Agnosia is a reduced or absent ability to understand sensory information. Several forms of agnosia are identified based on the affected sense.
Features of visual agnosia:
(1) inability to recognize objects
(2) inability to recognize more than one object (simultanagnosia)
(3) inability to recognize faces (prosopagnosia)
(4) associated with a lesion in the posterior part of the temporal lobe
Tactile agnosia:
(1) inability to recognize objects by the touch of hands and fingers
(2) associated with a lesion in the parietal lobe contralateral to the affected side
