Figure 4
Wagner’s model of stimulus processing. Wagner proposed that each stimulus is represented by a number of elements. When a stimulus is presented, a proportion of these elements go from being inactive (I state) and enter into a primary activity or attentional state, which might be considered as the forefront of attention or active short-term memory (A1 state). Elements then rapidly decay from this A1 state into a secondary activity state (A2 state) where they remain before gradually decaying back to the inactive state (I state). Stimulus elements can also go directly from the inactive state to the A2 state (which involves an associative retrieval process based on previously formed long-term memories). This is the basis of long-term habituation and is GluA1-independent; see upper horizontal arrow between I state and A2 state). When the elements of the stimulus are in the A1 state, higher levels of attention are paid to the stimulus, and it can generate strong levels of responding. Also, associations can form between elements of different stimuli that are concurrently active in the A1 state. In contrast, when elements are in the secondary, attentional or A2 state, relatively less attention is paid to the stimulus and it will generate weaker levels of responding. GluA1 deletion retards the transition of elements from the A1 state to the A2 state. This can potentially lead to their accumulation in the A1 state and hence to sensitization. For further details, see text and Sanderson et al.93,94
