Prelim Medicine years are, as the name suggests, almost completely medicine. TYs are more like a continuation of medical school -- a mix of a little bit of everything, with a few required medicine months, usually at least one surgery month, often some OB/GYN. The closest comparison would be to a condensed Family Medicine residency experience.
It is not unusual to have only one or no electives at all during a prelim medicine year. It likely consists of a few medicine subspecialty consult or clinic months, maybe a little Cardiology, an ICU month or two, and a bunch of wards medicine (something like that, anyway).
For Neurology, you need an intern year with at least 8 months of inpatient primary care, 6 of which need to be internal medicine. Nearly all prelim medicine programs satisfy this automatically, but TYs don't. Occasionally, you can use your elective time to do more medicine to fulfull the requirement.