Emotion (Physiology 2)

Emotion: A complex psychological and physiological state that involves emotional expression, emotional experience, and affects mood.

Emotional expression: The outward signs of emotion, such as facial expressions, body language, and vocalizations.

Studies in animals and humans examine how emotions are visibly communicated and how they manifest in behaviour.

Emotional experience: Refers to the internal subjective experience of emotion, such as feelings of happiness, anger, or fear.

Human studies explore how emotions are experienced and processed within the mind, often through self-reporting and psychological assessments.

Affective Neuroscience: The study of the neural basis of emotion and mood.

It examines how the brain processes emotions, including how specific brain regions are involved in generating and regulating emotional responses.

Mood is viewed as an extended emotional state lasting over time.

Anxiety-like behaviour: Refers to behaviours that resemble anxiety symptoms, such as restlessness, excessive worry, or hypervigilance, often seen in preclinical models (e.g., animals) after a period of opioid abstinence.

Long-term opioid abstinence: After discontinuing opioid use for a prolonged period, individuals may experience an increase in anxiety-like behaviours due to neurobiological changes in the brain’s reward and stress systems, including dysregulation in neurotransmitter systems like serotonin and dopamine.

Depressive-like behavior: Refers to behaviors observed in animals or humans that mimic symptoms of depression, such as decreased activity, withdrawal, or lack of motivation, often seen following long-term opioid abstinence.

Long-term opioid abstinence: After prolonged cessation of opioid use, individuals may experience symptoms akin to depression due to changes in brain chemistry, including alterations in neurotransmitter systems (e.g., serotonin, dopamine, and norepinephrine) that regulate mood and reward.

Forced-Swim Test: A behavioural test used in animals to assess depressive-like behaviour. It involves placing an animal in a container of water, where the animal is forced to swim.

Purpose: The animal's behaviour during the test (e.g., the amount of time spent swimming versus immobile) is measured to evaluate the level of despair or hopelessness, which can be indicative of depression-like states. Increased immobility is often used as a measure of depressive-like behaviour.

Social preference: Refers to the tendency to engage with social stimuli or individuals, often assessed in animal models.

Long-term morphine abstinence: After prolonged cessation of morphine use, animals may show a reduction or elimination of social preference, indicating withdrawal-related changes in social behavior, possibly due to alterations in the brain’s reward and motivation systems.

Purpose: A test used to evaluate social preference and social behavior in animals.

Habituation Phase: Animals are given 10 minutes to explore the environment and become familiar with the box.

Social Interaction Phase: The animal is allowed to interact with another animal (e.g., a conspecific) for 10 minutes to measure social preference.

Preference for Novelty Phase: The animal is given the option to explore a novel object or a previously encountered object for 10 minutes, allowing the assessment of novelty preference.

Use in Morphine Withdrawal: In morphine withdrawal studies, the test can show how social preference is affected after opioid abstinence, with morphine withdrawal typically leading to reduced social interaction compared to saline withdrawal controls.

Love

Hate

Disgust

Joy

Shame

Envy

Guilt

Fear

Anxiety

Emotion refers to complex psychological and physiological responses to stimuli that influence behavior, thoughts, and physical states.

Emotions involve both experiential (subjective) components (how we feel) and physiological (bodily) components (heart rate, sweating, etc.).

Emotions often lead to behavioral expressions (facial expressions, gestures, etc.).

The James-Lange theory proposes that emotions are the result of physiological changes in the body.

For example: We feel fear because our heart races, and we interpret this bodily change as fear.

Process:

Stimulus → Bodily response → Emotional experience (e.g., we feel fear after we notice a rapid heart rate).

The Cannon-Bard theory suggests that emotions and emotional expressions occur simultaneously and independently.

Unlike the James-Lange theory, it proposes that emotions are not caused by bodily responses but are experienced simultaneously as a result of stimuli.

Process:

Stimulus → Simultaneous emotional experience and physiological response.

Dissociation: Emotional experience can happen without physiological expression (e.g., feeling anxious without a noticeable change in body function).

The thalamus is a central relay station in the brain for sensory information.

According to the Cannon-Bard theory, emotions are produced when sensory signals reach the thalamus, either:

Directly from sensory receptors (e.g., sight or sound) or

Indirectly from descending cortical input (thoughts and memories).

The thalamus then sends signals to other brain regions (e.g., the amygdala) for emotional processing.

James-Lange theory:

Emotion is experienced in response to physiological changes in the body.

Example: We feel fear because our body experiences physiological changes like a rapid heartbeat.

Cannon-Bard theory:

Emotions occur independently of emotional expression, meaning that emotional experience is not directly tied to physiological changes.

Example: You can experience fear even without a noticeable change in bodily functions (e.g., a racing heart).

Broca’s Limbic Lobe:

Limbus (Latin) means "border," referring to the primitive cortical gyri that form a ring around the brainstem.

Includes:

The parahippocampal gyrus

The cingulate gyrus

The subcallosal gyrus

Broca’s Limbic Lobe:

Areas of the brain forming a ring around the corpus callosum.

Includes:

Cingulate gyrus

Medial surface of the temporal lobe

Hippocampus

Limbic structures: Involved in emotion, including areas of the cortex.

Emotional system: Located on the medial wall of the brain, linking the cortex with the hypothalamus.

The Papez circuit links the cortex with the hypothalamus, involving limbic structures in emotion processing.

The cortex is critical for emotional experience.

The hippocampus governs the behavioral expression of emotion, as shown in rabies infection cases leading to hyperemotional responses.

The anterior thalamus, when damaged, leads to spontaneous laughing or crying.

The limbic system attaches behavioral significance and responses to stimuli, particularly related to emotional content.

Damage to the limbic system leads to profound effects on emotional responsiveness.

The cingulate gyrus plays a role in complex motor control, pain perception, and social interactions, influencing mood.

The hippocampus and parahippocampal areas are primarily involved in memory, connecting sensations and emotions to these memories.

The amygdala is involved in learning and storing emotional aspects of experiences.

The diversity of emotions and brain activity makes it difficult to pinpoint a single emotion system.

Many structures are involved in emotion, with no clear one-to-one relationship between structure and function.

The limbic system's use as a discrete emotion system is questionable due to this complexity.

Early theories of emotion and the limbic system were based on introspection and inference from brain injury and disease.

Studies of disease and brain lesions are not ideal for revealing normal emotional function.

More recent theories include basic emotion theories and dimensional emotion theories.

The word "amygdala" comes from the Greek word for "almond."

It is a critical structure for emotion, particularly in the regulation of fear and aggression.

The amygdala is also involved in anxiety responses.

The amygdala receives input from the neocortex, including all lobes, hippocampal, and cingulate gyri.

The basolateral nuclei of the amygdala receive information from all sensory systems.

The corticomedial and central nuclei are involved in processing emotional information.

The amygdala has output to the hypothalamus, a region involved in the expression of emotion, through the stria terminalis and ventral amygdalofugal pathway.

Kluver-Bucy syndrome (in rhesus monkeys):

Temporal lobe removal (including amygdala, hippocampus) leads to poor visual recognition, psychic blindness, emotional changes (reduced fear), and altered sexual behavior.

Amygdalectomy (in humans):

Reduces fear and aggression.

Leads to hypersexuality and oral tendencies.

Reduces the ability to recognize fearful expressions, but happiness can still be recognized.

Causes flattened emotions.

Electrical stimulation:

Increases vigilance, anxiety, fear, and aggression.

The amygdala is involved in forming memories of emotional and painful events.

This has been confirmed by fMRI and PET imaging.

The amygdala gives emotional content to memories, particularly in fear conditioning.

It is involved in conditions such as PTSD.

Predatory aggression:

Attacks made against a member of a different species to obtain food.

No sympathetic activity is involved in this form of aggression.

Affective aggression:

Aggression used for show, such as threatening posture, or to assert dominance within a social hierarchy.

High levels of sympathetic activity are involved.

This type of aggression is related to social hierarchies.

Amygdalectomy and psychosurgery are used to reduce human aggression.

Psychosurgery is now considered a treatment of last resort.

Results of amygdalectomy:

Reduced aggressive behavior.

Relief from anxiety.

Profound, unpleasant side effects.

Amygdala removal caused a transformation from dominant to subordinate behavior.

Social hierarchy was affected, with reduced aggression.

Hypothalamus and aggression:

Removal of cerebral hemispheres (cats) but not hypothalamus -> leads to sham rage.

Removal of both cerebral hemispheres and anterior hypothalamus -> results in sham rage.

Removal of posterior hypothalamus -> no sham rage.

Electrical stimulation of hypothalamus -> leads to affective and predatory aggression.

Medial hypothalamus stimulation: Elicits affective aggression.

Lateral hypothalamus stimulation: Elicits predatory aggression.

Medial forebrain bundle: Leads to the ventral tegmental area, associated with predatory aggression.

Dorsal longitudinal fasciculus: Leads to the periaqueductal gray matter, associated with affective aggression.

The serotonin deficiency hypothesis suggests that aggression is inversely related to serotonergic activity.

5HT antagonists increase aggression.

Agonists of 5HT1A or 5HT1B decrease anxiety and aggressiveness.

In humans, there are reports of a negative correlation between serotonin activity and aggression.

Affective Neuroscience is the science of investigating the neural basis of emotion and mood.

The James-Lange theory suggests that we experience emotion in response to physiological changes in our body.

The Cannon-Bard theory proposes that emotional experience can occur independently of emotional expression.

The limbic system is a group of subcortical structures of the brain, such as the hypothalamus, hippocampus, and amygdala, that are involved in emotion and motivation.

The amygdala is considered the "emotion center" of the brain, while the hippocampus is crucial in the formation of new memories about past experiences.

Klüver-Bucy syndrome is a condition resulting from bilateral lesions of the medial temporal lobe, including the amygdaloid nucleus.

Symptoms include compulsive eating, hypersexuality, hyperorality (inserting inappropriate objects in the mouth), visual agnosia, and docility.