BIO Lecture 9 - Emotion

• Emotions are subjective feelings that influence behavior, with examples including anger, fear, disgust, sadness, and happiness.
• Emotions are survival mechanisms present in all animals, encouraging actions necessary for survival and reproduction.
• Brain systems generating emotional behaviors are rooted in evolutionary history, and the limbic system is primarily involved in generating emotional responses.

Emotional Responses

• Emotional stimuli range from everyday events to threatening situations.
• Sensory systems relay stimuli to the amygdala.
• The perception of emotion arises from both direct and indirect signals between the amygdala and the frontal cortex.
• The indirect path involves the hypothalamus, which communicates with the autonomic nervous system to produce physical changes like increased heart rate.
• Physical changes are fed back to the frontal cortex for interpretation of emotion.

Amygdala's Role

• The amygdala is part of the limbic system.
• Studies on lesioned amygdalas show the amygdala's role in emotional behavior.
• Kluver-Bucy syndrome, resulting from medial temporal lobe damage, causes tameness, loss of fear and aggression, examination of objects by mouth, increased sexual activity, and visual agnosia.
• A key symptom is the loss of fear, as demonstrated by monkeys handling snakes without aversion.

Emotional Memory

• The amygdala minimizes contact with dangers to improve survival chances.
• Awareness of danger is both innate and learned.
• An example of innate fear is a rat's fear response to the odor of a ferret, even without prior exposure.
• An experiment demonstrated that pairing a tone with an electric shock can result in the animal showing fear to the tone alone, showcasing the amygdala's role in linking neutral stimuli to threats.

Human Amygdala

• A case study (patient SM with bilateral amygdala damage) shows the amygdala's role in human emotional experience.
• SM had difficulty rating the intensity of emotions on photos, especially anger and fear.
• SM was unable to sketch a face displaying fear but could recognize and draw positive emotions like happiness.

Feelings and the Amygdala

• The question is posed whether amygdala activity alone is sufficient to feel emotion.
• The common-sense view was that changes in body state caused emotion.
• William James argued that emotions result from changes in body state, known as the James-Lange theory.

Hypothalamus

• The hypothalamus contains neurons that control body functions and receives connections from the amygdala.
• Studies involving animals with lesions to the cerebral cortex but an intact hypothalamus were very aggressive to any external stimulus.
• Interpreting emotional states requires an intact cerebral cortex.

Body State and Emotion

• The autonomic nervous system (ANS) receives input from the hypothalamus.
• The sympathetic nervous system prepares the body for action.
• The parasympathetic nervous system has the opposite effect on the body.
• The ANS has motor and sensory neurons; sensory neurons report physiological changes in the body caused by motor neurons.

Spinal Injury

• Changes in body state are vital for perceiving emotion.
• Patients with spinal-cord injury experience decreased perceived emotion, with severity correlating to the lesion's location.

Prefrontal Cortex

• Experiments in the 1930s showed that lesions to monkey frontal lobes resulted in more relaxed behavior.
• Egas Moniz used a similar procedure to treat behavioral disorders in humans, known as a frontal lobotomy or frontal leukotomy, which alters personality and removes the ability to understand emotions.
• Emotional responses are a function of rational decision making.

Amygdala, Hypothalamus & Frontal Lobes

• Emotional responses are initiated by the amygdala and hypothalamus before information reaches the frontal lobes.
• Frontal lobes can reduce or inhibit emotional responses, if unwarranted.
• Tantrums in children occur because of undeveloped connections between the frontal lobes and limbic system which can lead to phobias if these connections fail to develop in adults.

Neurotransmitters

• Happiness comes from a rush of dopamine in the reward system, triggered by sensory or sexual stimuli or by simply being with someone you love.
• It relies on an absence of negative emotion, for which the amygdala is responsible.
• Affective disorders, including depression, feature abnormal regulation of sadness and happiness and involve connections between the amygdala and prefrontal cortex.
• Depression is linked to decreased levels of serotonin.

Cerebral Hemispheres

• Emotionality is lateralized in the cerebral hemispheres two ways
• The right hemisphere is vital for expressing and understanding emotional aspects of speech.
• The left hemisphere is associated with positive emotions, while the right is more involved with negative ones.
• Lesions to the left hemisphere correlate with an increased incidence of depression, and patients with lesions to the right hemisphere appear unduly cheerful.

Face Expression

• Emotions are expressed in facial movements.
• Different facial expressions indicate happiness, anger, sadness, and fear.
• Darwin proposed that emotional expression is inherited, based on evidence that those responses are similar across cultures.
• Neurons that control face muscles receive input from the cerebral cortex and limbic system.
• Smiling for the camera produces an unnatural smile, while genuine happiness evokes a more symmetrical smile driven by the limbic system.

Monks and Control

• Tibetan monks use meditation to rid themselves of negativity.
• Those meditating can triple gamma-wave activity in the frontal and parietal-temporal regions.
• Synchronized gamma rhythms (bursts of 30-80Hz) across the cortex is associated with binding neural components into a perceptual construct.