stereognosis

Stereognosis is the ability to identify objects by touch in the absence of visual input. It relies on tactile and proprioceptive information to form a mental representation of an object's size, shape, texture, weight, and spatial properties, which the brain can match with memory and prior experience.

The process involvesPeripheral receptors in the skin and joints, ascending somatosensory pathways, and higher-order processing in the parietal cortex. Neuroanatomical studies link stereognosis to the contralateral parietal lobe, particularly the superior parietal lobule and adjacent somatosensory association areas, which integrate tactile with proprioceptive cues to generate object recognition. Lesions in these regions can cause astereognosis, the loss of stereognosis, even when basic touch and proprioception are intact.

Clinically, stereognosis is assessed with blindfolded or eyes-closed manipulation of everyday objects. The patient is asked to identify the object and describe its properties, sometimes naming or matching the object. Testing is usually performed bilaterally to detect unilateral deficits and to distinguish cortical from peripheral sensory loss.

Stereognosis is an important indicator of somatosensory integration and parietal lobe function. Deficits may accompany stroke, tumor, trauma, or degenerative disease affecting the parietal cortex. It is related to tactile agnosia and astereognosis, reflecting impairment in higher-level tactile processing rather than primary sensory reception.