No. USUALLY and LIKELY TO don't mean the same thing. "... which other neurotoxins are LIKELY TO affect DBD" means other neurotoxins that are thought to PROBABLY affect DBD. LIKELY means PROBABLE. In other words, people are not SURE which neurotoxins affect DBD, but people THINK that certain ones are LIKELY TO affect DBD. USUALLY means something like "in a lot of cases" or "in most cases".