The Mind's Machine: Chapter 11

Emotions and stress

Emotion

Subjective mental state that is usually accompanied by distinct cognition, behaviors, and physiological changes

James-Lange theory

Emotions we experience are caused by bodily changes. From this perspective, we experience fear because we perceive the activity that dangerous conditions trigger in our body. Different emotions thus feel different because they are generated by different constellations of physiological responses.

Cannon-Bard theory

It is the brain’s job to decide which particular emotion is an approximate response to the stimuli. According to this model, the cerebral cortex simultaneously decides on the appropriate emotional experience (fear, surprise, joy) and activates the autonomic nervous system to appropriately prepare the body, using either the parasympathetic (relax the body) or sympathetic (ready the body) system

Schacter-Singer experiment and theory

Emotional labels (anger, fear, joy) are attributed to relatively nonspecific feelings of physiological arousal. The specific emotion we experience is thought to depend on cognitive systems that assess the context—our current social, physical, and psychological situation.

Basic/core emotions

Emotions can be seen as evolved preprogramming that helps us deal quickly and effectively with a wide variety of situations. Other emotions arising from combinations of a basic set (joy, sadness, anger, fear, etc.)

Facial expressions

There are distinct expressions for anger, sadness, happiness, fear, disgust, surprise, contempt, and embarrassment. These are interpreted similarly across many cultures without explicit training.

Facial feedback hypothesis

Suggests that sensory feedback from our facial expressions can affect our mood. Consistent with the James-Lange notion that sensations from our body inform us about our emotions.

Purpose of (some) emotions

Give meaning to events. Help coordinate interpersonal relationships. Motivate future behaviors, prepare our bodies for immediate action.

Limbic system

Subcortical circuit of emotion. Includes the mammillary bodies of the hypothalamus, the anterior thalamus, the cingulate cortex, the hippocampus, the amygdala, and the fornix.

Fear conditioning

A type of associative learning task in which mice learn to associate a particular neutral Conditional Stimulus (CS; often a tone) with an aversive Unconditional Stimulus (US; often a mild electrical foot shock) and show a Conditional Response (CR; often as freezing).

Amygdala

Composed of about a dozen different nuclei, each with a distinctive set of connections. Thought to help form associations between emotional responses and specific memories of stimuli that are stored elsewhere in the brain.

Two routes to amygdala

Low road: direct projection from thalamus to the amygdala that bypasses conscious processing and allows for immediate emotional reactions to stimuli.

High road: routes information through sensory cortex, allowing for processing (while slower) is conscious, fine-grained, and integrated with higher-level cognitive processes.

Lateral vs. central amygdala (input vs. output)

Lateral nucleus serves as the interface with sensory systems that transmit the stimuli (input) and the central nucleus seves as the link to motor regions that control fear responses (output)

Patient SM (and responses to external vs internal threats)

Patient with no amygdala and no experience or recognition of fear, while other emotions remain intact. No amygdala, no response to external threats.

Stress

multidimensional concept that encompasses stressful stimuli, the stress-processing system (including cognitive assessment of the stimuli) and responses to stress.

Hypothalamic-pituitary-adrenal (HPA) axis

Involves the central nervous system and the endocrine system adjusting the balance of hormones in response to stress. Stress results in the hypothalamus stimulating the pituitary gland to release hormones that further cause the adrenal glands to release corticosteroid hormones (such as cortisol)

Adrenal gland

Adrenal glands produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other essential functions. Adrenal glands are composed of two parts (the cortex and the medulla) which are each responsible for producing different hormones.

Cortex: Adrenal corticosteroid hormones

Medulla: Epinephrine and norepinephrine

Norepinephrine

Neurotransmitter in your brain and spinal cord. Increases alertness, arousal and attention. Constricts blood vessels, which helps maintain blood pressure in times of stress. Affects your sleep-wake cycle, mood and memory. Released by adrenal medulla.

Epinephrine

Both a neurotransmitter and a hormone. It plays an important role in your body's “fight-or-flight” response. It's also used as a medication to treat many life-threatening conditions. Released by adrenal medulla.

Cortisol

Steroid hormone produced by adrenal glands. When you are stressed, increased cortisol is released into your bloodstream. Having the right cortisol balance is essential for your health, and producing too much or too little cortisol can cause health problems

Fast vs. slow stress response

In a fast response, the adrenal glands release epinephrine (nervous systems) and norepinephrine (brain). In a slow response, adrenal glands secrete glucocorticoid hormones like cortisol. Has prolonged effects all over body/brain.

Stress immunization

Rat pups clearly find it stressful to have a human pick them up and handle them. Yet rats that have been briefly handled as pups are less susceptible to adult stress than are rats that have been left alone as pups. For example, the previously handled rats secrete lower adrenal steroid amounts in response to a wide variety of adult stressors. A little stress early in life seemed to make the animals more resilient to later stress.

Why stress immunization occurs

To increase resilience to stress later in life.

Epigenetic regulation

Change in the expression of a gene due to maternal deprivation. The deprivation causes long-lasting changes in the expression of adrenal steroid receptors in the brain. Increases adult stress response.

Cortisol and immune function

Brief stress may enhance immune function, but in chronic stress, adrenal steroids (such as cortisol) directly suppress the immune system.