using dynamic causal modeling (dcm) to determine the connectivity of cortical networks, ishai et al. (2010) demonstrated that activation of the network mediating visual imagery is initiated by prefrontal cortex and posterior parietal cortex activity. generation of objects from memory resulted in initial activation of the prefrontal and the posterior parietal areas, which then activate earlier visual areas through backward connectivity. activation of the prefrontal cortex and posterior parietal cortex has also been found to be involved in retrieval of object representations from long-term memory, their maintenance in working memory, and attention during visual imagery. thus, ishai et al. suggest that the network mediating visual imagery is composed of attentional mechanisms arising from the posterior parietal cortex and the prefrontal cortex.