Stereognosis (also known as haptic perception or tactile gnosis) is the ability to perceive and recognize the form of an object using cues from texture, size, spatial properties, and temperature.[1] In humans, 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.[2] Typically, these tests involved having the patient identify common objects (eg. keys, comb, safety pins) placed in their hand without any visual cues. [3] Stereognosis is a higher cerebral associative cortical function.[4]:71
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.[5] It may be caused by disease of the sensory cortex or posterior columns.[6]:632 People suffering from Alzheimer's disease show a reduction in stereognosis.[7] 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.[5] For other types of dementia, stereognosis does not appear to decline.