Emotions and the Brain

Phineas Gage: The First Neuroscientific Study of Personality

In 1848, Phineas Gage, 25, lived and worked in Vermont as the foreman of a crew responsible for cutting a railroad bed. On September 13, he was using explosives to blast a path through rock. His process was to drill a hole, pack it with explosives, cover the hole with sand, tamp down the sand with an iron rod, light a fuse, and find a safe place to wait out the explosion.

For some reason, he lost his focus and forgot to fill the hole with sand, tamping the hole with the iron rod and causing a huge explosion. The explosion blew the rod, 43 inches long, 1.25 inches in diameter and weighing 13.25 pounds, skyward, through Gage’s left cheek, through his left eye, brain, and out his skull, landing about 100 yards from Gage’s stunned body.

He talked on his way to the hospital, and presumably climbed out of the hospital cart. Over the next few months, he lost vision in his left eye, but his sensory processing, motor skills, language, and memory all seemed in tact – and the same as before. What changed, noted Gage’s doctor John Martyn Harlow, was that his friends found him “no longer Gage.”

In other words, his personality changed dramatically. He couldn’t stick to plans, uttered “the grossest profanities,” made poor judgments, and went from being an upstanding citizen of his community to an outcast.

Through the years and the retelling and recording of the Phineas Gage story, he has become the most infamous individual in the neurosciences. Gage was the first known case to document a link between brain injury and personality change.

His brain is still one of the most famous items at the Warren Anatomical Museum on the Harvard Medical School campus.

Likert Scales

Up until recently, this has been the most common tool for measuring mood. A Likert scale is a questionnaire where people are asked to select a number that corresponds to how they feel in response to a specific question. So, for example, they are asked a question and asked to rate their response on a scale of 1 to 10: 1=strongly agree; 5=neutral; 10=strongly disagree.

Von Restorff Effect

Employing the theory that isolated or unusual items are more easily remembered, scientists isolate a word within a list and ask test participants to memorize the list. For example, one word in the list’s middle might be written in a different color, or represent an unpleasant thought or emotion in a list of otherwise pleasant thoughts – such as a swear word. Most people easily remember this “unusual” word above all others, leading scientists to conclude that the word’s emotional content facilitated cognition.

Face Emotion Processing

When Charles Darwin studied cultures from around the world, he stated that regardless of cultural differences, all people from every country and region share a core set of universal emotions. Drawing on Darwin’s theory, researchers Paul Ekman and W.V. Friesen in the early 1970s isolated six basic emotional expressions common to all people regardless of culture: happy, sad, fear, anger, disgust, and surprise. The two researchers designed facial tests using these emotions, and although many researchers realize that the reduction to only six emotions is overly simplistic, several research studies since have employed the use of these faces to test emotions.

Test participants view photographs of actors displaying faces demonstrating each emotion. Researchers ask the participants a series of questions based on a particular hypothesis they are testing. For example, researchers have found that test participants with antisocial personality disorder are impaired at identifying or recognizing sad faces.

In patients with brain damage to the amygdala, a deep brain structure that’s part of the limbic system, researchers starting in the mid-1990s began uncovering selective impairments in recognizing certain emotions. Attributed mainly to the researchers Ralph Adolphs, Antonio Damasio, and Dan Tranel, the studies of the connection of the amygdala to mainly negative emotions has been revealing – and startling. Here is a summary of their studies:

• Patient studies done on those with bilateral amygdala damage have shown that patients rated the degree of fear on fearful faces significantly lower than control groups. The deficits to the amygdala also caused patients to score lower on tests showing sadness or other negative emotions as compared to control groups. However, these individual were able to accurately rate the faces displaying happiness.
• Patients with amygdala damage also couldn’t make decisions on how approachable or trustworthy individuals tended to be based on facial expressions.
• Patients with amygdala damage are also somewhat impaired at identifying social emotions such as guilt or flirtatiousness.

Neuroimage Testing

Perhaps the most significant contribution to understanding the neuropsychology of emotion developed with the introduction of neuroimaging devices. Imaging devices allow researchers to watch areas of the brain become activated as certain emotions are evoked. Many studies use Ekman and Friesan’s face studies to image the brain as participants view photographs of sad, fearful, disgusted, and happy faces.

Fear, sadness, and disgust all activate areas of the amygdala. Fear has also been shown to activate the thalamus, anterior cingulate, and anterior insula. Disgust also has activated the insula as well as areas of basal ganglia. For more information on brain anatomy, see the basics of brain structure. Of the six faces studied, happiness is the only positive emotion. Unlike faces evoking negative emotions, the amygdala shows decreasing areas of activation when individuals view happy faces.

Other neuroimaging studies instead point to the brain’s prefrontal cortex and striatal structures as linked to happy emotions. In even more complex studies looking at perceived emotional responses versus responses from actual emotional experiences, it appears again that separate brain structures are involved.

For example, emotion measurements in participants asked to perceive emotional responses rather than directly experience them show significant activity in the amygdala. However, those participants directly experiencing emotions show more activity in the hippocampal and prefrontal cortex areas. These subtle differences are leading researchers to more precise emotional predictions and measurements, such as emotions elicited in differing social conditions, and how these conditions affect different brain processes.