The N400 window thus provides a temporally-delimited “electrical snapshot” of the intersection of a feedforward flow of stimulus-driven activity with a state of the distributed, dynamically active neural landscape that is semantic memory. As such, N400 activity can be modulated by factors that affect either the input stream or the configuration of activity in semantic memory. Manipulations of attention, for instance, may affect either or both of these levels. Attentional manipulations may serve to preactivate information in semantic memory by rendering some information more important and/or more predictable under one task condition than another, and/or by modulating the strategies that participants choose to or can use – for example, what kind of controlled processes are brought to bear in order to remember, integrate, or disambiguate inputs – with consequences for the state of semantic memory then encountered by subsequent stimuli. Such manipulations might thus affect the size of N400 effects observed. Van Berkum (2009) also emphasizes that semantic retrieval can be “intensified” by attention. On the view we are building here, one way that this could happen is by effects
