Neurobiology of Emotion: Midterm Review and Key Concepts

Emotion

An increase or decrease in physiological activity accompanied by feelings, expressions, and behaviors characteristic of the emotion.

Amygdala

The amygdala is involved in multiple emotions, not just fear. It processes emotional significance and connects to other brain areas to regulate responses.

Facial Feedback Hypothesis

Posed expressions produce the intended emotion and physiological arousal (e.g., faking a smile can make you feel happier).

Innate Emotions

Anger, sadness, happiness, fear, disgust, surprise, contempt, and embarrassment.

Culture-Specific Display Rules

Social norms that dictate which emotions can be expressed in different settings (e.g., suppressing laughter in church).

Physiological Activity in Fear

Slight fear: Elevated sympathetic, slightly reduced parasympathetic activity. Moderate fear: Stronger ANS response (e.g., heart rate increase). Strong fear: Fight-or-flight activation with muscle tremors and cognitive impairment.

Fear vs. Anxiety

Fear: A transient response to an immediate threat. Anxiety: A prolonged state related to anticipation of a potential threat.

Rational vs. Irrational Fears

Rational fears: Based on actual risk (e.g., fear of disease leads to vaccinations). Irrational fears: Based on false beliefs or unlikely threats (e.g., fear of flying when driving is riskier).

Knowledge in Reducing Fear

Understanding risk assessment can prevent misdirected fears (e.g., vaccines prevent disease but misinformation creates unnecessary fear).

Fear Conditioning

A learned response where a neutral stimulus (e.g., tone) is paired with an aversive event (e.g., shock), leading to conditioned fear responses.

James-Lange Theory

Emotions arise from physiological responses (e.g., 'I feel fear because my heart is racing').

Brain Structures in James-Lange Theory

The brainstem and autonomic nervous system (ANS) send signals to the cortex, interpreting physiological responses as emotions.

Cannon-Bard Theory

Emotions and physiological responses occur simultaneously, not sequentially.

Brain Structures in Cannon-Bard Theory

The thalamus processes sensory input and sends signals simultaneously to the cortex (emotion) and the hypothalamus (physiological response).

Schachter-Singer Two-Factor Theory

Emotion results from physiological arousal + cognitive labeling (e.g., 'I'm shaking, this must be fear').

Brain Structures in Schachter-Singer Theory

The hypothalamus (arousal) and the prefrontal cortex (cognitive labeling) interact to determine the emotional response.

Lazarus' Cognitive-Mediational Theory

Emotions arise from cognitive appraisal before physiological response (e.g., assessing a threat before reacting).

Brain Structures in Lazarus' Theory

The prefrontal cortex evaluates stimuli before the amygdala and hypothalamus generate an emotional response.

Emotional Brain Overview

The brain regions responsible for emotion include the limbic system, prefrontal cortex, and brainstem.

Effective Neuroscience

Effective neuroscience studies how the brain creates and processes emotions.

Limbic System

A complex set of brain structures involved in emotion, memory, and motivation.

Amygdala

Fear processing, emotional memory consolidation, aggression, and social behavior.

Hippocampus

Memory formation and context for emotions.

Cingulate Gyrus

Emotional pain processing and empathy.

Hypothalamus

Regulates autonomic and endocrine responses to emotions.

Nucleus Accumbens

Reward and motivation, linked to dopamine pathways.

Prefrontal Cortex (PFC)

Regulates emotional responses and controls behavior.

Orbital Prefrontal Cortex

Regulates emotional responses and controls behavior.

Dorsolateral Prefrontal Cortex

Executive functioning and decision-making.

Brainstem

A part of the brain that controls basic life functions.

Locus Coeruleus

Produces norepinephrine, involved in stress and arousal.

Ventral Tegmental Area (VTA)

Produces dopamine, key to motivation and reward.

Raphe Nuclei

Produces serotonin, associated with mood regulation.

Low Road

Fast, automatic reaction (thalamus → amygdala → response).

High Road

Slower, processed response (thalamus → cortex → amygdala → response).

Amygdala Inputs

Sensory information from thalamus, sensory cortices, and olfactory system.

Amygdala Outputs

Hypothalamus (autonomic response), brainstem (reflexes), cortex (conscious emotional experience).

Dopamine (DA)

Motivation and reward, produced in VTA & substantia nigra.

Norepinephrine (NE)

Stress response and alertness, produced in locus coeruleus.

Serotonin (5-HT)

Mood regulation, linked to depression, produced in raphe nuclei.

Insula

Processes both physical and emotional disgust.

Klüver-Bucy Syndrome

A condition resulting from amygdala damage, characterized by loss of fear, hyperorality, and inappropriate social behavior.

Prefrontal Cortex Damage

Impaired decision-making, aggression, and lack of impulse control.

Schizophrenia

A mental disorder linked to prefrontal cortex abnormalities.

Anxiety Disorders

Overactive amygdala leads to excessive fear and stress.

Amygdala's Role in Memory

Emotional events strengthen memory consolidation via connections to the hippocampus.

Avoidance and Risk-Taking Behavior

Anterior Cingulate Gyrus: Larger size correlates with harm avoidance; Insula: Linked to disgust and risk perception.

Stress

A physiological and psychological response to demanding situations.

Coping Mechanisms

Adaptive: Problem-solving, social support; Maladaptive: Avoidance, substance use.

Predictive Coding

The brain continuously updates mental models based on sensory input, influencing emotional responses.

Papez Circuit

An early model of emotional processing proposed by James Papez, focusing on connections between the hippocampus, thalamus, hypothalamus, and cingulate cortex.

Joseph Ledoux

Revised emotional processing models to place the amygdala at the center of fear processing.

Low Road vs. High Road pathways

Proposed pathways for emotional processing by Joseph Ledoux.

Lateral nucleus

Receives sensory information from the thalamus (except olfactory input).

Basolateral nucleus

Processes information and relays it to the central nucleus.

Central nucleus

Sends output signals to control behavioral and physiological responses.

Prefrontal cortex

Regulates fear and emotional responses.

Hippocampus

Provides contextual memory.

Hypothalamus

Controls autonomic and endocrine responses.

Brainstem nuclei

Modulates reflexive fear responses.

Low Road

Quick, automatic response (thalamus → amygdala → reaction).

High Road

Slower, processed response (thalamus → cortex → amygdala → reaction).

Visual system

Retina → Thalamus → Amygdala (via the superior colliculus and pulvinar nucleus).

Auditory system

Cochlea → Medial Geniculate Nucleus (Thalamus) → Amygdala.

Olfactory system

Unique direct projection bypassing the thalamus → Amygdala.

Clever-Bucy Syndrome

Bilateral temporal lobe lesions (including the amygdala) led to loss of fear and emotional blunting.

fMRI Studies

Fear-related stimuli activate the amygdala even when subjects are unaware.

BNST vs. Amygdala

Amygdala = Immediate fear response; BNST = Sustained anxiety and long-term fear.

Importance of the Amygdala in Emotional Memory

Modulates memory consolidation via connections with the hippocampus.

Emotional experiences

Strengthen memory encoding through stress hormone release.

Papez's Circuit

A neural pathway believed to be responsible for emotional processing, particularly emotional memories.

Brain structures in Papez's Circuit

Hippocampus, Mammillary bodies, Anterior thalamus, Cingulate gyrus.

LeDoux's High-Road and Low-Road Model of Emotion

Low Road: Quick, automatic fear response via the amygdala; High Road: Slower, more thoughtful fear processing via the cortex.

Brain structures involved in LeDoux's Model

Low Road: Thalamus → Amygdala → Fear response; High Road: Thalamus → Sensory Cortex → Prefrontal Cortex → Amygdala → Regulated response.

Papez's Circuit

Information flows through the following sequence: Hippocampus, Fornix, Mammillary bodies, Anterior nucleus of the thalamus, Cingulate gyrus, Cingulum bundle, Parahippocampal gyrus and entorhinal cortex.

LeDoux's High-Road and Low-Road Model

Low Road (Fast Response): Thalamus, Amygdala. High Road (Slower, Thoughtful Processing): Thalamus, Sensory Cortex, Prefrontal Cortex, Amygdala.

Classical (Pavlovian) Fear Conditioning

Associating a neutral stimulus (tone) with an aversive event (shock), leading to conditioned fear responses.

Brain Areas Involved in Fear Conditioning

Amygdala, Hippocampus, Prefrontal Cortex.

Fear Conditioning Definition

Fear conditioning is a form of Pavlovian (classical) conditioning where an initially neutral stimulus (e.g., a tone) becomes associated with an aversive stimulus (e.g., a foot shock), leading to a fear response.

Purpose of Fear Conditioning

Used to study emotional learning and associative memory.

Key Researcher in Fear Conditioning

Ledoux, who contributed to understanding the amygdala's role in emotional circuits.

Importance of Fear Conditioning

Helps in understanding emotional circuits in the brain, differentiates between learned and innate fear responses, used in both animal (rodent) and human studies to analyze fear mechanisms.

Neural Circuits in Fear Conditioning

Amygdala, Thalamus, Prefrontal Cortex, Hippocampus.

Amygdala Function in Fear Processing

Central to fear processing, with lateral nucleus as the first point of information reception, basolateral nucleus relaying sensory information, and central nucleus sending fear response signals.

Thalamus Role in Fear Conditioning

Sends sensory input to the amygdala (low road) or cortex (high road).

Behavioral Responses to Fear Conditioning

Freezing, Avoidance, Flight or hiding.

Physiological Responses to Fear Conditioning

Increased heart rate, Pupil dilation, Increased respiration, Hormonal responses (cortisol release).

Measuring Fear Conditioning in Research

Neuroscience Measures: Neuronal activity recordings in the amygdala. Behavioral Observations: Freezing time, avoidance behavior. Physiological Measures: Heart rate, blood pressure, hormone levels.

Olfactory System in Fear Responses

Olfactory inputs to the amygdala have a direct connection to the limbic system, bypassing the thalamus.

Unconscious Fear Processing

The vomeronasal organ (VNO) detects pheromones and can trigger instinctual behaviors.

Low Road Pathway

Quick, automatic reaction (thalamus → amygdala → response).

High Road Pathway

Slower, more processed response (thalamus → cortex → amygdala → response).

Fear Processing

Demonstrates how fear can be processed both unconsciously and consciously.

Amygdala Nuclei

Lateral nucleus, Basolateral nucleus, Central nucleus.

Lateral Nucleus of Amygdala

First point of information reception in fear processing.

Basolateral Nucleus of Amygdala

Relays sensory information in fear processing.

Central Nucleus of Amygdala

Sends fear response signals to other brain areas.

Prefrontal Cortex Function

Regulates fear responses and extinction.

Hippocampus Role

Stores contextual fear memories.

Research that helps understand PTSD and anxiety by analyzing overactive fear responses.

Fear conditioning.