of questions related to brain imaging techniques. For example, with millions of MRI scans being performed for research, scientists may discover what are referred to as incidental findings. Should an individual be told that he or she has a non-normal brain if a neurologist does not consider the findings related to the person’s physical health?
At this point in time, brain imaging techniques cannot absolutely determine if one individual has a mental disorder or not. What neuroscientists can say is that a group of individuals with a particular disorder will show different patterns of brain activity than another group of individuals who do not have the disorder.
Neuroethics takes us beyond the questions of traditional research ethics and focuses on the ethical, legal, and social policy implications of neuroscience (Illes & Bird, 2006). Because of this, a number of scientific neuroscience groups and governmental agencies have sought to understand the ethical problems that neuroscience will bring our society.
Thought Question: Neuroethics focuses on the ethical, legal, and social policy implications of neuroscience and asks complex questions. Choose a position on one of the questions presented in this LENS, and present evidence to support your position.
Networks of the Brain
Given that the human brain has some 86 billion neurons with some 5,000 synapses, each resulting in trillions of synaptic connections, it is clear that a higher-level analysis of brain function is necessary (Goldstone et al., 2015). A variety of brain imaging techniques have allowed for a network analysis that describes which areas of the brain are involved in specific tasks. The first step has been to describe the normal processing of networks such as those involved in rewards or fear. The next step is to understand how these networks become involved in more psychopathological states such as addiction and anxiety. The goal now is to better understand how the basic network becomes involved in psychopathological processes. Is it a lack of connections between brain areas, or is there a reorganization of normal processes that underlies specific psychopathologies? This is one question scientists are asking.
Following the discovery of brain areas involved in particular functions such as Broca’s area in the 1800s, researchers searched for specific areas involved in particular cognitive, emotional, and motor processes. With the increased sophistication of brain imaging technologies came a greater ability to view the manner in which certain parts of the brain work together as well as large-scale turning off and turning on of various areas. Some processes involve a pathway using only a few neurons. Being startled by a loud noise or touching a hot stove are examples of processes that have short neuronal pathways. Other processes use a more complex series of connections. More voluntary and complex processes use a much larger series of neuronal connections referred to as networks.
Researchers are now turning to examine how specific brain areas work together as networks. This search has also extended to psychopathology. Psychopathology can be seen in terms of problems involving either particular brain areas or the connections between areas that make up the network.
We all experience the brain organizing itself in terms of various networks throughout our day. One of the most familiar is sleep. Another is waiting for a lecture to start, when we just let our mind wander. Both of these cases are not responses to external stimuli but are self-organizing processes that occur. These types of processes are controlled by a large number of neurons working together in the form of a network.
Networks allow our brains to process information efficiently (Laughlin & Sejnowski, 2003; Sporns, 2011). Overall, cortical networks are influenced by experience and designed to be efficient in terms of connections between neurons in the network. This efficiency allows for less use of energy. One way energy is conserved is through not having every neuron connect with every other neuron.
Neurons Connect in a Network
How are neurons connected in a network? The answer may seem strange. Neurons are neither totally random in their connections with other neurons nor totally patterned. It appears that neurons are connected to one another in the same way that all humans on this planet are socially connected.
In the 1960s, the social psychologist Stanley Milgram (Travers & Milgram, 1969) asked the question, “What is the probability that any two people randomly selected from a large population of individuals such as the United States would know each other?” He answered this question by giving an individual a letter addressed to another person somewhere in the United States. This individual was to send the letter to someone he knew who might know the other person. In turn, this person was to send the letter to someone she knew who might know the person. Surprisingly, it only required five or six different people for the letter to go from the first individual to the final individual. This phenomenon has been referred to as the small world problem; more recently, the phrase six degrees of separation has been used.
Various studies have shown that the neurons in the brain can also be considered within a small world framework (Sporns, 2011). Neurons have numerous short-distance local connections, which taken together can be considered as a hub or module. From these hubs extend more long-distance connections to other hubs.
small world framework: a model of brain connectivity based on the idea that the ability to socially contact any two random individuals in the world can be accomplished in a limited number of connections
Local hubs can be made up of neurons that connect with each other over very short distances. Such connections are seen in gray matter. Underlying this are the axons, which transfer information throughout the brain. Their myelin sheaths are lighter in color, and thus, these areas are referred to as white matter. Myelin is made up of fats and proteins. It wraps around axons like insulation does around electrical cables and results in an increased speed in information transmissions. About 44% of the human brain is white matter. White matter generally represents longer connections between neurons. This allows for cortical networks over larger areas of the brain. Knowing this, it is possible to examine the network connections in individuals with a particular disorder and their matched controls. For example, individuals with schizophrenia have been shown to have disrupted global networks of the brain (O. Wang et al., 2012).
Figure 2.22 Major Networks of the Brain
Source: Raichle, M. E. (2015, March 30). The restless brain: how intrinsic activity organizes brain function. Philosophical Transactions of the Royal Society B.
central executive network: the neural network 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
salience network: the neural network involved in monitoring and noting important changes in biological and cognitive systems
Networks have been studied in terms of a variety of cognitive and emotional tasks (Bressler & Menon, 2010; Raichle, 2015). These include separate networks involved in the processing of visual or auditory information, sensorimotor processes, attentional processes, executive control, salience, and default mode (see Figure 2.22).
Three of these networks have been examined in terms of psychopathology (Menon, 2011). These are the baseline or default network (also called the intrinsic network), the central executive network, and the salience network. The default network is active when an individual is not performing a particular task, such as when one’s mind wanders or is processing internal information. The central executive network is involved in higher-order cognitive and attentional
