NEUR 2600 Lecture Notes - Lecture 12: Brainstem, Cholecystokinin, Libido
CHAPTER 12: WHAT CAUSES EMOTIONAL AND MOTIVATED BEHAVIOUR
● Identifying the causes of behaviour
○ Emotions
■ Cognitive interpretations of subjective feelings
○ Motivation
■ Behaviour that seems purposeful and goal-directed
○ Neuroanatomy of emotion and motivation
■ Hypothalamus
■ Limbic system
■ Frontal lobes
○ Behaviour for brain maintenance
■ Sensory deprivation
● Experimental setup in which a subject is allowed only restricted
sensory input; subjects generally have a low tolerance for
deprivation and may even hallucinate
● Hebb and Heron (1950s)
○ After about 4-8 hours, subjects became quite distressed;
few lasted more than 24 hours
○ Brain has an inherent need for stimulation; one reason that
we engage in behaviour is to stimulate the brain
■ Brain maintenance
● Rhesus monkeys in a dim room with a small door that could be
opened to view an adjoining room
○ Spent a lot of time opening the door and viewing whatever
was on display
○ Were willing to perform various tasks to look through the
window
○ The longer they were deprived of a chance to look, the
more time they spent looking when finally given the
opportunity
○ Neural circuits and behaviour
■ Researchers have identified brain circuits for reward and discovered that
they can be modulated to increase or decrease activity
● Hormones
● Chemical senses (taste and smell)
■ The main reason on a particular thought, feeling, or action occurs lies in
what is going on in brain circuits
● Chemical senses
○ Chemosignals (chemical signals) play a central role in motivated and emotional
behaviour
■ Identify group members
■ Mark territories
■ Identify favourite and forbidden foods
■ Form associations among odours, tastes, and emotional events
○ Odour and taste play a fundamental role in the biology of emotional and
motivated behaviour
○ Olfaction
■ We can discriminate thousands of odours, yet we have great difficulty
finding words to describe what we smell
■ Designed to discriminate whether information is safe or familiar
● Is the smell from an edible food?
● From a friend or from a stranger?
○ Receptors for smell
■ Scent interacts with chemical receptors
● Life of an olfactory receptor neuron is about 60 days
■ Olfactory epithelium: receptor surface for olfaction
■ Each olfactory receptor cell sends a process ending in 10 to 20 cilia into a
mucous layer, the olfactory mucosa
■ Chemicals dissolve in the mucosa to interact with the cilia
● Metabotropic activation of a specific G protein leads to an opening
of sodium channels and a change in membrane potential
■ Olfactory epithelium
●
● Any given odorant stimulates a unique pattern of receptors
● Summed activity or pattern of activity produces our perception of a
particular odour
● Olfactory system is estimated to contain about 400 kinds of
receptors
○ Olfactory pathways
■ Olfactory receptor cells project to olfactory bulb
■ Many olfactory targets (amygdala and pyriform cortex) have no
connection through the thalamus
■ Thalamic connection does project to the orbitofrontal cortex (OFC)
● Emotional, social, and eating behaviours
■ Accessory olfactory system
● Pheromones: biochemicals released by one animal that act as
chemosignals to affect the physiology or behaviour of another
animal
● Detected by a special olfactory receptor system known as the
vomeronasal organ (connected to the amygdala and
hypothalamus)
■ Human olfactory processing
● Humans have a surprisingly acute sensitivity to smells that are
behaviourally relevant
○ Can identify their own odour, the odour of kin versus
others, the odour of friends versus strangers with accuracy
well above chance
■ Body odours activate brain regions involved in
emotional processing
■ A stranger’s odour activates the amygdala and
insular cortex
● Processing body odours is mostly an unconscious, automatic
process
○ Gustation
■ In humans, clear differences in taste thresholds and preferences are
obvious
● Supertasters versus nontasters
■ Children are much more responsive to taste than adults
● By age 20, humans have lost at least an estimated 50% of their
taste receptors
■ Receptors for taste
● Each of the five taste receptor types responds to a different
chemical component of food
○ Sweet, sour, salty and bitter
● Fifth is call the umami receptor
○ Especially sensitive to glutamate
● Taste receptors are grouped into taste buds, each containing
several receptor types
● Gustatory stimuli interact with the receptor tips, or microvilli
○ Ion channels open, leading to changes in membrane
potential
■ Gustatory pathways
● Cranial nerves 7, 9, and 10 form the main gustatory nerve, the
solitary tract
○ Gustatory region in the insula is dedicated to taste
○ Primary somatosensory region is responsive to tactile
information (localizing tastes and textures on tongue)
Document Summary
Chapter 12: what causes emotional and motivated behaviour. Experimental setup in which a subject is allowed only restricted sensory input; subjects generally have a low tolerance for deprivation and may even hallucinate. After about 4-8 hours, subjects became quite distressed; few lasted more than 24 hours. Brain has an inherent need for stimulation; one reason that we engage in behaviour is to stimulate the brain. Rhesus monkeys in a dim room with a small door that could be opened to view an adjoining room. Spent a lot of time opening the door and viewing whatever was on display. Were willing to perform various tasks to look through the window. The longer they were deprived of a chance to look, the more time they spent looking when finally given the opportunity. Researchers have identified brain circuits for reward and discovered that they can be modulated to increase or decrease activity.
