Answer: The two brain structures that are primarily involved in the formation of implicit memories are the basal ganglia and the cerebellum.
Explanation: The basal ganglia and the cerebellum form implicit memories through their involvement in the processing, consolidation, and retrieval of various types of procedural and classical conditioning information. These brain structures work in conjunction with other regions of the brain to enable the automatic, unconscious encoding and retrieval of learned motor and cognitive skills.