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Cognitive Neuroscience (Fach) / Memory under Stress (Lektion)

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• Does stress during encoding enhance or impair memory? Name two studies to support you answer. There are findings that support both, enhancement and impairment. Thus, more research is needed to fully understand the effect stress during encoding has on memory. Kirschbaum et al. (1996): Stress-induced cortisol before learning of word list impairs memory. Domes et al. (2002): Stress-induced cortisol before learning of word list enhances memory.
• Does stress during consolidation enhance or impair memory? Name two studies to support your answer. Stress during consolidation seems to enhance memory, at least for avoidance learning and emotional material. Roozendaal et al. (1993): Glucocorticoids (Corticosterone or Dexamethasone) after learning boosts avoidance memory in rats. Catill et al. (2003): Stress (cold pressor stress) after learning enhances memory for emotional material in humans.
• Does stress during retrieval enhance or impair memory? Name two studies to support your answer. Results rather speak for impairment of memory when stress is induced during retrieval. At least for retrieval of moderately arousing words (humans) or performance in arousing tasks (rat). de Quervain et al. (1998): Stress-induced corticosterone increase impairs memory retrieval (rats, spatial memory in bucket to find platform). Buchanan et al. (2006): Cold-pressor induced stress before retention testing in humans impairs retrieval of moderately arousing words, but not retrieval of neutral or highly arousing words.
• Stress during encoding seems to change the quality of memory systems. Explain with two studies. Stress during encoding promotes a relative shift from spatial (flexible, but more challenging to learn) to S-R memory (easy to learn, but rigid).  Kim et al. (2001): Stress before training promotes shift from spatial to S-R memory (rats, bucket, platform). Schwabe et al. (2007): Stress before learning promotes relative shift from spatial to S-R learning (without affecting performance).
• Imaging Data - Encoding Schwabe et al. (2012): Stress reduces hippocampal activity during classification learning and changes hippocampal vs. striatal contributions to learning. Schwabe et al. (2013): Stress induces opposite changes in amygdala coupling with hippocampus and striatum, respectively.
• How can knowledge about stress effects on memory and involved brain areas be transfered to PTSD understanding and treatment? Describe the study of Pitman et al. (2002). In PTSD the traumatic experience can be seen as an extreme stressor, causing overconsolidation of trauma memory and possibly a shift towards non-declarative memory. Pitman et al. (2002): Patients were given a placebo (control group) or propranolol (beta blocker that impedes noradrenergic activation in basolateral amygdala and therefore inhibits stress response) within 6h and for 10 days after an accident. PTSD symptoms decreased from 87% in placebo group to 61% in propranolol group (not significant, but clinically relevant; tests were conducted 1 and 3 months after accident).
• Briefly describe the model of Roozendaal and McGaugh on interactive effects of glucocorticoids and noradrenaline. What predicitions can be made from the model? Explain the study of Roozendaal (2006). Roozendaal & McGaugh: Memory is altered by concurrent glucocorticoid and noradrenergic activity in the dorsolateral amygdala. stress effects should disappear after glucocorticoid or noradrenergic blockage. stress hormone effects should disappear after basolateral amygdala damage. Roozendaal et al. (2006): Cosolidation - Glucocorticoid effect disappears after beta-adrenergic (propranolol) blockade in the amygdala, but not in the hippocampus (rats explore new light bulb longer than old one). Habituation makes glucocorticoid effect disappear (no noradrenaline present). Glucocorticoid effect returns after pharmacological increase of noradrenergic activation by Yohimbine (alpha blocker). => Glucocorticoid-effect only present with noradrenergic activation in the amygdala!

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