PSY 507 Lecture Notes - Lecture 2: Cranial Nerve Nucleus, Papez Circuit, Triune Brain
8 Jun 2022
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Chapter 3:
Defining the Parts of the PNS
● Nervous system outside the brain and spinal cord (although some PNS neurons have
cell bodies in brain or spinal cord), subdivides into:
● Somatic Nervous System
- Motor neurons control muscle movement
- Sensory neurons control somatosensation (touch, pain, proprioception)
●Autonomic Nervous System regulates internal organs (heart rate, digestion, etc)
-Sympathetic Nervous System: prepares organism to act (“fight or flight”)
-Parasympathetic Nervous System: rest, digestion, restoration
Defining the Parts of the CNS
●Telencephalon:cortex: outer wrinkly layer; sensory, motor, language, memory,
inhibition, planning, etc
-Hippocampus,Basal Ganglia,Amygdala
●Diencephalon: includes thalamus and hypothalamus; coordinating sensory and motor
functions; homeostatic functions; autonomic nervous system regulation
●Brainstem: includes medulla and mesencephalon: cranial nerve nuclei;
emotion-related behaviors; breathing, sleeping, heart rate, etc
How Neurons Communicate
● Action Potentials (AP) are the changes in electrical potential that travel down the axon of
a neuron
● When the AP reaches a synapse, the neuron releases neurotransmitters, chemical
signals, that are received by the postsynaptic neuron ‘s receptors
Neurotransmitters
● Many substances can act as neurotransmitters
● Fit into own unique receptors
● Originally thought that each neuron releases just one type of neurotransmitter, but in
many cases this is not true
● Most common are glutamate (excitatory) and GABA (inhibitory)
Historical Models: Cannon & Bard
● The following historical models best fit an evolutionary approach to emotion
(comparative; looked at evolutionary age of different brain regions)
● 1920s they showed that decorticated cats displayed uncontrolled and unprovoked
emotional behaviors, such as aggression
● Concluded that subcortical are, hypothalamus, was source of emotional response, and in
healthy animals is inhibited by cortex
Historical Models: Papez Circuit
● Included more areas than hypothalamus
● Mostly medical and subcortical area, included hypothalamus, thalamus, hippocampus
and cingulate cortex
Historical Models: Maclean’s Triune Brain
● Three brain systems emerged over evolution, all preserved to some extent in human
brain
● Drives and emotions originate in reptilian and paleomammalian regions (aka limbic
system); neomammalian area regulates older parts of brain
Historical Models: Legacy
● Cannon & Bard’s, Papez’s and Maclean’s original formulations are oversimplifications
and considered outdated
- Hypothalamus is not sole seat of emotion (although important for regulating bodily states
associated with affect)
- Triune brain concept; unlikely that brainstem is perfectly preserved across animals or
limbic system is the same across mammals; all brain systems evolve and specialize
within species
● However, they had lasting influence:
- Concept of limbic system
- The role of subcortical structure in generation of emotion states and behaviors
- The notion that the cortex, especially prefrontal cortex, is larger in humans and plays a
role in emotion regulation
Competing Contemporary Models
● Locationist View:
- Endorsed by evolutionary theorists
- Specific areas or systems in brain are responsible for generating specific emotions
- Neural underpinnings of emotions are thought to be similar across species
(species-specific selection pressures notwithstanding)
- Comparative neurobiology is therefore key tool
- Brainstem considered central to emotions by some theorists, but difficult to study in
humans
● Constructionist View:
- Endorsed by psychological constructionists
- Notable failure to pinpoint “locations” of emotions in brain
- Focus on how mental processes are distributed throughout brain, not “localized”
- Building blocks of emotion also underlie other cognitive processes
- Comparative research is of limited use because animal behaviors that appear emotional
may not have accompanying feelings
The Amygdala
● Deep in medial temporal lobes
● Associated with attention and responding to emotional stimuli (salience detector)
● Classically associated with fear, based on lesion and electrical stimulation studies, and
patients like SM who does not experience, express, or recognize fear
The Insula
● Hidden by frontal and temporal lobes
● Associated with experiencing and expressing disgust, among other processes
● Possible role in maintenance and monitoring of bodily states (disgust is highly relevant to
this)
The Distributed Brain: Constructionism
●Core affect is innate; valence and arousal generated by distributed systems
Document Summary
Nervous system outside the brain and spinal cord (although some pns neurons have cell bodies in brain or spinal cord), subdivides into: Sensory neurons control somatosensation (touch, pain, proprioception) Autonomic nervous system regulates internal organs (heart rate, digestion, etc) Sympathetic nervous system: prepares organism to act ( fight or flight ) Defining the parts of the cns inhibition, planning, etc. Telencephalon: cortex: outer wrinkly layer; sensory, motor, language, memory, Diencephalon: includes thalamus and hypothalamus; coordinating sensory and motor functions; homeostatic functions; autonomic nervous system regulation. Brainstem: includes medulla and mesencephalon: cranial nerve nuclei; emotion-related behaviors; breathing, sleeping, heart rate, etc. Action potentials (ap) are the changes in electrical potential that travel down the axon of a neuron. When the ap reaches a synapse, the neuron releases neurotransmitters, chemical signals, that are received by the postsynaptic neuron s receptors. Originally thought that each neuron releases just one type of neurotransmitter, but in many cases this is not true.
