Emotions and Neural Architecture Quiz

Motivation and Emotions

• Affective neuroscience studies emotional experience, expression, and the behaviors related to internal emotions.
• Brain mechanisms of emotion are studied using animal models and human studies, including brain lesions.
• No single emotion system exists like sensory systems.

Early Theories of Emotion

• Darwin observed that people across cultures and animals express similar emotions.
• The James-Lange theory suggests emotions are a response experienced in response to bodily physiological changes.
• The Cannon-Bard theory proposes emotions occur independently of physiological changes; the stimulus creates both emotion and physiological responses simultaneously.

Implications of Unconscious Emotion

• Interoceptive awareness means being aware of your body's autonomic functions.
• Stimuli can have an emotional effect without conscious awareness.
• Aversive conditioning to masked stimuli increases skin conductance and amygdala activity.
• Many paths exist in brain processing emotional information.
• Emotions are dependent on different neural circuits.

Unconscious Emotional Brain Activity

• Unconscious emotional brain activity studies demonstrate that a fearful stimulus, even when not consciously perceived, causes increased autonomic nervous system activity, specifically skin conductance response and amygdala activation.

The Limbic System

• Broca's limbic lobe (1878) describes areas around the corpus callosum, including the cingulate gyrus, medial temporal lobe, and hippocampus.
• These areas are involved with emotion.

The Papez Circuit

• James Papez (1930) proposed a circuit connecting the cortex and hypothalamus for emotional processes.
• The cortex is critical for emotional experience.
• The hippocampus governs behavioral expression of emotion.
• Anterior thalamus lesions can cause spontaneous laughter or crying.
• Paul MacLean's limbic system concept broadened the understanding of emotions.

The Limbic System (cont.)

• The concept of a single emotion system is challenged by diverse emotions and brain activity.
• Numerous structures within the brain may be involved in emotions.
• Precise one-to-one relationships between brain structures and emotions are not always observed.
• Use of single, discrete limbic system function is questioned.

Emotion Theories and Neural Representations

• Early emotion theories use introspection and inference from brain injury/disease; these studies have limitations.
• Recent studies use various approaches (basic emotions, dimension emotion theories).

Basic Emotion Theories

• Some emotions (e.g., anger, disgust, fear, happiness, sadness, surprise) are considered distinct and universal.
• Emotions may have distinct representations in brain circuits/areas.
• Sensory experiences have analogous representations in the brain.
• Examples of regional brain activity correlated with emotion: sadness—medial prefrontal cortex, fear—amygdala.
• fMRI results show various "hotspots" for basic emotions, suggesting diverse activity patterns, not a single area for emotions.

Basic Emotion Theories (cont.)

• Brain imaging studies show different activation patterns associated with happiness, sadness, anger, fear, and disgust.

Dimension Emotion Theories

• Emotions can be understood as different combinations of basic elements.
• Emotions can be described by their valence and arousal.
• Valence refers to pleasantness/unpleasantness, while arousal refers to the strength of the emotion.
• Psychological constructionist theories of emotions include the concept that emotions are not isolated phenomena but a composite of non-emotional factors.

A Dimensional Representation of Basic Emotions

• A dimensional diagram illustrates how different emotions are positioned based on valence and arousal.

What is an Emotion?

• The natural characteristics of emotions are understood in various ways, and the locations of their representations in the brain are not fully known; some consider them to be specific locations/areas and others to be networks/circuits.
• Studies of emotional reactions use behavioral observations, physiological recordings, and lesion studies.

Fear and the Amygdala

• Research on fear/anger helps understand emotions.
• The amygdala plays a critical role in fear.
• Other brain areas are also involved in emotion.
• The amygdala is active in diverse emotional states.
• Much research has been performed on the amygdala.

The Klüver-Bucy Syndrome

• Temporal lobectomy studies in monkeys exhibit decreased fear and aggression, visual recognition problems, oral tendencies, and hypersexuality (Klüver-Bucy syndrome).
• Human lesions in the amygdala demonstrate similar patterns.

Anatomy of the Amygdala

• The amygdala is situated below the cortex and medial to the brain.
• It comprises several nuclei: basolateral, corticomedial, and central.

Effects of Amygdala Stimulation and Lesions

• Bilateral amygdala removal reduces fear and aggression.
• The amygdala's role in fear recognition involves a two-way interaction with the visual cortex, with the amygdala directing visual system attention to determine emotional expressions.
• Increased vigilance/anxiety occurs with amygdala stimulation.
• Imaging techniques like fMRI show that fearful faces activate the amygdala more than happy/neutral faces.

fMRI: Amygdala role in fear

• Amygdala is crucial for detecting fearful and threatening stimuli.
• Amygdala activity occurs with response to different facial expressions — happy, sad, and angry in additional to fear.

Neural Circuit for Learned Fear

• Emotional events, especially fear, have strong lingering effects.
• The amygdala forms memories of emotional/painful events; these impact visceral conditioned fear responses.
• Confirmation on humans has come through fMRI and PET imaging.

Anger and Aggression-Intertwined in Animals

• Anger and aggression are not always identical, especially in relation to evolutionary interpretations of animals.
• Predatory aggression is about acquiring food.
• Affective aggression is about challenging or showing dominance.
• Amygdala lesions relate to aggression/dominance in animals.

The Amygdala and Aggression

• Amygdalectomy surgery aims to reduce human aggression
• Psychosurgery, now a rarely used treatment, involves placing electrodes in the amygdala to reduce aggressive behavior. However, profound side effects are a significant concern.

Neural Components of Anger and Aggression Beyond the Amygdala

• The hypothalamus and the cerebral hemispheres are involved beyond the amygdala in anger and aggression responses.
• Lesions in the hypothalamus demonstrate that this region plays a key role in rage responses.

The Hypothalamus and Aggression

• John Flynn's research shows that stimulated medial hypothalamus produces threat attack and lateral hypothalamus produces predatory attack responses.
• The response in lateral hypothalamus is not accompanied by the dramatic gestures of affective aggression.

The Midbrain and Aggression

• Two hypothalamic pathways to the brainstem involve autonomic function; the medial forebrain bundle and dorsal longitudinal fasciculus.
• The ventral tegmental area (VTA) and the periaqueductal gray (PAG) are implicated in emotion/aggression.
• The amygdala influences behavior.

A Neural Circuit for Anger and Aggression

• A neural circuit diagram illustrating the pathways that link emotional states to behavior.

Serotonergic Regulation of Anger and Aggression

• Serotonin deficiency hypothesis: lower serotonin activity is related to more aggression.
• The raphe neurons, projections that send signals, project to hypothalamus and limbic structures through the medial forebrain bundle.
• Reduced serotonin turnover in the brain correlates to more aggression in rodents.
• Drugs like PCPA (p-chlorophenylalanine) block serotonin production -> increased aggression.

Special Interest: Phineas Gage

• Phineas Gage's accident and brain damage, provided influential evidence related to the function of the frontal lobe and its role in emotion/personality.
• He underwent dramatic personality changes after his accident with the iron rod.

Concepts : Antonio Damasio

• Emotions are programs that modify the body's state in response to threats/opportunities.
• Feelings are the mental experience of body states, which are influenced by emotions and create feeling states.

Concluding Remarks

• Controversy exists regarding whether emotions cause bodily changes, or vice versa.
• Brain imaging shows a widespread activation pattern associated with emotions; some areas respond to multiple emotional states, whereas others respond more specifically to particular states.
• Emotional experiences are complex interactions of multiple components; including sensory stimuli, brain circuitry, past experiences, and neurotransmitter systems.