Emotion - Neuroscience and Behaviour (C82COG)

Emotion

 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