Читать книгу Abnormal Psychology - William J. Ray - Страница 93

What does your brain do when you are just sitting and waiting or daydreaming or talking to yourself? This is a question that is just now beginning to be explored. In psychology, most of the research you read about involves a person doing something. Reacting to emotional pictures or solving cognitive problems are common examples. In these cases, one’s attention is focused on a task in the external world.

In the same way that the brain is organized to process spatial and verbal material differently and involve different cortical networks, it also appears that different circuits are involved with internal versus external information. A variety of studies have examined brain imaging procedures in which individuals performed internal tasks versus external tasks (e.g., Ray & Cole, 1985).

However, we all know that even without an external task to do, our mind is constantly working. It jumps from one thought to another. The psychologist William James called this process the stream of consciousness. Recent researchers refer to this process as mind wandering.

Those neural networks that are active during internal processing have come to be referred to as the brain’s default or intrinsic network (Buckner, Andrews-Hanna, & Schacter, 2008; Raichle, 2011; Raichle & Snyder, 2007). It has been suggested that intrinsic is a better term than default, since a variety of internal tasks use this network (C. Kelly, Biswal, Craddock, Castellanos, & Milham, 2012). The default network is separate from, but one that can be understood as similar to, other networks such as those involved in visual perception or motor activities. It is made up of a set of interacting brain regions. Those areas involved are pictured in Figure 2.23 and represent periods of brain imaging when individuals are not engaged in any active task.

default or intrinsic network: neural network that is active during internal processing

executive functions: cognitive functions involved in planning, understanding new situations, and cognitive flexibility

Figure 2.23 The Brain’s Default Network

Source: James King-Holmes/Henry Luckhoo/Science Source

Overall, the default network is involved during internal or private considerations that do not require processing external sensory information. In fact, it appears as if there is a negative correlation between activities in the default network versus networks associated with processing information from the environment. That is, when someone begins some cognitive activity, then new networks associated with that task become active and the default network becomes less active. This suggests that separate brain mechanisms evolved for dealing with information involving the external environment as opposed to considerations internal to the person. A variety of psychopathology disorders show problems with the default network in terms of being able to turn it off and engage in a more active external task. People with schizophrenia are one group that has difficulty turning off the default network and moving to an active task that uses a different network.