Exam 4: Affective Disorders Pt 2 Flashcards
characteristics of depression- circadian rhythms
altered in depressed individuals
-these are controlled by the molecular biological clock in the suprachiasmatic nucleus of the hypothalamus
what systems do circadian rhythms control
NE, 5-HT, DA systems - may be the basis for mood dysfunction
depression and circadian rhythms
abnormal circadian rhythm in cortisol secretion
many depressed people fail to respond to ____
dexamethasone
dexamethasone
a synthetic glucocorticoid that should act as a negative feedback to suppress release of CRF and ACTH resulting in lower cortisol levels
the most consistent neuroendocrine abnormality in depressed individuals is an abnormal secretion of
cortisol
-many depressed patients have elevated cortisol levels in response to greater than normal release of ACTH and CRF
-hypersecretion most likely due to abnormal regulation of CRF by hypothalamus
early life traumas alter the set point for what
the HPA axis
- becomes permanently over responsive
- inc risk for depression, anxiety disorders, alcohol abuse
Sleep changes in MDD
-altered sleep is most common and persistent symptom
-onset of sleep is delayed
onset of REM sleep occurs earlier
dec i slow wave or deep sleep with repeated awakenings during the night
sleep changes in bipolar disorder
during depressive episodes: sleep resembles unipolar depression
during mania sleep is greatly reduced or absent with no loss of energy
-when manic patients are treated with a sleep inducing benzo manic symptoms subside
PET scans of blood flow in depressed patients show inc activity where
orbitofrontal cortex and amygdala
inc metabolic activity in amygdala correlated with
severity of depression and returns to normal after antidepressant drug treatment
corticolimbic changes in MDD amygdala and ACC
amygdala: at rest and in response to danger
ACC: emotional conflict-should I be happy or sad about this
corticolimbic changes in MDD
hyperactivity in dorsomedial PFC
dmPFC: judgement and decision making-tells amygdala we are fine
weakened connectivity between dmPFC and amygdala in depressed individuals
-failure to properly regulate amygdala response in depressed individuals
insula in MDD
hyperactive, more aware of body states, inc HR bc nervous, pit in stomach
thalamus (PVN) in MDD
visual relay of thalamus activated when viewing emotional faces
-good at picking up on emotions of others - why they think so many people upset with them
depression is associated with lack of cortical control over what
the limbic system
- resting state fMRI shows successful treatment is associated with inc connectivity btw PFC and limbic areas
- antidepressants inc connectivity
glucocorticoid hypothesis
focuses on stress-related neuroendocrine abnormalities of depression
-depressed patients have abnormally high CRH secretion from HPA axis
HPA axis
amygdala stimulates HPA axis activity
hippocampus has inhibitory control
hippocampus and depression
-involved in shutting down activity of HPA axis - overrides and shuts down amygdala induced HPA activity to limit duration of stress response
when stress is prolonged and intense, glucocorticoid levels remain high and what happens
hippocampal neurons are damaged
-can no longer regulate stress response
damage: dec dendritic branches and spines in PFC and hipocampus
formation of new hippocampal cells is inhibited
-dec neurogenesis and dec BDNF
antidepressants have what actions involvig hippocampus and depression
reduce CRH levels and reverse loss of hippocampal dendrites in animal studies
Hippocampal BDNF and depression
BDNF is low in hippocampus and PFC
dec BDNF due to genetic polymorphisms associated with depression
chronic stress dec BDNF in hippocampus
chronic antidepressant treatment inc BDNF
antidepressants prevent stress induced reduction in BDNF and neuronal atrophy - protect brai from stress
changes in brain with bipolar disorder - mania
- PET scans show inc brain activity in manic episodes
- some similarities with schizophrenia like enlarged ventricles (meaning tissue death)
- altered corticolimbic activity (connectivity reduced)
changes in amygdala function throughout bipolar stages
hyperactivity in resonse to emotional faces in mania - euphoria, insomnia, inattention, distractibility
- dec amygdala function during depressive episodes
- dec activity in ventrolateral PFC in all stages (less contorl of amygdala in bipolar patients)
functional connectivity btw vlPFC and amygdala - poor reguation in Bipolar patiens
