Astereognosia = inability to determine the nature of an object by means of skin-muscle-joint sensation. For example, it is not possible to separate a coin from a pen stump by means of a hand alone, for example in your pocket. The condition does not mean that sensory signals are not perceived, "Of course I feel that I have something in my pocket.... ", it is "just" that the signals are not coordinated when they reach the cerebral cortex, "...... But what is it???". The disorder occurs, among other things, in injuries in the anterior parital cortex area (in SS I).
A similar inability to interpret sensory impressions sometimes occurs in injuries in the lower part of the posterior parietal cortex on the left side. One then speaks of tactile a-gnosia. The victim can here quite well describe the object she/he examines with the help of her hands, but the name of the object "has disappeared".