Complex sentence: When the seizure occurs during sleep, the person will often become semi-conscious and act out a dream while engaging with the environment as normal, and objects and people usually appear normal or only slightly distorted, being able to communicate with them on an otherwise normal level.
Split into simpler sentences: When the seizure occurs during sleep, the person will often become semi-conscious and act out a dream they were having while engaging with the real environment as normal. Objects and people usually appear normal or only slightly distorted to them, and will be able to communicate with them on an otherwise normal level.