Neuro 43: Limbic System and Memory

1. emotions and responses

2. behaviors activities

3. memory

4. olfaction ?

functions of the limbic system?

1. sensory areas in the cerebral cortex

2. monoamine neuronal groups of brainstem reticular formation

inputs to the limbic system?

1. hypothalamus (behavior, visceral responses)

2. various areas of cerebral cortex (some thalamic nuclei and brainstem areas)

primary outputs of the limbic system

1. cingulate gyrus

2. subcallosal gyrus

3. uncus

4. parahippocampal gyrus

cortical areas of the limbic system

hippocampus

subcortical structure of the limbic system responsible for learning and memory

amygdala

subcortical structure of the limbic system responsible for emotional learning and response, drive-related behavior

nucleus accumbens

subcortical structure of the limbic system responsible for reward system and addiction

septal nuclei

subcortical structure of the limbic system responsible for reward system and rage

medial temporal lobe

where is the hippocampal formation located?

convert short term to long term memories (memory consolidation)

key function of the hippocampal formation

entorhinal cortex

primary source of afferent fibers to hippocampal formation (olfactory bulb, cingulate gyrus, amygdala, visual, auditory, taste association cortices)

dentate gyrus

portion of the hippocampal formation that receives afferent info from the entorhinal cortex via the perforant pathway

perforant pathway

how does the dentate gyrus receive afferent info from the entorhinal cortex in the hippocampal formation

1. subiculum

2. hippocampus (CA 1, 2, 3)

what sends out efferents from the hippocampal formation

fornix

projects from the hippocampal formation to the hypothalamus, nucleus accumbens, septal nuclei, thalamus, and various parts of the frontal cortex

entorhinal cortex also receives input from the subiculum and projects to the amygdala and neocortex

how does the hippocampus communicate with the amygdala?

amygdala

links perception with memory, which determines visceral and behavioral responses

amygdala

what exerts the most control over the visceral processes of the hypothalamus?

basolateral nuclei

amygdala input from several areas; attaches emotional significance to stimuli

central nuclei

major amygdala output that regulates the visceral response to emotional stimuli

corticomedial nuclei

amygdala area that processes olfactory information, influencing behaviors like male sexual behavior and social interaction

striae terminalis

pathway from amygdala to hypothalamus

ventral amygdalofugal pathway

pathway from amygdala to several areas of the brain

mammillothalamic tract

pathway from mammillary bodies to the anterior thalamic nucleus

medial forebrain bundle

link VTA (ventral tegmental area), nucleus accumbens, and prefrontal cortex

reward

key factor for driving incentive-based learning, appropriate response to stimuli, goal-directed behavior

nucleus accumbens

VTA projects dopaminergic fibers through medial forebrain bundle (mesolimbic pathway) to ?

dopamine

__________ in the VTA in the midbrain plays a key role in the reward system

VTA to nucleus accumbens (other areas of the brain are also involved)

what does the mesolimbic pathway primarily connect?

dopamine

euphoria (high) involved in drug addiction behavior is due to the drugs increases the _______ level

septal nuclei

humans with infarcts in this area display inappropriate rage

prefrontal cortex

short-term memory depends primarily on?

long-term memory

alterations in the strength and number of synaptic connections in the cerebral cortices that requires the hippocampus (medial temporal lobe) and association cortical areas (storing and retrieving)

forgetting

normal _____ enables new information to be learned

anterograde amnesia

inability to create new memories

retrograde amnesia

inability to recall previous memories

nondeclarative (implicit procedural) memory

• information recalled unconsciously

• training reflexive motor and perceptual skills

• implicit memory involves the neocortex, striatum, amygdala, cerebellum = reflex

declarative (explicit) memory

• recall by deliberate, conscious effort

• highly flexible and involves the association of multiple pieces of information

• hippocampus and neocortex

episodic

memory for events and personal experiences

semantic

memory for knowledge of objects, facts, concepts, words and meanings

bilateral temporal ischemia

• fail to form new memory

• heart attack or near drowning

• damage of hippocampus or regions connecting to hippocampus

dementia

acquired disorder that is characterized by a decline in cognition involving one or more cognitive domains (learning and memory, language, executive function, complex attention, perceptual-motor, social cognition)

episodic memory (recalling events in specific time and place)

what is mostly affected by dementia

1. alzheimer disease (AD)

2. dementia with lewy bodies (DLB)

3. frontotemporal dementia (FTD)

4. parkinson disease dementia (PDD)

most common neurodegenerative conditions causing dementia (4)

vascular dementia

most common cause of non-neurodegenerative dementia

alzheimers and vascular dementia

most common mixed dementia

alzheimer’s disease

most common dementia

impairment of recent memory function and attention

earliest signs of alzheimers?

1. neurofibrillary tangles

2. senile or amyloid plaques

3. diffuse loss of neurons (most apparent in neocortex and limbic structure)

3 hallmarks to confirm alzheimer’s disease

entorhinal cortex

what area of the brain often exhibits the earliest alterations in alzheimer’s disease

thiamine (vitamine B1); chronic alcoholism

wernicke-korsakoff syndrome is associated with a severe lack of _______ which causes damage to the brain and is most associated with __________

wernicke encephalopathy

• acute, reversible

• medical emergency

• confusion

• ataxia, LE sensory loss

• visual changes, ophthalmoplegia, nystagmus

korsakoff syndrome

• long-term (chronic) memory disorder

• irreversible!

• limbic system (mammillary bodies!)

• severe memory impairment both anterograde and retrograde amnesia

korsakoff syndrome

buzzword: confabulation

confabulation

generating false memories (make-up memories); associated with korsakoff syndrome

kluver-bucy syndrome

• bilateral lesion of the medial temporal lobe including amygdala

• placidity (no display of fear or anger, even when you should)

• hyperplagia

• hypersexuality

• hyperorality

• impaired memory

anxiety

excessive activity in the amygdala, with failure of “top-down” control by the frontal cortex

schizophrenia

• most common psychotic illness

• positive and negative symptoms

• hyperactivity of mesolimbic dopamine pathway accounts for positive symptoms

dopamine

antipsychotic drugs usually block _______ receptors

extrapyramidal side effects (e.g. parkinsonism)

major side effect of antipsychotic drugs?

depression

• deficiency of monoamine NT (serotonin 5-HT, dopamine, NE)

• may be related to altered function of limbic networks including prefrontal cortex, hippocampus, nucleus accumbens, and VTA

serotonin (SSRI)

antidepressants often block _______ reuptake