lecture 7 - memory and emotion

What is the function of the amygdala?

Processes emotions (especially fear) and enhances memory retention by modulating the strength of emotional memories.

Outline the HPA axis pathway.

Hypothalamus → CRH → Anterior pituitary → ACTH → Adrenal cortex → Cortisol.

How fast is the HPA axis response compared to adrenaline?

It is slower—acting over minutes to hours.

What is cortisol, and what does it do?

A glucocorticoid steroid hormone released during stress; regulates metabolism, immune response, and increases threat vigilance.

Can cortisol cross the blood-brain barrier (BBB)?

Yes, it can readily cross the BBB.

What is adrenaline, and where is it secreted from?

A hormone and neurotransmitter released by the adrenal medulla during stress to trigger the fight-or-flight response.

Does adrenaline cross the BBB easily?

No, it influences the brain indirectly via the vagus nerve.

How do adrenaline and cortisol affect the basolateral amygdala (BLA)?

Both boost BLA activity, enhancing emotional memory formation.

How does adrenaline activate the BLA?

Indirectly, via peripheral nervous system activation during stress.

How does cortisol enhance emotional memory?

Acts on BLA receptors to strengthen synaptic changes and make memories more durable.

What is corticosterone, and what is its human equivalent?

A glucocorticoid from the adrenal cortex (mainly in rodents); equivalent to cortisol in humans.

How does corticosterone (CORT) affect neurons in the BLA?

Makes principal neurons more easily activated, strengthening emotional memory formation.

How does stress affect synaptic plasticity at different levels?

Low/moderate stress enhances plasticity; high stress impairs or damages it.

What are the core symptoms of PTSD?

Intrusive memories, nightmares, flashbacks, and re-experiencing triggered by trauma reminders.

What causes memory flashbacks in PTSD?

Overactivation of the dorsal visual stream.

Name two categories of PTSD symptoms beyond flashbacks.

Avoidance symptoms (social withdrawal, emotional numbing) and physiological reactivity (hypervigilance, exaggerated startle, perspiration, shortness of breath).

How does cortisol affect hippocampal connectivity?

Increases functional connectivity, strengthening encoding and retrieval—but can overconsolidate traumatic memories in PTSD.

How does hippocampal dysfunction contribute to PTSD?

Smaller or impaired hippocampus fails to inhibit the stress response and cannot distinguish safe from dangerous contexts.

How does cortisol dysregulation affect PTSD?

Causes overconsolidation of traumatic memories and impairs contextual discrimination by the hippocampus.

What cognitive deficits are seen in PTSD related to the hippocampus?

Impaired episodic memory and allocentric (spatial) processing.

What is Dual Representation Theory of PTSD?

Proposes that traumatic memories are stored in two systems—verbal (narrative) and sensory (situational); flashbacks arise when sensory memories dominate.

What is chronoception?

The study of time perception.

What happens during a saccade in vision?

Visual input is briefly suppressed to prevent blur; the brain later “fills in” missing information.

What is chronostasis?

The illusion where the first moment after a saccade feels longer than it is, because the brain backdates perception to cover suppressed input.

What is the flash-lag illusion?

A moving object appears ahead of a flashed stationary one because the brain predicts the moving object’s future position to offset processing delays.

How does THC affect time perception?

Produces the perception that time slows down.

What is the pacemaker in time perception?

An internal neural mechanism that generates regular pulses (“ticks”) used to estimate durations.

How does pacemaker speed affect perceived time?

A faster pacemaker leads to the feeling that time is slowing down (longer duration estimation).

What is Scalar Expectancy Theory (SET)?

A model proposing that an internal pacemaker’s ticks are counted and compared in memory to judge elapsed time, with longer intervals showing greater variability.

Why is time important in episodic memory?

It structures event sequencing; without it, temporal order and duration perception are impaired.

How does patient H.M.’s case relate to time perception?

After ~20 seconds, his ability to perceive time intervals breaks down.

How do hippocampal lesions affect temporal processing?

Impair sequencing and the ability to order events correctly.

What are time cells?

Neurons in the hippocampus that fire at specific moments within a time interval, encoding temporal order.

Where are time cells located?

Mainly in the hippocampus.

How does PTSD affect time cells and memory sequencing?

Hyperactive amygdala signaling and stress hormone imbalance disrupt time cell activity, causing fragmented, poorly sequenced, and distorted temporal memories.