Neurobiological Substrates of Thought and Perception

Performing even routine speech, visual, and motor tasks like carrying on a conversation, following a map to a new classroom, and reading these lecture notes is extraordinarily complex. These tasks become even more complex when environmental demands change. To successfully complete these tasks, a person must selectively attend to specific sensory information, recall relevant stored sensory information, compare the stored information with new information, consider a variety of behavioral responses, select a response, perform that behavior, evaluate its effectiveness, and select an alternative response if the first behavior was ineffective. At the same time, irrelevant thoughts, perceptions and behavioral responses need to be inhibited. Disturbances in one or more of these steps can lead to marked disability. For example, a hallucinating person may recall auditory memories of voices even when sitting in a silent room, or may have considerable difficulty in attending selectively to a conversation due to intrusion of these abnormal perceptions. A person who has impaired ability to evaluate the effectiveness of her speech in communicating meaning may ramble in an incoherent and illogical manner. This can lead to marked social, occupational, and other disabilities. Research indicates that critical brain structures are involved in regulating these aspects of thought and perception. These brain structures include the prefrontal cortex, cortical and subcortical temporal lobe, and the related VTA-mesocorticolimbic system discussed earlier. This section examines the role these brain structures and systems play in thought and perceptual processes.