The Frontal Lobes and Their Function

Human Brain
Human Brain. Matt Cardy / Stringer / Getty Images

The frontal lobes are the regions of the brain that are thought to control many of the things that make us human. In fact, this region is proportionately much larger in humans than in other animals. It also takes the longest to mature, with development extending into young adulthood.

Functions of the frontal lobes include holding onto an idea and letting this notion guide our future behavior. The frontal lobes help us set goals and tasks for ourselves, to choose between appropriate actions, suppress unacceptable reactions and responses and determine the relationships between objects and concepts.

There are two main divisions of the frontal lobes: the cortex and the paralimbic regions. The cortex consists of the bodies of nerve cells laying right on the brain's surface. These cells communicate with each other via long wire-like processes called axons. Some axons plunge deep into the brain, where they communicate with structures closer to the brain's core.

Among the structures closer to the center of the brain are the paralimbic regions, which are thought to be related to basic emotions, functions, and drives. This is contrast to the cortical regions that are thought to be more complex, and which may allow us to think. Together, the cortex and paralimbic divisions of the frontal lobes allow us to perform tasks that are central to how we think of ourselves.

Setting Tasks

Unlike animals who just respond instinctively to what is in front of them, humans have the ability to plan in advance. To do this, we need to be able to hold information in our mind. Otherwise, we would constantly forget what we were thinking about. This holding of information, even in the face of distraction, takes place in the ventrolateral region of the prefrontal cortex. The dorsolateral prefrontal cortex is then able to manipulate information in order to form a plan.

Initiating and Sustaining Activity

The structures in the middle and frontal part of the brain (medial frontal structures) are thought to drive behavior. If these areas become damaged, a person may lose all motivation to do even the simplest task. This is known as abulia or akinetic mutism in extreme cases.

Monitoring Activity

The orbitofrontal cortex decodes and anticipates the reward values of signals, objects, and choices. For example, this region may help us determine whether something is likely to hurt or harm us in the future. The medial orbitofrontal cortex is thought to respond to rewards and the lateral orbitofrontal cortex to punishment. The region closer to the back of the brain (posterior) is more concrete—this is the part that may immediately recognize the emotional significance of a slice of chocolate cake as being tasty and desirable. The parts of the orbitofrontal cortex that are closer to the front of the brain (anterior) deal with more abstract and symbolic rewards, like the money that can go towards buying chocolate cake.

Anticipating and Monitoring Stimuli

The anterior cingulate cortex helps keep track of signals coming both from the outside world and our own mind and body. Anything unexpected can trigger additional processing before a response is given. For example, in the famous Stroop test, a list of brightly colored words is shown. The trick is that the word "red" may be printed in the color green. Someone taking a Stroop test is told to ignore the written word and just say the color. This careful selection and focus on just one aspect of the outside world require the use of the anterior cingulate.

Emotional Regulation

The orbitofrontal cortex shows increased activity when someone is regulating their emotions. This is inversely related to activity in the amygdala. Damage to the orbitofrontal cortex leads to disinhibition and thoughtless behavior, as seen in the famous case of Phineas Gage.

Responding to Change in Salience

Salience is the measure of how important and relevant a particular signal is to you at a particular time. For example, if you're hungry, a piece of chocolate cake is quite salient. After eating half a cake, the desirability of that cake changes. To determine the significance of a piece of information, the brain must rapidly integrate sensory, visceral, and autonomic signals. The salience network involves the insula and part of the frontal cortex which helps us give things meaning.

Switching Attention

Humans have the ability to choose what deserves our attention. That said, depending on circumstances, our attention can quickly switch between different things in our environment.

The ventral attention network includes parts of the middle and inferior frontal gyrus and the temporoparietal cortex. This helps us orient to something rapidly, even if it interrupts a goal, and lets us decide whether we should continue to focus on the new stimulus or go back to the task at hand.

Executive Control

The abilities of the frontal lobes could all be seen as contributing to what neurologists call "executive control." This signifies our capability to control our responses to our environment, rather than just react to whatever is in front of us at the moment.

The executive control allows us to filter out distractions around us. It also allows us to control what we are thinking, and shift our focus in a way so that we are not distracted by our own thoughts. Executive control over emotion allows us to regulate how we appear to others and motivate ourselves when we are not normally motivated. Finally, executive control over the motor network allows us to move our eyes or reach for something.

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