Bodily Defenses Image Map

What Does the Brain Do?

 The Brain Controls Emotions

Emotions Are Part of What Makes Humans Different

Laughter is one clear difference from animals ("laughing" hyenas are not really laughing).  For more on the brain's role in laughing, click here

Likewise, emotion-based crying seems unique to humans. All animals produce tears in response to eye irritants.

Feel excited? ... happy? ...  sad? ... depressed? ... mad? These, and other feelings are called emotions and they are controlled by the brain. They arise from outside stimulation, "inside" thoughts that may be influenced by memories.

Emotions are processed by a group of a system of brain areas known as the limbic system. Some structures are shown in the diagram. When emotionally relevant stimuli evoke activity in the amygdala, for example, neurons there send signals to forebrain areas that in turn trigger avoidance behavior or to the brainstem that trigger fear and freezing behavior. In both cases, fear and anxiety are part of the response. 

The limbic system is a highly integrated set of brain areas that process emotions. What you experience or think about is processed in this system to generate emotions.

This processing can be over-ridden by "executive functions" of the cerebral cortex, especially the part under the forehead ("frontal cortex").

Conscious meditation, for example, can convert anxiety or fear to calmness.


The Brain Controls Motivation

The brain has systems that cause us
to seek pleasure and to avoid pain or unpleasantness

Pleasure seeking system

Pain/displeasure avoidance area

As seen in a midline slice of human brain, areas outlined in white contain the indicated system (usually extends out laterally from the midline)

LEFT- reward/pleasure pathway in brain. Stimulation along the darkened area of diagram induces pleasure.
RIGHT - Drug addicted rats  will work feverishly to press lever to self-administer the drug into a vein (left). They do the same if the drug is delivered by way of small tubes implanted into the "pleasure seeking system" (right). Similar effects can be produced by implanting small wires into the system that deliver small electric current stimulation. This reward system has been confirmed to exist in humans  and operate in a similar way.



Brain Reinforces Its Preferences

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