PHYL 1400
January 21, 2010
Complex Brain Functions
A. Sleep and wakefulness Literature:
Vander’s Human Physiology,
B. Motivation and emotion 11th Ed., pp. 232-253
C. Cognition
Instructor:
Dr. Stefan Krueger
Dept. of Physiology & Biophysics
Tupper Building, Room 5-F
stefan.krueger@dal.ca
http://alturl.com/2m6s
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- SLEEP AND WAKEFULNESS
A. Sleep and wakefulness
• Why do we sleep?
• Factors controlling sleep and wakefulness
• Stages of sleep
• Brain activity during sleep and wakefulness
• Brain regions and neurotransmitters involved in the regulation of
sleep and wakefulness
• Medications affecting sleep and attention
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PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- SLEEP AND WAKEFULNESS
Sleep: Functions, influencing factors
Function
• Sleep deprivation ⇒ weight loss, impaired cognitive abilities,
ultimately death
• Sleep may be needed to replenish glycogen (energy) stores in brain
• Sleep may be required for consolidation of memories
Sleep regulated by
• Internal clock: Circadian rhythm
• Light: Internal clock synchronized with light-
dark cycle
Next: Stages of sleep Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- SLEEP AND WAKEFULNESS
Sleep: Stages
A. NREM (=Non-rapid eye movement) sleep
• Heart rate, respiratory rate decrease
• Different stages
• Longer and deeper earlier during sleep
B. REM (=Rapid eye movement) sleep
• Frequent rapid eye movements, but skeletal muscle
tension inhibited
• Increase in heart rate, respiratory rate
• Longer and more frequent later in sleep phase
• Dreams
Next: Brain activity during sleep Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- SLEEP AND WAKEFULNESS
Brain activity during sleep and wakefulness
Electroencephalography (EEG):
Allows measurement of neuronal activity (mainly cortex)
EEG during wakefulness
• High-frequency, low-amplitude oscillations:
Activity of neurons in cortex asynchronous
• Inattentive state: Alpha rhythm (8-13 Hz oscillations)
• Alert state: Beta rhythm (> 13 Hz)
EEG during NREM sleep
• Low-frequency, high amplitude oscillations: Activity of
neurons in cortex more synchronized
• Progressively lower frequency in stage II - IV
EEG during REM sleep
• EEG shows high-frequency, low-amplitude oscillations
similar to awake state
EEG during epilepsy
• EEG shows low-frequency, high-amplitude oscillations
and spikes: Highly synchronized neuronal activation
Next: Brain regions and neurotransmitters involved in the regulation of sleep Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- SLEEP AND WAKEFULNESS
Regulation of sleep: Brain regions and neurotransmitters
Brain region Transmitter Function
Hypothalamus
-- Suprachiasmatic ncl. Internal clock
-- Posterior Histamine Promotes wakefulness
-- Lateral Orexin Promotes wakefulness
-- Preoptic area GABA Promotes sleep
Reticular Activating
System (RAS)
-- medial Serotonin Promotes wakefulness,
suppresses REM sleep
-- lateral Acetylcholine Promotes REM sleep
Norepinephrine Promotes wakefulness,
suppresses REM sleep
Locus ceruleus Norepinephrine Promotes wakefulness,
attention
Next: Medications, sleep and attention Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- SLEEP AND WAKEFULNESS
Medications affecting sleep and attention
Medication Pharmacological action Effects on sleep and attention
Benzodiazepines Potentiate actions of GABA Promote sleep
Nonbenzodiazepines Potentiate actions of GABA Promote sleep
Antihistamines Histamine antagonist Cause drowsiness
Antidepressants Inhibit reuptake or breakdown Suppress REM sleep
of monoamines
Methylphenidate Norepinephrine reuptake Treatment of Attention-deficit
(Ritalin®) inhibitor hyperactivity disorder
Back to Sleep and wakefulness Back to Complex brain functions
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- MOTIVATION AND EMOTION
B. Motivation and emotion
• Neural system generating motivation and emotions
• Role of the hypothalamus
• Function of the amygdala
• Role of the mesolimbic dopaminergic system
• Psychoactive drugs and addiction
• Mood disorders
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PHYL 1400 --COMPLEX BRAIN FUNCTIONS -- MOTIVATION AND EMOTION
Neural system generating
goal-directed behavior and emotion
In response to external stimuli, the limbic system
generates
• Goal-directed behavior
Reinforced by rewards, diminished by
aversive stimuli
Subserves both primary needs and acquired
desires
• Emotions
Outward expressions, autonomic and
hormonal responses
Conscious experiences or inner feelings
Next: Role of hypothalamus and amygdala Back to index
PHYL 1400 --COMPLEX BRAIN FUNCTIONS -- MOTIVATION AND EMOTION
Limbic structures (1): Amygdala and hypothalamus
Amygdala
• Gets sensory input, initiates emotional,
especially fear-related behavior
• Fear learning: Association of initially neutral
and aversive stimuli
Hypothalamus
• Elicits changes in heart rate, respiration etc. via autonomic nervous system
• Elicits changes in hormonal secretions
• Elicits somatic motor responses generating outward expression of emotion
• Involved in reenforcement of behavior through rewarding stimuli
Next: Role of the mesolimbic dopaminergic system and basal nuclei Back to index
PHYL 1400 --COMPLEX BRAIN FUNCTIONS -- MOTIVATION AND EMOTION
Limbic structures (2): Mesolimbic dopaminergic pathway
Function
• Involved in generation of pleasure and reward-
oriented behavior
How reward reenforces behavior
• Ventral basal nuclei normally repress initiation of
goal-directed behavior
• De-repression through input from limbic cortex,
amygdala & hippocampus
• De-repression facilitated by activity of
dopaminergic neurons in brainstem (ventral
tegmental area): Represents rewarding effect
Next: Psychoactive drugs Back to index
PHYL 1400 --COMPLEX BRAIN FUNCTIONS -- MOTIVATION AND EMOTION
Psychoactive drugs
• Often structurally related to dopamine
• increase activation of the ventral striatum
• Frequent use causes addiction: Drug
tolerance, psychological and physical
dependence
• Even psychoactive substances structurally
unrelated to dopamine (cocaine, opiates,
alcohol) act by enhancing the dopaminergic
activation of the ventral striatum
Next: Mood disorders Back to index
PHYL 1400 --COMPLEX BRAIN FUNCTIONS -- MOTIVATION AND EMOTION
Mood disorders
Types
• Unipolar depression
• Bipolar spectrum disorder (=Manic depression)
Causes
• Combination of genetic and social factors
• Altered blood flow (=neuronal activity) in limbic
cortex and amygdala
Figure: Functional magnetic resonance
• Monoamine theory of depression: Cause is relative imaging (fMRI) allows detection of
lack of serotonin, norepinephrine, and dopamine alterations in neural activity
Treatment
• Monoamine oxidase inhibitors (MAOIs; block breakdown of serotonin, DA, NE)
• Tricyclic antidepressants: Block re-uptake of serotonin and NE
• Selective serotonin re-uptake inhibitors (SSRIs)
Back to Sleep and wakefulness Back to Complex brain functions
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- COGNITION
C. Cognition
• What is cognition?
• Neural circuits underlying cognition
• Schizophrenia: Symptoms and causes
• Cortical lesions affecting cognition
• Cortical regions involved in language processing
• Brain structures involved in the acquisition and storage of memory
• Dementia
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PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- COGNITION
Cognition: Neural circuits
What is cognition?
High level functions carried out by brain:
• Identifying relevant features in complex stimuli
• Recognizing related objects
• Storing information on novel stimuli and their relation to
familiar objects
• Planning appropriate responses
• Special aspects: Visual perception; analysis and use and
analysis of speech
Brain structures involved
• Association cortex
• Basal nuclei: Represses cognitive processes
• Dopaminergic input to basal ganglia: Facilitates de-repression
Next: Schizophrenia Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- COGNITION
Schizophrenia
Symptoms
• Positive: Auditory hallucinations, paranoid delusions
• Negative: Apathy, lack of emotion, social anxiety and isolation
• Cognitive: Disorganized thoughts, difficulty completing tasks
Causes
• Combination of genetic, developmental and social factors
• Structural changes in frontal cortex (reduction in volume)
• Dopamine hypothesis: Increased activity of dopaminergic system
- Dopamine agonists can cause hallucinations and delusions
Treatment
• Neuroleptics: Dopamine antagonists; reduce positive symptoms
• Atypical antipsychotics: Dopamine and serotonin antagonists
Next: Cortical lesions affecting cognition Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- COGNITION
Cortical lesions affecting cognition
• Localized lesions of the association cortex
(e.g. due to stroke) lead to specific defects
Deficits in problem solving,
planning, and social behavior
Deficits in attention:
Contralateral neglect syndrome
Deficits in recognition: Agnosia
(Inability to recognize familiar objects)
• Generalized lesions of the association cortex, e.g. in
- Alzheimer’s disease
- Vascular dementia
lead to generalized defects in cognition: Memory, language, perceptual skills, social behavior,
problem solving
Next: Cortical regions involved in language processing Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- COGNITION
Cortical regions involved in language processing
Many areas in association cortex involved in specialized
aspects of language analysis and generation
Lesions in two areas of the association cortex lead to aphasia
(= deficits in language generation):
Lesions in Wernicke’s area ⇒
Lack in language comprehension
Lesions in Broca’s area
⇒
Expressive aphasia (difficulty in
forming words and sentences
Next: Brain structures involved in acquisition and storage of memory Back to index
PHYL 1400 -- COMPLEX BRAIN FUNCTIONS -- COGNITION
Acquisition and storage of memory
Categories of memory
• Qualitative
- Declarative (can be expressed by language)
- Procedural (unconscious)
• Temporal
- Short-term (sec - min)
- Long-term (days - years)
Brain regions involved; mechanism
• Procedural
Cerebellum, premotor cortex
(especially motor skills), basal nuclei
• Declarative
- Hippocampus (short-term)
Impairment of hippocampal function leads to amnesia (retrograde - anterograde)
- Many areas of association cortex (long-term): Selective defects due to trauma
• Memories likely stored as long-lasting changes in the effectiveness of synapses: Synaptic plasticity.
Back to Cognition Back to Complex brain functions