Limbic System Flashcards
Major function of limbic system:
The site where cortical information and hypothalamic impulses are integrated.
Homeostasis, olfaction, memory, emotion (HOME)
Components of Papez’ circuit:
Anterior thalamus Cingulate Hippocampus Fornix Mammillary bodies
What is the Default Mode Network?
Dorsal portion of the Papez circuit interconnected through the dorsal cingulum. Activated when the mind is at rest (zoning out, day-dreaming, etc).
Cingulate cortex functions:
Rostral: emotions and motor.
Caudal: visual spatial and memory.
Orbital frontal lobe functions:
Personality, behavioral control, self-awareness.
Temporal lobe functions:
Visual memory, language comprehension.
Amygdala functions:
“Preservation of self”, emotion, fear
Septum function:
“Preservation of species”, sexual behavior, emotionality.
Connects the hippocampus and mammillary bodies:
Fornix
Connects the mammillary bodies and thalamus:
Mammillothalamic tract
Connects the entorhinal cortex and dentate:
Perforant path
Updated Papez’ circuit includes:
Prefrontal cortex, hypothalamus, amygdala.
Function of mammillothalamic tract:
Connect visceral perception with emotion and behavior.
Function of perforant path:
Major afferent to the hippocampal formation
Function of fornix:
Major efferent from the hippocampal formation
Common physiologic and neurochemical properties
- Herpes virus has a special affinity for limbic system (leads to severe memory and behavioral disturbance).
- Susceptible to kindling and development of seizure foci.
- High density of cholinergic innervation and opiate receptors.
Description of updated limbic system model:
3 distinct but partially overlapping networks
Describe Kluver-Bucy syndrome:
Cause: bilateral large temporal lobe lesions including amygdala, hippocampus, uncus.
Symptoms: Oral tendencies, hypermetamorphosis, placidity, hypersexuality, visual agnosia, bulimia.
Describe Geschwind syndrome:
Cause: Sensory limbic hyperconnection-strengthening of synaptic connections.
Symptoms: Increased concern with philosophical, cosmic, religious issues; hyposexuality; hypergraphia; viscosity.
Function of amygdala:
Integration of emotions, fear, memory.
Lesions lead to tameness or reduced emotionality.
Orbital frontal lobe syndrome:
Disinhibited, tactless, grandiose, tendency to dress carelessly and eat gluttonously.
Frontal/convexity or dorsolateral lobe syndrome:
Apathetic, responding in an automation-like manner, vacancy of expression.
Medial frontal lobe syndrome:
“Motionless, mindless, wakefulness”, loss of drive to move or speak.
Lesions in hippocampus, dorsal medial nucleus of the thalamus, mammillary nuclei lead to:
Amnesia and memory disorders (declarative memory)
Episodic vs semantic memory:
Episodic memories are actively remembered. Semantic memories are facts known rather than actively remembered.
Describe Wernicke Korsakoff’s Syndrome:
Cause: Chronic alcoholism and nutritional deficiency (thiamine). Lesion in mammillary bodies and thalamus.
Symptoms: Confusion, disorientation, oculomotor dysfunction, ataxia, chronic anterograde and temporally-graded retrograde amnesia.
Damage to septal region produces:
Increased sexual activity and emotionality.
Brain pleasure regions:
- Lateral hypothalamus
- Medial forebrain bundle
- Nucleus accumbens
Lesions to the ventromedial nucleus of hypothalamus produces:
Pain, rage, or strong aversive reactions and long-lasting hyperemotionality.
Contralateral motor neglect results from a lesion where?
Posterior cingulate gyrus.
Behavioral changes after lesions of the anterior cingulate gyrus:
Apathy, disinhibition, placidity, depression, anxiety, OCD, heightened sexuality, bulimia.
Lesions of AC can relieve obsessive compulsive behaviors and reduce Tourette syndrome symptoms.
Function of anterior cingulate gyrus:
Integration of emotion with movement.
