M. Danet S. Lapiz-Bluhm , Alexandra E. Soto-Piña, Julie G. Hensler , David A. Morilak

1. Chronic Intermittent Cold Stressand Serotonin Depletion Induce Deficits of Reversal Learning in an Attentional Set-shifting Task in Rats M. Danet S. Lapiz-Bluhm, Alexandra E. Soto-Piña, Julie G. Hensler, David A. Morilak

2. Brain Jargon • Primarily concerned with the Prefrontal Cortex (PFC)in the main paper, specifically the Orbitofrontal Cortex (OFC). • PFC – implicated in cognitive flexibility, ability to attend tochanges in the environment, and adapt behavioral response strategies accordingly • mPFC involved in shifting attention b/n perceptual features of complex stimuli.

3. Brain Jargon (cont.) • Output of decision making processes influenced/determined by interaction b/n two forebrain loops. • Limbic (affective/motivational) loop • OFC, amygdala, and ventral striatum • Cognitive (executive/motor) loop • Dorso-lateral prefrontal cortex and dorsal striatus

4. Cold Stress • CIC leads to an increase in Hypothalamic-Pituitary-Adrenal response. • Hypersensitizes the individual to respond to acute stress, specifically increases noradrenergic receptor activity. • Dysregulation of both the HPA axis and noradrenergic system leads to anxiety like behaviors

5. Cold Stress

6. Serotonin Depletion • Tryptophan -> 5-HT • Depleted through pharmacological (main paper) or dietary means (background paper) • Low 5-HT levels linked to poor decision making and gambling proneness • Assesed through the rIGT and rodent Probabilistic Delivery Test (rPDT)

7. Serotonin Depletion • rIGT • Istead of four choices, onlytwo this time • Advantageous • Disadvantageous

8. Serotonin Depletion • rPDT • 10 days • 2 choices • Large Luck Linked • Small Sure • 6 vs. 2 pellets • Indifferent point • LLL and SS choice equally wise.

9. Serotonin Depletion • The authors believe that • 5-HT depletion leads to a lower sensitivity to punishment • 5-HT depleted rats (T-) show only slight reduction in LLL preference. Indicative of a tolerance of reward uncertainty • (T-) rats also exhibit motor impulsivity. Not hitting the button long enough • (T-) rats stuck on short term focus

10. The Paper Proper • Objectives • To assess the effects of chronic intermittent cold (CIC) stress on performance of rats in an attentional set-shifting task (AST) • Assess a possible role for serotonin in CIC-induced deficits and test the effects of acute serotonin reuptake blockade • Model organism • Sprague-Dawley rats

11. Attentional Set-shifting Task (AST) • …subjects must learn a series of reward contingencies, using cues that vary along multiple stimulus dimensions (e.g., odor and texture, shape and color, etc). Extra Dimensional set shifting involves the acquisition of a new contingency requiring a shift in attention (and responding) away from the stimulus dimension that had been established previously as the relevant or informative dimension (i.e., formation of a cognitive set) to a previously irrelevant stimulus dimension… • …reversal learning, another form of cognitive flexibility in which a previously positive cue becomes negative and a previously negative cue becomes positive, but within the same stimulus dimension.

12. AST Terracota pots Rat • Various digging media • Various scents • ¼ cheerio as reward Divider Removable Divider Hypothetical “no-mans land”

13. Procedure • Immediately following 14 day CIC treatment (or control housing) • Day 15 – Habituation. Train rat to dig for food. • Day 16 – Training. Train to a series of SD. First odor, then medium • Day 17 – Testing. Increasingly difficult discriminations. • Trials to criterion • 6 correct choices in a row.

14. Testing • 1st stage – Simple Discrimination (SD) • Discriminate b/n two odors or two types of medium. • 2nd stage – Compound Discrimination (CD) • Same as above but also included a second irrelevant stimulus (medium or odor) • 3rd stage – Reversal 1 (R1) • Same as above, but the (-) stimulus is now (+)

15. Testing (cont.) • 4th stage – Intradimensional shift (ID) • Same setup as CD except all new odor and medium. Relevant stimulus still the same as 2nd stage. • 5th stage – Reversal (R2) • Same setup as above except (-) stimulus now (+)

16. Testing (cont.) • 6th stage – Extradimensional shift (ED) • All new mediums and odor introduced, relevent stimulus now switched. If odor was relevant cue originally, now medium is the relevant cue. • 7th stage – Reversal 3 (R3) • Same as above but (-) stimulus now (+)

17. Protocol

18. Experiments • Experiment 1 • Effect of CIC stress on rAST • 24 rats. 12 control - 12 CIC • Note – CIC protocol was 14 days not 7 as in previous papers • 7 days prior to testing food was restricted to 14g/day (promote reward seeking)

19. Results – Exp. 1

20. Experiment 2 • Effect of 5-HT depletion on rAST performance • 20 rats randomly assigned to two groups, vehicle (control) or PCPA (4-chloro-DL-phenylalanine methyl ester hydrochloride) delivered intraperitonealy. • PCPA – tryptophan hydroxylase inhibitor. Depletes serotonin levels (96.6%) • Note: 5-HT depletion isn’t localized, whole body.

21. Results – Exp. 2

22. Experiment 3 • Effects of acute citalopram administration on CIC rats in the rAST • Citalopram – SSRI, not sure of exact mechanism • 43 rats randomly assigned to two groups. • Control • Citalopram • Vehicle Control • CIC • Citalopram • Vehicle Control

23. Results – Exp. 3 Citalopram = 5-HT reuptake inhibitor.

24. Experiment 4 • Effects of CIC on 5-HT release in Orbitofrontal cortex • 24 rats randomly assigned to two groups • CIC • Control • All had microdialysis probes implanted into the Orbitofrontal Cortex to monitor 5-T release.

25. Results – Exp 4

26. Reversal Learning Effective reversal learning involves a number of specific and distinct operations, including: • Detection of the shift in contingency (i.e. “error detection”) • Inhibition of the prepotent, previously learned positive response • Overcoming learned avoidance of the previously negative stimulus • Acquisition of the new association.

27. Conclusions • Apparent dysregulation of serotonergic function in the OFC of rats exposed to CIC stress.

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