Stress Transforms Lateral Habenula Reward Responses Into Punishment Signals

Stress transforms lateral habenula reward responses into punishment signals Steven J. Shabela,b,1,2, Chenyu Wangc,1, Bradley Monkd,e, Sage Aronsone,f, and Roberto Malinowe,f,g,2 aDepartment of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390; bDepartment of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390; cNeuroscience Graduate Program, University of California, San Francisco, CA 94143; dBiology Graduate Program, University of California, San Diego, La Jolla, CA 92093; eDepartment of Neurosciences, University of California, San Diego, La Jolla, CA 92093; fNeuroscience Graduate Program, University of California, San Diego, La Jolla, CA 92093; and gDivision of Biology, Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093 Contributed by Roberto Malinow, April 25, 2019 (sent for review February 26, 2019; reviewed by Hailan Hu and Bo Li) Neuronal activity in the lateral habenula (LHb), a brain region Methods for details). We injected into the LHb viruses expressing implicated in depression [C. D. Proulx, O. Hikosaka, R. Malinow, a genetically encoded calcium indicator, GCaMP6S, and a cy- Nat. Neurosci. 17, 1146–1152 (2014)], decreases during reward and toplasmic marker, tdTomato. We gained chronic optical access increases during punishment or reward omission [M. Matsumoto, to the LHb, which is several millimeters deep in the mouse brain, O. Hikosaka, Nature 447, 1111–1115 (2007)]. While stress is a major by permanently implanting a gradient refractive index (GRIN) risk factor for depression and strongly impacts the LHb, its effect lens (SI Appendix, Fig. S1). Three-to-four weeks after injection on LHb reward signals is unknown. Here we image LHb neuronal and implantation, individual LHb neurons expressing GCaMP activity in behaving mice and find that acute stress transforms LHb and tdTomato were observed in awake, head-fixed mice with 2- reward responses into punishment-like neural signals; punishment- photon laser-scanning microscopy. After several sessions of ac- like responses to reward omission also increase. These neural changes climatization, neuronal activity was monitored during trials matched the onset of anhedonic behavior and were specific to LHb consisting of a 10-s auditory stimulus (CS+) followed 0.5 s after neurons that distinguished reward and its omission. Thus, stress dis- CS+ termination with a drop of sucrose presented from a spout torts LHb responsivity to positive and negative feedback, which could close to their mouth. Behavioral (licking) responses were mea- bias individuals toward negative expectations, a key aspect of the sured as the percent of time during which a light beam posi- NEUROSCIENCE proposed pathogenesis of depression [A. T. Beck, Depression: Clinical, tioned between the animal’s mouth and the spout was crossed. Experimental, and Theoretical Aspects, sixth Ed (1967)]. Such sucrose reward trials were interleaved with control trials wherein a different auditory stimulus (CS−) was terminated habenula | stress | reward | anhedonia | prediction error without a reward. After several days of such training trials, mice licked more during the CS+ than CS− (compared with licking ateral habenula (LHb) neurons encode numerous stimuli before CS, ΔCS; ΔCS+=13 ± 4% and ΔCS− = −2 ± 1%; P < Lincluding rewards, their omission, and punishment (1–7). In 0.02, n = 4 mice, paired t test; each mouse, P < 0.02, n = 32–36 particular, the LHb provides reward prediction error (RPE) (2) trials, bootstrap; see Materials and Methods). Mice were then in- signals—the difference between expected and actual reward termittently exposed to trials wherein sucrose was omitted after value—a computation thought to be essential for an animal to learn from its environment (8–10). In this way, LHb activity, which is Significance aversive (1, 11–13), can provide “teaching” signalstoananimal: increased LHb activity (i.e., if actual reward value is less than Activity in the lateral habenula (LHb), a brain region implicated expected) discourages repeating a behavior in the future (11, 12, in depression, provides a reward prediction error (RPE): re- 14), while decreased LHb activity is thought to reinforce a behavior. wards reduce, while punishment or expected-reward omission Human and nonhuman animal studies indicate that stress- increase LHb activity. These signals are important in shaping induced changes in LHb activity may contribute to depression by – future choices. Here, we image the activity of individual LHb suppressing reward-based behavior (1, 15 18). While stress de- neurons in behaving mice. We find that stress, a major risk creases reward sensitivity (19, 20), is a major risk factor for de- factor for depression, acutely transforms LHb signals in a re- pression (21, 22), forms the basis for most animal models of – – markable manner: under stress, rewards produce punishment- depression (23 25), and causes plasticity in the LHb (26 31), its like LHb output, and reward omission increases its punishment- effects on LHb reward and RPE signals are not known. Here, we like output. That is, under stress, LHb signals interpret “good as use calcium-imaging techniques to monitor RPE from individual bad and bad as worse.” This effect is rapid and coincides with LHb neurons in awake, behaving mice in the absence and reduced reward responsivity. These results potentially explain presence of intermittent tail shock stress. Surprisingly, we find why an individual under stress is more prone to depression. that stress causes the LHb to respond to rewards as if they were punishment. This switch is tightly linked temporally with onset of Author contributions: S.J.S. and R.M. designed research; S.J.S. and C.W. performed re- anhedonic behavior, suggesting that this aberrant LHb respon- search; B.M. contributed new reagents/analytic tools; S.J.S., B.M., S.A., and R.M. analyzed sivity contributes to anhedonia (29–35). These changes were also data; and S.J.S. and R.M. wrote the paper. accompanied by a larger (i.e., “more negative”) LHb signal to Reviewers: H.H., Zhejiang University; and B.L., Cold Spring Harbor Laboratory. reward omission. Our results indicate that stress causes a nega- The authors declare no conflict of interest. tive shift in LHb signaling of reward and its omission. While Published under the PNAS license. potentially adaptive in some conditions (e.g., suppressing Data deposition: Imaging raw data are available on Zenodo (https://zenodo.org/record/ reward-seeking behavior during threat), repeated occurrence of 3226985#.XOgT-hZKhhE). such effects could contribute to the pathogenesis of depression. 1S.J.S. and C.W. contributed equally to this work. 2To whom correspondence may be addressed. Email: [email protected] Results or [email protected]. RPE Encoding in a Subpopulation of LHb Neurons. We monitored the This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. activity of multiple independent LHb neurons in awake, behav- 1073/pnas.1903334116/-/DCSupplemental. ing mice using calcium-imaging techniques (see Materials and www.pnas.org/cgi/doi/10.1073/pnas.1903334116 PNAS Latest Articles | 1of6 Downloaded by guest on September 30, 2021 the CS+ (sucrose omission trials). Such omission trials confirmed showed this decrease was due to a reduction in the duration of that mice learned to expect sucrose after the CS+ and not the licking bouts (3.4 ± 0.8–1.7 ± 0.8 s; P < 0.02, n = 4 mice, paired CS−, as evidenced by significantly more licking during the su- t test; each mouse, P < 0.001, n = 33–216 trials, bootstrap; Fig. 2J; crose omission period after the CS+ than during a similar period see Materials and Methods) consistent with reduced reward value after the CS− (P < 0.05, n = 4 mice, paired t test; each mouse, (42–47), with no effect on the interlick interval within a licking P < 0.001, n = 33–108 trials, bootstrap; Fig. 1C). burst, excluding a motor impairment (interlick interval: 12.7 ± 0.8– Two-photon imaging using both GCaMP and tdTomato 12.2 ± 1.2 ms, P > 0.05, n = 4mice,pairedt test). There was also channels and normalizing the GCaMP signal by the tdTomato reduced licking before sucrose delivery (39 ± 9% to 18 ± 10%; P < signal (ΔG/T; see Materials and Methods) permitted correction of 0.05, n = 4 mice, paired t test; each mouse, P < 0.002, n = 66–324 the neural signal for movement artifacts that could not be corrected trials, bootstrap; Fig. 2 G and K) as well as during sucrose omission by single-channel movement-correction software (e.g., transient (13 ± 2% to 7 ± 2%; P = 0.07, n = 4 mice, paired t test; 3/4 mice movement of tissue out of the imaging plane; Fig. 1 D–O). Activity P < 0.05, n = 33–108 trials, bootstrap; Fig. 2 D, F, H,andL), of the same LHb neurons could be imaged daily for several weeks consistent with reduced motivation to receive a reward. (Fig. 1 A and B). Neurons were classified according to their activity patterns. Consistent with primate studies (2, 36, 37), many neurons Stress Distorts Reward Signaling in LHb Neurons. To determine the were “reward-selective” (18 of 42; 43%), displaying significantly neural basis by which such a stress protocol could produce these different activity during sucrose consumption and sucrose omission behavioral effects, we examined reward-processing signals in the (Fig. 1 D–G and P). However, there was also a large population of LHb. As expected, stressful stimuli (i.e., the intermittent shock “nonselective” neurons (19 of 42; 45%) displaying activity that did trials) produced an increased neural response, consistent with not differ significantly between sucrose consumption and sucrose LHb responses to punishment seen in primates (4) and rodents omission (Fig. 1 H–K and P); and a small number of neurons dis- (3) (Fig. 3 I and J, shock traces; SI Appendix, Fig.

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