Final answer:
The basal ganglia are primarily involved in the formation of implicit memory, particularly procedural memories such as motor learning and classical conditioning, and not in the formation of iconic, echoic, or explicit memory.
Step-by-step explanation:
The basal ganglia play a critical role in movement control and posture, among other things. When it comes to memory, the basal ganglia are not primarily responsible for the formation of iconic or echoic memory, which pertain to visual and auditory sensory memories, respectively. Nor are they mainly involved in explicit memory, which is the conscious recollection of information. Instead, implicit memory, particularly procedural memories such as motor learning and habits, is more closely associated with the basal ganglia. These are the kind of memories that are formed and used unconsciously, such as riding a bike or playing an instrument.
The cerebellum is known to facilitate the processing of procedural memories, while the hippocampus deals with the encoding of new explicit memories. Moreover, the amygdala determines the emotional significance of memories, playing a part in determining where they're stored. The basal ganglia's role in movement and procedural learning suggests that implicit memory, specifically procedural memory, is what the basal ganglia contribute to most significantly.