Disorders of perception, attention, and memory frequently accompany the major diseases. To understand the neural mechanisms of these mental processes, we are (1) recording the activity of neurons in the extrastriate cortex of monkeys engaged in tasks requiring visual discrimination, attention, and memory, and (2) testing the effects of lesions or chemical deactivation of these neurons on performance of monkeys in the same tasks. We have developed neural network models that predict the responses of cortical neurons to complex patterns. We found that cortical area V4 is a focal point for many critical operations underlying object recognition, including color vision, form vision and the construction of invariant object representatives. We found that information processing in the cortex is modulated by selective attention, and that the source of the modulation is a network of critical structures, including the lateral pulvinal and the superior colliculus. Attention thus determines which visual information reaches neural mechanisms for memory storage. We have found evidence for neural mechanisms in the inferior temporal cortex that underlie both working memory and long-term memory. Inferior temporal neurons appear to maintain active working memories of visual patterns even while animals process new inputs. Further, the responses of neural populations in temporal cortex change as a result of experience, providing a basis for long term memory.