Cognitive Neuroscience: Emotion

Defining Emotion

• Emotion:
  • A state associated with stimuli that are rewarding or punishing.
  • Often have survival value.
  • Transient (unlike moods).
  • Elicit particular motor expressions in the face and body.
  • Prepares the body for fight/flight response (heart rate, sweating, hormone release).
  • Attention-grabbing and subjectively liked or disliked.

Evolutionary Significance of Emotions

• Evolutionary survival mechanism: Associating rewarding/punishing stimuli with subjective internal states can guide future behavior.
• Subjective internal states (emotions) lead to bodily changes that increase the chances of survival (approach/avoidance behavior).
• Emotions also lead to bodily changes that can communicate information to others (facial expressions).

Universality of Human Emotions

• Response to emotional events is associated with consistent body language across people.
• Sighted vs. congenitally blind athletes demonstrate similar body language (Tracy & Matsumoto, 2008).
• Similar facial expressions are made in similar contexts across the globe.
• Machine learning applied to analyze people’s facial expressions (Cowen et al., 2020).
  • Analyzed 6 million YouTube videos from 144 countries.
  • Algorithm identified 16 typical/canonical facial expressions across countries.
• Examples of universal emotions: anger, happiness, fear, disgust, sadness, surprise (Ekman, 1973).

Dimensions of Emotion

• Two primary dimensions:
  • Valence (positive or negative).
  • Arousal (level of intensity).
• Examples:
  • High arousal, positive valence: ecstasy, passion.
  • Low arousal, positive valence: contentment, desire.
  • High arousal, negative valence: terror, rage.
  • Low arousal, negative valence: boredom, sadness.
• Approach vs. Avoidance behavior is related to positive and negative valence of emotion respectively.

Measuring and Manipulating Emotion

• Direct methods:
  • Manipulation of emotional state via stimulus/context.
  • Recognition of facial expression.
• Indirect methods:
  • Arousal of the autonomic nervous system (Galvanic skin response - GSR or SCR, measuring sweating).
  • The effect of emotional arousal on other judgments and/or decisions.

Example: Learning from Aversive Stimuli

• Fear conditioning.
  • Before training:
    • Light alone (CS): no response.
    • Foot shock alone (US): normal startle (UR).
    • Loud noise alone (US): normal startle (UR).
  • During training:
    • Light and foot shock: normal startle (UR).
  • After training:
    • Light alone: normal startle (CR).
    • Light and noise but no foot shock: potentiated startle (potentiated CR).

Misattribution of Arousal

• Arousal (due to the context) affects an unrelated decision.
• Example: manipulating emotional arousal (Dutton & Aron, 1974).
• Heightened physiological state (dangerous bridge) leads to more follow-ups.

Emotional Learning and the Amygdala

• The amygdala plays a key role in how stimuli become associated with emotions/emotional responses.
• Amygdala responses are larger and faster to fearful stimuli (e.g., spider for phobic individuals) CS- > CS+. Larson et al (2006). Biol Psych
• Two potential pathways for learning about (and responding to) the emotional value of stimuli in the environment:
  • Fast route to the amygdala via the thalamus (implicit).
  • Slow route to the amygdala via the cortex (explicit).
• Different nuclei within the amygdala project to distinct areas of the nervous system.
  • Hypothalamic and autonomic connections promote full-body hormone-mediated response (fight/flight).
  • Projections to hypothalamus, autonomic areas, hippocampus, and prefrontal cortex.

Amygdala and Conditioned Fear Response

• Amygdala lesions impair fear conditioning in animals and humans.
• Impairment of implicit learning: human patients learn explicitly that a stimulus is associated (predicts) a shock but show no skin conductance response (sweating) to the conditioned stimulus.
• Amygdala damage causes a deficit in implicit learning (skin conductance response) but intact conscious knowledge of the association between the stimulus (blue square) and shock (LeBar et al., 1995, J. Neuroscience, 15, 6846-6855).

Indirect Fear Learning

• The amygdala is critical for the acquisition and expression of fear conditioning CS- > CS+.
• Humans can learn the aversive properties of an event through direct experience, but they can also learn through observation.
• The human amygdala plays a similar role in learning through the direct experience of an aversive event and through indirect observation.
• This is important because learning about stimuli that should be feared through social means is more efficient and has fewer costs.
• Phelps et al., 2001, Nature Neurosci., 4, 437-441
  • Instruction: Blue square predicts shock, yellow is neutral CS+ > CS-.
  • Amygdala active in response to.
  • Amygdala activity correlated with skin conductance response (sweating).

Amygdala and Emotion Recognition

• Amygdala damage impairs emotion recognition from facial expressions.
• Amygdala damage leads to patterns of eye movements that differ from controls.
• Restored emotion perception with instruction to “focus on eyes”.

Amygdala Modulations of Declarative Memory

• The amygdala modulates the strength of explicit memory for emotional events.
  • Explicit memory can be formed despite amygdala lesions (i.e., the hippocampus!) but the amygdala allows better recall over long-term for emotional events.
  • Arousing and nonarousing events are remembered equally well after the event, but arousing events are not forgotten as quickly.
• Emotional stimuli are typically better remembered than neutral stimuli.
• The amygdala is necessary for this enhancement (patients with bilateral amygdala damage do not show this).
• Example: Controls vs. Patient BP
  • Phase 1: Neutral events. Story about a child walking with their mother to visit their father at work.
  • Phase 2: Emotional events. Memory for story elements 1 week later.

Amygdala's Role in Declarative Memory

• What exactly is the amygdala’s role in producing better declarative memory for emotional events?
• Interactions with the hippocampus, prefrontal cortex, hypothalamus, and autonomic areas.

Amygdala-Hippocampal Interaction

• Kensinger & Corkin (2004).
  • Encoding: sorrow, slaughter.
  • Retrieval (memory test): remembered (“yes”) vs. forgotten (“no”).
  • Arousing (and valenced) words.
• Greater hippocampal activity during all types of remembered words.
• Greater amygdala activation for remembered arousing words.
• Activity in the amygdala and hippocampus is correlated, suggesting coordination/interaction between regions.
• When a stimulus is arousing, the amygdala modulates hippocampal memory encoding.
• Kensinger & Corkin (2004) correlation for arousing words.

Model of Amygdala-Hippocampal Interaction

• An emotional event engages the amygdala, which enhances activity in the hippocampus, leading to stronger long-term memory.
• Test this directly by activating the amygdala with electrical stimulation during memory encoding (Inman et al., 2018).

Experiment: Amygdala Stimulation and Memory

• Inman et al (2018).
• Study Phase.
• SPALDING
• TF-1000
• 160 Trials
• 3 s.
• 1 s 5.5-6.5 s ITI.
• Indoor or Outdoor?
• Stimulation applied during encoding to a subset of items.
• Memory tested twice (but for different items each time!): immediate and 24-hr delayed.

Results of Amygdala Stimulation Experiment

• No immediate difference in memory for stimulated vs. unstimulated words (Inman et al., 2018).
• Stimulation-related enhancement emerges after 24 hrs (sleep/consolidation) (Inman et al., 2018).
• No subject noticed stimulation being applied (Inman et al., 2018).
• Addresses a potential confound of just drawing increasing attention to stimulated items.