Stereognosis
Encyclopedia
Stereognosis is the ability to perceive and recognize the form of an object using cues from texture, size, spatial properties, and temperature. In human
s, this sense, along with tactile spatial acuity, vibration perception, texture discrimination and proprioception, is mediated by the posterior column-medial lemniscus pathway
of the central nervous system
. Stereognosis tests determine whether or not the parietal lobe of the brain is intact. Typically, these tests involved having the patient identify common objects (eg. keys, comb, safety pins) placed in their hand without any visual cues.
Stereognosis is a higher cerebral associative cortical function.
Astereognosis
is the failure to identify or recognize objects by palpation in the absence of visual or auditory information, even though tactile, proprioceptive, and thermal sensations may be unaffected. It may be caused by disease of the sensory cortex
or posterior columns. People suffering from Alzheimer's Disease
show a reduction in stereognosis. Astereognosis can be caused by damage to the posterior association areas of the parietal, temporal, or occipital lobes, or the postcentral gyrus of either hemisphere. For other types of dementia
, stereognosis does not appear to decline.
Human
Humans are the only living species in the Homo genus...
s, this sense, along with tactile spatial acuity, vibration perception, texture discrimination and proprioception, is mediated by the posterior column-medial lemniscus pathway
Posterior column-medial lemniscus pathway
The posterior column-medial lemniscus pathway is the sensory pathway responsible for transmitting fine touch, vibration and conscious proprioceptive information from the body to the cerebral cortex; as well as tactile pressure, barognosis, graphesthesia, stereognosis, recognition...
of the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. Stereognosis tests determine whether or not the parietal lobe of the brain is intact. Typically, these tests involved having the patient identify common objects (eg. keys, comb, safety pins) placed in their hand without any visual cues.
Stereognosis is a higher cerebral associative cortical function.
Astereognosis
Astereognosis
Astereognosis is the inability to identify an object by touch without visual input. It is a form of tactile agnosia in which an individual is unable to identify objects by handling them, despite intact sensation. With the absence of vision , an individual with astereognosis is unable to identify...
is the failure to identify or recognize objects by palpation in the absence of visual or auditory information, even though tactile, proprioceptive, and thermal sensations may be unaffected. It may be caused by disease of the sensory cortex
Sensory cortex
The sensory cortex can refer informally to the primary somatosensory cortex, or it can be used as an umbrella term for the primary and secondary cortices of the different senses : the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the primary olfactory cortex on...
or posterior columns. People suffering from Alzheimer's Disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
show a reduction in stereognosis. Astereognosis can be caused by damage to the posterior association areas of the parietal, temporal, or occipital lobes, or the postcentral gyrus of either hemisphere. For other types of dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...
, stereognosis does not appear to decline.