Limbic system Flashcards
paleocortex
- oldest “phylogentic” age
- associated with olfaction and contributes to survival behavior
archicortex
- the hippocampus
- contributes to behavior through an organism’s ability to learn and remember significant events
allocortex
- i think refers to the hippocampus and paleocortex
- usually are three-layered
mesocortex
- typically 5 layered
- can be peri-allocortex (closer to the allocortex)
- can be pro-isocortex (closer to the isocortex)
isocortex
- determined to be phylogenetically “newer”
- 6 layers
Describe the Papez Limbic circuit
- hippocampus to the mamillary bodies (hypothalamus) via the fornix
- the mamillary bodies to the anterior thalamus via the mammillothalamic tract
- the anterior thalamus to the cingulate cortex via the thalamocortical projections
- the cingulate back to the hippocampal region
What are the main problems with Papez’s limbic circuit
- the hippocampus is not a main regulator of the hypothalamus
- the hippocampus does provide important contextual information to emotional experience
- the hippocampus only has minor projections to area of the hypothalamus that are actually outside of the mammillary bodies
Areas that are damaged in Korsakoff’s amnesia that indicates their importance in memory formation
-mammillary bodies and anterior thalamus
Kluver-Bucy symptom
- visual agnosia
- hypersexuality
- hyperorality
- emotional blunting/placidity
- willingness to approach previously fearful stimuli
**later studies showed the importance of the amygdala
amygadala
- key regulator of the hypothalamus
- is located deep within the temporal lobe
the amgydala is essential for conditioned learning of:
-emotions… particularly fear
-
the amygdala receives sensory information from the ____ and ____ into its ___ nucleus
- cortex and thalamus
- lateral
the output of the amygdala arises mainly from the _____ and targets:
- central nucleus
- hypothalamus and the brainstem
amygdala efferents:
periaqueductal gray to _____
lateral and paraventricular hypothalamus to regulate ____
- periaqueductal gray to regulate skeletomotor behaviors
- lateral and perivenricular hypothalamus to regulate autonomic and endocrine responses
What did Joseph LeDoux demonstrate about the amygdala ?
- he found that certain sensory stimuli reach the amygdala directly by way of the thalamus before being routed through cortex (low road)
- more processed sensory information arrives from the cortex at a later time (high road)
Cognitive behavioral therapy
- ability of cognitive reasoning to correct and reverse maladaptive emotions is the basis for this therapy
- ventromedial and orbital divisions of the prefrontal cortex can suppress emotional expression by inhibiting the amygdala output
Describe the paradox of major depressive disorders
- early functional imaging studies showed reduced blood flow in orbitofrontal and cingulate regions. This correlated withb reduced gray matter volume in these regions.
- recent studies show that these areas are actually hyperactive in depression and they are targeted for therapy by deep brain stimulation
orbitofrontal cortex
-helps to guide behavior based on past rewards and punishments
damage to the oribitofrontal cortex would result in
-associated with blunted or inappropriate emotions
-poor judgement
often due to failure to inhibit maladaptive responses
what were often performed on patients with violent mental illnesses to try to calm them down?
-frontal lobotomies and cingulatomies
Targeted cingulatomies are still performed in cases of:
- medically intractable obsessive compulsive disorder
- chronic pain syndromes
- refractory depression or bipolar disorder
cingulate gyrus
- lies immediately above the corpus collosum
- is visceromotor
- can produce some somatic function and even produce aggressive reactions
- major area involved in conscious perception of pain and other emotions
septum
-a telencephalic structure lying beneath the corpus callosum
-inputs: hippocampus and cingulate cortex
-projections: amygdala, hypothalamus, and brainstem
lesions alter aggressive and sexual behaviors
nucleus accumbens
- ventral extension of the striatum
- limbic-motor interface
- processes limbic cortical input and provides adaptive motor strategies for motivated behaviors
visceral sensory input to the hypothalamus and amygdala arises from
-nucleus of the solitary tract
multimodal processed sensory input derives from association cortices to:
-amygdala, hippocampal region, cingulate and prefrontal cortex
motor output of the limbic system:
visceral motor
visceral motor output originates from the hypothalamus and amygdala to brainstem autonomic centers
somatic motor output of the limbic system
-comes from prefrontal to premotor cortex
-it is relayed through the basal ganglia nucleus accumbens
aka the limbic motor interface
