Pleasure, feeding & reward Flashcards
what is the liking circuit in the brain?
hedonic circuit - circuits composed of interconnected hedonic hotspots
hedonic feeding is driven by what
the pleasure of consuming the food
what are the three components of feeding and reward
‘liking’ (hedonic: pleasure)
‘wanting’ (motivation) - via sensory cues
Learning (association and predictions)
what is incentive salience
motivation for rewards that is driven by both physiological state and previously learned associations about a reward cue
give three examples of eating disorders
obesity, bulimia and anorexia
ablation of orexigenic neurons in adult rodents causes what
causes cessation of eating and death
where do the inputs to the hypothalamus come from after feeding
brainstem, pancreas, intestine, liver
what are the two outputs of the hypothalamus that regulate appetite
orexigenic (increases appetite) & anorexigenic (decrease appetite)
how did Olds and Milner identify the rewards center in the rodent brain stimulation reward in 1954
Implanted electrode into brain, to deliver electrical stim. The rodent was able to use a lever to start the stimulation. Putting the electrode on different parts, some places it caused the lever to be pressed over 200 times - the work led to the idea that there is a reward system in the brain
robust self stimulation behaviour is obtained with electrodes along the______________
medial forebrain bundle MFB
other than the MFB what other brain areas result in self stimulation when electrodes are placed on there
- Nucleus Accumbens (NAcc)
- Lateral hypothalamus (LH)
- Ventral Tegmental Area (VTA)
- Cortical structures (prefrontal cortex, orbitofrontal cortex, insular cortex?)
what are the key structures of the reward circuit
- Medial forebrain bundle
- Reward circuit includes axons that project from the VTA (ventral tegmental area) to the nucleus accumbens (Mesolimbic Dopamine Pathway)
- VTA connects to the amygdala, septum and regions of the cortex
- Hypothalamus receives inputs from structures within the reward circuitry
how can you measure liking reactions?
behavioral analysis of ‘liking’ reactions - positive facial liking: relaxed facial expression and rhythmic tongue protrusions
what aversive reactions indicate dislike
facial disliking expression: gapes, turning away and head shakes
what neurochemicals are involved in hedonic circuits
Opiods and endocannabinoids
give three endogenous opiods
enkephalins, dynorphins and endorphins
what are the three opioid receptor subtypes and what kind of receptor are they
mu, kappa and delta (are GPCRs)
give an example of an agonist and antagonist of opioid receptors
Agonists morphine
Antagonist Naloxone
endogenous opiods are _____
neuropeptides
endogenous endocannabinoids are ______
lipid molecules
give two types of endocannabinoid
anandamide and 2-arachidonoylglycerol (2-AG)
what are the two cannabinoid receptor subtypes - what kind of receptor are they
CB1 and CB2 - GPCR receptors
injection of what discovered the different functional regions of the nucleus accumbous
an opioid receptor agonist DAMGO (specific for mu subtype
what opiod wanting and liking zones are in the NAcc
what opioid wanting and liking zones are in the NAcc
hedonic hotspot (liking increase), hedonic coldspot (liking decrease), wanting hotspot (eating increase) and disliking decrease
where are the hedonic hotspots in the brain
orbitofrontal cortex, insular cortex, nucleus accumbens, ventral pallidum, parabrachial nucleus
what is c-Fos
is a protein that is expressed when neurons are activated, and so increased expression of this protein provides a readout for when neurons are being activated by the drug that is being injected
how was the functional connectivity between hedonic regions of the brain mapped
• One region of the animal’s brain is injected with the DAMGO and then the brain is removed and immunohistochemical staining was used to quantify the expression of a protein called c-Fos in regions of the brain outside of the injection site.
how do you induce suppression of the liking responses
Inject noloxane into tissue blocking opioid signaling in one hotspot while simultaneously stimulating another hotspot causes the suppression of enhanced liking responses
what region is essential for the liking of pattern of behavior (if removed you completely lose the liking reaction)
ventral pallidium
where does the endocannabinoid hotspot overlap with the opioid hotspot
the CB1 and mu receptors have been identified co-localising in neurones of the Nacc to function in the release of neurotransmitters
how did experimentation determine that dopamine is responsible for the wanting motivational aspects of food reward
using the facial expression paradigm combined with neurochemical lesions in the brain to reduce dopamine signaling
•depletion of dopamine did not affect orofacial expression of liking in response to sweetness
•BUT: reducing dopamine caused the rats to no longer seek out or consume food
what is the mesolimbic pathway
aka the reward pathway, is a dopaminergic pathway in the brain. The pathway connects the ventral tegmental area in the midbrain to the ventral striatum of the basal ganglia in the forebrain.
what is the ventral striatum
a subcortical brain region innervated with dopaminergic neurons and involved in tracking the subjective value of stimuli, signaling the presence of/expectation of reward, and encoding errors and outcomes of such predictions
include the nucleus accumbens and the olfactory tubercle.
what key structure facilitates crosstalk between the reward and homeostatic systems of the brain (what does it coordinate)
the lateral hypothalamic area (orexin neurons) - coordinating appetite and motivation
