Extinction (neurology)
Encyclopedia
Extinction is a neurological disorder
characterized by inability to recognize two simultaneous stimuli
on opposite sides of the body, or proximally and distally, though either one can be sensed alone. For example, a person displaying tactile
extinction could feel a thumbtack
pressed into the forefinger on either side normally, but if two thumbtacks were applied simultaneously, one to each forefinger, the subject would only feel one.
Extinction is a subtle form of hemispatial neglect
that is usually associated with lesion
s of the right parietal lobe
. It is less common in lesions of the dominant
(usually left) parietal lobe
, possibly because the dominant hemisphere is more specialized for language than it is for visuospatial functions. More rarely, it can be seen in right frontal or subcortical lesions. Whatever the location, the extinction will manifest on the opposite side of the body.
It can take several forms including tactile, visual extinction
and less commonly, auditory
. In visual extinction, a person could see a blinking light in either the left or right visual field
alone, but if lights blinked in both fields simultaneously, the subject would only see one(or at least see the light less efficiently). If the left-side light were the one neglected (or extinguished), the subject would presumably have a lesion on the right side of the brain.
Testing tactile, visual, or auditory extinction are useful tests of sensory hemispatial neglect. In clinical practice, extinction can be measured with double simultaneous stimulation, in which stimuli are randomly presented to the patient unilaterally and bilaterally
(as well as proximally and distally for tactile) and the patient verbally communicates whether the stimulus is on the left side, right side, or both sides. In order for the results to be accurate, the examiner must first establish normal primary sensation by testing each side of the patient’s body alone, and the patient’s eyes must be closed for tactile and auditory testing.
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...
characterized by inability to recognize two simultaneous stimuli
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....
on opposite sides of the body, or proximally and distally, though either one can be sensed alone. For example, a person displaying tactile
Somatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
extinction could feel a thumbtack
Thumbtack
A drawing pin , thumbtack , or push pin is a short nail or pin with a circular, sometimes domed, head, used to fasten items such as documents to a wall or board for display. Various designs and names are used. They are inserted and removed by hand, hence the terms "thumbtack" and "push pin"...
pressed into the forefinger on either side normally, but if two thumbtacks were applied simultaneously, one to each forefinger, the subject would only feel one.
Extinction is a subtle form of hemispatial neglect
Hemispatial neglect
Hemispatial neglect, also called hemiagnosia, hemineglect, unilateral neglect, spatial neglect, unilateral visual inattention, hemi-inattention or neglect syndrome is a neuropsychological condition in which, after damage to one hemisphere of the brain, a deficit in attention to and awareness of...
that is usually associated with lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s of the right parietal lobe
Parietal lobe
The parietal lobe is a part of the Brain positioned above the occipital lobe and behind the frontal lobe.The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the...
. It is less common in lesions of the dominant
Lateralization of brain function
A longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. The sides resemble each other and each hemisphere's structure is generally mirrored by the other side. Yet despite the strong anatomical similarities, the functions of each...
(usually left) parietal lobe
Parietal lobe
The parietal lobe is a part of the Brain positioned above the occipital lobe and behind the frontal lobe.The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the...
, possibly because the dominant hemisphere is more specialized for language than it is for visuospatial functions. More rarely, it can be seen in right frontal or subcortical lesions. Whatever the location, the extinction will manifest on the opposite side of the body.
It can take several forms including tactile, visual extinction
Visual extinction
Visual extinction is a neurological disorder which occurs following damage to the parietal lobe of the brain. It is similar to, but distinct from, hemispatial neglect...
and less commonly, auditory
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
. In visual extinction, a person could see a blinking light in either the left or right visual field
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
alone, but if lights blinked in both fields simultaneously, the subject would only see one(or at least see the light less efficiently). If the left-side light were the one neglected (or extinguished), the subject would presumably have a lesion on the right side of the brain.
Testing tactile, visual, or auditory extinction are useful tests of sensory hemispatial neglect. In clinical practice, extinction can be measured with double simultaneous stimulation, in which stimuli are randomly presented to the patient unilaterally and bilaterally
Bilateral
Bilateral may refer to any concept including two sides, in particular:*Bilateralism, the political and cultural relations between two states*Bilateral symmetry, symmetry between two sides of an organism...
(as well as proximally and distally for tactile) and the patient verbally communicates whether the stimulus is on the left side, right side, or both sides. In order for the results to be accurate, the examiner must first establish normal primary sensation by testing each side of the patient’s body alone, and the patient’s eyes must be closed for tactile and auditory testing.