It is likely that Dr Frankenstein "rewired" neural connections in the monster’s thalamus.
Step-by-step explanation:
The ears and eyes convey sensory information to the thalamus which in turn passes this sensory data to the "cerebral cortex". Other functions of the thalamus are to regulate sleep, alertness and consciousness. It is located above the brain stem between the mid-brain and cerebral cortex.
Any serious damage or change to the "thalamus" may lead to coma while minor damage leads to sensory changes in body parts. Other effects of damages include movement disorders, lost vision, decrease taste, word-finding difficulties, a minor stroke, etc.