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The HPA axis & Memory Function In Humans
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Impact of stress on memory 2 principal effects Forget something due to stress e.g. wedding anniversary Vivid memory of an emotional situation e.g., car accident
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Differences between STRESS and EMOTION Similarity --> Stress : Always cause an emotion --> Emotion : Can cause a stress In both cases: --> Can identify the source --> Lasts for a brief moment --> Creates physical reactions - Cardiac rhythm perspiration
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Difference between STRESS and EMOTION Differences : --> Stress always causes an emotion --> Emotion is not always stressful Laboratory : --> Emotion : Images, words, etc. --> Stress : public speaking
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Impact of EMOTION on Memory
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MEMORY is a processus that develops in time ENCODING -Vigilance -Attention consolidation -Attention : Permits elaboration …more elaborate…better recalled RECALL
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Attention, Emotion and Memory.... The amount of attention allowed to an event will depend on the VALENCE of this event An example…..
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A question ….. --> Which one would you remember best? --> the traumatic ones. --> High Valence: Increased Attention --> Better encoding … --> Better encoding… Better recall later A demonstration….
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The ‘ Flashbulb Memory ’ Phenomenon … September 26, 1997... A certain date Emotion Attention Attention =Elaboration Explication
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Memory of an emotional event Study of trauma victims --> Excellent memory of traumatic event --> Poor recall of surrounding events First particularity: -Memory for details vs periphery ‘Weapon Focus Phenomenon’
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Weapon Focus Phenomenon
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Memory of an emotional event Study by Christianson : -Series of Slides: 2 groups Group 1 : Neutral slides through the series Group 2 : One slide depicts a traumatic events In both series : the background is the same (e.g. bicycle/house) Results : Group 1 remember more background information than Group 2 --> Trauma : Focussing on central details
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Memory of an emotional event -Trauma : Can lead to Post-Traumatic Stress disorder --> Dissociation (might be related to high focus on central) --> Depersonalization (Detachment from self) --> Derealization (Everything seems unfamiliar) --> Flashback (Intrusive Flashbulb memory phenomenon) --> Hyperarousal (Red Flags everywhere) --> Intrusive Symptoms (« Reliving » of the trauma)
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Acute Stress Disorder vs Post-Traumatic Stress Disorder Months TRAUMA Acute Stress Disorder 1 month3 months Acute PTSD 6 months Chronic PTSD
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Memory of an emotional event Focus on Central Details : Memory Bias in ANXIETY Feelings of Lack Of control over « threatening » Situations
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Anxiety Symptoms Panic Attacks Generalized Anxiety Disorder
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Anxiety & Memory In anxiety, there is an attentional bias for threat Anxious patients (and also PTSD patients) have a tendency To systematically attend to threatening informations and to Avoid processing non-threatening information Problem in SELECTIVE ATTENTION: --> Capacity to discriminate between RELEVANT and IRRELEVANT information In anxious patients : RELEVANT = THREATENING
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Anxiety & Memory Study 1 : Eysenck et al., (1987) --> 2 groups AnxiousNon-Anxious Task : Listen to words and write them down later --> 2 types of words : Neutral vs Homophones with threat e.g. Die vs Dye --> Results : Anxious patients remember all the negative homophones Conclusion : Memory bias for threatening information
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Anxiety & Memory Study #2 : Eysenck et al., 1993 2 groups : Phobics for spiders vs controls Task : Stroop neutral vs emotional words RedBlueYellowJeansHouse Spider GreenBlackPinkCatWeb Dog Results : Phobics have longer Reaction times to name the color of phobic words Conclusion : Attentional bias against threatening information
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Second particularity : -Immediate vs Delayed memory Emotional Events : --> Immediate Recall : Poor --> 2 weeks after : Excellent Memory of an emotional event
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Immediate vs Delayed Memory of emotional events Study by Cahill et al., 1998: 2 groups of controls Task 1 : 12 slides all neutral Task 2 : 12 slides, those 4 in the middle (5-8) are emotional Slide number 1-4 5-8 9-12 Neutral group Emotional Group Recall : performed 2 weeks after encoding
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Biological Explanation Release of Adrenaline Cardiac Rhythm Perspiration Tremors Consciousness of state : Memory Memory of an emotional event Implication : « False-Feedback »
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Memory of an emotional event Study #2 Cahill et al., (1998) : --> 2 Groups : Placebo vs Propanolol (antagonist adrenaline) --> Both groups received the emotional story with 12 slides Slide number 1-4 5-8 9-12 Propanolol group Placebo Group Results : Conclusion : if you block adrenaline secretion, you block the enhancing effects of emotion on memory
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Memory of an emotional event Antagonist adrenaline block memory enhancing effects of emotion Application to traumatic syndrome --> New York Scientists : Clinical trial in ASD victims --> Administer propanolol very close to the time of trauma Rationale : By blocking adrenaline surge induced by trauma (with administration of antagonist adrenaline) one might prevent the induction of the traumatic flashbulb phenomenon
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Hormonal dysfunctions in PTSD Other hormonal dysfunction in relation to trauma Cortisol levels in PTSD patients : --> DECREASED basal cortisol levels --> ENHANCED negative feedback inhibition
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Hormonal dysfunctions in PTSD 1. Decreased Basal cortisol secretion Yehuda et al., 1992 : Women with a prior history of rape had significantly lower cortisol levels in the immediate aftermath of a rape Conclusion : First trauma : decreased cortisol levels These decreased cortisol levels prevent further stress-related « normal » cortisol response
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Hormonal dysfunctions in PTSD 2. Enhanced negative feedback sensitivity CRF ACTH GCs - - Dex : 0.5 mg (usual dose = 1 or 2 mg) PTSD : Suppress cortisol levels faster and with a stronger response Hyper-suppressor to DEX Remember : Depressed are non-suppressor to DEX so this is a major difference between PTSD and depression
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Hormonal dysfunctions in PTSD Yehuda 1999 : Personal communication The children of Holocaust survivors Suffering from PTSD also present The hormonal dysfunction of PTSD Possibility of a Genetic component
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Impact of STRESS on Memory
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HORMONES CRF ACTH GCs + + - - Stress ResponseRecovery GLUCOCORTICOIDS
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Circadian Rhythm 81216202448 Krieger, 1978 GCs Time
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HORMONES CRF ACTH GCs Stress Response + + - - GC Receptors -Type I : High Affinity -Type II : Low Affinity
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Animal Studies Receptor affinity High GCs : -Decreased Memory -Negative Effects on Hippocampus Adrenalectomy : -Decreased Memory -Negative Effects on Hippocampus Inverted-U shape function between GC levels & cognition Memory Performance Circulating Levels of GCs Same Inverted-U Shape between GCs and LTP In rats
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Adrenal Steroid Receptors : AFFINITY Levels of circulating glucocorticoids Type I receptor activation (6 fold higher affinity) Type II receptor activation (low affinity for GC) BASAL Levels of GC STRESS Levels of GC Localization of Steroid Receptors in the Brain
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Mechanism? Receptors : 2 Types Different Affinity Different Distribution in the Brain Type I : High Affinity Type II: Low Affinity AFFINITY Hippocampus : Frontal : DISTRIBUTION
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Circulating Concentrations GCs Memory Performance Important implications For the effects of Glucocorticoids on Memory function
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Memory Performance CIrculating Levels of Glucocorticoids facilitationinhibition Activation Type I Activation Type II Young AFFINITY & HIPPOCAMPUS Decrease in Cortisol Replacement of Cortisol Hormone Replacement Protocol
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Young 8% MR GR SST Mnesic Performance Circulating Glucocorticoid Levels facilitationinhibition Activation Type I Activation Type II Moderate Cortisol - Young
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This is not the end of the story….. …There are also GC receptors in the frontal lobe
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Type I Type II Anatomical Distribution of Type I and Type II Type I : Tonic Influence on HPA Acute Increase Of Cortisol Working Memory Hypothesis : Working memory should be more sensitive than declarative memory to an acute increase in cortisol levels
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Population : Young Task : Working vs Declarative Memory Drugs : Placebo vs 60 vs 300 vs 600 mcg/kg/h hydrocortisone (infusion)
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Cortisol Cortisol (µg/dl) Placebo 40µg/kg/h 300µg/kg/h 600µg/kg/h 845900920105513001345 0 25 50 75 100 Time **
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RelatedUnrelated 0 2 4 6 8 10 1212 Placebo 40µg/kg/h 300µg/kg/h 600µg/kg/h Word Pair Association Correct Recall Declarative Memory Results :
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Effets of Stress Hormones on Human Memory …. A lot of methodological implications related to the : Inverted-U shape curve Receptors in Frontal Lobe
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Circulating Concentrations GCs Memory Performance Stress/GCs
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Circulating Concentrations GCs Memory Performance GCs AM Levels GCs PM Levels Fehm-Wolfsdorf et al., 1993: Placebo : Memory > Placebo : Memory <
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Circulating Concentrations GCs Memory Performance AM PM Stress/GCs Fehm-Wolfsdorf et al., 1993: Lupien et al., 2002
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Circulating Concentrations GCs Memory Performance -Young -Normal Adults -PTSD -Burn-Out -30% Elderlies -Alzheimer -Depressed
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Circulating Concentrations GCs Memory Performance -Young -Normal Adults -PTSD -Burn-Out -30% Elderlies -Alzheimer -Depressed Stress/GCs Lupien & McEwen, 1997
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Conclusion : --> The impact of stress hormones (glucocorticoids) on memory function are RELATIVE, I.e. They depend on --> Time of day --> Population --> Dose
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