This unit covers Structure and function of the autonomic nervous system (V-A1-2), and Psychophysiological Concepts (V-B).
Students completing this module will be able to discuss:
Green, Green, and Walters (1970) proposed a revolutionary psychophysiological principle of the bidirectional relationship between physiological and psychological functioning:
"Every change in the physiological state is accompanied by an appropriate change in the mental emotional state, conscious or unconscious, and conversely, every change in the mental emotional state, conscious or unconscious, is accompanied by an appropriate change in the physiological state."
The central nervous system includes the brain, spinal cord, and retina. The peripheral nervous system consists of the somatic nervous system and three branches of the autonomic nervous system.
Caption: This image illustrates the three-quarter right anterior-lateral view of the male torso, with the nervous system highlighted. The central nervous system CNS (brain and spinal cord) is colored blue, and the peripheral nervous system PNS (major peripheral nerves) is colored yellow. Shown are the brain inside the cranium, spinal cord inside the vertebral column, and the spinal nerves exiting the intervertebral foramen.
The somatic nervous system controls the contraction of skeletal muscles and transmits somatosensory information to the CNS. The autonomic nervous system regulates cardiac and smooth muscle, and glands, transmits sensory information to the CNS, and innervates muscle spindles.
The autonomic nervous system is divided into three main systems: sympathetic division, parasympathetic division, and enteric division.
The sympathetic division regulates activities that expend stored energy, such as when we are excited. Sympathetic cell bodies are found in the gray matter of the thoracic (from T1) and lumbar (to L2) segments of the spinal cord. The sympathetic division is thoracolumbar.
Sympathetic preganglionic neurons exit the spinal cord via the ventral root. Most of these axons synapse with the ganglia (collection of neurons) of the sympathetic chain, which parallels the spinal cord on each side. This produces mass activation since the ganglia are connected to adjacent ganglia in the chain. The sympathetic chain’s postganglionic neurons project axons to target organs, like the heart, lungs, and sweat glands.
Sympathetic preganglionic axons directly innervate the adrenal medulla (the central portion of the adrenal gland). The adrenal medulla releases epinephrine and norepinephrine when stimulated, which reinforces sympathetic activation of visceral organs. Release of epinephrine and norepinephrine increases muscle blood flow converts stored nutrients into glucose for use by skeletal muscles.
Sympathetic preganglionic axons secrete acetylcholine while the postganglionic axons secrete norepinephrine. Sweat glands and skeletal muscle blood vessels are the exceptions to this rule. The postganglionic axons that innervate them release acetylcholine.
The parasympathetic division regulates activities that increase the body’s energy reserves: salivation, gastric and intestinal motility, gastric juice secretion, and increased blood flow to the gastrointestinal system.
The parasympathetic division regulates activities that increase the body’s energy reserves, including salivation, gastric (stomach) and intestinal motility, gastric juice secretion, and increased blood flow to the gastrointestinal system.
Parasympathetic cell bodies are found in the nuclei of four of the cranial nerves (especially the vagus) and the sacral region (S2-S4) of the spinal cord. The parasympathetic division is craniosacral.
Unlike the sympathetic division, parasympathetic ganglia are located near their target organs. This arrangement means that preganglionic axons are relatively long, postganglionic axons are relatively short, and parasympathetic changes can be selective. Both parasympathetic preganglionic and postganglionic axons release acetylcholine.
The enteric division ensures rhythmic and coordinated intestinal contraction. While it can operate independently of the CNS, it is innervated by both the sympathetic and parasympathetic divisions.
Berntson, Cacioppo, and Quigley (1993) challenge the concept of a continuum ranging from sympathetic to parasympathetic dominance. They argue that the two autonomic branches do not always act antagonistically (reciprocally). They can also act independently or coactively (change in the same direction),
The sympathetic and parasympathetic branches compete for control of target organs, like the heart. Since these divisions generally produce contradictory actions, like speeding and slowing the heart, their effect on an organ depends on their current balance of activity.
Sympathetic and parasympathetic actions are complementary when they produce similar changes in the target organ. Saliva production serves as an example. Parasympathetic activation produces watery saliva and sympathetic activation, which constricts salivary gland blood vessels, produces thick saliva.
Sympathetic and parasympathetic actions are cooperative when their different effects result in a single action. Sexual function provides an example. Parasympathetic activation produces erection and vaginal secretions and sympathetic activation produces ejaculation and orgasm.
Several organs are only innervated by the sympathetic division and are controlled by increasing or decreasing firing of sympathetic postganglionic fibers: adrenal medulla, arrector pili muscle, sweat glands, and most blood vessels.
The medulla of the brainstem directly controls the autonomic nervous system. The medulla is influenced by sensory input and the hypothalamus.
The hypothalamus is a forebrain structure located below the thalamus. The hypothalamus is the body’s homeostat (device that maintains homeostasis), and dynamically maintains balance through its control of the autonomic nervous system, endocrine system, survival behaviors (four F’s), and interconnections with the immune system.
The hypothalamus is influenced by the cerebellum, cerebral cortex, and limbic system.
Caption: This image illustrates the limbic system in the brain from a three-quarter superior view of the cerebrum. Cortical areas are semi-transparent so as to show the limbic system deep within the brain. Structures include the thalamus, hypothalamus, hippocampus, and amygdala.
Homeostasis is the maintenance of the body’s internal environment within healthy physiological limits. Claude Bernard introduced the basic concept of homeostasis and stated, "The stability of the internal environment is the condition of a healthy life." Cannon (1939) introduced the term homeostasis in 1932 and elaborated on this concept in The wisdom of the body.
The body achieves homeostasis for specific variables, like blood pressure, through interlocking negative and positive feedback systems.
Two important modifications to the principle of homeostasis are the boundary model and allostasis.
The boundary model challenges the maintenance of set points as rigid and proposes that physiological processes are maintained within acceptable ranges.
Allostasis means the maintenance of stability through change, and is a process that complements homeostasis. Allostasis is achieved by mechanisms that anticipate challenge and adapt through behavior (including learning) and physiological change. Therapists utilize allostasis when they teach patients to use an abbreviated relaxation exercise (QR) when they anticipate distress (traffic jams).
Wenger (1972) called the ratio of sympathetic to parasympathetic excitation, autonomic balance. He proposed that resting individuals are located along a continuum ranging from sympathetic to parasympathetic dominance. Normally distributed A-bar scores, which measure location on this continuum, are calculated from a battery of autonomic measurements. Low A-bar scores indicate sympathetic dominance, while high A-bar scores suggest parasympathetic dominance. Most subjects show intermediate scores. Wenger and colleagues reported that individuals with low A-bar scores, whom he called sympathicotonics, suffered an elevated incidence of neurotic, psychotic, psychosomatic, and medical disorders.
Generally, both low and high A-bar scores seem to predispose individuals to psychological and medical disorders. Where sympathetic dominance (low A-bar scores) may result in cardiac arrhythmia and essential hypertension, parasympathetic dominance (high A-bar scores) may be associated with asthma, colitis, and hypotension. The healthiest pattern of autonomic balance involves intermediate A-bar scores where neither the sympathetic or parasympathetic branch overwhelms the other.
Clinicians can obtain both tonic and phasic autonomic measurements. A tonic measurement represents the background level of physiological activity (a five-minute average of hand temperature). A phasic measurement represents a brief change in physiological activity in response to a discrete stimulus (a single skin potential response in reaction to a sudden tone).
Psychophysiologists monitor tonic, phasic, and spontaneous psychophysiological activity.
Tonic activity measures background activity and is the magnitude of physiological activity over a specified period of time before stimulating the subject.
Phasic activity is a discrete response evoked by a specific stimulus like a tone or mild shock. Since subjects continuously react to environmental stimuli and internal stimuli we cannot directly observe, interpreting phasic activity can be a challenge.
Spontaneous responses are physiological changes in the absence of detectable stimuli. These changes are important to researchers because they can confound measurement of phasic activity. For example, if a spontaneous increase in skin conductance occurs as a subject is shown an emotionally-charged slide, the researcher could mistakenly conclude that the slide increased conductance more than it did (Stern, Ray, & Quigley. 2001).
When we are exposed to a novel stimulus, an orienting response prepares us to deal with this challenge. Pavlov's (1927) orienting response is a "What is it?" reaction to stimuli like the sound of a vase crashing. The orienting response includes (1) increased sensory sensitivity, (2) head (and ear) turning toward the stimulus, (3) increased muscle tone (reduced movement), (4) EEG desynchrony, (5) peripheral constriction and cephalic vasodilation, (6) a rise in skin conductance, (7) heart rate slowing, and (8) slower, deeper breathing. An orienting response rapidly habituates since it is no longer needed once we respond to a novel stimulus.
In contrast, a defensive response is a very slowly habituating response pattern that limits harm from intense stimulation. This pattern includes (1) reduced sensory sensitivity, (2) a tendency to move away from the stimulus, (3) heart rate increase, and (4) both peripheral and cephalic vasoconstriction. For example, a defensive response might be elicited by a loud work place environment.
Activation was Duffy’s (1972) term for arousal. This concept originated in Cannon's (1915) idea of the body's integrated preparation to fight or flee a potential threat. Activation implies a unidimensional continuum that ranges from low to high activation. For example, high activation might be associated with elevated blood pressure, heart rate, and respiration rate. Low activation might be associated with reduced responses on these variables.
Duffy (1957) hypothesized that performance rises with increased physiological arousal up to a level that is optimal for a specific task and then declines with further arousal. This relationship is an inverted U-shaped curve. Task complexity and novelty may determine the optimal level of arousal. The optimal level of arousal will be lower for more complex and novel tasks.
Lacey (1967) and others have strongly criticized activation theory. Their main concerns are that arousal is not a single dimension, different stimuli elicit specific response patterns in most people, different emotions are associated with unique physiological changes, and responses can be complex.
First, Lacey argued that arousal is not a single dimension. He believed that researchers should differentiate among autonomic, behavior, and cortical arousal since these different forms of arousal are not interchangeable. For example, when heterosexual men observe slides of nude women, heart rate may increase while finger blood flow may not change. If we only use finger blood flow as our index of arousal, we might mistakenly conclude that the male subjects are not aroused (Stern, Ray, & Davis, 1980).
Second, specific stimuli elicit a distinctive response pattern in most subjects, instead of simply altering activation. This is the principle of stimulus-response specificity. For example, subjects may increase their skeletal muscle tone when they are challenged to compete.
Third, primary emotions are associated with unique physiological changes. This is the concept of emotional response specificity. Research with facial expressions shows that (1) anger increases heart rate and skin temperature, (2) fear increases heart rate and decreases skin temperature, and (3) happiness increases heart rate, but does not affect skin temperature.
Fourth, responses to a stimulus can be complex with some physiological indices increasing and others decreasing. This builds on the principle of stimulus-response specificity. Specific stimuli elicit a distinctive response pattern and this pattern is often complex. Lacey called this complex pattern directional fractionation. For example, when a NATO solider on guard duty in the Balkans hears a noise, EEG and skin conductance may show arousal while heart rate decreases.
Habituation is the opposite of arousal. A person gradually ceases to respond or reduces his or her response to a constant stimulus. For example, after 15 trials of listening to a moderate intensity tone, heart rate might no longer increase. Predictable, low-intensity stimuli that convey no new information and require no response readily produce habituation. Habituation is inhibited when a stimulus is intense, complex, and unique, and the subject must respond to it (rate its unpleasantness).
The orienting response and defensive response differ in their speed of habituation. Orienting responses rapidly habituate while defensive response habituate very slowly .
Situational specificity means that a physiological response (blood pressure elevation) does not occur randomly and is most likely in situations with special characteristics. A situation's properties may include physical location (office), time of day (morning), activity (conference), individuals present (employer), and personal emotional state (anxiety). A client's hypertensive response may be classically or operantly conditioned, which means that he or she may be unaware of learning this response since its symptoms are largely "silent" and both processes involve implicit learning. Due to associative learning, the presence of one or more situational cues may elicit the complete physiological response.
Clinicians investigate the situational specificity of presenting complaints when they conduct a history, perform a psychophysiological profile (PSP), ask the client to maintain a symptom journal, and monitor the client in multiple real-world settings (blood pressure measurement in the office and while stalled in traffic). Situational information is crucial to the creation of stimulus hierarchies when using systematic desensitization to treat phobia.
Clients may show consistent physiological responses when they encounter stimuli that share the same intensity and elicit similar emotions. For example, a client may raise heart rate and blood pressure when delivering a report during a business meeting or completing an assignment under time pressure, Individual response stereotypy occurs because our clients possess different diatheses (vulnerabilities) and enter treatment with unique learning histories. During assessment, a clinician conducts a psychophysiological profile (PSP) to determine a client's response stereotypy by presenting several mild stressors.
The six primary facial expressions are surprise, anger, sadness, disgust, fear, and happiness. The concept of emotional response specificity proposes that primary emotions are associated with unique physiological changes.
Research by Ekman and colleagues with facial expressions showed that anger increases heart rate and skin temperature, fear increases heart rate and decreases skin temperature, and happiness increases heart rate, but does not affect skin temperature.
Schwartz, Weinberger, and Singer (1981) studied cardiovascular patterning in six emotions using imagery, nonverbal expression, and exercise tasks. Their dependent variables were diastolic and systolic blood pressure, and heart rate. Participants' cardiovascular responses discriminated anger from fear (blood pressure), and anger and fear from happiness and sadness (all three variables).
Ax (1953) reported that 7 of 14 autonomic measures discriminated between fear and anger.
Malta et al. (2001) reported that aggressive drivers significantly increased muscle tension and blood pressure during driving vignettes compared with controls. Aggressive drivers also responded differently to a fear vignette and mental arithmetic than controls: they increased muscle tension and blood pressure, but showed lower heart rate and electrodermal reactivity.
Wilder (1967) argued that the size of our response to a stimulus depends on a physiological variable's starting value. Wilder’s law of initial values (LIV) predicts that the higher the initial value of a physiological variable, the lower its tendency to change. For example, a subject who normally breathes rapidly should only slightly increase his or her respiration rate when exposed to a loud sound. Homeostatic mechanisms (negative feedback) are responsible for this phenomenon.
Hord, Johnson, and Lubin (1964) found that the LIV applies to heart rate and respiration rate, but not to skin conductance or skin temperature.
Stern, Ray, and Quigley (2001) reported that studies support the LIV for heart rate and skin resistance, but not skin conductance.
Researchers studying phasic (rapidly changing) measures may consider employing statistical methods to control for the influence of prestimulus values on the size of physiological responses.
The LIV is a principle—not a law—and does not apply to all subjects and response systems. Jamieson (1993) questioned the LIV’s value for psychophysiological research since it can be influenced by several factors (measurement errors, reactivity or response to the measurement process, skew or asymmetrical distribution of scores, and variance or score differences).
Researchers can determine whether the LIV is relevant by computing the correlation between prestimulus and poststimulus values. Geenen and van de Vijver (1993) suggested that the LIV may be less common than perceived and that correction methods may be more harmful to the data than the phenomenon itself.
Thompson (2005) has recently reported that the human cortex contains mirror neurons that may help us understand others' intentions and emotions.
Mirror neurons fire weakly when we see another person perform a movement (reaching for a glass) and fire rapidly when the action implies intention (reaching for a glass as if to drink from it). Neurons responsible for somatosensations like touch fire when we see others touched. Similarly, neurons responsible for feelings of fear and disgust are activated by others' expressions of these emotions. Mirror neurons may trigger "empathic emotions" through their connections with the limbic system's emotional circuitry (Begley, 2005).
The mirror neuron system has important implications for applied psychophysiology since it may be responsible for the generation of conditioned emotional reactions, including distress and relaxation, and provides a mechanism through which clients may model a clinician's non-verbal behaviors like muscle bracing and thoracic breathing.
Two issues, the key muscle hypothesis and hand-warming specificity, have important implications for biofeedback training.
The key muscle hypothesis is the belief that a single muscle indexes activity in other muscle groups. Research strongly contradicts this view: (1) SEMG values across different sites are uncorrelated, (2) single site SEMG values are not correlated with generalized tension or autonomic arousal, and (3) SEMG reductions at one site (frontalis) do not automatically generalize to other sites.
The key muscle hypothesis is invalid because there is no key upper body or lower body muscle group. The musculoskeletal system functions very specifically--we simultaneously contract and relax adjacent agonist-antagonist muscle pairs at a joint. This belief has resulted in clinicians mistakenly training the frontalis muscle to lower autonomic arousal or relax muscles on the upper trunk.
The cardiovascular system can function very specifically just like the musculoskeletal system. Temperature training can produce extremely site-specific changes. For example, vasodilation in the left hand need not generalize to the right hand or to the feet.
Clinicians should never expect hand-warming to generalize beyond the actual site (digit) trained. Depending on training procedure and individual differences, hand-warming will generalize to other digits on the same hand or to the digits of the other hand for some clients but not for others.
The temperature map below shows mean undergraduate finger and web dorsum temperatures detected using infrared temperature scanning (White & Lammy, 2004).
Placebos are pharmacologically inert substances that can produce a significant clinical response. In a placebo response, both the symptoms and therapeutic response are real and measurable. Placebos produce the greatest effects in symptoms or disorders that wax and wane over time. The placebo response may increase the client’s therapeutic response to a drug. Client response to a placebo is about 30%, active placebo (placebo combined with an additive that produces a side effect), 60%, and medication, 70%.
Placebos seem to trigger a homeostatic response via stimulus-response learning, expectancy, and self-liberation of endogenous neurotransmitters like endorphins and adrenaline-like catecholamines. This may mirror changes (therapeutic effects, time course, and duration of effect) produced by prescription drugs.
Petrovic and colleagues (2002) showed that opioid analgesia and placebo analgesia both increased activity in the rostral anterior cingulate cortex and the brainstem.
Wager et al. (2004) used the functional MRI (fMRI) to study the placebo effect. They exposed volunteers to painful shocks or heat. Subjects told that an "anti-pain" had been applied to their arms reported less pain than those who were not told about the cream. The fMRI showed that subjects in the "anti-pain" cream condition increased activity in the prefrontal cortex and decreased activity in pain-processing regions of the thalamus, the somatosensory cortex, and cerebral cortex.
Now that you have completed this module, think of how you measure tonic and phasic activity when your conduct a psychophysiological profile.
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