Limbic system

Question 1

Describe the limbic system

Answer 1

• Brings together short-term memory and learning (hippocampus), expression of primal emotions such as fear and libido (amygdala), responses to odors (olfaction) and higher older modulatio of autonomic NS (hypothalamus)
• Related to behavior responses, both motor and visceral, appropriate to the sensory stimulus and cortical thought process

**Concered with memory, defense, and reproduction**

Question 2

define the limbic structures

Answer 2

• Cingulate gyrus
• parahippocampal gyrus
• subcallosal gyrus
• hippocampus (memory)
• Amygdala (emotions)
• septal area/nuclei
• hypothalamus and uncus-olfactory cortex

**concerned with memory, defense and reproduction**

Question 3

describe the olfactory input

Answer 3

• via medial and lateral stria from OLFACTORY TRACT/BULB
• Piriform lobe (UNCUS) considered primary olfactory cortex

–> DIRECT input to amygdala (emotions and drives)

–> INDIRECT input to hippocampus (memory)

–> from hippocampus connextions to hypothalamus (visceral responses to odors)

–> orbitofontral cortex (conscious awarness of odors)

–> anterior olfactory nucleus in tract sends axons through anterior commissure to both sides which FINE TUNES olfactory sensitivity

Question 4

what is the inputs to hippocampus

Answer 4

• amygdala
• cingulate gyrus
• prefrontal cortex via entorhinal cortex
• alvear and perforant pathway is MAJOR INPUT PATHWAY to DENTATE gyrus (“input” gate”) of hippocampal formation

Question 5

describe the Outputs of hippocampus

Answer 5

• SUBICULUM = OUTPUT GATE
• fornix to hypothalamus and septal region
• recurrent path to entorhinal area (repetition, reinforcement leads to consolidation of memories?)

Question 6

Which interal field is most vulnerable to anoxia and ischemia

Answer 6

• CA (1)
• belived to be trigger zone for temporal epilepsy

Question 7

describe function of hippocampus

Answer 7

• temporary memory until conscious decision to memorize or strong emotional overtones stimualtes hippocampus to fire neuron circuits repetitively producing a memory code PERMANENTLY establish in association cortex of cerebral hemisphere
• CALLED CONSOLIDATION of memory

Question 8

define working memory

Answer 8

• Found in cortex
• immediate information like adding a series of numbers to get a balance
• typically, quickly forgotten unless there is repetition or decision to memorize

Question 9

define declarative memory

Answer 9

• Found in Hippocampus
• Semantic: facts, figures, names and other MEMORIZED information
• Episodic: remembering personal events; hippocampus CONVERTS short term to long term memorys (consolidation) to be stored in cerebral association cortex thought to be related to original mode of sensory input

–> ex: visual memories sotred in areas 18 and 19, visual assocaition cortex

Question 10

define Wernicke-Korsikoff syndrome

Answer 10

• Manifestation of thiamine (vitamin B1) deficiency
• Mainly causes vision changes, ATAXIA and IMPAIRED MEMORY
• often secodnary to alcohol abuse

Question 11

describe the major nuclei in amygdala

Answer 11

• basolateral and corticomedial nuclei = INPUT GATEWAY to amygdala
• Central nuclei - OUTPUT GATEWAY from the amygdala

Question 12

describe major input to amygdala

Answer 12

• general and special sensory cortex (sights, sounds, smells, tastes, touches, pain) = monitoring sensoyr input for threats to survival
• OLFACTORY = arrtibute emotional significance to odors
• cigulate cortex = sense of physical and emotional comfort level
• thalamus
• hypothalamus = visceral sensory
• olfactory DIRECT input to corticomedial

Question 13

major output of amygdala

Answer 13

• STRIA TERMINALIS provides RECIPROCAL connections with septal area and hypothalamus (MODULATING VISCERAL RESPOSNES)
• Cingualte cortex connects to all cerebral lobes = emtoions can affect decision-making (frontal lobe)
• VENTROAMYGDALOFUGAL pathway to central striatum (nucleus accumbens) and brainstem ALLOWS EMOTIONS to INFLUENCE movements and brainstem nuclei (VII, X)

Question 14

what role does ventromedial prefrontal cortex play in amygdala

Answer 14

• Ventromedial prefrontal cortex integrates EMOTIONS with DECISION-MAKING
• also, conscious control of emotions

Question 15

describe function of amygdala

Answer 15

• Provide appropriate behavior responses and reactions to sensory information (especially if threatening or dangerous)
• Assess sensory input to determine if non-threatening, frightening, enraging, sexually arousing
• visceral responses called from hypothalamus (autonomic rxns) and septal area
• motor respones from MOTOR CORTEX
• Conscious perceptions of
  how we feel about it formed in the cingulate gyrus and prefrontal cortex

Question 16

damage to the amygdala results in…

Answer 16

• inability to express appropriate behavioral and visceral respones to known stimuli, and INABILITY TO LEARN appropriate resppones to noval stimuli
• MAY los the ability to read facial expressions (ability to interpret their emotional content and meaning)

Question 17

what is the function of the septal area

Answer 17

• relate emotions to respiratory, cardiovascular centers, salivatory nuclei and autonomic centers
• Pleasure/reward centers?

Question 18

describe the major inputs and outputs of septal area

Answer 18

• INPUT = from hippocampus via fornix; Amygdala via stria terminalis
• SENS RECIPROCAL connections with hypothalamus, amygdala and cingulate gyrus
• OUTPUTS = medial forebrain bundle to hypothalamus and brainstem nuclei

Question 19

describe papez circuit

Answer 19

• transfers information within limbic system
• although amygdala is part of limbic system, IT IS NOT PART OF PAPEZ CIRCUIT!!!
• hippocampus, forniz, septal area, hypothalamus, mammilothalamic tract, thalamus, thalamocingulate tract, cingulate gyrus, cingulum, parahippocampal gyrus, back to hippocampus