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Summary Arousal & Attention PSY4064
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Extensive summary of the NP master course Arousal and Attention with all the literature and important notes from tutorials.
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Neuropsychology period 2Arousal and Attention
Task 1 Arousal theory and practice - Stress & Arousal, autonomic nervous system, endocrine
system
Focus (from course book):
- Strengths and weaknesses of the most frequently used model for explaining the relation between
arousal and performance: The Yerkes-Dodson law.
- In addition, the task concerns biological processes accompanying fast changes in arousal, i.e. orienting
response (phasic arousal) & the startle reflex
- Methodological problems associated with measuring psychophysiological correlates of arousal.
Exam question last year:
People were tested under three conditions (1) sleep deprivation and noise, (2) sleep deprivation and incentives,
(3) noise and incentives
a) Indicate how each factor (sleep deprivation, noise, incentives) affects arousal (increase, decrease). (3p)
b) Draw two graphs one for an easy task, one for a hard task, that indicate the relationship between
arousal and performance. Don’t forget to label it correctly. (4p)
c) Indicate how the combination of the incentives named above (1), (2), (3), affect task performance. (3p)
Definitions of stress and arousal
Stress → a physical, mental, or emotional factor that causes bodily or mental tension.
- Stresses can be external (from the environment, psychological, or social situations) or internal
(illness, or from a medical procedure).
- Stress can initiate the "fight or flight" response, a complex reaction of neurologic and endocrinologic
systems.
Arousal → is the physiological and psychological state of being awoken or of sense organs stimulated to a point
of perception.
- It involves activation of the ascending reticular activating system (ARAS) in the brain, which
mediates wakefulness, the autonomic nervous system, and the endocrine system, leading to increased
heart rate and blood pressure and a condition of sensory alertness, mobility, and readiness to respond.
Stress concepts - (historical) overview
Cannon, homeostasis and the sympathoadrenal system → important but incomplete explanation
Cannon coined the term homeostasis to describe the maintenance within acceptable ranges of several
physiological variables, such as blood glucose, oxygen tension and core temperature.
- Mechanisms for maintaining this stability sensors to recognize discrepancies between the sensed and
set acceptable values and require effectors that reduce those discrepancies – i.e., negative feedback
systems.
➔ For example, when the core temperature of a mammal rises, the thermoregulatory system evokes
sweating and diversion of blood ow from the viscera to the skin, which enhances heat loss; and
when core temperature falls, shivering increases heat production, while cutaneous vasoconstriction
diminishes heat loss by diversion of blood to internal organs.
- Cannon extended his concept to include psychosocial threats to homeostasis.
- He described the acute changes in adrenal gland secretion associated with what he called
fight or flight responses.
- A wide variety of threats to homeostasis, such as exposure to cold, hypotensive hemorrhage,
traumatic pain, insulin-induced hypoglycemia, or emotional distress, elicit activation of the
adrenal medulla and sympathetic nervous system.
- These two effectors were thought to function as a unit – termed the sympathoadrenal or
sympathico-adrenal system – to restore homeostasis.
, - Rapid activation of the sympathoadrenal system then preserves the internal environment by
producing compensatory and anticipatory adjustments that enhance the likelihood of
survival.
➔ Cannon proposed adrenaline as the active principle of the adrenal gland and also as the
neurotransmitter of the sympathetic nervous system, consistent with the functional unity of the
sympathoadrenal system.
We now recognize that activities of daily life, such as meal ingestion, public speaking, changing posture, and
locomotion – i.e., not only emergencies – are associated with rapid adjustments in sympathetic nervous
system outflows.
→ Each of these activities is associated with a somewhat different set of apparent steady-states, directed by the
brain and determined by coordinated actions of a variety of effector systems.
→ These observations contributed to the development of the concept of “allostasis,” discussed below.
Selye, the doctrine of non-specificity, and the hypothalamic, pituitary-adrenocortical system
Selye popularized the concept of stress. He redefined the word, stress, from its meaning in the physical world as
a force that result in a deformity and results in strain, the opposing force tending to restore the unstressed state.
His definition remains widely used today.
- By non-specific selye meant a set of shared elements of response – regardless of the nature of the
causative agent, or stressor.
Selye proposed three universal stages of coping with a stressor – the general adaptation syndrome (GAS):
- Initial alarm reaction → analogous to cannon’s fight-or-flight response
- A stage of adaptation → associated with resistance to the stressor
- Eventually a stage of exhaustion and organismic death
Selye also found that prolonged stress can produce physical disease and mental disorders. Changes are
associated with, and to at least some extent result from, activation of the HPA axis.
Selye acknowledged that responses to stressors have specic components that tend to reverse the effects of
the stressor; however, in addition to the specic responses, there is a non-specic stress-syndrome
➔ Nevertheless, modern lay and even scientic literature continues to accept the notion of a unitary
stress response.
➔ The stress response is the set of physical and emotional changes the human body makes in
response to a threat or stress. → It sometimes is called the ‘ght-or-ight’ response.
heterostasis → the establishment of a new steady-state by changing the setpoint to resist unusually high
demands.
- This new steady-state, however, is attained by treatment with remedies that have no direct curative
action but enhance the body’s natural defenses, e.g. immunization to combat infection (as in treatment
of rabies).
Modern concepts of stress
More modern concepts view stress as a consciously or unconsciously sensed threat to homeostasis, in which
the response has a degree of specicity, depending on:
- The particular challenge to homeostasis
- The organism’s perception of the stressor
- The perceived ability to cope with it
Adaptations to different stressors include alterations in acceptable levels for monitored variables.
- Sterling and Eyer introduced the term, “allostasis,” to describe the attainment of stability by natural
alterations in acceptable ranges of variables attending the adjustments of the cardiovascular system
during rest and activity.
➔ Adaptations involving allostasis to cope with real, simulated, or imagined challenges are
determined by genetic, developmental and previous experiential factors.
➔ While they may be effective for a short interval, over time the alterations may have cumulative
adverse effects.
, ■ For instance, chronic elevation of blood pressure to ensure adequate blood ow to the
brain might eventually lead to atherosclerosis and stroke or coronary occlusion.
■ Risk of such adverse effects is termed “allostatic load.”
Homeostatic systems
Central to a systems concept of stress is that the body possesses numerous
homeostatic comparators, which have been called “homeostats”.
- Each homeostat compares information supplied by a sensor with a
setpoint for responding, determined by a regulator or set of regulator
mechanisms (Figure 1).
- A sufciently large sensed discrepancy between afferent information
about the level of the monitored variable and the setpoint for
responding elicits altered activities of effectors, the actions of which
decrease the discrepancy in the monitored variable.
Negative vs positive feedback
In a home temperature control system, the thermostat plays a central role, by
sensing discrepancy between the setpoint, determined by a regulator (the
home-owner) and the temperature, which produces differential bending of metal
bands in the thermostat (the sensor).
- This type of system is a classic example of regulation by negative feedback.
- In a negative feedback loop, there is an odd number of negative relationships in the loop.
- In response to a constant perturbing influence (e.g., cold external temperature), a system
regulated by a negative feedback yields a stable level of the monitored variable somewhere
between the sensed and set values.
Physiological homeostatic systems also include regulation by negative feedback.
- Increases in values of the monitored variable result in changes in effector activity that oppose and
thereby “buffer” changes in that variable.
- This feedback regulation can be modulated at several levels and therefore can be quite complex.
- A large array of homeostatic systems detect perturbations (verstoringen) of monitored variables.
- This includes afferent information to the brain about cutaneous and blood temperature, leading
to altered activities of cholinergic and noradrenergic nerve bers in the skin that regulate
sweating and vasomotor tone.
- Disruption of a negative feedback system, such as by blockade of afferent information or by
dysfunction of a homeostat, increases the variability of levels of the monitored variable.
A positive feedback loop threatens homeostasis, by accelerating
changes in levels of the monitored variable.
- Examples of positive feedback loops include tilt-induced
neurally mediated syncope and heat shock.
Ordinarily, humans can tolerate even extremely hot external temperature,
(by evaporative heat loss, promoted by thermoregulatory sweating
mediated by the sympathetic cholinergic system and cutaneous
vasodilation mediated by local sympathetic noradrenergic inhibition)
(figure 4).
In this setting plasma noradrenaline levels increase, probably
reecting increased sympathetic outows to visceral organs and
skeletal muscle, promoting shunting of blood from the core to the
periphery, while plasma adrenaline levels change relatively little
activation of the adrenomedullary hormonal system, such as by
exceeding an anerobic threshold during exercise, dehydration,
hypoglycemia, emotional distress and myocardial dysfunction, might
, interfere with evaporative heat loss and also induce a positive feedback loop, with rapid precipitation of heat
shock and even death (Figure 5).
→ dus door positieve feedback verhelp je het ene maar
komen er nieuwe dingen bij
Multiple effectors
When a single effector fails to function, others are
activated to compensate, helping to maintain the
temperature at about the set level; and one can pattern the
use of the effectors as appropriate to maximize economy
and efciency.
➔ An example of a homeostatic system with
multiple effectors would be insulin, glucagon,
adrenaline, cortisol and growth hormone in
regulation of blood glucose levels.
➔ Effector redundancy extends the ranges of
control of monitored variables.
Stressor-specificity
After adequately sensitive assay methods of plasma levels
of noradrenaline and adrenaline became available,
evidence rapidly accumulated for different noradrenergic vs. adrenergic responses in different situations. A
new concept began to emerge, in which
- noradrenaline levels, and thereby overall sympathetic nervous “activity,” would play key roles in
appropriate distribution of blood volume and homeostasis of blood pressure (or blood delivery to the
brain), such as during orthostasis, cold exposure, mild blood loss, locomotion, exercise, altered salt
intake and water immersion.
o Evidence also accumulated for an association between noradrenaline and active escape,
avoidance, or attack, and an association between adrenaline and passive, immobile fear.
- Adrenaline levels, reflecting the adrenomedullary hormonal system “activity,” respond to global or
metabolic threats, such as hypoglycemia, hemorrhagic hypotension, exercise beyond an anerobic
threshold, asphyxiation, emotional distress and shock.
Thus, in contrast with Selye’s doctrine of non-specificity, according to the allostatic concept of stress
responses, acceptable activities of effector systems are coordinated in relatively specific patterns, including
neuroendocrine patterns.
- These patterns serve different needs, and the sympathetic nervous and adrenomedullary hormonal
systems play important roles in many of them.
- For instance, the level of sympathetic nervous system activation predominates in response to
orthostasis, moderate exercise and exposure to cold,
- whereas the level of adrenomedullary hormonal system activation predominates in response to
glucoprivation and emotional distress.
o Adrenomedullary hormonal system activation seems to correlate better with HPA
axis activation than with sympathetic nervous system activation, in contrast with
Cannon’s concept of a unitary sympathoadrenal system.
- “Sympathoadrenal imbalance,” with high adrenaline levels and smaller or no increases in
noradrenaline levels, often precedes fainting; and in response to hypoglycemia, increases in
plasma noradrenaline levels result entirely from adrenomedullary stimulation.
Effector redundancy introduces the potential for patterned effector responses. → Patterning of neuroendocrine,
physiological and behavioral effectors increases the likelihood of adaptation to the particular challenge to
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