Answer: Sensory Input

Agnosia is a medical term that, broadly, refers to the inability of a patient to process sensory input to their bodies. The disorder is not a defect of the memory, but a symptom of injury or damage to specific parts of the brain, or as a side effect of a neurological illness that disrupts the patient’s ability to process the input. The disorder can take many different forms depending on which part of the brain is affected.

Patients with astereognosis (also known as somatosensory agnosia), for example, have extreme difficulty distinguishing objects by touch. While most people could feel a paper clip, pencil, or golf ball while blindfolded and accurately identify what it was based just on the shape and texture, someone with astereognosis could only identify it by looking at it.

Or, in the case of amusia (also known as interpretive or receptive agnosia), a type of auditory agnosia, the patient cannot understand music. In the most mild forms, the patient simply has dysrhythmia (poor or no ability to detect the rhythm of music) and in the most severe form, distimbria, the patient cannot understand music at all and hears musical compositions as chaotic and discordant—what everyone else hears as a symphony they hear as something akin to construction noise, drainpipes, drills, or other invasive forms of background noise.