Full lecture notes for Emotion lecture in Neuroscience and Behaviour module (C82NAB). Includes biological information, evolution, rewards, dopamine, processing.
Problem = showing and measuring emotion objectively for science.
Emotions are states elicited by rewarding or aversive stimuli and their omission or termination.
These states compromise thoughts “feelings” and physiological behavioural responses to
emotional stimuli.
Evolutionary considerations
Physiological / behavioural responses to aversive and positive stimuli have fundamental survival
value and therefore, have been relatively preserved throughout evolution and are often very
similar in different animals including humans.
The principal organisation of the brain is very similar among all mammalian species.
Key structures with relation to emotion – hippocampus, amygdale, hypothalamus.
Rats
- Easy to breed and keep – low demands
- Well established behavioural tests
- Brain large enough to apply selective manipulations to distinct brain structures and brain
anatomy very well characterised.
- But genetic manipulations difficult – so use mice – gene knockout is possible in mice.
Hippocampus, amygdala and hypothalamus
- Papez theory of emotion (1937) – limbic circuit
- Kluver and Bucy’s description of temporal lobe lesion effects in monkeys
Prefrontal cortex
- Case of phineas gage
Meso-corticolimbic dopamine system
- VTA midbrain
- Brain-stimulation induced reward
Fear and Anxiety
Animal research on brain substrates of emotion over the last 30 years has focused on fear and
anxiety – normally elicited by aversive stimuli.
Fear refers to phasic escape or avoidance responses to distinct aversive stimuli.
Anxiety refers to a tonic response to diffuse aversive situations and is associated with conflict
and uncertainty.
There are many different types of fear and anxiety responses, and the brain substrates of these
different responses may differ.
Fear and anxiety related disorders in human include generalised anxiety –disorder, OCD, panic
disorder, PTSD, and phobias.
20% of the population suffer from an anxiety disorder.
Drugs treating anxiety disorders – anxiolytics, benzodiazapines, very striking similar effects to
removing the hippocampus.
, Amygdala
Classical fear conditioning – tone & shock. Then just tone causes freezing.
CHECK SLIDES – diagram
Lesions to lateral and central amygdala in conditioned fear
- Sham: (needle inserted but not no damage) caused freezing.
- Basal lesions (control group) caused freezing.
- Central Lesion: caused much less freezing.
- Lateral Lesion – even less freezing.
Patient SM046 – damaged amygdala. Looked at conditioning – unpleasant noise (aversive)
conducts a GSR (objective measure). Doesn’t show emotional conditioning, even though she can
remember the noises.
PTSD sufferers show hyperactivity in the amygdala when presented with aversive stimuli.
CHECK SLIDES
Hypothalamus
Lesions of lateral hypothalamus and caudal central gray before fear conditioning
Lesions to the central grey shows intact blood pressure response but abolished freezing
response.
Damage to the lateral hypothalamus abolished blood pressure response.
Hippocampus
Ventral hippocampus
- Rat will stay in arms of maze – scared
- If dorsal lateral lesions : stays the same
- Ventral lesion or complete lesion: diminished fear response.
Rewards
A reward is an object or event that elicits approach and is worked for.
Reward is association with wanting and liking. Wanting is characterised by ‘feeling’ of desire and
approach behaviours.
Liking is characterised by feeling of pleasure (explicit liking) and other objective responses
(implicit liking) e.g. facial impressions.
Alterations in the brain substrates of reward-related processes and are likely mechanisms
underlying addiction.
Instrumental conditioning
- Reward (food) reinforces motor response.
Intracranial electrical self-stimulation
- Which brain sites spontaneously excite when having a reward?
Intracranial drug self-administration
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