Phillips & Silverstein emphasize the gain-control properties of NMDA synapses in cognitive coordination. We endorse their view and suggest that NMDA synapses play a crucial role in biased attentional competition and (visual) working memory. Our simulations show that NMDA synapses can control the storage rate of visual objects. We discuss specific predictions of our model about cognitive effects of NMDA-antagonists and schizophrenia.

We note two important problems in the Theory of Event Coding. First, because the representational format of features and events is unspecified, the theory is difficult to test. Second, the theory lacks a mechanism for the integration of features into an event code when the features are shared by different events. Possible ways of solving these problems are suggested.