Emotion 1 Flashcards
what are emotions?
- states elicited by rewarding or aversive stimuli (S+ or S-) and their omission (-) or termination (!)
- these are states compromise thoughts (“feelings”) and physiological behavioural responses to emotional (i.e., rewarding or aversive) stimuli.
why have physiological/behavioural responses to aversive and positive stimuli been preserved throughout evolution?
- as they have fundamental survival value
- often similar in different animals including humans
- principle organisation of the brain is very similar along all mammalian species
what are the advantages of using a rat as a model system?
- easy to breed and keep
- well-established behavioural tests
- brain large enough to apply selective manipulations to distinct brain structures and brain anatomy very well characterized
what are the disadvantages of using rats as a model system?
- genetic manipulations (used to be) difficult (alternative:mouse)
what are the key milestone studies for the hippocampus, amygdala and hypothalamus?
- Papez theory of emotion (1937)
- Kluver and Bucy’s description of temporal love lesion effects in monkeys (1939)
- MacLean’s limbic system theory (1949)
what are the key milestone studies for the prefrontal cortex?
- Case of Phineas Gage described by Harlow (1868)
- Nauta (1971): Frontal lobes and interoception
what are the key milestone studies for Meso-corticolimbic dopamine system?
- Olds and Milner (1954): Brain stimulation induced reward
- Wise et al., (1978): Neuroleptoc-induced anhedonia
when fear and anxiety compromise protective/defensive responses what stimuli is normally elicited?
aversive stimuli
what does fear refer to?
phasic escape or avoidance responses to distinct aversive stimuli
what does anxiety refer to?
a tonic response to diffuse aversive situation and is associated with conflict and uncertainty
what are some fear and anxiety related disorders in humans?
- generalised anxiety disorder
- obsessive compulsive disorder (OCD)
- panic disorder
- phobias
- post-traumatic stress disorder (PTSD)
conditioned fear and the amygdala
- classical fear conditioning
- functional-anatomical model of conditioned fear: central role for the amygdala
what is the amygdala and its divisions?
- the amygdala is a subcortical structure
- lateral amygdala: input region of the amygdala, e.g. receives auditory input from the auditory area of the brain and somatosensory input from the somatosensory cortex. Plasticity can occur in th amygdala which is why we can become scared of things when they have negative associations
- central amygdala: produces the fear responses such as freezing, blood pressure changes and hormone changes
what are some examples of fear responses?
- defensive behaviour
- autonomic arousal
- hypoalgesia
- reflex potentiation
- stress hormones
Requirement of lateral and central amygdala in conditioned fear, Amorapanth et al. (2000)
- measured lesions in different amygdala nuclei before conditioning
- then subjected them to far conditioning and found that animals with lesions in the lateral and central amygdala has a higher potential for freezing in response to fear
Different CE outputs mediate different conditioned fear responses, LeDoux et al. (1988)
found that if the central brain was damaged
fear-conditioning-related plasticity in LA neurons
- stuck electrode into lateral amygdala and looked at how the response of neurones changed throughout fear conditioning
- before conditioning they respond very little to the tone, no strong response as lateral amygdala isn’t activated
- after exposed to conditioning, more readily the neurones activate in response to the tone so a response is quite quickly fired to lateral amygdala to produce fear response
- shows plasticity of the fear response
Fear in human amygdala, Bechara et al. (1995)
impairs conditioning to fear
- administered an electric shock to wrist
- measured autonomic arousal
- compared to patients response with amygdala damage to participants without amygdala damage
- found that after fear conditioning the control condition showed increase skin conduction, so showed more fear than ps with amygdala damage
fear in the amygdala, LaBar et al. (1998)
- created a fear conditioned experiment by pairing an unconditioned stimulus with an aversive stimulus (and a control condition)
- looked for amygdala activity during the acquisition of a fear response
- seemed as there was more activity in the early acquisition, and some ps showed more activity than others
- but overall doesn’t tell us much, BUT this does not mean the amygdala isn’t involved in fear conditioning, more likely to highlight issues in functioning imaging.
hippocampus in fear and anxiety, Richmond et al. (1999)
- make lesions to different parts of the hippocampus and then fear conditioned to look at a freezing response
- control conditioned showed the highest response
- conditions with lesions showed reduced freezing
- when the hippocampus was completely removed the freeezing response greatly reduced, suggesting the hippocampus was important for freexing
ventral hippocampus and innate/unconditioned anxiety responses, Kjelstrup et al. (2002)
- used an elevated plus maze, involving the animal being exposed to a high drop or closed off safer areas
- normal animals stay in the closed off space as this is an innate response to be more safe
- looked at how many times the rat ventures into the open space as a measure of anxiety, if they have less anxiety they will go into the open
- study found control animal stayed in the closed area, showed normal anxiety response
- the experimental group with hippocampal lesions go into the open areas more
- this means hippocampal lesions reduce anxiety
Hippocampal lesions as anxiolytics, McNaughton and Gray (2002)
- found that hippocampal lesions act as anxiolytics
- anxiolytics reduce activity in the hippocampus and as a result reduce anxiety
- suggests anxiety can result from too much activity in the hippocampus
Decreased hippocampal benzodiazepine receptor binding in panic disorder, Bremner at al (2000)
- scan picks up positrons emitted by tracers given to patients.
- tracer given is a benzodiazapine which binds to GABA receptors
- GABA receptors are important in the inhibition of GABA which is found that in panic disorders there was reduced binding in the hippocampus
- suggesting binding in the hippocampus is too active
