Transient physiologic, cognitive, and behavioral outputs that
constitute adaptive responses to survival-relevant or otherwise
Term used to characterize the predominant emotional state over time.
They interact bidirectionally with emotional responses to particular stimuli
What two categories can emotions be divied into?
What elicits negative emotions, and what do these stimuli lead to?
Danger, pain, or other noxious conditions
Generally lead to avoidance, escape, or protective responses
What elicits positive emotions, and what do these stimuli lead to?
Food, safety, comfort, or reproductive opportunities
Generally lead to approach behaviors
What is the primary function of emotion processing circuits in the brain?
To appraise the valance and potency of stimuli and activate
Different emotions utilize distinct circuits involving limbic
structures, frontal regions of cortex, and the hypothalamus
Appraisal of a stimulus requires that highly processed sensory and
cognitive information from the association cortex gain access to
emotion processing circuits, which then activate adaptive
What do these downstream responses include?
Stimulation of arousal and attention - mediated via activation of
monoamine, cholinergic, and other widely distributed neurotransmitter
systems in the brain - as well as by activation of the autonomic
nervous system and certain neuroendocrine systems
Strong emotion suppresses ongoing behaviors in favor of automatic
defensive or approach behaviors - additionally experienced encoded
under the influence of strong emotions lead to:
Experiences encoded under the influence of strong emotions lead to
the enhancement of diverse types of memory processes to make
subsequent responses to similar stimuli maximally efficient
How can fear be roughly divided? (2 categories)
Learned (conditioned) fear
Information about threatening stimuli is transmitted from:
The sensory thalamus and sensory and association areas of the
cerebral cortex to the lateral nuclear complex of the amygdala (the
amygadala's major input nuclei)
- Information is processed and sent by both direct and indirect
routes to the central nucleus (the major output nucleus of the amygdala)
When presented with the same fearful stimuli (that isn't painful),
the afear response (signal elevation in amygdala) does this over time:
What mediates activation of the sympathetic nervous system?
Projections to the lateral hypothalamus
What induces the synthesis and release of corticotropin-releasing
Projections to the paraventricular nucleus (PVN) of the hypothalamus
The release of CRF activates a cascade that ultimately leads to what?
The release of glucocorticoids from the adrenal cortex
Glucococorticoids cause the body to:
Enter a catabolic state, suppress inflammatory responses and heighten arousal
In depression, this axis often becomes hyperactive
The hypothalamic-pituitary-adrenal (HPA) axis
This can supress pain in response to intense fear and stress
Projections from the amgydala to the periaqueductal gray matter (PAG)
in the core of the brainstem activate descending analgesic responses
that involve endogenous opioid peptides
Projections to the noradrenergic locus ceruleus, the serotonergic
raphe nuclei, and the dopaminergic ventral tegmental area do what?
Increase arousal and vigilance and enhance the formation of explicit
and implicit memories of circumstances under which danger has occurred
How is anxiety different from fear?
Anxiety, unlike fear, is triggered in the absence of an immediately
What may be the underlying cause of the generalized symptoms of anxiety?
The BNST - the bed nucleus of the stria terminalis
- Considered an extended region of the amygdala, and resembles the
central nucleus with regard to its cellular organization
May respond to less specific stimuli than the central nucleus and
have anxiety-like behaviors induced through CRF in this region
Memories produced by fearful situations have a cognitive and an
emotional component. What brain structure seems to be predominant in
each what do these brain structures do?
Cognitive - Hippocampus
- Records the precise setting in which danger was experienced and
details of the experience
Emotional - Lateral nuclear complex of the amygdala
- Activates physiologic and behavioral responses to danger when
learned predictors of danger are encountered (autonomic responses)
The enhanced memories associated with strong emotion seem to depend
on what receptors?
Beta-adrenergic receptors in the amygdala, which then interacts
strongly with the hippocampus
- This enhancement can be blocked by Beta-adrenergic receptor
antagonists such as propranolol administered prior to certain stages
of memory consolidation
If propranolol can efficiently and effectively reduce traumatic
memories to the level of ordinary memories without causing amnesia, it
may be effective against this disorder:
Positive emotional experiences also promote memory. Under normal
circumstances these memories produce reinforcement in response to
natural rewards such as food, safety, and mating opportunities.
Abnormal stimulation of reward circuitry however may be a central
cause of this:
Accumulated data suggest that circuits involved in mood regulation
and mood disorders include the
Orbital and medial F=PFC, the cingulate gyrus, the amygdala, ventral
striatum, hippocampus, and hypothalamus
Anxiety and mood disorders seem to have shared
Genetic risk factors
This brain area has been implicated in depression and may monitor
performance for signs of failure, just as the amygdala monitors
sensory inputs for signs of threat
The anterior cingulate gyrus (the subgenual cingulate cortex) AKA
Brodadmann area 25
For patients with unrelenting major depression, for whom other
therapies have not been successful, 2/3 of them have had sustained
improvement from this treatment
DBS in the subgenual cingulate cortex
The current categorization of anxiety and mood disorders is based on
Exclusively syndromal groupings of subjective and behavioral symptoms
Hyyperactivity of this brain area has been associated with PTSD in
PET and fMRI scans
Overall it appears that patiens with certain anxiety disorders
exhibit this in thier brain circuitry:
Hyperresponsiveness of amygdala-based fear circuitry and decreased
activity of medial and orbital prefrontal cortical regions that
normally serve to suppress fear and anxiety
Provide the treatments used for the following conditions:
- Acute anxiety
- Generalized anxiety disorder
- Panic disorder
Benzodiazepines bind here:
The alpha subunit of GABAa receptor complex, increasing the affinity
of the beta subunit for GABA
This drug, an inverse agonist of the benzodiazepine binding site on
the GABAa receptor alpha subunit, is proconvulsant and proconflict
Beta-CCE or Beta-carboline
Benzodazepines are a class of drugs with what properties?
Anxiolytic, sedative, muscle relaxant, and anticonvulsant properties.
- They produce anterograde amnesia
Anticonvulsant actions of benzodiazepines are believed to occur in the:
Cerebral cortex, hippocampus, or amygdala
Barbituates do this to Cl- channels
Increase the probability that they will open and the duration of
Barbituates can act ______ of GABA, leading to a far greater
inhibition of the nervous system than can benzodazpeines
- Increases risk of serious respiratory depression and death when overdosed
Because ethanol facilitates the GABA-mediated opening of GABAa
receptor Cl- channels, this is among the most prominent effects of ethanol:
A reduction in anxiety
What may explain actue tolerance?
Covalent modification of the GABAa receptor by phosphorylation
Longer-term tolerance and dependence may be explained by:
Altered expression of GABAa receptor subunits leading to altered
An azaspirodecanedione marketed as an anxiolytic
A partial agonist at 5HT1a serotonin receptors
- Approved for use in the treatment of generalized anxiety disorder,
but isn't very effective
- Virtually without abuse libability
What role does adenosine play in anxiety?
It is a purine neurotransmitter that inhibits the release of ACh, NE,
gluatamte, DA, 5Ht, and GABA in specific regions of the brain through
actions at its A1 receptors.
- Mediated through the opening of K+ channels, inhibition of Ca2+
channels opening, and the inhibition of adenylyl cyclase
Adenosine is sedative, anticovulsant, analgesic, and anxiolytic