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      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.

      Different Networks Are Involved in Different Tasks

      In addition to the default network, the executive and salience networks are dysfunctional in different psychopathologies (Menon, 2011). The central executive network is involved in performing such tasks as planning, goal setting, directing attention, performing, inhibiting the management of actions, and the coding of representations in working memory (Eisenberg & Berman, 2010). These are sometimes referred to as frontal lobe tasks, since damage to the frontal areas of the brain compromises performance of these tasks. These tasks are also referred to as executive functions, because they assist in planning, understanding new situations, and having cognitive flexibility. The salience network, as the name implies, is involved in monitoring and noting important (i.e., salient) changes in biological and cognitive systems.

      The three networks—default, executive, and salience—show deficits in individuals with specific psychopathologies. Menon (2011) has reviewed the research literature and suggests that these networks play a prominent role in schizophrenia, depression, anxiety, dementia, and autism. As you will see throughout this book, the role of these networks may be dysfunctional in the network itself or in the ability to activate or deactivate specific networks in changing situations.

      Figure 2.24 shows those areas of the brain that Menon (2011) found to be associated with each of these networks. The figure shows an MRI structural image of the brain in black and white. The areas that are activated during the task are displayed in color. The brain is shown in terms of a three-dimensional image along an x-, y-, and z-axis. The x-axis shows the brain from the side, the y-axis from the back; and the z-axis from above. The numbers below the image represent the location along each axis. Using these three numbers, brain imaging programs can identify the areas in relation to traditional anatomical structures.

      In Figure 2.24, the central executive network, which is involved in higher order cognitive and attentional demands including planning for the future and remembering concepts, is shown in blue. The salience network, which is important for monitoring critical external events and internal states, is shown in yellow. The default network, which is active during mind wandering and when the person is not engaged in active problem solving, is shown in red.

      modularity: the concept that specific areas of the brain are dedicated to certain types of processing

      Let’s take a moment to understand how researchers describe brain function in terms of networks. One important concept is modularity. Modularity describes how specific areas of the brain are dedicated to certain types of processing. For example, as discussed early in the chapter, we know that a particular part of the temporal lobe, the FFA, is involved in processing responses to the human face. fMRI measures, for example, would show greater brain activation in this area when observing the human face as opposed to nonhuman faces.

      Another important concept is connectivity. This asks how different areas of the brain work together in specific conditions. To determine connectivity, researchers examine fMRI or EEG measures from a large number of locations throughout the brain. It is assumed that those areas whose activity is correlated are in some way working together.