Agenda: Neuroscience

Transcription

1 Agenda: Neuroscience Announcements Gender & trauma Neuroanatomy and functionality Hippocampus, stress, and memory Brain function studies amygdala, Broca's area, frontal lobes Findings in children Ethical issues 16POT5b - 1

2 Midterm Midterm on Tues (5/3) Study guide on ecommons in Handouts folder Call numbers for films on schedule page Today s material (lecture/readings) not on test 16POT5b - 2

3 Walk a Mile in Her Shoes Proceeds support sexual assault survivors Sponsored by Monarch Services More info: 16POT5b - 3

4 Trauma & Trans People Transgender people are at high risk of discrimation and violence In Shipherd et al. 98% experienced traumatic event of these, 42% had a gender identity related trauma 18% had PTSD 64% had depressive symptoms 91% had more than one trauma 16POT5b - 4

5 Discrimation & PTSD Reisner et al. surveyed 412 transgender adults Reported experiences of discrimination and attributions top 5: gender identity/expression, masc/ fem appearance, sexual orientation, sex, age Discrimination correlated with PTSD symptoms 16POT5b - 5

6 The Nature of Stress series60.html Stress and brain; stress and race: 10:45-15:45 Can also review PTSD: 31:10 43:45 16POT5b - 6

7 Brain Anatomy 16POT5b - 7

8 Neuroanatomy and Functionality Corpus callosum Primary pathway for information exchange between left and right hemispheres Left hemisphere verbal tasks, especially language (Broca s area) Right hemisphere spatial information emotional information (especially negative emotions) 16POT5b - 8

9 Hippocampus Important for short-term memory and consolidation into long-term memory Categorizes stimuli (esp. as reward, punishment, novel) creates simple maps or summaries evaluates how stimuli relate to long-term memory (LTM) essential for formation of explicit, declarative memories 16POT5b - 9

10 Amygdala Important for processing emotional information Assigns a "feeling" (or affective label) to input neocortex elaborates and connects it with episodic (personal) info to give it meaning Integrates emotional and non-emotional information about stimuli Alarm center, smoke detector 16POT5b - 10

11 Frontal Lobes More specifically, pre-frontal cortex "Central executive": planning, thinking, executing Medial prefrontal cortex inhibit responses from more primitive brain areas (e.g., limbic system) Mood regulation 16POT5b - 11

12 Hippocampus, Stress, Memory Exposure to prolonged stress results in deficits in short-term memory (STM) function experiments on animals also, correlational studies in humans on PTSD and cognitive functioning 16POT5b - 12

13 Glucocorticoids Adrenal steroids secreted during stress In humans, cortisol is the main glucocorticoid Helps us respond to threat and attack suppresses functions not immediately needed (e.g., digestion, immune system) directs energy to brain and muscles Causes pathology under prolonged stress 16POT5b - 13

14 Glucocorticoids & Hippocampus High levels of GC (due to stress) results in damage to neurons of hippocampus decrease in # of neurons changes in "cytoarchitecture" (e.g., less branching, fewer connections) Overexposure to GC results in degeneration or "accelerated aging" of hippocampus 16POT5b - 14

15 Brain Structure: MRI Studies Magnetic Resonance Imaging looks at structure of brain PTSD and stress associated with reduced hippocampal volume 16POT5b - 15

16 Gurvits et al. : Vietnam vets Participants 7 Vietnam vets w/ptsd 7 Vietnam vets w/no PTSD (ever) 8 controls (non-veterans; no history of trauma or PTSD) Method completed neuropsychological tests MRI analyzed to examine hippocampal volume 16POT5b - 16

17 Gurvits et al. Results PTSD group performed more poorly on most neuropsych tests esp. attention/concentration Hippocampal volume PTSD group 26% lower volume than non- PTSD group negative correlation between severity of combat exposure and hippocampal volume 16POT5b - 17

18 Stein et al. - CSA survivors Participants 21 women w/csa history 21 women wo/csa history MRI to measure hippocampal volume HV 5% smaller in CSA group severity of dissociative symptoms correlated to left hippocampal volume 16POT5b - 18

19 Critique 1: Replication Some studies have failed to replicate children vs. adults meta-analysis 16POT5b - 19

20 Meta-analysis Multiple meta-analyses Consistent finding of link between PTSD and low HV O Doherty et al. 36 studies ( ) 1623 participants lower HV in PTSD vs. healthy controls lower HV in PTSD vs. traumatized controls 16POT5b - 20

21 Critique 2 - Causality Maybe low hippocampal volume (HV) makes you more susceptible to PTSD, if you experience a trauma But, HV correlates w/severity of trauma numerous studies But, study of identical twins shows similar HV for twins w/ and wo/trauma/ PTSD small number of studies 16POT5b - 21

22 Other Limitations No repeated measurements of HV what happens over time? when does the volume loss occur? No links to process and experience relation to clinical symptoms? what are specific mechanisms whereby reduced HV leads to flashbacks or other memory impairment Control groups adequate? Small samples 16POT5b - 22

23 Hippocampus and Dissociation Hippocampus important in integrating stimuli into one coherent memory Obvious link to dissociation Evidence that hippocampus is implicated in dissociation in surgery, stimulating Hippo. leads to dissociative symptoms ketamine (which blocks certain receptors w/high concentration in Hippo.) leads to dissociative symptoms 16POT5b - 23

24 Interesting Implication Peritraumatic dissociation we know it's a risk factor for later PTSD Bremner (p. 122) "may represent not a risk factor for later pathology, but instead the initial onset of a PTSD-dissociative spectrum disorder. Dissociation at the time of trauma may represent the subjective sensation of hippocampal damage at the time of stress" 16POT5b - 24

25 Brain Function: PET/FMRI Studies Positron Emission Tomography (PET) Useful for studying brain function "Tagged" (radioactive) O 2 molecules Allows tracing of glucose uptake on real-time basis More glucose = more activity Can see what parts of brain are "firing" moment by moment 16POT5b - 25

26 PET Methodology Ps listen to a verbal script specific to their trauma Control condition: they listen to a neutral script Within-participant study Goal is to understand what happens during flashbacks Prediction: flashbacks involve different brain regions than regular memory 16POT5b - 26

27 Rauch et al. Symptom provocation study Participants Child abuse, combat, assault, witnessing death of others All met criteria for PTSD 3 Conditions two traumatic events two neutral events (brush teeth, empty dishwasher) teeth-clenching 16POT5b - 27

28 Results Manipulation check Ps reported that emotions aroused in trauma condition were similar to their dayto-day experience of PTSD symptoms heart rate higher in trauma than neutral condition 16POT5b - 28

29 Results: Trauma vs. Control Main differences in (increased) activity right hemisphere limbic and paralimbic including amygdala Also differences (increases) in right secondary visual cortex Decreases in Broca's area No difference hippocampus 16POT5b - 29

30 Study of Combat Vets Similar results found in study of combat vets comparing those with vs. those without PTSD PTSD group had: increased activity in right amygdala decreased activity in Broca's area 16POT5b - 30

31 Frontal Lobes Frontal lobes function executive control (planning, organizing) inhibit response from lower brain regions Medial prefrontal cortex functioning may be impaired in PTSD patients symptoms: can't distinguish real from simulated threats PET studies: decreased blood flow to this area 16POT5b - 31

32 Studies of Children: Teicher (2002) Trauma may lead to impaired lefthemisphere development Ps children and adolescents 15 survivors of intense physical or sexual abuse 15 controls Method: EEG (electroencephalogram) measures overall activity 16POT5b - 32

33 Results: Left hemisphere Right-hemisphere development equal Left-hemisphere development diminished in abuse group Left hemisphere dominant for control group typical for right-handed Right hemisphere dominant for abused group 16POT5b - 33

34 Results: Corpus Callosum In boys, corpus callosum smaller in abuse group than in control group In girls, corpus callosum smaller in sexually abused group than control group CC important for information exchange related to dissociative symptoms? 16POT5b - 34

35 Tentative results small numbers Questions what does impairment of left hemisphere mean? Question: Does trauma affect the developing brain differently than the mature brain? 16POT5b - 35

36 Your Brain Vidoe Your brain on stress and anxiety Use as an additional review, if desired note that this video covers more than I did in class you won t be tested on this extra material 16POT5b - 36

37 Baard Article: Ethics "New Science Raises the Specter of a World Without Regret: The Guilt-Free Soldier" (Baard, Village Voice, 2003) Preliminary studies on how to reduce impact of traumatic events Psycho-pharmaceutical treatments at the time of trauma might reduce later symptoms in part by affecting memory storage 16POT5b - 37

38 Treatment example Propranolol: ("beta blocker") drug to block effects of epinephrine and norepinephrine treatment for cardiac problems and hypertension off-label for stage fright experimental work administering immediately post-trauma to accident victims perhaps damage to hippocampus can be prevented 16POT5b - 38

39 Ethical Questions Do we want to eliminate memory for trauma? We have an obligation to "Never forget" (the Holocaust) (Bremner, ch7) Perpetrator vs. victim Morally ok for survivor, but not perpetrator? For survivor, pain/mental health vs. having ownership of self and one's history 16POT5b - 39

40 Some Thoughts For survivors, goal of treatment could be to get control of memories not to forget, but also not be subject to flashbacks For perpetrators, they deserve healing too "But is treating that worse than saying, 'Don't worry if your leg is shot off, we've got penicillin and surgery to prevent you from dying of infection'? Why is it any worse to give them a drug that prevents them from having PTSD for the rest of their lives? The moral dilemma is sending people to war in the first place." (McGaugh, quoted in Baard) 16POT5b - 40

41 Jessica Williams: Black Friday Profiling video-clips/ kqm9ge/thedaily-show-withjon-stewart-blackfriday-profiling Closing 16POT5b - 41