Disordered Brain Exam 1 - Corticolimbic Anatomy

Corticolimbic System Anatomy and Behavior

What is a circuit hub? For the corticolimbic system, what is the hub?

It is the region that coordinates info processing for a circuit (is most important). Amygdala.

What is Caudal and Rostral? Superior and Inferior? Dorsal and Ventral? Medial and Lateral? Anterior and Posterior?

Caudal = Posterior = back

Rostral = Anterior = front

Superior = Dorsal = top

Inferior = Ventral = bottom

What is Axial, Coronal, and Sagittal slicing of brain?

Axial = horizontal

Coronal = crown

Sagittal = slice body in half basically

Where is the amygdala located in the brain? What does it look like?

It is located bilaterally in the ventral area, between medial line and lateral and is rostral to the hippocampal formation.

List all relevant structures of the amygdala. What parts are amygdala proper? What parts are extended amygdala?

ICMs: GABA-ergic, inhibitory cell masses that form a line between the ventral and dorsal amygdala.

NBM: Cholinergic neurons (sends neurotransmitters to acetylcholine receptors)

SLEA: Neurons that make up the BNST and link to the main structure of the amygdala (glutamatergic)

BNST: structure that is medial relative to the amygdala and mainly contains SLEA neurons

BLC: Big ventral part of amygdala

Central medial amygdala: Dorsal part of amygdala

SI: Region in between the BNST and main amygdala that contains NBM and SLEA neurons

Amygdala proper = BLC + ICMs

Practice the labelling diagram in notes

What is the high road input to the amygdala? What is the low road?

High: Info goes from thalamus to sensory cortices to the BLC

Low: Info goes from thalamus directly to the BLC

Is the BLC predominantly afferent or efferent? What info does it recieve, and what info does it output, if any?

It is both, but more so afferent (receiving info). It receives sensory info basically, so includes visual, gustatory, olfactory, auditory, and somatosensory. It outputs to the ventral striatum.

Is the central medial amygdala predominantly afferent or efferent? What info does it recieve, and what info does it output, if any?

It is mainly efferent (outputs). It outputs to the hypothalamus and brainstem and modulatory systems involved in arousal.

How is the hippocampal formation involved with the amygdala?

It can provide input to the BLC of the amygdala to provide context for emotion and also to increase memory of emotionally charged events.

How is the midbrain involved with the amygdala? Name one of the structures and the behavior it controls.

It receives projections from the amygdala (primarily glutamatergic) that causes changes in physiology (like heartrate, breathing, etc). The PAG of the midbrain controls freezing.

How is the hypothalamus involved with the amygdala?

It receives glutamatergic projections from the central amygdala to release hormones for appropriate responses (LIKE STARTING THE HPA AXIS)

Practice labelling the fear learning (IN SLIDES)

Explain the HPA axis in detail.

HPA axis is the pathway responsible for the release of cortisol, the stress hormone. It starts in the hypothalamus, which releases Corticotropic Releasing Hormone, that then causes the Anterior Pituitary Gland, located on top of the kidneys, to release ACTH, which stimulates the Adrenal Gland to release cortisol.

How is the amygdala involved in the HPA axis (which part of the amygdala)? How is the hippocampus involved? What region of the hypothalamus is regulated?

The amygdala (BNST) regulates the hypothalamus by both exciting and inhibiting it, specifically the PVN of the thalamus. If excitatory, CRH is released. The hippocampus inhibits the hypothalamus, but the hippocampus is inhibited by cortisol. Cortisol also inhibits the PVN though.

What are some key components of the brainstem that are connected to the amygdala?

PAG: responsible for freezing, startling, and other fear

Substantia Nigra: very black area full of dopamine (normally)

What is the insula responsible for? Where is the insula (be able to label on brain image)

Interoceptive processing: assigning subjective values to physiological responses

It is sort of located on the lateral sides of the brain, middle area so a bit posterior to the PFC regions.

What insula is sympathetic? What it do?

The right insula. It sends info to the OFC and also is activated in subjective feelings.

What is the function of the fusiform gyrus? Where is it located?

Expert object recognition. Contains both FFA and PPA.

It is towards the back of the brain, occipital lobe area!

What is the Capgras Delusion? Explain how it can happen.

The Capgras Delusion is a condition where someone believes a close family member or someone they know is an imposter. AKA looks exactly like them, but is not them. This happens because the lack feeling the familiarity/closeness/emotion to them. It happens because of an interruption to the connections between the amygdala and FFA (Fusiform gyrus).

What is the ACC a part of?

dmPFC

What part of the PFC-amygdala connection anatomically is the hub that does explicit (top-down) processing?

Lateral PFC (dlPFC and vlPFC)

What part of the PFC-amygdala connection anatomically is the hub that integrates explicit and implicit processing (does both top-down and bottom-up?)

The medial PFC (both dmPFC and vmPFC)

What part of the PFC-amygdala connection anatomically is the hub that does implicit (bottom-up) processing?

The amygdala

As activity in the amygdala increases, how does activity in the vmPFC and dmPFC get affected? What about the dlPFC/vlPFC?

vmPFC activity is increased, which then increases dmPFC, which negatively regulates (inhibits) the amygdala

dlPFC activity is decreased (negative coupling)

What acts as an inhibitory “gate” between the major input and output structures of the amygdala?

Intercalated cell masses (ICMs/ITCs)

Low-road (i.e., direct) sensory input to the amygdala comes from the:

Thalamus

Reciprocal connections between the amygdala and hippocampus function to:

Provide context and increase memory for arousing experiences or events

This brain region serves as a hub of integration in which cortical (top down) and subcortical (bottom-up) processing merge.

vmPFC

Reciprocal connections between the amygdala and what target structure mediate awareness of our bodily states and related subjective feelings (i.e., interoception)?

Insula

Amygdala projections to the brainstem and midbrain serve to potentiate:

Startle, heart rate, freezing

Which prefrontal region supports the relatively highest level of explicit cognitive processing?

dlPFC (and vlPFC)

Amygdala projections to the hypothalamus result in the secretion of:

Cortisol

These neurons are present in the central amygdala, and the extended amygdala and make up the BNST.

SLEA

Where are the thalamus and amygdala located in brain (relative to each other)? What about the hypothalamus?

Thalamus is sort of directly above it, a big oval region. Hypothalamus is a bit posterior to the thalamus and is a bit lower as well, but also near amygdala.