The contents and structure of semantic networks have been the focus of much recent research, with major advances in the development of distributional models. In parallel, connectionist modeling has extended our knowledge of the processes engaged in semantic activation. However, these two lines of investigation have rarely brought together. Here, starting from a standard textual model of semantics, we allow activation to spread throughout its associated semantic network, as dictated by the patterns of semantic similarity between words. We find that the activation profile of the network, measured at various time points, can successfully account for response times in the lexical decision task, as well as for subjective concreteness and imageability ratings.