neuro-biology of depression Flashcards
function of frontal lobe?
(planning + organisation) primary motor cortex supplementary motor cortex executive functions broca's area (originates speech) affect on behaviour in conjunction with the temporal lobe
function of parietal lobe?
sensory cortex Wernicke's area (understanding of language) orientation recognition construction
function of temporal lobe?
primary auditory cortex music recognition memory emotion behaviour
function of occipital lobe?
primary and secondary visual cortex
what are the areas of the limbic system?
cingulate gyrus hippocampus amygdala hypothalamus septum olfactory bundle dentate gyrus anterior nucleus of the thalamus mammillary bodies
what are the main functions of the limbic systems?
emotion
motivation
memory
function of the amygdala?
critical for conditioning and emotional processing
input from a range of sensory areas
connected to areas that control autonomic function, motor action, neuro-endocrine responses
types of imaging done on the brain?
MRI
f MRI
SPECT
PET
what do MRI and CT show in patients that are depressed?
white matter changes are related to depression
patients with white matter changes have relatively poor response to treatment
structures in the brain can be measured
changes in the size of the hippocampus in depression?
hippocampus has major role in memory functions
in depressed patients, the hippocampal volume is consistently and significantly reduced
reduction in hippocampus correlated with duration of illness
functional imaging used to measure relative activity of parts of brain?
fMRI
PET
SPECT
describe fMRI
focuses on blood flow
measures the difference between oxygen rich and oxygen poor blood flow
therefore measures neuronal activity in brain areas and spinal cord
fMRI in depression (pre and post treatment of amygdala and cingulate gyrus)
amygdala and cingulate gyrus signals are abnormal before CBT treatment and normalise after treatment
pre-treatment decreased reactivity in the cingulate gyrus and increased reactivity in the amygdala are related to better outcomes post treatment
what is SPET?
single-photon emission tomography
principles of PET and SPET?
gamma emitting radio-isotopes
the isotopes connect to certain structures in the brain
cameras to detect the emitting radiation
computer programmes to quantify
(PET shorter 1/2 life isotopes and more expensive)
what can PET and SPET measure?
blood flow
brain activity
receptors
mal-function of the prefontal areas in depression
enhanced sensitivity to pain, anxiety, depressive ruminations
psychomotor retardation, apathy and deficits in attention
disconnectivity between the prefrontal areas and the limbic system results in disregulation of emotional control
cortisol / HPA axis in depression
cortisol levels found to be consistently high in depression
disregulation in the HPA axis appears to be related to hippocampal atrophy
neuroendocrine changes in depression
cortisol
thyroid
(GH)
function of cortisol
implicated in responses to stress
exogenous cortisol has an effect on mood
dexamethasone suppression test
thyroid abnormality in depression
TSH response to TRH blunted
thyroxin sometimes used in depression
cytokines and depression
evidence of over activity of cytokines in depression possibly caused by:
increase in sympathetic tone (caused by HPA axis overactivity and amygdala disregulation)
disruption caused by cytokines can result in?
fatigue
loss of appetite
loss of libido
hypersensitivity to pain
also disrupts other hormone systems e.g. blood sugar control
negative effects on neurotransmission and neuro-trophic factors
main substance of neuro-trophic factors?
brain derived neuro-trophic factor (BDNF)
