This is a very detailed summary of problem 1 (stress) from the 2.6 clinical course at EUR. I would still recommend that you read the sources through carefully to get a good grade but my summary will help you get an overview of what is most important. I got a 7.7 in the exam, so I hope this will hel...
LEARNING GOALS
1. What is stress? + different types of stress
2. Effect of cortisol on the body
3. How do different people react to stress?
4. When is stress good/bad?
5. Pros and cons of stress
STRESS AND HEALTH: PINEL
Stress/stress response: physiological changes that results from harm or threat
Stressors: experiences that induce the stress response.
all produce the same core pattern of physiological changes, whether psychological or physical
Chronic psychological stress: most frequently conveyed in ill health
THE STRESS RESPONSE
Hans Selye:
ST stress: produces adaptive changes that help the animal respond to the stressor e.g. mobilization of
energy resources
LT stress: produces changes that’re maladaptive
Selye attributed the stress response to the activation of the Anterior-Pituitary Adrenal-Cortex system
The stressors acting on neural circuits stimulate the release of Adrenocorticotrophic hormone (ACTH)
from the anterior pituitary. ACTH triggers the release of glucocorticoids from the adrenal cortex
the glucocorticoids produce many of the components of the stress response
stressors activate the SNS, increasing epinephrine and norepinephrine released from the adrenal
medulla
both physical and psychological stressors induce the same general stress response
all common psychological stressors act like physiological stressors
BUT, stress responses are more complex and varied than this: the exact response depends on the stressor,
its’ timing, the nature of the stressed person, how the stressed person reacts to the stressor.
stressors produce an increase in blood levels of Cytokines: a group of peptide hormones that are released
by many cells and participate in a variety of physiological and immunological responses, causing inflammation
and fever. Cytokines are now classified with the adrenal hormones as major stress hormones.
ANIMAL MODELS OF STRESS
early research on stress was conducted on animals
these involved extreme forms of stress: repeated exposure to electric shock or long periods of physical
restraint
2 problems:
1 Ethics (“over the top” studies)
2 Often used extreme and unnatural forms of stress that’re of questionable scientific value. Responses
to extreme stress tend to mask normal variations in the stress response, it’s hard to relate the results
of studies to common human stressors
Animal models of stress involve the study of conspecifics (those of the same species), leads to
subordination stress
AMYGDALA AND FEAR: BOOK CHAPTER GAZZANIGA
INTERACTIONS BETWEEN EMOTION AND OTHER COGNITIVE PROCESSES
THE INFLUENCE OF EMOTION AND LEARNING
Èdouard Claparède: provided evidence that 2 types of learning, implicit and explicit, are associated
with 2 different pathways
Had a Korsakoff’s patient (no ST memory) that always greeted him whenever they met. Once, Claparède
shook the patient’s hand with a pin in his hand that pricked him. The next day, the patient hesitated for a while
before shaking Claparède’s hand.
IMPLICIT EMOTIONAL LEARNING
Implicit learning: a neutral stimulus (handshake) acquires aversive properties when paired with an
aversive response (pin prick)
fear conditioning: form of classical conditioning where the conditioned stimulus is aversive
+ Emotional learning works the same way across a wide range of species
FEAR CONDITIONING RAT STUDY
- Conditioned stimulus (CS): light
rat is conditioned to associate this neutral stimulus with an aversive stimulus
, - Pre-training stage: rat responds with a normal startle response to any innately aversive
unconditioned stimulus (US) e.g. loud noise that invokes an innate fear response.
- Training: light is paired with a shock that is delivered immediately before the light is turned off
[Acquisition stage]
After a few pairings of the light (CS) and the shock (US), the rat learns that the light predicts the shock and
eventually the rat exhibits a fear response to the light alone [conditioned response]
The CR can be enhanced in the presence of another fearful stimulus/anxious state e.g. startle can occur
when the rat sees the light at the same time it experiences a different loud noise.
- The CS and CR can be unpaired [extinction] if the light is presented without the noise in the next
several trials
Damage to the amygdala impairs conditioned fear responses, blocks the ability to acquire and express
a CR to the neutral CS that is paired with the aversive US.
TWO PATHWAYS: THE HIGH AND LOW ROADS
Lateral nucleus of the amygdala: region of convergence for information from multiple brain regions,
allows for the formation of associations that underlie fear conditioning.
Superior dorsal lateral amygdala cells: have the ability to rapidly undergo changes that pair the CS to
the US. After a few trials, the cells reset to their starting point; but by then, cells in the inferior dorsal
lateral region have undergone a change that maintains the adverse reaction (this might be why fear
that’s been seemingly been eliminated can return under stress bc it’s retained in the memory of these
cells)
TWO SEPARATE AND SIMULTANEOUS PATHWAYS:
1. LOW ROAD: Thalamus amygdala
- No filtering through conscious control
- Signals reach the amygdala rapidly, although the info sent is crude
- Faster; takes 15 ms in a rat
allows for the amygdala to receive quick info to ready it for a fast response if the info from the high road
confirms that the sensory stimulus is the CS
2. HIGH ROAD:
- Sensory info thalamus sensory cortex (finer analysis) amygdala
- More thorough analysis of info
- Slower; takes 300 ms in a rat
It’s adaptive to have 2 pathways send info to the Amygdala at once bc it’s fast
WHEN SEEING A BEAR
- The low road sets in motion the fight or flight response
- The high road provides the learned account of the bear and his weaknesses to the cortex
THE AMYGDALA IS PARTICULARLY SENSITIVE TO CERTAIN CATEGORIES OF STIMULI LIKE ANIMALS
1. Biological motion: the visual system extracts subtle movement info from a stimulus that it uses to
categorize the stimulus as either animate or inanimate (this is an innate ability)
2. Single-cell recordings from the right amygdala: responds preferentially to images of animals
AMYGDALA’S EFFECT ON IMPLICIT LEARNING
Ppl with Amygdala damage can’t demonstrate an indirect CR (they wouldn’t avoid Claparède’s
handshake)
BUT, the patients are able to explain the parameters of fear conditioning explicitly “The handshake
will hurt a bit” – thus we know that they learned that the stimulus is associated with an aversive
event.
There’s a dissociation btwn intact explicit knowledge of events during fear conditioning and impaired
conditioned responses
Explicit memory for events also depends on the hippocampus (when damaged, it impairs the ability to
explicitly report memory for an event
patients with an intact amygdala and a damaged hippocampus showed normal acquisition of the CR
(showed skin conductance responses to the blue square), but unable to report that presentations of the blue
square had been paired with the shocks.
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