Networks in the brain

Networks in the brain

1. Subcortical memory

   • Structure of the diencephalon
   • Korsakoff's syndrome - B1 deficiency
     • (1) Wernicke's Encephalopathy: Confusion, ataxia, thiamine treatment (2) Korsakoff's: retro- and anterograde amnesia, confabulation
       • Double dissociation with Parkinson's
     • Destruction of mammillary bodies
   • Patient BJ and Patient NA
   • Neurotoxically lesioned animals demonstrated impaired spatial memory
   • Controversy - does this represent separate memory systems?

2. Basal Ganglia

   • Structure
   • Parkinson's Disease - damage to substantia nigra = less dopamine = difficulty 'turning off' inhibition of motor movements
     • Impaired procedural memory (Tower of Hanoi)
       • Rats lesioned in caudate = impaired learning of S-R; lesioned in putamen = disruption to habitual behaviours
         • McDonald & White (1993): win-shift/win-stay radial arm task in lesioned rats
     • Double dissociation with Korsakoff's

3. Emotion

   • Definition of emotion
     • Physiology
     • Behaviour
     • Feelings
   • James-Lange Theory of Emotion
     • Stimulus => ANS => Fear
     • Cannon-Bard
       • Fear without SNS therefore emotion in the brain
   • Hypothalamus coordinates peripheral expression of emotion (Ranson & Hess)
     • Papez Circuit/Limbic system
   • Weiskrantz (1950s) avoidance conditioning locates amygdala as source of weird behaviour
     • Kluver-Bucy syndrome - removing temporal lobe s results in weird behaviour
     • Pavlovian fear conditioning modulated by amygdala+ lesioned amygdalas result in atypical fear response to robotic "predator"
     • Patient SM (with amygdala lesions) had no fear response or recognition of fearful faces, depite intact face recognition
     • No conditioned response to shock-predictive stimuli
     • Recent evidence for amygdala involvement in positive reinforcement

4. Reward

   • Positive vs negative reinforcement
   • Olds & Milner (1954) - accidentally discovered self-stimulation in septal area close to hippocampus
     • Always chose stimulation over food
     • (1) Septum, (2) Amygdala (3) hypothalamus, (4) nucleus accumbens (NAc), (5) Prefrontal cortex
       • Medial forebrain connects Ventral Tegmental Area (VTA) with NAc
   • Dopamine release drives self-stimulation,
     • Dopamine antagonists/lesions to VTA/NAc pathway disrupts reward seeking behaviour
     • Dopamine released in NAc to rewarding images (e.g. food, sexual)
     • Most drugs release dopamine into NAc
     • Related to reward PREDICTION, not pleasure: Wise anhedonia theory contradicted by Parkinson's patients not reducing liking
       • Incentive Salience