Fear conditioning
Encyclopedia
Fear conditioning is a behavioral paradigm in which organisms learn to predict aversive events. It is a form of learning
in which an aversive stimulus (e.g. an electrical shock) is associated with a particular neutral context (e.g., a room) or neutral stimulus (e.g., a tone), resulting in the expression of fear responses to the originally neutral stimulus or context. This can be done by pairing the neutral stimulus with an aversive stimulus (e.g., a shock, loud noise, or unpleasant odor). Eventually, the neutral stimulus alone can elicit the state of fear. In the vocabulary of classical conditioning
, the neutral stimulus or context is the "conditional stimulus" (CS), the aversive stimulus is the "unconditional stimulus" (US), and the fear is the "conditional response" (CR).
Fear conditioning has been studied in numerous species, from snails to humans. In humans, conditioned fear is often measured with verbal report and galvanic skin response
. In other animals, conditioned fear is often measured with freezing (a period of watchful immobility) or fear potentiated startle
(the augmentation of the startle reflex
by a fearful stimulus). Changes in heart rate
, breathing, and muscle responses via electromyography
can also be used to measure conditioned fear.
Fear conditioning is thought to depend upon an area of the brain called the amygdala
. Ablation or deactivating of the amygdala can prevent both the learning
and expression of fear. Some types of fear conditioning (e.g. contextual and trace) also involve the hippocampus
, an area of the brain believed to receive affective impulses from the amygdala and to integrate those impulses with previously existing information to make it meaningful. Some theoretical accounts of traumatic
experiences suggest that amygdala-based fear bypasses the hippocampus during intense stress and can be stored somatically or as images that can return as physical symptoms or flashbacks
without cognitive meaning. A number of theorists have argued that conditioned fear coincides substantially with the mechanisms, both functional and neural, of clinical anxiety disorders. Research into the acquisition, consolidation
and extinction of conditioned fear promises to inform new drug based and psychotherapeutic treatments for an array of pathological conditions such as dissociation, phobia
s and post-traumatic stress disorder
.
finds two amygdala
pathways in the brain of the laboratory mouse by the use of fear conditioning and lesion study. He names them the "high road" and "low road". The low road is a pathway which is able to transmit a signal from a stimulus to the thalamus, and then to the amygdala, which then activates a fear-response in the body. This sequence works without a conscious experience of what comprises the stimulus, and it is the fast way to a bodily response. The highroad is activated simultaneously. This is a slower road which also includes the cortical parts of the brain, thus creating a conscious impression of what the stimulus
is. The low road only involves the sub-cortical part of the brain and is therefore regarded as a more primitive mechanism of defense, only existing in its separate form in lesser developed animals who have not developed the more complex part of the brain. In more developed animals, the high road and the low road work simultaneously to provide both fear-response and perceptual feedback.
Learning
Learning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning...
in which an aversive stimulus (e.g. an electrical shock) is associated with a particular neutral context (e.g., a room) or neutral stimulus (e.g., a tone), resulting in the expression of fear responses to the originally neutral stimulus or context. This can be done by pairing the neutral stimulus with an aversive stimulus (e.g., a shock, loud noise, or unpleasant odor). Eventually, the neutral stimulus alone can elicit the state of fear. In the vocabulary of classical conditioning
Classical conditioning
Classical conditioning is a form of conditioning that was first demonstrated by Ivan Pavlov...
, the neutral stimulus or context is the "conditional stimulus" (CS), the aversive stimulus is the "unconditional stimulus" (US), and the fear is the "conditional response" (CR).
Fear conditioning has been studied in numerous species, from snails to humans. In humans, conditioned fear is often measured with verbal report and galvanic skin response
Galvanic skin response
Skin conductance, also known as galvanic skin response , electrodermal response , psychogalvanic reflex , skin conductance response or skin conductance level , is a method of measuring the electrical conductance of the skin, which varies with its moisture level...
. In other animals, conditioned fear is often measured with freezing (a period of watchful immobility) or fear potentiated startle
Fear potentiated startle
Fear potentiated startle is a reflexive physiological reaction to a neutral stimulus or environment as a result of fear conditioning, a process that occurs when a benign stimulus comes to evoke fear and anxiety upon being paired with a traumatic or fear-provoking stimulus/event...
(the augmentation of the startle reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
by a fearful stimulus). Changes in heart rate
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
, breathing, and muscle responses via electromyography
Electromyography
Electromyography is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph, to produce a record called an electromyogram. An electromyograph detects the electrical potential generated by muscle...
can also be used to measure conditioned fear.
Fear conditioning is thought to depend upon an area of the brain called the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
. Ablation or deactivating of the amygdala can prevent both the learning
Learning
Learning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning...
and expression of fear. Some types of fear conditioning (e.g. contextual and trace) also involve the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
, an area of the brain believed to receive affective impulses from the amygdala and to integrate those impulses with previously existing information to make it meaningful. Some theoretical accounts of traumatic
Psychological trauma
Psychological trauma is a type of damage to the psyche that occurs as a result of a traumatic event...
experiences suggest that amygdala-based fear bypasses the hippocampus during intense stress and can be stored somatically or as images that can return as physical symptoms or flashbacks
Flashback (psychological phenomenon)
A flashback, or involuntary recurrent memory, is a psychological phenomenon in which an individual has a sudden, usually powerful, re-experiencing of a past experience or elements of a past experience. These experiences can be happy, sad, exciting, or any other emotion one can consider...
without cognitive meaning. A number of theorists have argued that conditioned fear coincides substantially with the mechanisms, both functional and neural, of clinical anxiety disorders. Research into the acquisition, consolidation
Memory consolidation
Memory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...
and extinction of conditioned fear promises to inform new drug based and psychotherapeutic treatments for an array of pathological conditions such as dissociation, phobia
Phobia
A phobia is a type of anxiety disorder, usually defined as a persistent fear of an object or situation in which the sufferer commits to great lengths in avoiding, typically disproportional to the actual danger posed, often being recognized as irrational...
s and post-traumatic stress disorder
Post-traumatic stress disorder
Posttraumaticstress disorder is a severe anxiety disorder that can develop after exposure to any event that results in psychological trauma. This event may involve the threat of death to oneself or to someone else, or to one's own or someone else's physical, sexual, or psychological integrity,...
.
Joseph Ledoux and his research on Fear Conditioning
Joseph E. LeDouxJoseph E. LeDoux
Joseph E. LeDoux is a neuroscientist, the Henry and Lucy Moses Professor of Science, and professor of neuroscience and psychology at New York University. He is also the director of the Center for the Neuroscience of Fear and Anxiety, a multi-university Center in New York City devoted to using...
finds two amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
pathways in the brain of the laboratory mouse by the use of fear conditioning and lesion study. He names them the "high road" and "low road". The low road is a pathway which is able to transmit a signal from a stimulus to the thalamus, and then to the amygdala, which then activates a fear-response in the body. This sequence works without a conscious experience of what comprises the stimulus, and it is the fast way to a bodily response. The highroad is activated simultaneously. This is a slower road which also includes the cortical parts of the brain, thus creating a conscious impression of what the stimulus
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
is. The low road only involves the sub-cortical part of the brain and is therefore regarded as a more primitive mechanism of defense, only existing in its separate form in lesser developed animals who have not developed the more complex part of the brain. In more developed animals, the high road and the low road work simultaneously to provide both fear-response and perceptual feedback.
See also
- Classical conditioningClassical conditioningClassical conditioning is a form of conditioning that was first demonstrated by Ivan Pavlov...
- Eyeblink conditioningEyeblink conditioningEyeblink conditioning is a form of classical conditioning that has been used extensively to study neural structures and mechanisms that underlie learning and memory. The procedure is relatively simple and usually consists of pairing an auditory or visual stimulus with an eyeblink-eliciting...
- Extinction (psychology)Extinction (psychology)Extinction is the conditioning phenomenon in which a previously learned response to a cue is reduced when the cue is presented in the absence of the previously paired aversive or appetitive stimulus.-Fear conditioning:...
- Measures of conditioned emotional responseMeasures of conditioned emotional responseIn experimental psychology, there are multiple measures of conditioned emotional response used by researchers as the measure of conditioned emotional response in a subject in classical conditioning experiments.-Movement ratio:...