PSYC10003 Lecture Notes - Lecture 10: Orbitofrontal Cortex, Biological Neural Network, Temporal Lobe
MBB1 – Lecture 10
The neural basis of emotion
The concept of emotion
• Emotions consist of patterns physiological response and species-typical behaviours
• In humans, these responses are accompanied by feelings, which are powerful
motivators
o Thus exert influence on how we are likely to behave in certain situations
o Emotional behaviours likely played a big part in the evolution of the CNS
• Darwin suggested certain responses accompany similar emotional states in all
members of the same species – facial expressions accompany the same feelings for
all humans
o Thought expressions of emotion evolved through natural selection – evolve
from behaviours indicating what an animal will do next
• E.g. behaviours originally serving the function of fighting would evolve to become a
display of the intention to fight
o So a threat display may remove the need for a real fight, causing fewer
deaths
▪ So these displays must be easily distinguishable from other displays
Emotions as responsive patterns
Three components of emotional responses:
• Behavioural – muscular changes that are appropriate to the situation that elicits
them
o E.g. dog defending territory against robber may adopt aggressive posture
▪ hopes of robber adopting submissive posture
▪ Darwin called these clearly distinguishable opposite movements the
principle of antithesis
• Autonomic – physiological changes induced by the ANS facilitate behavioural
responses
o dog example, sympathetic branch of ANS increases so dogs heart rate
increases and blood is diverted from digestive system to muscles
• hormonal – reinforce autonomic changes
o dog eaple, dogs adeal edulla seetes epiephie ad
norepinephrine to further increase blood flow to muscles
Neural control of emotional response patterns
• Bad oseed a sha age i ats hose cerebral hemispheres had been surgically
removed
o Sham rage – excessively aggressive manner in response to slight stimulation
(e.g. simple touch made them hiss, bare teeth and arch back)
o Sham rage absent after removal of hypothalamus
▪ Conclusion: hypothalamus is responsible for expression of aggressive
behaviour
▪ And cortex normally inhibits and controls such behaviour
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The limbic system of emotion
• A distinct circuit of brain structures sub-serves emotional expression
o Includes hypothalamus, anterior thalamus, cingulate gyrus, fornix and
hippocampus, amygdala, orbitofrontal cortex and some nuclei of the basal
ganglia
o This neural circuit is the limbic system
• Hippoapus foed the etal eleet i Mleas lii sste (eeied iputs
from various senses and internal organs), but it is now clear that the hippocampus
has a more important role in learning and memory than emotion
o Despite shortcomings, the concept of the limbic system is still used
Klüver-Bucy syndrome and the amygdala
• Bilateral ablation of temporal lobes in rhesus monkeys resulted in impaired visual
recognition
• The monkeys ate anything that was edible, showed increased sexual activity,
exploration of all items with mouth and the absence of fear
• Thought that this arises from damage to amygdala (in anterior temporal lobe)
• Syndrome is occasionally described in humans – a patient became indifferent to
people and events after brain damage caused by an infection
o Would gaze for hours at the TV even when it was off, would imitate actions
of others and engaged in oral exploration of anything within reach
o Despite being heterosexual before damage, he often made sexual advances
towards other male patients
Structure of the amygdala
It plays a key role in the physiological and behavioural reactions to objects and situations
that have certain biological significance – E.g. painful, signifying presence of food or a mate
• Medial nucleus – receives sensory input (including from olfactory system) and relays
info to basal forebrain and hypothalamus
• Lateral/basolateral nuclei – receive sensory info from MSC, association cortex,
thalamus and hippocampus. They send axons to basal ganglia, thalamus and central
nucleus of amygdala
• Central nucleus – sends axons to regions of hypothalamus, midbrain, pons and
medulla that are responsible for the expression of various emotional responses
o Most important part of brain for expression of emotional response to
threatening stimuli → damage abolishes fear responses to stimuli associated
with aversive events
o Electrical stimulation induces a reaction of fear or agitation
• Basal nucleus – receives axons from lateral and basolateral nuclei, and sends axons
to amygdaloid nuclei and midbrain
Orbitofrontal cortex and decision making
• Located on ventral surface of frontal lobes, immediately above orbits with the eyes
• More medial region is known as the ventromedial prefrontal cortex, and lateral
region is called the lateral-orbital prefrontal cortex
• Precise role is unclear, partly because behaviours it is responsible for are difficult to
categorise
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