Lab 13: Emtion And Memory Components Of The Limbic System

Question 1

Cortical Part of the Emotional System (overview)

Answer 1

Anterior Cingulate Gyrus
Ventromedial Prefrontal Cortex
Orbitofrontal gyri

Question 2

Amygdala (overview)

Answer 2

-key integrator and “emotional grader” of incoming sensory information

Question 3

Ventral or limbic Basal Ganglion (overview)

Answer 3

Ventral striatum (nucleus accumbens)
Ventral Pallidum (output nucleus)

Question 4

Hypothalamus (overview)

Answer 4

Nodal point in organizing visceral and somatic emotion responses

Question 5

Emotion Structure Connections (overview)

Answer 5

Cingulum (corticospinal-cortical connections)

Ventral Amygdalofugal Pathway: input/output of amygdala

Medial forebrain bundle (MFB): bidirectional multipurpose tract in the lateral hypothalamus

Question 6

Anterior Cingulate Cortex (ACC)

Answer 6

The anterior part of the cingulate gyrus that bends around the anterior part of the corpus callosum and extends to the level of the posterior end of the SMA

Question 7

Ventromedial Prefrontal Cortex (VMPC)

Answer 7

The ventromedial area of the medial frontal lobe

Question 8

Orbitofrontal Cortex (OFC)

Answer 8

Ventral part of the frontal lobe that lies above the orbit

Question 9

Functions of the 3 Prefrontal cortical areas

Answer 9

• conscious awareness of emotion
• awareness of what are socially-acceptable norms of behavior
• inhibition of socially-inappropriate behavior

Question 10

Orbitofrontal Cortex Lesion

Answer 10

Marked personality changes, including impulsivity, explosiveness, tactlessness, lability, and lack of interpersonal sensitivity

Question 11

Anterior Cingulate Cortex Lesion

Answer 11

Akinetic mutism, profound apathy, abulia (lack of motivation) and immobility

Question 12

Ventromedial Prefrontal Cortex Lesion

Answer 12

Psychopathy, characterized by a severe absence of empathy, emotion, and complete lack in the ability to be remorseful

Question 13

Hypothalamus

Answer 13

Located medial to the basal forebrain and ventral to the thalamus; is a major organizer of emotional responses and motor activity
Blood Supply: anterior=anteromedial striate arteries
caudal+Posterior=posteromedial striate arteries

Question 14

Basal Forebrain (a.k.a. anterior perforated substance)

Answer 14

Medial telencephalic area that is located between the hypothalamus and the medial temporal lobe; contains scattered nuclei that are important parts of the emotion and attention systems. It also contains a major output pathway for the amygdala (the ventral amygdalofugal path)

Question 15

Anterior Commissure

Answer 15

Connects the amygdaloid nuclei and cortical structures of the anterior temporal lobes

Question 16

Basal Nucleus of Meynert (Nucleus Basalis)

Answer 16

A nucleus involved in enhancing cortical attention via its choinergic pathways to the cortex

Question 17

Ventral Pallidum (basal forebrain)

Answer 17

Scattered cell groups in the basal forebrain that are output nuclei of the emotion basal ganglia

Question 18

Ventral Amygdalofugal Pathway (basal forebrain)

Answer 18

Major output/input pathway of the amygdala connecting it to other neuroanatomical centers of the emotion system

Question 19

Hypothalamus (anterior area)

Answer 19

-surrounds anterior part of III ventricle; its lateral area contains the medial forebrain bundle

MFB: the major bidirectional fiber bundle that connects structures of the emotion system with each other and with their targets

Question 20

Cingulum

Answer 20

Fiber bundle that connects ACC to other emotion cortices and to the posterior cingulate gyrus, frontal cognitive cortex, and medial temporal cortex

Question 21

Lateral Hypothalamic Area

Answer 21

Located lateral to the fornix; contains the MFB (the major 2 way connector between components of the emotion system pathways to their brainstem and spinal cord targets. The descending fibers of the MFB continue as a part of the reticular formation of the brainstem; called hypothalamospinal tract

Question 22

Medial Hypothalamic Area

Answer 22

Location of most of the nuclei of the hypothalamus

Question 23

Dorsomedial Nucleus of the Thalamus

Answer 23

Processing center in communications between amygdala, emotion cortex, and limbic basal ganglia

Question 24

Circuit Features of the emotion system with previously learned info

Answer 24

1: emotional “grading” of a sensory stimulus
2: organization and execution of responses to that assessment
3: the relation between emotional and cognitive awareness

A: subconscious fear
B: behavioral responses to it
C: conscious awareness of this clinically-important emotion

Question 25

“Fast-track” Pathway of Visual Info to the amygdala for “emotional Grading”

Answer 25

The output of the LGN is not limited to fibers en route to the visual cortex. Some LGN interneurons send fibers anteriorly to the amygdala to provide rapid but low resolution input for emotional assessment

-amygdala: receives fibers directly from the LGN for high-speed, subconscious assessment and “survival” grading of the visual image of the grizzly bear (i.e. Judging that the grizzly bear is dangerous)

Question 26

Pathway from the amygdala to centers for organizing an emotional response or behavior

Answer 26

Amygdala: processes low resolution sensory input and determines its emotional value (or valence)

Ventral Amygdalofugal Pathway: major output system from the amygdala; passes medially thru the basal forebrain to reach the hypothalamus and medial forebrain bundle to announce its decision about the stimulus to other emotional centers

Hypothalamus: receives news of the danger grade via the VAFP and processes info for circuits needed for appropriate responses

Medial Forebrain Bundle: receives output fibers from the hypothalamus (esp. paraventricular nucleus) to notify motor centers and neurons about the need for rapid “danger approaching” reactions

Question 27

Pathway from the Hypothalamus for SOME emotional expressions (emotion generated behavior)

Answer 27

Nuclei of the hypothalamus are the target of the amygdala (esp. the paraventricular nucleus). It’s found in the anterior hypothalamus and contains neurons that send axons thru the descending part of the medial forebrain bundle in the lateral hypothalamus to activate sympathetic preganglionic neurons (T1-L2 levels) for danger or stress responses such as; tachycardia, paleness, pupillary dilation, blood pressure elevation. These fibers descend ipsilaterally in the reticular formation of the brainstem and synapse in the intermediate gray of the spinal cord

Question 28

Paraventricular Nuclei

Answer 28

-also contain cells that send axons to the median eminence which secrete corticotropin releasing factor (CRF) into the hypophyseal portal system from the hypothalamus, for increased anterior hypophyseal release of ACTH (adrenocorticotropic hormone) into the blood during stress for increased production and release of cortisol from the adrenal cortex. An increased release of cortisol, the “stress” hormone, generates behavioral/observable signs of fear

Question 29

In the Clinic: CRF and Cortisol

Answer 29

The have the inhibitory effect on hippocampal functioning. Long term or chronic exposure to theses hormones can result in stress-induced atrophy of hippocampal neurons and decreases in memory function. At the same time, cortisol ACTIVATES the amygdala, resulting in exaggeration of the danger or stress response. Chronic stress can also lead to clinical depression and other affective disorders

Question 30

Position of the descending fibers from the MFB [hypothalamospinal tract] of the hypothalmus

Answer 30

Travel in the periaqueductal gray (PAG) before moving to the lateral reticular formation

Question 31

Ventral Tegmental Area (VTA)

Answer 31

Is located in the ventral reticular formation near the midline; has dopaminergic neurons that project to numerous forebrain centers, including the amygdala. In response to input from the amygdala, the VTA increases its firing rate, and thus dopaminergic transmission, to these higher centers

Question 32

NOTE (Stimulation of dopaminergic neurons of VTA area and nor-Epi containing neurons of the locus ceruleus)

Answer 32

Result in behavioral/observable signs of fear such as: arousal, increased brain electrical activity, increased vigilance

Question 33

Fibers from the MFB (rostral pons)

Answer 33

In the PAG and the area of the lateral reticular formation that will contain these descending fibers in the pons and medulla

Question 34

Parabrachial Necleus (rostral pons)

Answer 34

Located medial to the superior cerebellar peduncle in the rostral pons; receives excitatory input from the amygdala to send signals to medullary respiratory centers to increase respiration (hyperventilation is observed)

Question 35

Locus Ceruleus

Answer 35

A group of pigmented cells at the lateral edge of the PAG in the pons/midbrain junction that are a part of the upper brainstem chemospecific nuclei that modulate firing patterns in their targets. Their nor-Epi containing cells send ascending fibers to the amygdala to increase it’s activity. They also receive amygdala fibers via the MFB, forming a feed-back system between them

Question 36

Raphe Nuclei

Answer 36

Close to the midline of the tegmentum; contain serotonergic neurons that are part of the brainstem chemospecific nuclei system; are involved in emotional tone or mood and sleep-wake rhythms

Question 37

Pathway for conscious perception of the feeling of fear

Answer 37

The amygdala receives its 1st announcement of danger subconsciously, via low-resolution input from the LGN of the thalamus. It then sends signals to both the hypothalamus for a response AND to the emotion cortex via the dorsomedial thalamic nucleus, at which time you become consciously aware of the feeling of fear. You’re not aware of the “grizzly bear” features until data from the retina have been processed in the visual cortex and compared with past memories in the temporal association cortex. This info reaches the amygdala milliseconds after the subconscious processing, by way of fibers from the temporal association cortex and the hippocampus. This specific and high-fidelity info is reassessed by the amygdala and may result in a correction if the initial grading of the sensory input was inappropriate (e.g. The beast you saw was really an actor in an authentic grizzly bear costume). A change in the emotional grading of the sensory input by the amygdala will result in a change in info delivered to the hypothalamus and to the emotion cortex

Question 38

In the Clinic (response to danger)

Answer 38

A person’s response to an unexpected danger begins before there’s an understanding of the full circumstances. this is particularly true in individuals who are suffering from chronic stress, as the activity of the amygdala is increased. In battle conditions such as those in Iraq, military personnel can suffer from chronic stress and are often faced with ongoing threatens of violence, which tend to increase the speed of reaction to presumed danger. This can result in “friendly fire” deaths and injury

Question 39

Pathway for Cognitive Recognition of the Grizzly bear

Answer 39

While the amygdala makes an initial subconscious assessment of the grizzly bear silhouette, the LGN sends impulses to the primary visual cortex for conscious perception of the bear

Question 40

Inferior Temporal Cortex (area IT)

Answer 40

Temporal association cortex that receivers input from visual areas of cortex via the ventral stream. This input is compared with related memories for recognition of the sensory info as a grizzly bear (real or staged)

Question 41

Hippocampal Formation (medial to temporal horn of lateral ventricle)

Answer 41

Receives and processes input from the visual cortices and Area IT to reinforce or update grizzly bear memories

Question 42

Amygdala (area IT)

Answer 42

Receives high-fidelity input from the area IT and from the hippocampal formation

Question 43

Amygdala and Memory (in the clinic)

Answer 43

In addition to assessing level of danger, the amygdala participates in emotional learning (context conditioning). Sensory input from frequently-repeated positive or negative experiences leads to long-term potentiation in the amygdala during emotion processing, so that the emotional grade, behavior and feelings associated with the experience are linked together. This learned emotional sequence can be initiated by sensory events that represent some feature of the negative experience. These features serve as “triggers” for the positive or negative emotional processing. The value of emotional learning is that it retains us to 1: increase contact with previously encountered ENVs or things that are useful and essential and 2: minimize contact with ENVs or things that are aversive or dangerous. In this way, ENV conditions that are either favorable or unfavorable but that were not preprogrammed in the human can be added to the list of things to approach or avoid over many repeated trials. Fearful anxious feelings and behaviors can be generated after a sensory trigger that is not even recognized by the patient, resulting in anxiety attacks that appear “out of the blue”

Question 44

Papez’s Circuit

Answer 44

Association cortex—–Cingulate cortex (mostly posterior)—–cingulum—–entorhinal cortex—–hippocampal formation—–fornix—-mammillary nucleus of the hypothalamus—–mammillothalamic tract—–anterior thalamic nucleus—-thalamic radiations—–cingulate cortex

Question 45

Cingulate Gyrus (PCC)

Answer 45

Part of the memory consolidation pathway

Question 46

Cingulum (memory)

Answer 46

Association bundle that connects the cingulate gyrus with the parahippocampal gyrus

Question 47

Parahippocampal Gyrus

Answer 47

Involved in the transfer of info between the hippocampal formation and areas of sensory association cortex

Question 48

Hippocampal formation

Answer 48

Processing center for short term and long term memory storage via long-term potentiation in its circuitry

• bulges into the inferior horn of Lateral Ventricle; a component of the limbic cortex
• contains subsections including hippocampus proper (forms the floor of the temporal horn of the lateral ventricle), the dentate gyrus (faces the subarachnoid space) and the subiculum (the most inferior part of the hippocampal formation)

Question 49

Fornix

Answer 49

A C-shaped fiber tract that carries info from the hippocampus; near the anterior commissure, the fornix divides into:

• precommissural fibers: an anterior segment that travels to the septal nuclei
• postcommissural fibers: a posterior segment that travels thru the hypothalamus to terminate in the mammillary nuclei

Question 50

Mammillary Nuclei

Answer 50

Located in the posterior hypothalamus; is a site of termination of post commissural fornix fibers; is involved in long-term memory circuit

Question 51

Mammillothalamic tract

Answer 51

Fibers from the mammillary nuclei to the anterior Nucleus of the thalamus

Question 52

Anterior Nucleus of thalamus

Answer 52

Thalamic nucleus involved in memory processing

Question 53

Cingulate Gyrus (memory)

Answer 53

Termination of thalamocortical fibers from anterior nucleus of thalamus; sends input to association areas of cortex via cortico-cortical fibers

Question 54

Alveus

Answer 54

A thin layer of white matter on the ventricular surface of the hippocampus that consists of axons from the hippocampus that coalesce to form the fornix

Question 55

Fornix (fimbria)

Answer 55

Medial to the Alveus

• a consolidation of fibers of the Alveus
• an important input to mammillary nucleus of the hypothalamus

Question 56

Internal Medullary Lamina (of thalamus)

Answer 56

Partition that separates regions of the thalamus

Question 57

mammillary nucleus

Answer 57

Nuclei of the posterior hypothalamus

• involved in declarative memory processing
• receives fibers from the hippocampal formation via the fornix
• sends fibers to the anterior nucleus of the thalamus via the mammalothalamic tract

Question 58

Fibers of the Fornix (path)

Answer 58

1: from its origin at the consolidation of fibers of the alveus of the hippocampal formation
2: toward the midline, under the corpus callosum
3: and anteriorly along the lower edge of the septum pellucidum
4: ventrally, to split at the anterior commissure into precommisural fibers to the septal area
5: the post commisural fibers to reach the mammillary nucleus by traveling thru and dividing the hypothalamus into medial and lateral parts