Lecture 2: Evolution, Emotion & Motivation (NSBED, UU)

When talking about emotions, it’s important to not only talk about electrical connections, but also chemical connections: neurotransmitters.

1. Glutamate (excitatory)
2. GABA (inhibitory)

These cause synaptic transmissions.

Neurotransmitters relating strongly to emotion:

• Norepinephrine (noradrenalin)
  • Locus Coeruleus: fight-flight / arousal
• Serotonin
  
  • Raphe nuclei: mood / impulsivity
• Dopamine
  
  • Ventral tegmental area: Mo(tiva)tion / reward

These are neuromodulators: made in the brainstem and then transported to other parts in the brain, where they are released and influence the synaptic transmissions (G&G).

Neuropeptides are a different type of neuromodulators. Are produced in the pituitary gland, based on signaling from the hypothalamus. So: hypothalamus > pituitary > peptide > emotion:

• Opioids (endorphins)
  • Pleasure
  • Motivation
• Vasopressin
  
  • Social aggression
• Oxytocin
  
  • Maternal bonding

Steroid hormones are also neuromodulators. Hypothalamus > pituitary gland sends precursors > body > hormones > emotion.

• Testosterone
  • HPG axis
  • Social aggression
  • Sex
• Cortisol
  
  • HPA axis
  • Fear
  • Arousal

Cognition is in the brain, and emotion in the body.

The hypothalamus directly coordinates the autonomous nervous system (ANS; parasympathetic and sympathetic nervous system).

The autonomous nervous system is part of the reptilian complex (approach / avoidance system. Behavior based on reactivity.

The paleomammalian complex/limbic system contains the:

• Hypothalamus (control of ANS and hormones)
• Striatum (reward, joy)
• Amygdala (fear)
• Insula (disgust)
• Hippocampus (memory)

Behavior is based on attention and conditioning.

The neommalian complex/neocortex: behavior based on subjective / affective experience, social interaction and ratio.

Motivation: states in which rewards are sought and punishers are avoided (approach / avoidance (action based))

Emotion: states associated with stimuli that are rewarding and punishing (liking / disliking (subjective)):

• Emotional reacting: acute state in response to something (surprised)
• Emotional feeling: the subjective experience of emotions (joy)
• Emotional mood: a diffuse affective state that is often of lower intensity than emotion but considerably longer in duration (happiness)

We have the physical ‘arousal’ caused by the ANS, and we have the mental experience that comes with it.

• James-Lange theory: Event > arousal > experience. But: arousal doesn’t always lead to the same experience.
• Reversed in Cannon-Bard theory: arousal after experience. But: we can experience arousal without any conscious recollection why.
• Papez & Maclean: Event > independent arousal and experience. However, the brain has a lot of connections so it is unlikely that it is fully independent.
• Schachter & Singer: event > (arousal + interpretation) > experience. ButL some emotional experience exist without interpretation.

Cognitive empathy: our ability to experience what someone else is experiencing.

Basic emotions can be looked at through an evolutionary perspective.

Sad, happy, disgust, surprised, anger and fear are thought to be universal emotions, but there is debate about whether this is driven by western emotion labels.

But different research suggests that fear and happy may be the actual basic emotions.

So combining the theories of basic emotions and evolution, we consider the three basic emotions to be:

• Fear: avoidance of threat / punishment   amygdala
• Disgust: avoidance of illness / contamination   insular cortex
• Happy: approach of rewards / goals  striatum

These are all important for survival.

The basic social emotions are:

• Anger: competition, social hierarchy
• Sadness: care for offspring and family

These are also a product of approach / avoidance motivation.

Amygdala and fear

The amygdala consists of the BLA (cortical-like part) and the CeA (striatal-like part).

LeDoux introduced a low and a high route. The high route is the normal route (see picture). The low route is directly from the thalamus to the amygdala (pre-conciously).

Urbach-Wiethe patients have no fear recognition because they have no eye gaze (and have a damaged amygdala). But this is only the case if there is full amygdala damage.

Central-medial amygdala: fear expression part

Basolateral amygdala: fear regulation part

The basolateral amygdala has been shown to be essential for threat condition, and also important for reward learning (Pavlov).

The amygdala activates irrespective of whether positive/negative.

Amygdala and threat; it manages:

• Reactivity (fight-flight)
• Attention
• Recognition
• Learning and memory
• Fear experience and regulation

But it is also important for reward and relevant events in general!

The amygdala provides limbic control over motivational drives

• It facilitates rapid action
• Adjustment of behavior to the current situation

The insula and disgust

Insula damage in humans impairs disgust recognition in faces and voices, but not other types of emotion. But it’s also important for taste and pain perception and bodily perception.

• So basically the insula is involved in subjective experience of any emotion.

The insula is the main node of the salience network  activates in response to any relevant stimulus.

So overview:

The fear system (amygdala) looks outward for threat and emotional salience. 

The insula looks inward for threat and emotional salience.

Happy (reward system)

Involved structures:

Midbrain/brainstem

• Ventral tegmental area
• Substantia nigra

Striatum

• Dorsal (putamen, caudate nucleus)
• Ventral (nucleus accumbens)

Cortex

• Orbitofrontal
• Anterior cingulate

Midbrain and striatum

• The midbrain provides the striatum with dopamine as neuromodulator.
  • The SN (substantia nigra) provides the dorsal striatum
  • The VTA (ventral tegmental area) provides the ventral striatum

The dorsal striatum is important for the expression of motivated behavior (habit formation, reward-driven motor behavior. Because of the lack of dopamine from the SN in Parkinson’s disease, it causes the motor problems.

The ventral striatum (nucleus accumbens) is important for reward experience (anticipation and prediction).

So:

Dorsal striatum: reward seeking / habit formation

Nucleus Accumbens: reward prediction / anticipation

SN & VTA: dopamine projections

Orbitofrontal cortex

• Predicts whether a stimulus is currently rewarding
• With lesions, patients lose flexibility of giving the reward value into context and behave impulsively.
• Fail to regulate behavior using social norms.

Anterior cingulate cortex

• Conflict monitoring (both self and observed)
• Dorsal part: cognitive part of monitoring (stroop task)
• Ventral part: affective monitoring

Emotions and decision making

Emotional decision making is intuitive and fast, and prone to error.

Rational decision making is calculated, slower and more likely to be correct.

Somatic marker theory: a theory on how emotions can improve decision making.

Problem > (Solutions and related arousal) > decision.

We learn association thanks to somatic signals (automatically driven by emotional processing).

After vmPFC damage, people make more rational decisions.

So:

• Traditionally cognition and emotions are separate systems
• But the somatic marker theory states that our decisions are guided by affective-somatic reactions, which improves decision-making.
  
  • Criticism: no real evidence of guidance in terms of timing
  • No real evidence for a truly somatic contribution

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