Decoding semantic meanings from brain activity has attracted increasing attention. Neurolinguists have found that semantic perception is open to multisensory stimulation, as word meanings can be delivered by both auditory and visual inputs. Prior work which decodes semantic meanings from neuroimaging data largely exploits brain activation patterns triggered by stimulation in cross-modality (i.e. text-audio pairs, text-picture pairs). Their goal is to develop a more sophisticated computational model to probing what information from the act of language understanding is represented in human brain. While how the brain receiving such information influences decoding performance is underestimated. This study dissociates multisensory integration of word understanding into written text, spoken text and image perception respectively, exploring the decoding efficiency and reliability of unisensory information in the brain representation. The findings suggest that, in terms of unisensory, decoding is most successful when semantics is represented in pictures, but the effect disappears in the case of congeneric words which share a related meaning. These results reveal the modality dependence and multisensory enhancement in the brain decoding methodology.