Transcript ANPS 019 Beneyto 12-04

Limbic System and Higher Functions
December 4, 2013
Chapter 13: 515-520
Dr. Diane M. Jaworski
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• What is the limbic system?
• How does the limbic system regulate emotions?
• How does the limbic system regulate
learning and memory?
• How does the limbic system regulate sleep?
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What is the Limbic System?
The limbic system consists of widespread regions of the cerebrum and diencephalon.
Three major components are located surrounding the third ventricle: 1) amygdala
(emotion, especially fear), 2) hippocampus (learning/memory), and 3) basal forebrain
nuclei, including the nucleus accumbens (addiction). These structures have
connections with cortical regions including the cingulate gyrus (motivation) and
prefrontal cortex (storage of long-term memories & personality). The limbic system is
sometimes referred as the emotional brain.
© McKinley et al. A & P 2013
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Components of the Limbic System:
Nuclei
• Amygdala!!!!!
= Emotion
(Hypothalamic and
thalamic nuclei also
contribute to emotion
based on past
experience info from
hippocampus)
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Amygdala and Emotion
Amygdala plays a role in aversive (negative) behaviors
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Amygdala and Emotion - FEAR!!!
Cells in the temporal lobe recognize whether something IS a face
Cells in the amygdala help to recognize the emotion OF the face
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Is there a purpose to fear?
What happens if the fear is irrational?
Schizophrenia is characterized by disturbances in
perception, affect, and behavior lasting longer than 6
months
Paranoid Schizophrenia is dominated by feelings of
persecution, grandiose delusions and auditory
hallucinations
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Other limbic nuclei play a role in reward/
self-gratification behaviors
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Addiction
A state in which the body develops physical dependence such that if
the substance is removed it will cause physical withdrawal symptoms.
Generally is associated with drug tolerance.
This is distinguished from compulsion = psychological dependence
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Components of the Limbic System:
Cortex
Hippocampus
= learning and
memory
Fornix = white matter tract
connects hippocampus to
hypothalamus and prefrontal
cortex
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© 2005 Pearson Education
Model for
Learning and Memory
Acquisition
Hippocampus
Immediate recall
Short-term
Long-term requires
consolidation, which
occurs during sleep
Storage
Prefrontal cortex
(mostly factual data)
Retrieval
Hippocampus
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Memory Disorders
Amnesia
Can’t recall past memories
Can’t form new memories
Procedural (“how”) memory is preserved in amnesia
Declarative (“what”) memory affected in amnesia 302
Amnesia
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© McKinley et al. A & P 2013
Tower of Hanoi
See how you do:
http://www.mazeworks.com/hanoi/index.htm
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Memory Disorders
Hyperthymestic Syndrome
Highly Superior Autobiographical Memory
Forgetting is an important part of learning!
We do not NEED to (mundane things like
what you had for dinner 2 weeks ago) or
WANT to (bad experiences) remember
everything that happens to us. Part of
learning is sorting through what to store
and what to discard (called consolidation).
People with hyperthymestic syndrome
remember everything that happened to
them. They are not more
intelligent!!!Interestingly, they exhibit brain
anatomy similar to people with Obsessive
Compulsive Disorder (OCD). You can think
of hyperthymestic syndrome as personal
OCD.
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Components of the Limbic System:
Cortex
• Limbic cortex is located in the frontal lobe:
cingulate gyrus + prefrontal cortex = use past experiences to
control emotions and perform abstract intellectual activities (e.g.,
predicting consequences of actions)
Prefrontal
Cortex
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© 2005 Pearson Education
Limbic Cortex
social & emotional decision making
• Personality
- impulsive choices
- regret
- motivation
- post-traumatic stress
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Prefrontal Cortex
Prefrontal cortex provides
inhibition to limbic system
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What we learned from Phineas Gage
BEFORE Accident:
Reliable, industrious, nice guy
AFTER Accident:
Unreliable & rageful
Conclusion: The frontal lobes play a
critical role in long-term
planning and judgement
Center of behavioral responses
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© McKinley et al. A & P 2013
Consciousness
• The property of being aware of oneself and one’s
place in the environment
• clinically: The ability of an individual to respond
appropriately to environmental stimuli
• The Electroencephalogram (EEG) is a clinical tool
for measurement of brain activity
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© McKinley et al. A & P 2013
The Electroencephalogram (EEG)
• Billions of neurons in brain; each generates small amount of
electrical activity
• Measurable from outside brain
• As pattern of neuronal activity
changes, recordings look different
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Reticular Activating System (RAS)
• Important midbrain area
• Stimulation w/norepinephrine
and acetylcholine leads to a
more alert individual
• Neural fatigue reduces RAS
activity. After many hours,
RAS becomes less
responsive to stimulation,
serotonin levels increase and
individual becomes more
lethargic, leading to sleep.
Once asleep, melatonin
maintains sleep.
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© 2005 Pearson Education
Circadian Rhythms
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Circadian Rhythms
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Nighttime Sleep Pattern
• Alternate between REM and deep sleep phases
• Begin in deep sleep
• REM periods increase throughout the night
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Deep Sleep
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•
•
Also called slow wave sleep
Entire body relaxes
Cerebral cortex activity minimal
All metabolic functions are significantly reduced
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© 2005 Pearson Education
Rapid Eye Movement (REM)
Sleep
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•
Active dreaming occurs - Eyes move rapidly as dream unfold
Changes in blood pressure and respiratory rate
Less receptive to outside stimuli
Muscular activities are inhibited while cerebral activity is similar to
that seen in awake individuals. This is when short-term memories
are converted to long-term memories, by a process called
consolidation, and stored in the prefrontal cortex.
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Ending Sleep
• Any stimulus that activates the RAS
• Arousal occurs rapidly
• Effects of a single RAS stimulation lasts less than a minute
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Insomnia
Difficulty falling asleep or staying asleep
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Hypersomnia
More than 10 hours sleep per day for at least 2 weeks
or need to nap repeatedly during the day
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Sleep Apnea
A sleep disorder characterized
by pauses in breathing during
sleep
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Narcolepsy
Sudden attack of sleep
Altered neurotransmitter communication between the
hypothalamus and pons
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Consequences
• Disasters (e.g. Chernobyl, Three Mile Island) and accidents (e.g
Exxon Valdez, Challenger, Colgan air crash in Bufallo) have been
officially attributed to errors in judgment caused by sleepiness
• Car crashes, in the US, due to falling asleep at the wheel exceed
100,000/year and result in 1,500 deaths
• This death rate may surpass that of alcohol-related crashes among
young Americans
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