Brain basis of emotions

Plutchik (1994): 8 basic emotions

• joy/sadness
• acceptance/disgust
• anger/fear
• anticipation/surprise

Plutchik's system is popular, but there is no agreement about the exact number of basic emotions. Empirical support has been derived from studying facial expressions. Ekman & Friesen (1971) proposed that there are 7 facial expressions.

It was previously thought that emotions were unrelated to cognition. Western philosophy suggests that emotions are antithetical to reason. To make good, logical deductions, one must supress one's emotions. Patients who experience a dramatic loss of emotion due to prefrontal cortex damage tend to make "terrible" moral decision (Damasio, 1994).

Difficulties in studying emotion:

• Problems with defining the term
• How many emotions are there?
• Should we bother studying emotion?
• How can we study subjective experiences?
• How do we integrate cognition into emotion?
• What about the brain?

We can measure emotion by looking at physiological responses (heart rate, skin conductance), cognition (self-report or neuroimaging), brain activation (MRI, EEG), subjective experience (self-report).

Folk psychology theory example: perceive a snake -> experience feeling of fear -> physiological response

James Lange theory example: perceive a snake -> physiological response -> experience feeling of fear

Strong emotions are related to the activation of the autonomic nervous system (ANS), particularly sympathetic arousal (fight or flight). We experience physiological responses in fear inducing situations. What is the direction of this relationship? Hypothesis: putting on a happy or angry face will affect mood. If this is true, physiological factors can cause a subjective emotional experience.

Strack et al (1988): participants held a pen between their teeth or lips while rating cartoons. Those with pen between teeth judged cartoons to be more funny than those who held the pen. Suggests that facial expressions can have a causal effect on levels of amusement.

Can we experience emotion without a physiological response?

Pure autonomic failure: patients experience no change in heart rate, blood pressure, or sweating when under physical or psychological stress. Sufferers experience emotions but with very little subjective feelings. They recognise the types of emotions they should be feeling without actually becoming aroused.

How do we measure physiological response? Skin conductance, heart rate, and respiratory rate.

Rainville et al (2006): 43 healthy adults were asked to describe personal emotional memories during physiological recording. Anger, fear, happiness, sadness or neutral conditions. Multiple measures of physiological response. Found that while physiological processes affect the strength of our emotional experiences, they don't seem to be entirely responsible for them.

Schachter-Singer (1962): 184 students given an injection of epinephrine, told it was a new drug. In 1 of 4 conditions: told arousing symptoms of drug, told different (unlikely) symptoms, told nothing, or given a placebo injection. Participants were placed with a happy or angry confederate, and after were asked about drug effects.

Participants seemed effected by the confederate; angry when with an angry confederate and happy when with a happy confederate. In the forewarned and placebo conditions, people were much less likely to report emotional experience, regardless of the behaviour of the confederate. The context and interpretation of arousal had a direct effect on the nature of emotional response.

There is some evidence that emotional memories may be enhanced compared to non-emotional memores, but may depend on type of information being recalled. Interpretation of emotion influences reaction / strength of response, as well as other aspects of cognition

Anatomical components

• Cingulate gyrus
• Hippocampus
• Amygdala
• Thalamus
• Limbic system

Related components

• Orbital and prefrontal cortex
• Mammillary body and hypothalamus

The traditional focus for investigating emotion is the limbic system. The limbic system is a collection of brain structures near the cortex, in midbrain and deep grey matter structures. It has extensive connections to other brain regions. Includes hippocampus, hypothalamus, amygdala, cingulate gyrus, parahippocampal gyrus, among other structures.

Studies on emotion have not found a simple one-to-one relationship between a particular emotion and a change of activity in a particular brain region. Each emotion activates several brain regions and the same brain region seems to participate in more than one emotion. There are complex interactions across a widespread network.

Kluver & Bucy (1939): Kluver and Bucy removed a large portion of monkeys' temporal lobe, including the amygdala. The animals became calm and didn't show normal aggressive or fearful reactions. Kluver-Bucy syndrome describes the separation between sensory processing of stimuli and attribution of emotional valence to them. Similar changes can be found with bilateral lesion of the amygdala. Milder changes in behaviour with more exact lesions.

Case study of a 42 year old woman who had seizure from around 20 years of age. Severe atrophy of both amygdale due to Urbach-Wiethe disease. She could last recall being scared at age 10. Could identify emotions except from fear. Could still describe situations that would evoke fear. In an eye-tracking study, she did not show the regular pattern of focusing on eyes when looking at faces; she did not look at the eyes on any face.

The amygdala is closely associated with fear and negative emotions. Patients with amygdala damage do not attend to fearful faces. Amygdala may direct attention to more salient features, and therefore may be important in emotions other than fear.

Cunningham & Kirkland (2013): 42 adults viewed positive, negative or neutral pictures and rated whether the pictures made them feel positive or negative. Activation in both left and right amygdala correlated with positive feelings. No correlation with negative feelings.

The amygdala is important for both positive and negative feelings. During stimulation of the amygdala, different emotions were reported depending on which nuclei stimulated. Information from other brain regions is brought together in the amygdala where emotional significance may be added.

Emotional content can capture attention at encoding or alter the ease with which it is remembered. Activation in the amygdala when viewing emotional pictures predicts later memory for positive and negative stimuli.

The hippocampus is involved in the formation of long-term meories, and involved in emotion regulation. It is important for forming emotional memories. Emotional content may be easier to remember than neutral content.

Kensinger & Corkin (2004): 28 students in fMRI scan while encoding and retrieving words that were neutral - negative and arousing, and negative and non-arousing. At encoding, left amygdala, hippocampal and inferior parietal lobule activation was greater for negative than neutral words. Left hippocampal activation was greater for later-remembered versus later-forgotten words. Left amygdala activity was greater only for later remembered arousing words. Correlation between activity in amygdala and hippocampus.

Flashbulb memories: vivid, long-lasting memories for events that are unexpected, emotional, and significant. On the 12th of September, 54 university studients recalled events of 9/11 (Talarico & Rabin, 2003). Everyday memories were also tested; there was no difference between flashbulb memories and everyday memories over time.

Initial visceral reactions (heart racing, sweating etc) correlates with later confidence in memory (Talarico & Rabin, 2003).

Sharot et al (2007): 24 university students completed MRI in 2004 while remembering events from 9/11 or summer 2001. Also recorded proximity to world trade centre. Individuals who were downtown (around 2 miles from WTC) rated memories as stronger recollection than those who were in midtown (around 4.5 miles from WTC). There was greater activation in amygdala for 9/11 vs 2001 summer memories for the downtown group, but not midtown.

The prefrontal cortex integrates information on event/stimuli, emotional memories, and anticipating emotional consequences of actions.