptive,
 appetitive decision making.
description: <i>Behavioral
 analysis.</i> Behavioral data were processed with Microsoft Excel
 (Microsoft, Redmond, WA).<i> </i>Left and/or right lever
 presses and/or entries into the food-delivery port were collected
 continuously for each training and test session. Acquisition of the
 Pavlovian conditional food-port approach response was assessed by
 computing an elevation ratio of the rate of entries into the food-delivery
 port (entries/min) during the CS prior to reward delivery (CS-probe)
 relative to 2-min baseline periods immediately prior to CS onset [(CS
 probe entry rate)/(CS probe entry rate + preCS entry rate)]. Data were
 averaged across trials for each CS and then averaged across the two CSs.
 We also compared the rate of food-port entries between the CS probe and
 the preCS baseline periods (see data 1-1a, 3-2a, 4-2a, 5-2a). Press rates
 on the last day of instrumental training were averaged across levers and
 compared between groups to test for any differences in the acquisition of
 lever press responding during instrumental training (see data1-1b, 3-2b,
 4-2b, 5-2b). For the PIT
 test, lever pressing during the 2-min baseline periods immediately prior
 to the onset of each CS was compared with that during the 2-min CS
 periods. For both the baseline and CS periods, lever pressing was
 separated for presses on the lever that, during training, earned the same
 outcome as the presented cue (i.e., preCS-Same and CS-Same presses) versus
 those on the other available lever (i.e., preCS-Different and CS-Different
 presses). To evaluate the influence of CS presentation on
 lever pressing, we computed an elevation ratio for each lever [(CS-Same
 presses)/(CS-Same presses + preCS-Same presses)] and [(CS-Different
 presses)/(CS-Different presses + preCS-Different presses)]. To evaluate
 the influence of CS presentation on food-port entries, i.e., the
 conditional goal-approach responses, we also computed an elevation ratio
 [(CS entries)/(CS entries + preCS entries)]. Data were averaged across
 trials for each CS and then averaged across the two CSs. We also compared
 the rate of pressing on each lever and, separately, food-port entries
 between the CS and preCS baseline periods (see data1-1c-d, 3-2c-d, 4-2c-d,
 5-2c-d). <i>Fiber photometry data
 analysis. </i>Data were pre-processed using a custom-written
 pipeline in MATLAB (MathWorks, Natick, MA). Data from the 415 nm
 isosbestic control channel were used to correct for motion artifacts and
 photobleaching. Using least-squares linear regression, the 415 signal was
 fit to the 470 signal. Change in fluorescence (DF/F) at each time point
 was calculated by subtracting the fitted 415 signal from the 470 signal
 and normalizing to the fitted 415 data [(470-fitted 415)/fitted 415)] (See
 Figure 1-2). The DF/F data were then Z-scored [(DF/F - mean
 DF/F)/std(DF/F)]. Using a custom MATLAB workflow, Z-scored traces were
 then aligned to CS onset, reward delivery, reward retrieval (first
 food-port entry after reward delivery), and food-port entries without
 reward present during the CS probe period (after CS before first reward
 delivery) during the CS for each trial. Peak magnitude and AUC were
 calculated on the Z-scored trace for each trial using 3-s pre-event
 baseline and 3-s post-event windows. Data were averaged across trials and
 then across CSs. Session data were excluded if no transient calcium
 fluctuations were detected on the 470 nm channel above the isosbestic
 channel or if poor linear fit was detected due to excessive motion
 artifact. To examine the progression in BLA activity across training, we
 compared data across conditioning sessions 1, 2, 3/4, 5/6, and 7/8. Thus,
 data from the mid and latter training sessions were averaged across bins
 of 2 training sessions.  <i>Ex vivo
 electrophysiology. </i>The number of action potentials evoked by
 suprathreshold current injection was compared before and during exposure
 to green light to confirm the inhibitory effect of ArchT in BLA principal
 neurons. To assess the effect of ArchT activation in lOFCàBLA terminals,
 the frequency of sEPSCs was compared before and during green light
 exposure.