Chapter Six

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22 Apr 2012
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Chapter Six - Page 1 of 7
Chapter Six: Emotions and the Brain
Sleeping sickness encephalitis lethargica
o Started in Europe in the winter of 1916-17
o Lasted for ten years
o A virus that attacked the striatal regions of the brain
o People fell into a suspended state, sitting motionless and speechless, observing but doing nothing
o A precursor of dopamine was discovered in 1969 that became the drug L-Dopa
Some striatal system transmitter functions were restored
They experienced awakenings and began to act spontaneously and schedule their
daily activities
It gave rise to mood swings and emotions
Violent appetites and passions, and certain obsessive ideas/images
L-Dopa’s effects may have occurred because the neural activity it caused in the
damaged regions wasn’t exactly the same as the activity of normal coordinated
functions, and as well as restoring partial function to the striatal region, it sent
nerve impulses to the limbic system where emotions arise
How do brain mechanisms of emotion work?
Neuroimaging widely used
o A machine that monitors biochemical events in a series of conceptual slices through a person’s
brain while a computer takes this info and constructs visual images of the brain to show which
regions have been metabolically most active
o Non-invasive methodsd
o Positron Emission Topography and functional Magnetic Resonance Imaging
Movie pictures are constructed to show brain activity changing over time in the course of
things like different emotional states
Hindbrain
o Includes regions that control basic physio processes
o The medulla regulates cardiovascular activity
o Pons control sleep
o Cerebellum controls motor movement
Forebrain
o Includes the thalamus which is involved in integrated sensory info
o Hippocampus memory processes
o Hypothalamus regulates biological functions + four f’s
o Limbic system has the cortex and structures involved in emotions like the amygdala
Descartes proposed that sensory stimuli pulled little strings that ran inside the sensory nerves to open
valves which would let fluids from a central reservoir in the brain run down tubes to inflate muscles
o Said it was the mechanism underlying the human reflex
o Wrong because signals are electric and chemical
o Emotions are more than reflexes
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Chapter Six - Page 2 of 7
Early research on brain lesions and stimulation
First theory of brain mechanisms of emotion was proposed by Cannon
Bard indicated that cats deprived of their cortex made sudden, inappropriate and ill directed attacks
o Sham rage
o Led to Cannon proposing that the cortex usually inhibits this expression
Hess and Brugger
o Complemented the research on lesions with experiments using electrical stimulation that elicited
angry behaviour from the hypothalamus (not the thalamus as Cannon had said)
The limbic system
MacLean’s theory
o Found inspiration for Papez who argued that sensory impulses from the body and outside world
reach the thalamus and split into three main pathways
One goes to the striatal region the stream of movement
One goes to the neocortex the stream of thought
One goes to the limbic system the stream of feeling (observation that rabies attacks the
limbic system, and they experience extreme terror; tumours there sometimes cause a
loss of feeling and memory
o Macleane proposed that the human forebrain includes three systems, each of which developed in
a distinct phase of vertebrate evolution
Earliest and most basic part striatal region
Became enlarged with the evolution of reptiles
Devoted to scheduling and generating basic behaviours
Damage (such as from Huntington’s chorea) causes patients to be unable to
organize daily activities they sit and do nothing, though they happily partake in
activities planned for them
Damaged in encephalitis lethargica patients
Second part limbic system
Allows for the maternal caregiving/infant attachment, vocal signaling and play,
which are observed in mammals but not reptiles
Mammals are social creatures
Has close connections with the hypothalamus which controls the ANS and also
the hormonal system via the pituitary gland
Developed to enable mammals’ increasing sociality
Removing large portions of the limbic system (particularly the amygdala) makes
aggressive creatures docile and approach everything without fear
Pleasure centers Olds and Milner
o Electrodes in septal parts of the limbic system
Stimulation of the limbic system’s septal region also induces a tendency to
approach
Glickman et al. if the mood produced is based on approach, it’s a mood of
encouragement and facilitates curiousity/exploration. Patterns based on
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