The Limbic System, Learning & Memory Flashcards
Telencephalic components of the limbic system.
cingulate gyrus, subcallosal gyrus, parahippocampal gyrus
Diencephalic components of the limbic system.
thalamic and hypothalamic nuclei
Cingulate gyrus
sexual behavior, pain/pleasure, addictive behavior
Subcallosal gyrus
emotional memory, reward/punishment (basal forebrain)
Parahippocampal gyrus
entorhinal cortex (smell memory), hippocampal formation (spatial navigation, ST-LT memory), amygdala (fear, emotional behaviors, hijacking, emotional learning)
Thalamic nuclei
sensori-motor integration (most important is anterior nucleus)
Hypothalamic nuclei
motor control of emotion
“The Triune Brain”
Breaks brain into 3 parts based on development:
Reptilian brain - brainstem and cerebellum
Paleomammillian brain - the limbic system
Neocortex - the primate/human brain
Major function of limbic system.
- govern emotion of individual
- All functions geared toward the preservation of self and the species
Mammillothalamic tract
mammillary bodies to anterior thalamic nucleus
Main pathway of the limbic circuit.
cingulate gyrus–>hippocampus–>mammillary bodies–>anterior thalamic nucleus–>cingulate gyrus
Damage to the frontal lobe could result in what?
person could act in an inappropriate way because the prefrontal cortex might not overrule the limbic system reactions
Pathways from hypothalamus to prefrontal cortex.
Emotion is generated in the amygdala and then is sent to the prefrontal cortex in order to help you decide how to react to an emotional stimulus (i.e. laugh, cry, don’t react)
Amygdala and hippocampal transmitters and receptors.
GABA, 5-HT, Dopamine, Glutamate, Steroid hormones
Klüver–Bucy syndrome
hyperphagia, hypersexuality, hyperorality, and docility (bilateral lesions of the amygdala)
Clinical hallmark is loss of ability to make new memories, consolidation of short term into long term is lost.
Alzheimer’s disease
Amygdaloid Nuclear Complex
- Made up of 5 sub-nuclei that all have their own neurotransmitters
- very sensitive to steroid hormones
Ischemic injury to hippocampus (as a result of CVA for example) will result in what?
memory loss
Hippocampal Formation
- Entorhinal complex (EC) to subiculum to CA1 to CA3 to cingulate gyrus
- EC gets input from all cortical areas into internal capsule stria
Hippocampus 3 major structures:
subiculum, ammon’s horn, dentate nucleus
T/F Information travels to and from the cortex to the hippocampus.
true
Pavlov’s Experiments
classical conditioning
Lashley’s Experiments
Equipotentiality - No matter where the lesion was, there was a decrement to the memory of the task= memory is stored everywhere
Hebb’s Experiments-Systems Organization
“neurons that fire together, wire together”
When you use a group of neurons for a certain task, they wire together and become more efficient = practice makes perfect!
Penfield & B. Milner’s Experiments - “Cortical homunculus” & “Mr. H.M.”
- Temporal lobe ablations
- Mapped out motor and sensory homonculi by stimulating different parts of the cortex and then asking the person what they felt
R. F. Thompson’s Experiments- “Eye Blink Response”
Thompson mapped out pathway for that eye blink - found that cerebellum has a very large influence in basic reflexive pathways
So “motor learning”= some major changes going on neurologically are changes in the cerebellum
Explicit “Conscious” Memory
hippocampus, temporal lobe, thalamus
Implicit “Unconscious” Memory
striatum, motor cortex, cerebellum, amygdala
Sensitization
ionic channels open, enhances reflex, gets stronger motor response
Habituation
ionic channels closed, if you don’t use the pathways, collateral branches retract
Types of Cortex
Neocortex (Isocortex) - 6 layers
Mesocortex (Paleocortex) - 5 layers
Allocortex (Archicortex) - 3 layers *oldest cortex
Fibrous Organization (Weigart Stain)- by the axons
Tangential layer- outermost Dysfibrous Layer Suprastriate Layer External band of Baillarger Internal striate layer Infrastriate Layer- innermost layer
Cellular Organization (Nissl Stain)- by cell bodies; named by their stain
Molecular layer External granular layer External pyramidal layer Internal granular layer Internal pyramidal layer Multiform layer *Each layer is very distinct
Pyramidal Cells - Layers II - VI
Projection Cells= one level to another level (lower to upper)
Commissural Fibers= one side of brain to another
Associations Fibers= connect one gyrus to another gyrus (short= adjacent gyri; long= one lobe to another)
- one apical dendrite, can have multiple branches
- multiple spines on the dendritic trees
- At the bases of the pyramids, there are going to be dendrites given off
- one axon that will project vertically toward the white matter
Stellate - Layers II-VI
- look like stars; are multipolar
- rounded nucleus with multiple dendrites and a single axon
Fusiform Cells - Layers II - VI
- look like spindle (wide in center, elongated on sides)
- two major processes from each side of the cell body and may have multiple cell branches coming off of them
- oriented in a horizontal fashion
Horizontal Cells of Cajal - Layer I
- look like fusiform cells (their processes run horizontally), but horizontal cells are only in layer 1
- central cell body, 2 processes coming off, multiple dendritic branches
- large cells
- found in the most superficial lamina
Cells of Martinotti- Layers IV-VI
- unusual because their axon projects from deeper levels to more superficial levels (upward rather than downward)
- one large cell body
- horizontally running dendrites with axon projecting upwards to synapse in lamina I (layer 1) of the cortex
Granule Cells - Layers II-VI
- small cells, very densely packed
Thalamus to Pyramidal Cells
- major set of interactions from thalamic nucleus to pyramidal cells of cortex
Ex: from VA and VL of thalamus, will have large connection to pyramidal cells in M1 (primary motor cortex); lateral geniculate body connected to visual cortex
Efferent Organization
Corticothalamic projections
Corticostriatal projections - has major projection to basal ganglia
Corticopontine projections - has projection from cortex to pons to cerebellum
Corticobulbar projections - has projection to the bulbar nuclei (CN nuclei)
Corticospinal projections - has projection from cortex to motor neurons in spinal cord
Afferent Organization
Thalamocortical Projections
Corticocortical Projections - via association fibers
Striatalcortical Projections
Primary Motor
4
Pre-Motor
6
Supplemental motor
8
Primary Somatosensory
3, 1, 2
Somatosensory Association
5, 7
Primary Auditory
41, 42
Auditory Association
20, 22
Multimodal Association, Language
39, 40
Primary Visual
17 - cuneus and lingula
Visual association
18, 19
Cognitive Behavior, executive planning
9, 10, 11
Limbic Association
23, 24, 26, 28, 38 (anterior and posterior cingulate gyrus)
Broca’s
44
Pre-Frontal Cortex
Orbitofrontal Region (areas 11,45,47) Dorsolateral Region (areas 9,10,11,44) Pre-motor, supplemental motor (areas 6,8,9)
Pre-frontal cortex afferent connections.
Parietal lobe - sensory Occipital lobe- Visual Temporal-auditory, language Thalamus, hypothalamus- emotions and mood Basal Ganglia - Motor Activity
Pre-frontal cortex efferent connections.
Hypothalamus - Emotions, autonomic Function
Thalamus - Motor Activity
Basal Ganglia-motor activity
Cerebellum - Motor Activity
Pre-frontal lobe damage.
loses flexibility of behavior, poor concentration, easily distracted, sensory perceptual disorders, perseveration, memory disorders, disorders of construction, spatial orientation dysfunction, personality disorders
