Limbic System Flashcards

Question

Hippocampus in Alzheimer's Disease

Answer 1

* hippocampus among 1st damaged * **memory problems** and **disorientation** among 1st symptoms * **CA1 region particularly affected** * extracellular **plaques** * intracellular **tangles**

Answer 2

Hypothalamus very susceptible to ischemia. **Selectively attacks CA1.** See pyramidal cell death d/t ischemia or stroke.

Answer 3

Hippocampus **very electrically excitable**. Often the **focus of epileptic seizures**. Presence of **strong glutamatergic transmission** contributes.

Answer 4

* Results in: * **visual agnosia** ⟾ psychic blindness * **oral tendencies** ⟾ examine surroundings with mouths * **hypermetamorphosis** ⟾ compulsion to explore * **emotions dulled** * **loss of normal fear** * **placidity** * **hypersexuality** * **Herpes simplex encephalitis** most common cause in humans * visual agnosia, hypersexuality, loss of fear/anger * **anterograde amnesia** * **dementia** * **distractibility** * **seizures**

Answer 5

Brain disorder caused by **chronic alcoholism**, **malnutrition**, and **thiamine (B₁) deficiency**. Likely damages **medial thalamus**, **hippocampus**, and **mammillary bodies**. _Major symptoms:_ * **anterograde amnesia** * **retrograde amnesia** * **confabulation** ⟾ making up stories Often occurs along with **Wernicke encephalopathy**: * ataxia * confusion * vision changes

Answer 6

Interacts with parahippocampal region for memory formation but mechanism unclear. Prefrontal cortex Temporal lobe Parietal lobe Cingulate gyrus Olfactory bulb

Answer 7

1. **attaching emotional significance** to incoming stimuli 2. form/store **implicit (non-declarative) memory** associated with **emotional events** 3. **unconscious emotional responses** 4. **conscious feelings** 5. **modulation of attention** 6. involved in **explicit memory** via processing of emotional meaning

Answer 8

_∆ in amydala function associated with:_ * **stress** * psychiatric conditions * **anxiety** **disorders** ⟾ PTSD, phobias, panic * **depression** * **schizophrenia** * **autism**

Answer 9

B/l temporal lobectomy ⟾ **∆ emotional behavior** **tame and fearless** Animals ⟾ **loss of fear conditioning** Humans ⟾ **impaired perception of emotional stimuli & emotional expression** Electrical stimulation in humans ⟾ feelings of **fear and apprehension**

Answer 10

Small almond-shaped **subcortical structure**. Buried in **anterior-medial portion of temporal lobe**. Near anterior end of hippocampus. Found **beneath uncus** in CS @ thalamus.

Answer 11

**_Deep group_** ⟾ responsible for collecting input from sensory corticies. 1. **Lateral nucleus (LA)** * major input nucleus for **sensory info** 2. **Basal nucleus (B)** * major input nucleus for **contextual info** from hippocampus 3. **Accessory basal nuclei** **_Dorsal group_** ⟾ receives projections from deep group & sends signal out to autonomic centers. 1. **Central nucelus (CE)** * main **output** nucleus 2. **Medial nucleus**

Answer 12

Receives 5 main types of input: 1. **Olfactory input** 2. **Sensory input** from _sensory thalamic relay nuclei_ * vision, audition, gustation, somatosensation 3. **Contextual input** from _hippocampus_ 4. **Cortical input** 5. **Visceral sensory input** from _hypothalamus_ and _brainstem_

Answer 13

**Must be able to control ANS.** Projects to **hypothalamus** and **brainstem autonomic centers** incuding **vagal nuclei** and **SNS neurons**. _Fibers leave via 2 main pathways:_ 1. **Stria terminalis** (ST) ⟾ _hypothalamus_ 2. **Ventral amygdalofugal pathway** (VAFP) ⟾ _hypothalamus_ & _MD thalamus_ Also involved in **mood** and **conscious emotional response** to an event. Has projections to **cortical areas,** **hippocampus, medial striatum.**

Answer 14

Visual, auditory, gustatory, and somatosensory inputs to amygdala via 2 pathways: 1. **_Short route:_** * **sensory thalamus** (VPL, VPM, LGN, MGN) directly to **amygdala** * shorter and **faster** * provides **low-level info** about objects and events (crude representation) * designed to start fight-or-flight response * info processed at **unconscious level** 2. **_Long route:_** * **sensory thalamus ⟾ sensory cortex ⟾ amygdala** * **slower** d/t processing time * provides more **complex and accurate info** * confirms or denies a threat Entire process occurs **unconsciously**. Involves **implicit processing** and **implicit learning**. Olfactor inputs directly from olfactory bulb and olfactory cortex.

Answer 15

**Amygdala works at subconscious level:** - identify potential threats - initiate behavioral responses and autonomic reactions - freeze, fight, or flight - increases likelihood of surviving danger **1.** See a spider **2.** Info ⟾ thalamus **3a.** **_Short route:_** - **crude representation** of potential danger ⟾ _amygdala_ - **lateral nucleus ⟾ central nucleus** - info processed **subconsciously** - many outputs: - hypothalamus, memory center, motor structures, reflex centers - recognized as a threat (**_implicit memory store_**) - **fight-or-flight response initiated** **3b. _Long route:_** - crude representation ⟾ _visual cortex_ - quality of representation improved d/t processing by primary and associative cortical areas (_what & where regions_) - more **complex and accurate representation** of object ⟾ amygdala - if threat confirmed, fight-or-flight strategy persued

Answer 16

**Learn by associating situation, object, or event with an emotional experience.** Associative process for emotional memories occurs in **amygdala**. Involves **LTP-related synaptic plasticity**. _Lesion of amygdala_ ⟾ **loss of fear conditioning**.

Answer 17

* Events linked to strong negative emotional experience are better recalled * Amygdala facilitates hippocampal consolidation of explicit memories tied to emtional situations * Too much stress ↓ explicit memory performance * maybe d/t stress hormones * disrupts hippocampal and prefrontal pathways * enhances amygdala's contribution to fear

Answer 18

Emotional implicit memories (e.g fear) stored: * **directly in amygdala** * **in adjacent regions requiring amygdala for access** Amygdala lesions abolishes emotional component of learned fear responses.

Answer 19

* **Amygdala response ↑ as fearfulness ↑ and happiness ↓** * extract expression from eye shape * **Perceive fearful expression faster than neutral or happy face** * happy face signals safety * do not need immediate action

Answer 20

* Genetic disease causing b/l calcification & atrophy of anterior-medial temporal lobes * **Results in b/l destruction of amygdala** * Presenation: * **pt judges face showing fear to be much less intense** * **unable to link visual representations of facial expressions with fear emotion** * no motor/sensory or intellect ∆ * no declarative memor ∆ * no language function ∆ * no difficulty recognizing people by faces * can rapidly learn new faces

Answer 21

* Theory for social deficits * Amygdala damaged * **Unable to link emotional meaning with stimuli** * Babies unable to connect faces with comfort/food * **Early social bonds needed for normal development not formed** * Pt w/ autism **bad at judging emotional state** of a person from a picture * **little amygdala activation** * **Eye-gaze processing deficit** * inability to use gaze to spontaneously to understand others * Amygdala **much smaller** in size

Answer 22

* In PTSD: * **fragment of a experience**"flashback" triggers full force of original emotion * b/c **implicit memory well preserved** * Pt's with PTSD show exaggerated amygdala responses to neg. stimuli by fMRI * **Normal** **fear extinction d/t brain regulation of fear response** * **Not forgetting emotional response** * Fear, stress, and trauma form permanent memories * survival strategy * Actual mech. for PTSD unknown * Treat with psychotherapy or antidepressants

Answer 23

Amygdala ↔ Neocortex * **memory & imagination can cause emotional response** * promotes use of emotional info in cognitive processing * **cortex → amygdala** * **conscious thoughts can suppress emotional responses** * ability to stop initial reaction judged inappropriate * **amygdala → cortex** * **too much emotion** from amygdala to working memory **can disrupt prefrontal cortex function** * leads to bad decisions * ex. stressful situations * **amygdala → cortex \>\> cortex → amygdala** * anxiety often control thoughts * thoughts have trouble supressing anxiety

Answer 24

Most commonly caused by **herpes simplex encephalitis.** * **Damage to b/l hippocampi & temporal association cortices** * anterograde & graded retrograde amnesia * dementia * seizures * **Damage to amygdala** * emotional deficits * fearless * decreased affect * docile * placid * **Loss of decending cortical control over hypothalamus** * hyperphagia * hypersexuality * distractibility * **Damage to "what" portion of visual pathway** * visual agnosia/psychic blindness * can see but cannot recognize or interpret visual information * inability to recognize faces/objects

Answer 25

* **Promotes pleasure associated with certain actions** * Encourages repetition of behaviors * May or may not be essential for survival * _Involves:_ * **Ventral tegmental area ↔ Nucleus accumbens ↔ Prefrontal cortex, ventral pallidum, thalamus** * **Reward ↔ Memory ↔ Emotion** * Major component from **limbic structures** * motivation, goal directed behavior, memory, emotion, and autonomic functions * **Rewarding experience or anticipation releases dopamine** * brain forms **implicit (amygdala) and explicit (hippocampus) memories** * drugs of abuse ∆ release → addiction

Answer 26

1. **Learning** * via positive reinforcement 2. **Appropriate behavior** * taking rewards as goals of behavior 3. **Positive emotion (hedonia)** * reward elicits pleasure and mood changes,

Answer 27

Involves: * attention * anticipation * perception (visual and sensation) * motivation * emotion * judgement * movement coordination * thinking and decision making * short and long term memory

Answer 28

1. **Dopamine** → well-being, arousal, reward 2. **Opiods** → reward and reinforcement 3. **Serotonin** → behavioral inhibition 4. **GABA** → inhibitory 5. **Glutamate** → excitatory 6. **Ach** → addiction to nicotine and other drugs

Answer 29

Found near midline in midbrain. Next to substantia nigra and red nucleus.

Answer 30

* Contains **dopaminergic neurons** * _Origin of two major dopamine pathways:_ 1. **Mesolimbic pathway** * VTA → nucleus accumbens 2. **Mesocortical pathway** * VTA → prefrontal cortex * **Rewarding activities activates VTA** → dopamine release to all targets

Answer 31

Part of the **ventral striatum (basal ganglia).** Important role in **reward, pleasure, and addiction**. Part of the **cortico-striato-thalamo-cortical loop**. * Includes a core and shell * 95% of neurons are **medium spiny neurons** secreting **GABA**. * _main output neuron_ * **Large aspiny cholinergic interneurons fewer** * **N. accumbens activated by:** * dopaminergic afferents from VTA * via mesolimbic pathway * amygdala * hippocampus * prefrontal cortex * **Output:** * **inhibitory to ventral pallidum** * VP is also inhibitory * ⟾ disinhibition of MD thalamus * ⟾ excitation of prefrontal cortex * inhibitory to **substantia nigra** and **pontine reticular formation**

Answer 32

* N. accumbens is part of the **"reward center"** * Direct relationship b/t **[DA] released** at VTA/NA synapse & **rewarding effect** * **Natural reinforcers** (food, sex, eating) have some rewarding effect by **↑ DA transmission** * **Drugs of abuse** tap into system * produce reinforcing effect by **↑ DA transmission** * **∆ chemistry of system**

Answer 33

**Dopamine Reuptake Inhibitor** * **prolonged ↑ [DA] at VTA/n. accumbens synapse** * causes rewarding effects * **Tolerance** * repeated use → ↓ DA receptors → ↓ 2nd messenger signaling → tolerance * **∆ sensitivity of reward system** * natural reinforcers less rewarding * **Dependence** * cocaine use stops → low [DA] in reward circuit → **withdrawal** * depression, insomnia, fatigue, restlessness * **Craving** * **prefrontal cortex hyperresponsive** to stimuli releated to drugs * overstimulates nucleus accumbens * promotes goal-directed behaviors for drug seeking → relapse * **Implicit emotional memories** tied to drug use **can** **activate prefrontal cortex and amygdala** _years later_

Answer 34

Directly or indirectly enhance DA signaling in nucleus accumbens. * **Cocaine, amphetamines, related stimulants** * block DA reuptake * increase DA release by VTA * **Nicotine** * stimulates VTA release of DA * **Alcohol and opiates** * inhibits local interneurons normally inhibitory to VTA * indirectly promotes VTA release of DA Drugs can also **∆ response of n. accumbens to glutamate input** from other regions. **DA circuits** more involved in "**wanting**" → incentive salience **Mu-opioid circuits** more involved in "**liking**" → hedonic aspect

Answer 35

1. Pleasurable thoughts, memories, and activities activate VTA dopaminergic neurons 2. DA released into reward circuit → activates GABA neurons in nucleus accumbens 3. GABA neurons in n. accumbens inhibit GABA neurons in ventral pallidum 4. GABA neurons in ventral pallidum inhibition on MD thalamic neurons decreased 5. MD thalamic neurons disinhibited and excitation to prefrontal cortex increased * **Activation** associated with **pleasure** and **goal-directed behaviors** * **Drugs of abuse** tap into circuit and ↑ DA * **Memories of past drug experiences & stress** * from amygdala, hippocampus * can directly affect circuit * promotes relapse * **Prefrontal cortex influence over VTA & n. accumbens** * allows throughts to be rewarding * way to exert cortical control over pleasure and goal directed behaviors

Answer 36

Regulates **metabolic, immune, and brain function** in response to stressors. 1. **Hypothalamic-Pituitary-Adrenal (HPA) Axis** 1. Stress **⟾ ⊕** **paraventricular nucleus** (PVN) of **hypothalamus ⟾** _CRH release_ 2. CRH **⟾** **anterior pituitary** **⟾** _ACTH release_ 3. ACTH **⟾** **adrenal cortex** **⟾** _cortisol release_ 4. Anti-inflammatory and immunosuppressive actions 2. **Sympathetic-Adrenal-Medullary (SAM) Axis** 1. Stress **⟾ ⊕ postganglionic SNS fibers****⟾**_synaptic norepi release_**⟾****adrenal medulla****⟾** _systemic norepi & epi release_ 2. ∆ immune function

Answer 37

↑ [cortisol]_plasma ⟾ ⨂ hypothalamus/pituitary/adrenals ⟾ ↓ cortisol production via negative feedback

Answer 38

**Corticolimbic, hypothalamic, and brainstem centers** have regulatory influence on HPA/SAM axes. **Hippocampus mostly ⊖** **Amygdala mostly ⊕**

Answer 39

Chronic stress ⟾ prolonged cortisol secretion ⟾ ↓ glucocorticoid receptors ⟾ glucocorticoid resistance ⟾ inability to shutdown immune responses ⟾ ↑ [inflammatory cytokines]

Answer 40

Acute activation of SAM-axis for fight-or-flight response SNS fibers & circulating norepi/epi ∆ immune function including: cell proliferation, cytokine/Ab production, cell trafficking Chronic activation of SAM ⟾ dysregulaton of SAM effects on immune system

Answer 41

**Stressful life events & HPA-axis dysfunction** ∝ risk, onset, and course of pyshiactric orders. * Chronic ± HPA/SAM function ⟾ ∆ regulatory feedback mechs ⟾ dysfunction * **↑ cortisol common** w/ depression, anxiety, substance abuse, psychosis * normal neg. feedback mech impaired * **toxic to limbic structures** * ex. **↓ hippocampus size** * **impaired inhibition of HPA-axis** * **memory loss** * _HPA-axis functional tests_ with depression * **↓ dexamethasone suppression** * **↓ CRF stimulation**

Answer 42

**Stress, emotion, disease ↔ ∆ immune system ↔ ∆ brain** * Stress ⟾ pro-inflammatory cytokines in children ⟾ risk of mental illness in adults ⟾ ⊕ neuroinflammation markers in limbic regions * Induces sick sx, depression, anxiety * Ass. w/ bipolar d/o, schizophrenia, neurodegenerative diseases * Bipolar & schizophrenia linked to: * childhood autoimmune diseases * maternal infecitons * inflammation during pregnancy * Targeting immune system for treatment of psychiatric d/o being studied

Answer 43

* Proinflammatory cytokines / bacterial endotoxins ⟾ sickness/depression ⟾ better w/ antidepressants * Cytokines interact w/ depression pathways * neuroendocrine & central neurotransmitter ∆ * similar to depression * Severe depression w/ signs of immune activation & ↑ cytokines * \> inflammatory response to stress ⟾ \> chance of developing depression * Cytokines ↓ DA release ⟾ ↓ reward circuit ⟾ anhedonia & no motivation * ↑ inflammation ⟾ ↑ activation of threat/anxiety circuits

Limbic System Flashcards

(70 cards)