My work examines how the brain acquires, stores, and retrieves information. I first present a theoretical model of the retina, and use the model to explore how the design of sensory systems affects our ability to make inferences about the physical world. I next present three analyses of electrocorticographic recordings taken as human neurosurgical patients participated in experimental cognitive tasks. In the first analysis, I measure the relation between single-neuron spiking and local field potentials, which reflect the aggregate activity of large populations of neurons. In the second analysis, I ask how the brain represents the meanings of individual words as they are studied and remembered. In the third electrocorticographic analysis, I address the question of how our brains retrieve memories of past experiences.