Thalamus and Limbic System Flashcards
Thalamic Relay (TR) Neurons
- located in thalamus
- receive input from sensory system
- relay sensory information to cortex via Glu in layer 4 of cortex
- ex. LGN and visual sense
- awake: ~-55mV, depolarized when neurons fire high frequency action potentials
- sleep: slow wave stage inhibits TR neurons by releasing GABA, ~85mV, fire in bursts of action on top of Ca++ spike (Ca spike happens with 3Hz frequency)
T Type Ca Channel
- voltage gated
- found in thalamic relay neuron
- has activation gate (closed at /80mV) and inactivation gate (open at -80mV)
- movement of gates is very slow
Optogenetics
- used in mouse models to control seizures
- channelrhodopsin: blue light opens and depolarizes cell
Dorsomedian (DM) Nucleus of Thalamus
-to frontal associated cortex
Anterior Nucleus of Thalamus
-to cingulate gyrus of cortex
VA/VL Nucleus of Thalamus
-to motor cortex
VPM/VPL Nucleus of Thalmus
-to somatosensory cortex
Pulvinar Nucleus of Thalamus
-to parieto-occipital associated cortex
LGN of Thalamus
- to visual cortex
- incoming optic tract
MGN of Thalamus
- to auditory cortex
- incoming inferior brachium
General Concepts of Thalamocortical Connections
- all connections are reciprocal
- R thalamus deals with L side of body and interacts with R cortex
Centromedian Nucleus of Thalamus
-motor
Reticular Nucleus of Thalamus
- a sheet of cells on lateral surface of thalamus
- primarily inhibitory interneurons with connections to all the other nuclei
Papez Circuit
- limbic system circuit
- memory
- mammilary body -> anterior n. -> cingulate gyrus -> hippocampus (all connected by fornix?)
Amygdala
- Limbic System Circuit
- emtion
- outputs: BNST, septal area, hypothalamus, thalamus
- involved in: fear, motivation, attention, sexual drive
Output of Hippocampus
-CA1 and CA3 through the fornix (basis for long term memory consolidation)
NMDA Receptors
- to open, requires tetanus and Ca
- involved in learning
Condition Flavored Aversion
- applies to odor and taste
- novel stimulus paired with negative stimulus up to half an hour afterward will cause avoidance of novel stimulus
Procedural Memory
- memory of how to accomplish tasks (motor memory)
- HM was not aware he had procedural memory
- frontal cortex, basal ganglia
Feedforward Mechanisms
-predict appetitive v. aversive events and engage more complex behaviors accordingly
Insula
- links between insula, VMPFC, and amygdala relate these senses to emotion
- constitues primary olfactory, gustatory, and visceral sensory cortex
Channelrhodopsin-2
-Na/K channel
Halorhodopsin
-Cl channel
Amygdala
-links aversive and appetitive stimuli with physiologic responses, action patterns, perceptions, and predictions
VMPFC and Ventral Striatum
-critical for generating and reinforcing predictions about risks and rewards associated with actions
Ventral Tegmental Area (VTA)
- reward, punishment, salience in various subregions
- releases DA in response to errors in predictions
- signals contribute to synaptic plasticity and associative learning in the amygdala, ventral striatum, and VMPFC
- VTA activation releases DA onto nucleus accumbens neurons, pleasure perceived and identifies stimulating activity as one to be repeated
Iowa Gambling Task
- people with damaged orbitofrontal cortex had impaired ability to estimate the risk/reward associated with certain behaviors
- implies suppression of behaviors felt to be excessively risky, esp in context of social situations (ex. “gut feeling”)
Mesolimbic Pathway
-subserve the integration of sensory input and motor responses with affective or emotional data
Mesocortical Pathway
-involved in communication and social abilities
Nigrostriatal Pathway
-part of basal ganglia (aka extrapyramidal tract) plays a central role in planned, coordinated movement
Tuberoinfuncibular Pathway
-hypothalamic neurons release DA in pituitary to inhibit prolactin release
Stria Terminalis
- a band of fibers running along the lateral margin of the ventricular surface of the thalamus
- Serving as a major output pathway of the amygdala, the stria terminalis runs from its centromedial division to the ventral medial nucleus of the hypothalamus.
Kluver Blucy Syndrome
- a syndrome resulting from bilateral lesions of the anterior temporal lobe (including amygdaloid nucleus)
- may present with hyperphagia, hypersexuality, hyperorality, visual agnosia, and docility
Red Nucleus
- projects to spine
- comes from contralateral cerebellum
