Lecture 3: Socio-Emotional Disorders (NSBED, UU)

Highlights of paper by Porcelli et al.:

• The human brain shows levels of specialization for social stimuli processing
• Social brain could be affected by several psychiatric disorders
• Mechanisms underlying social dysfunction are largely similar across disorders
• Social dysfunction and social withdrawal may represent a transdiagnostic domain

The core message: complex social environments were a selective pressure for the human brain. This high complexity is associated with a high susceptibility to social psychopathology.

Social deficits can be the first signs of a ‘non-social’ psychiatric disorder.

In one sentence: the article provides neurobiological substrates of how in 3 frequent disorders (AD, SCZ and MDD) similar maladaptive mechanisms underlie social withdrawal.

There is dense white matter tract between the orbitofrontal cortex and the amygdala. This tract has been linked to a range of social disorders.

There are five large-scale brain networks for social behavior:

Amygdala networks:

• Perception network
• Affiliation network
• Aversion network

Non-amygdala networks:

• Mentalizing network
• Mirror network

What you need to know:

Social perception: detection and processing of social stimuli:

• Amygdala is the hub in the face processing network, involving the
  • Fusiform face area
  • Posterior STS
  • Occipital face area

Social affiliation network:

• Role: to form and maintain social bonds
• Ventromedial PFC, ACC and medial temporal cortices

Emotion regulation:

• Amygdala is connected to vmPFC
• Increased functional couplic is related to increased ability of emotion regulation

Social aversion network:

• Amygdala is hub
• ACC, insula and connectional targets in striatum, hypothalamus and brainstem.

Mirror network:

• Selection of temporal, parietal and sensory motor brain regions

Mentalizing network:

• ACC, mPFC, inferior frontal gyrus and temporopartietal junction
• Is decomposed into:
  
  • Dorsal subnetwork: abstract third-person (others) information
  • Ventral subnetwork: engages when embodies first-person information is required.

Social functioning is highly impaired in AD, SCZ and MDD. All groups show a reduction in social connections.

Part 2: neuro-evolutionary model of depression

Adaptive functions of depression (or low mood):

• Communicating a need for help
• Saving valuable resources
• Giving up commitment to unreachable goals

According to some scientists, pessimism and lack of motivation inherent to depression, or low mood, give a fitness advantage by preventing actions which led to nothing. The ability to feel bad and do nothing about it is an adaption.

Active coping: sympathetic activation

Passive coping: parasympathetic activation

Passive coping strategies, such as social withdrawal, can result in clinical depression.

Conservation withdrawal response (passive coping) started by e.g. jawless armoured fish: because they only use the parasympathetic system. Timeline:

450 myo: jawless armoured fish with only parasympatethic system

350 myo: reptiles with both parasympathic and sympathetic

200 myo: social caring

Maternal bonding is hormonally regulated by mostly opioids and oxytocin – both involved in pain and social pain.

Depression hurts, because the physical pain and social pain are overlapping brain networks.

First it was thought that depression was caused by a shortage of serotonin. Now there is increasing evidence for the opposite being true: many patients have higher levels of serotonin. Many scientists now think:

1. Serotonin has little to do with depression
2. Anti-depressants surely do not cure depression
3. The long-term effects of antidepressants might be bad, especially in children

What helps?

1. Social support
2. Opioids (morphine, cocaine)

Why do opioids work?

1. They act on brain pathways of social reward which are activated during social interactions
2. Humans depend on social others to be happy, opioids kill this dependence
3. Makes social problems disappear, but it comes with a cost

Depression is largely prevalent in the US, Europe and Asia, but less in Africa. Why?

1. Social differences (individualism vs collectivism)
   1. UBUNTU in Africa: a person is a person through other people. Western people think they have a ‘self’ independent of others.
2. Stereotypes and social trends
   
   1. They do not see depression as part of their ‘options’; it belons to the western people. US and EU people also have a tendency to seek a diagnosis for a mental disorder.
3. Neanderthal genetics
   
   1. African people did not interbreed with neandertals. Neandertal genes have been linked to modern diseases.
4. Environment / climate
   
   1. Northern seasonal climates increase prevalence for seasonal affective disorder and MDD. So we might have inherited depression from the Neanderthals, and we are boosting depression by living in cold seasonal climates.

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