Lecture 16 &17 -Limbic, Olfactory System, Learning Systems Flashcards
List the two direct pathways to the limbic system.
- Olfactory receptors → olfactory bulbs → sensory cortex → limbic system
- Other sensory receptors → dorsal spinal cord/cranial nuclei → thalamus → sensory cortex → limbic system
Where do the olfactory bulbs terminate at? What does this structure form?
Terminate at ethmoid bone, forms basis of upper nose
Where do the olfactory receptor cells project from, & where do they project to?
Project from nasal epithelium to 2nd-order neurons in olfactory bulb
Where are the olfactory nuclei located? Do 2nd-order projections terminate in the nuclei?
Olfactory nuclei found further down olfactory tract → MOST 2nd-order projections DON’T terminate in nuclei
What are the six layers of the olfactory bulb? List them from the most bottom/deep to top.
Olfactory nerve layer → glomerular layer → external plexiform layer → mitral cell layer → inner plexiform layer → central fibre core
In the olfactory bulb, what is the main cell that is sending output projections? What layer of the olfactory bulb are they found in?
Mitral cell in mitral cell layer
Where do most of the olfactory projections exit from? What two structures do these projections then split off to go to?
Lateral olfactory stria (tract) → amygdala OR primary olfactory complex (piriform complex)
What are the three main structures discussed in lecture that are associated/part of the limbic system?
- Hippocampus
- Amygdala
- Hypothalamus
What is the hippocampal formation involved with? What is it able to do in context to memory?
Episodic memory formation & retrieval, smell
Has long-term potentiation to change synaptic weights for memory formation
What response is given when the hippocampus is connected with the amygdala? With the hypothalamus?
Strong connections w/ amygdala for EMOTIONAL RESPONSES to remembered stimuli
Strong connections w/ hypothalamus for IMMEDIATE ANS RESPONSES to remembered stimuli
What is the amygdala involved with? What is it connected to?
Involved w/ expression of emotions (specifically fear/stress)
Reciprocal connections w/ all sensory cortices (“what should my emotional response be?”)
What is the hypothalamus responsible for? What two structures discussed in lecture does the hypothalamus stimulate? For what purpose/role?
Control centre for ANS
1. Stimulates pituitary gland to release various hormones
2. Stimulates reticular formation to control synaptic responses to stimuli
What is the fornix? What two structures does it help connect?
Paired, arch-shaped white matter structure connecting hippocampal formation to hypothalamus
When looking at the hippocampus, what are the four main parts? List what each part includes/is responsible for.
- Hippocampus proper →has intermediary neurons & processes input from dentate gyrus
- Dentate gyrus → receives input from various sources, including the entorhinal cortex
- Subiculum → sends output from hippocampus
- Fornix: primary tract out of subiculum to other brain areas
What are the three layers of the hippocampus from the farthest to the subiculum to the closest?
- Polymorph layer
- Pyramidal layer
- Molecular layer
What is the significance/importance of the subiculum in terms of layers?
Goes from three-layered to six-layered cortex
What is the uncus? What is it responsible for?
Primary olfactory cortex, one of the main olfactory terminations of the lateral olfactory stria
What major structure provides major input to the hippocampal formation?
Entorhinal cortex
What are the little folds of the dentate gyrus called? What are they responsible for?
Fimbra: white matter tracts wrapping around outside of dentate gyrus & hippocampus → facilitate connections within the hippocampus itself and between the hippocampus and other brain regions.
What are the three layers of the dentate gyrus from closest to the entorhinal cortex to furthest from the entorhinal cortex?
- Molecular layer
- Granular layer
- Polymorph layer
What does the limbic lobe wrap around? What is the superior part called? The inferior temporal part? What is the general function of the limbic lobe?
Wraps around outer surface of corpus callosum
Superior part: cingulate gyrus/cortex
Inferior temporal part: parahippocampal gyrus
Function: send inputs to hippocampus via dentate gyrus
What is the frontal part of the parahippocampus called, & where does it receive projections from?
Frontal part: entorhinal cortex → receives projections from all sensory & other parts of cortex
Where does the mammillothalamic tract start, & where does it go to?
Mammillary bodies in the hypothalamus to the thalamus, projects to cortex
List the path of the hippocampus starting from the entorhinal cortex.
Entorhinal cortex → perforant path (lateral)/alvear path (medial) → dentate gyrus → hippocampus → subiculum
List the pathway of the papez circuit(sara’s furry monkey threw chocolates happily)
Subiculum → fornix → mammillary bodies → thalamus → cingulate gyrus → hippocampus via parahippocampal cortex
What is the papez circuit responsible for?
1) Memory formation via long-term potentiation (changing synaptic weights),
2) Associating appropriate ANS effects w/ appropriate stimuli, & memory retrieval consolidation
In context to emotional circuitry, what are the three general structures that the hypothalamus projects to? What is each structure responsible for?
- Amygdala: fear/stress emotions
- Brainstem, reticular formation, vagus nerve: ANS activity (BP, glucose levels, BR, adrenaline)
- Pituitary gland: release cortisol for stress
List the pathway for the motivational circuit.(harry helps vicky navigate places)
Hippocampus → hypothalamus → ventral tegmental area (upper midbrain reticular area) → nucleus accumbens → prefrontal cortex
What are the two significant structures in this motivational circuit, & what are they responsible for?
Nucleus accumbens: experiences of pleasure
Prefrontal cortex: evaluation of pleasure
Define prediction error.
Comparison of expected & actual outcome where error is difference between the two
What response is given when the amygdala is connected with the hypothalamus?
Strong connection w/ hypothalamus for ANS RESPONSES to scary/stressful stimuli
