Actions have reasons. You pull your hand off the hot stove reflexively to avoid severe tissue damage. But you also turn the stove on, prepare a tasty meal, and organize how a multi-course dinner should be served. Tightly interwoven with attentional abilities are executive abilities, the goal-setting and planning abilities that drive human behavior and distinguish it from almost all other behavior in the animal kingdom. Read on and take a peek at the big cheese, the head honcho, the you, the executive brain.
Suppose you decide to have a snack. You stand up and walk to the kitchen to make a sandwich. Several things happened in the sequence: many of them reflexive and many of them more conscious. Standing and walking are activities that you typically do not think about; they become reflexive. Thinking about getting up and thinking about a roast beef sandwich require more conscious mental energy. Walking is a reflexive action; however, you can take direct conscious control of this process. Historically, there has been a debate between the existence of conscious and unconscious mental processes, highly mediated by Freudian thought regarding the unconscious mind. Contemporary views acknowledge that a great deal, if not the majority, of human behavior is performed without conscious awareness. In fact, it is the only way it can be performed.
Social cognitive theorists understand the need to explain behavior from a view that includes conscious and unconscious thought. The Dual Process Theory of Cognition is a well-established paradigm in cognitive neuroscience that recognizes two modes of processing information: The first one is a controlled mode of processing information that is slower in execution, conscious, and reflective. This is what most people think of when they think of “the mind.” It consists of logic, reflection, and reasoning. However, it is slow and can be indecisive. If one had to think “put my foot on the brake” when driving or think out the entire process of braking, accelerating, etc., like a novice driver, there would be many more traffic accidents. In terms of its efficiency, conscious processing is not practical for most daily activities.
The second mode of processing is an automatic mode. This automatic mode is fast in execution and processing, uses less energy, is difficult to change or stop once implemented, and does not conform to rational thinking or logic. A person uses little thought and attentional direction when processing, remembering, and acting in this mode. Automatic processing is driven by schemas and scripts, mental representations or models of the world that are formed from subjective experience.
Schemas are activated during certain contexts, such as evaluating a situation or to determine action or rules for acting. Habits are enacted out of automatic processes, but typically are learned via controlled processes, as in the case of driving a car. Much day-to-day behavior has become automatized, and nearly everything people automatically do was initially a controlled process molded through practice and execution. Many of these patterns are resistant to change; however, nearly every automatic process can be interrupted or changed through conscious effort (this does not apply to purely reflexive movements such as the patellar reflex). Changing automatic processes requires the utilization of energy and attention, and can be difficult.
The extent to which a behavior is “automatic” or “controlled” is not an all-or-nothing situation. There may be some degree of control or automaticity in the same behavior. It is also a mistake to think that controlled behavior requires a “controller” who is totally autonomous. Decisions are often made based on environmental factors or under the influences of motivations (or drives).
Executive functions consist of complex mental processes that allow you to optimize your performance in situations that require the use of a number of cognitive processes or strategies. Executive functions refer to “the big cheese,” or the functions that conduct and instruct other areas of the brain to perform, and these also include the capability to inhibit certain processes. Most research associates executive functions with the frontal lobes of the brain. More precisely, executive functions are associated with the prefrontal areas of the frontal lobe and are not tied to one particular cognitive domain (in fact, brain damage anywhere can disrupt executive control). These functions are associated with all thinking and perceiving abilities.
The prefrontal cortex is simply the most anterior part of the frontal lobes. Most neuroanatomists divide the surface of the prefrontal cortex into three different sections:
The lateral prefrontal cortex lies just in front of the pre-motor areas and lies closest to the skull.
The medial prefrontal cortex lies in between the right and left hemispheres of the brain, in front of the corpus callosum, and anterior to (in front of) the anterior cingulate cortex.
The orbitofrontal cortex (sometimes called the ventromedial prefrontal cortex) is positioned right above the orbits of the eyes and the nasal cavity.
The prefrontal cortex has vast connections with all the sensory systems, motor systems, and areas of the brain involved in memory and emotions. These connections allow the timing and coordination of many different cognitive processes. The lateral prefrontal cortex appears to be associated with sensory inputs; the orbitofrontal cortex appears to be important in the regulation of behaviors; and the medial prefrontal cortex is also important in behavioral regulation, memory, and emotions.
Recall that the primary motor cortex neurons are responsible for voluntary body movements. Something has to inform these neurons when and how they should fire. Setting goals, determining the strategy of a goal-directed plan, and actually executing this plan are functions of the frontal and prefrontal cortex.
The label prefrontal cortex can be confusing because the prefrontal cortex comprises about half of the frontal lobes. It is so large in humans because humans have a complex hierarchy of goals, sub-goals, and programs. These flexible representations of goals (programs) are stored in the prefrontal cortex, so it has massive connections within itself and with the rest of the brain.
Complex systems of goals and plans exist at multiple levels in the brain, may be stored as long-term memories or short-term (working) memories, and require numerous connections to implement them. These connections require a well-developed and larger brain compared to animals that respond from a stimulus-response perspective (a stimulus or cue implements a specific plan or response). Humans sometimes respond in such a manner but also have the capacity to rationalize, contemplate, and initiate much more complex and varied responses.
The prefrontal cortex also mediates the consideration of the context of the situation when developing and initiating goal-related behavior. Clinical studies of people with brain damage demonstrate how context and goals interact.
In some cases of people with damage to the prefrontal lobe, there is a utilization behavior, where the brain-damaged person will respond by using an available object, even if it is not appropriate to use it. For example, the brain-damaged person may see a fork and spoon in the sink, still dirty, and may pick it up and attempt to eat with it. Another type of problem that can arise due to damage to the prefrontal cortex is called perseveration, where the person will continually repeat an action that has already been performed even though the action may no longer be relevant.
Executive functions influence basic cognitive functions, such as attention, memory, and motor skills. Because of this, executive functions are often difficult to assess directly, and many cognitive tests designed to measure other abilities—especially tests that tap complex aspects of attention, memory, verbal abilities, and decision-making—are used to evaluate executive functions.
In order for the type of complex information associated with goals and plans to be stored, it must somehow be represented in the prefrontal cortex of the brain. One must be able to somehow form an image or model of what is happening in the environment, how to implement a goal relevant to the situation, and at the same time, filter and process other stimuli in the environment. The ability to maintain this image or model in the brain is the function of working memory.
Working memory is the technical term for what many people view as short-term memory. It has a limited capacity and a limited duration (therefore it is also considered a component of attention). The classic research indicates that working memory has the capacity of holding five to nine “chunks” of information. A chunk of information is defined as any coherent group of stimuli, such as the letters in a word, a face, a number, etc. The duration of short-term memory is variable but typically is listed at about thirty seconds, although it certainly can be somewhat longer than that and its length varies somewhat from person to person. More modern theories concerning the capacity of working memory indicate that it has different components, such as separate visual and verbal components. Items from working memory can be transferred into longer-term storage as a function of learning.
Chunks of information can be of varying lengths. For example, the numbers 9-2-5 are three chunks of information, whereas 925 is one chunk. A human face with all its complexity is one chunk of information. Chunking like information together can improve executive control over working memory.
The neurons in the lateral prefrontal cortex are responsible for creating a temporary active link between other areas in the brain that code for information to be remembered. Any particular thought is represented in the brain by the activation of a unique set of neurons in the cortex. The prefrontal cortex receives projections from every area in the cortex, and many of these connections are reciprocal. These connections allow information to flow both ways. For instance, you can imagine a hamburger and develop a mental image of it, or you can see a hamburger, close your eyes, and still have an image of it. The activity of the prefrontal cortex neurons results in brain states that are very similar to those states evoked by the object itself. Therefore, one can pursue long-term goals even though the goal may not be physically present. The neurons in the prefrontal cortex become active and remain active while the goal is being processed and/or formed. Once the goal is realized, the brain activation can cease.
A popular model of executive functions is the Supervisory Attentional System model (SAS). The key distinction the SAS model makes is between actions that are performed intentionally (those that require some type of attention to be performed) and those that are performed automatically, as discussed earlier in the dual process model. Working memory is utilized during intentional actions. In the SAS model, there are a number of different components.
Familiar actions are stored as schemas. Schemas are well-learned plans or templates for action, such as the expected behavior one should engage in while at church. Schemas also consist of certain beliefs and attitudes. A complex task or belief may be stored as a hierarchical collection of schemas, which are often referred to as scripts. Schemas and scripts are activated and then utilized by the prefrontal cortex. They are often automatic and result in a swift and defined plan of action.
In the SAS model, the prefrontal cortex is associated with instances that involve making a plan or decision, instances that involve correcting errors or troubleshooting, instances where the response is not well-learned or contains new and unlearned sequences of action, instances that require one to overcome a habitual response, and dangerous or very difficult situations (controlled processing).
Often people who have damage to their brains offer clues about brain functioning. For instance, lateral prefrontal cortex damage can result in a tendency to perseverate, the process of sticking to a particular behavior even if it is no longer relevant to the situation. For example, people with severe brain damage may try to tie the laces of their lace-less slippers over and over again. This ability to recognize changes in the “rules” governing a situation is often associated with being flexible and wise. The inability to be flexible in one’s behavior can be quite a burden, as the rules governing action in daily situations often change frequently.
While the lateral prefrontal cortex appears to be involved in the ability to consider the context of the situation, some decisions are made based on experience. The orbitofrontal cortex appears to be involved in processing one’s life experience and helping to decide whether a choice might be dangerous or inappropriate based on past events. The orbitofrontal cortex is connected to a number of brain structures; the particular structure relevant to connecting experience and action is the amygdala. The amygdala is located in the medial temporal lobe area just in front of another very important structure that deals with memory, the hippocampus. The amygdala appears to be specialized in learning and in memories of instances of past experiences that have high emotional content associated with them, particularly fear-related events. For example, suppose that when you were young, you were attacked and bitten by a big black dog. You may find that for years afterward, you feel anxious whenever you see a big black dog, even if you don’t remember the original incident. This is an example of how the orbitofrontal-amygdala system works. This type of experience or memory is often associated as intuition. Intuition has its uses in the sense that it may be a warning based on past experiences; however, intuition can also lead to stereotyping and behavioral rigidity.
Intuition can often prove useful, but it often fails miserably on certain tasks. Automatic cognitive processes like intuition are poorly designed for weighing out decisions that require an understanding of probability or statistics. Good poker players understand this and attempt to learn to ascertain the probability of the cards the other players are holding instead of betting solely on their hand or on hunches.
The orbitofrontal-amygdala circuit communicates its memories with consciousness through “feelings” and not via logic or reasoning. For instance, it has been shown that people with orbitofrontal cortex damage can have difficulties with excessive gambling because they do not weigh their feelings with logic (this is not to say that everyone who gambles excessively or has a gambling problem has brain damage). It is believed that the potential for an occasional high payoff overrides a lack of fear regarding the penalty of engaging in risky behavior when this area of the brain is damaged. The orbitofrontal cortex is also involved in social intelligence, situation-based reasoning, and other vague recollections of earlier experience.
As everyone knows, habits are hard to break. Considerable cognitive resources are required to recognize that certain actions are counterproductive, develop a plan for change, and then implement a plan in the context of behaviors that have become reinforcing and habitual. The function of specific areas of the prefrontal cortex is to be able to recognize errors, both current and potential, override established patterns, and implement correctional action. Individuals who have dysfunctions in these areas of the brain often have difficulties changing their behavior or shifting from one task to another.
The medial prefrontal cortex appears to compare a chosen plan of action with reality. For example, if you are trying to escape from an obnoxious pestering person, and you are at the top of a long staircase, you may feel like jumping, but hopefully you can inhibit this action, because the reality of jumping would likely have very negative consequences. Because the environment in which people live can be unpredictable, it is important to be able to compare goals and plans with what is happening in the real world, evaluate the situation, and make necessary adjustments if need be. There are two areas in the medial prefrontal cortex that are associated with these functions: the anterior cingulate cortex and the posterior cingulate cortex.
Recall that the cingulate cortex is in-between the cerebral hemispheres. The anterior cingulate cortex appears to be involved in the performance of difficult tasks when one is prone to making errors. This area monitors progress toward your goals, corrects problems, and recruits other areas of the brain toward meeting goals. Thus, this area of the brain is activated during difficult or novel tasks, when you make a mistake, or when you must override a habitual response pattern. The anterior cingulate has strong connections with the lateral prefrontal cortex, allowing it to influence working memory with regard to your progress toward goals. Some people with depression, obsessive-compulsive disorder, or schizophrenia have abnormal PET scan profiles in the area of the anterior cingulate cortex that suggest that this area is under-activated. There also appears to be some lateralization in the anterior cingulate cortex such that the depressive disorders are more associated with left anterior cingulate cortex dysfunction, whereas those with anxiety disorders appear to be associated with right anterior cingulate cortex dysfunction.
The posterior cingulate cortex appears more reflective and emotional and may involve taking in social context regarding your goals. The connections of the posterior cingulate cortex are similar to the anterior cingulate cortex.
Recent revisions in the SAS model have divided executive functions into smaller modular processes. Some of these models suggest that executive functions are composed of partially independent processes like:
The ability to reject a schema when you realize that a mental model is inappropriate for the situation
Goal setting, particular goals are set based on desired outcomes
Control of monitoring and checking, where you consciously monitor goals and progress toward them, checking outcomes with the desired response and reality
These sub-processes can be grouped into three different stages of planning, such that one stage is devoted to developing a new schema; one stage is devoted to implementing a goal; and one stage is for monitoring progress. These functions may be lateralized such that the right prefrontal cortex may be concerned with monitoring progress, whereas the left prefrontal cortex may be concerned with setting up and developing new schemas.
Models that break down processes into different types of executive functions have been somewhat controversial in cognitive neuroscience; however, studies of individuals with damage to areas of the prefrontal cortex indicate there is some specialization in the prefrontal cortex consistent with these models.
Just because many actions are performed without conscious awareness does not mean that a person is not thinking. Likewise, only a small percentage of all brain activity actually reaches conscious awareness, but that does not mean that the brain is not processing these stimuli. People with extensive damage to their primary visual cortex do not respond to visual stimuli that are projected to the damaged areas. In clinical experiments, these individuals claim that they cannot see anything in these visual fields; however, when pressed to guess at what was presented to them, they consistently guess correctly at a significantly higher rate than expected by chance. These experiments indicate that while these patients are unaware of the stimuli in their visual fields, it is quite possible that some processing in the brain is still occurring. This phenomenon has been called blindsight. It is unclear whether the conscious processing in these cases occurs in the subcortical areas associated with vision, or whether there is leftover processing being accomplished in areas of the cortex, but some form of processing stimuli in these damaged visual fields is still occurring.
In a much-cited series of experiments, Benjamin Libet asked participants to sit calmly and watch a special clock, and whenever they decided to move their hand, they were to notice the position of the clock hand (recording the time). The participants were also monitored by EEGs recording their brain’s electrical activities. Libet compared the EEG recordings to the time the participants noted that they decided to move. What was typically found in these cases was that the EEG recorded brain activity in the appropriate area of the motor cortex about one-half second before the participant’s awareness of their desire to move, which is called the readiness potential. The idea here is that the brain appears to be active before you are consciously aware of your actions. This particular phenomenon has been used to denounce notions of free will and to claim that free will is an epiphenomenon (a secondary or additional phenomenon; a byproduct). Libet’s and others’ experiments resulted in quite a debate regarding free will in human behavior. However, there are a number of issues with this.
The first issue goes back to the notion of the dual processing theory and that movement is an automatic process that operates outside of conscious awareness. Philosophically, the choice was made when the participant chose to be part of the experiment. Once that happened, a different process took over that is more efficient. More recent replications of this study have indicated that the readiness potential is not as Libet envisioned it and probably represents a slow buildup of electrical activity prior to spontaneous movement, which reflects the goal-directed neural operations that lead to these movements.
Interestingly, society is based on the principle of autonomous behavior. One would be hard-pressed in a court of law to explain the reason for an infraction as “My brain did it!” It is doubtful that, in the absence of any brain damage or psychiatric disorder, one could blame his brain for his behavior and absolve himself of legal responsibility for his actions.
Where is free will in the brain? That is a good question, because damaging any of several different brain areas can result in the loss of the capacity to make decisions. Moreover, extensive damage to the brain that occurs in diseases like Alzheimer’s disease or other neurological conditions like strokes can also leave one incapable of making informed choices. The issue of “what is free choice?” is a complicated philosophical question muddled by a number of internal and external variables. For example, at one end of the extreme, some argue that people have total free choice in everything they do; however, this is obviously not the case. People are restricted by their own physical limitations, the environment, and their station in life as to what their choices are. On the other hand, some say that people have no free choice and that everything is dictated by genetics and/or the environment. This point of view is equally untenable as people always have control over how they react to their limitations and opportunities. Probably the best answer to the question of where free will is located in the brain is that volitional choice is dependent on a number of brain structures working together, and that disrupting any particular one of them, or several of them, can lead to limitations in the ability to make choices.