Lecture 1: Introduction & Methods (NSBED, UU)

Social neuroscience is a combination of sociology, psychology and neuroscience.

The social brain is non-modular: social behavior is the result of a network.

Evolution of social (and non-social) behavior:

• Bigger brains lead to changes in both social and non-social intelligence
• Alternative (social intelligence hypothesis): social pressure to outwit peers may lead to increased intelligence in social and non-social domains.

Triune brain model: the human brain is an accumulation of brain regions that can be roughly divided in three phylogenetic stages:

• The reptilian brain (sub-cortex)
  • Action-reaction machinery
• The mammalian brain (limbic system)
  
  • Emotionality: behavioral flexibility
• The primate brain (neo-cortex)
  
  • Rationality: the behavioral control

Sometimes a part of our behavior is still driven by similar brain mechanisms.

Reptilian brain: quite modular. Consists of small nuclei with distinct (non)social roles.

Mammalian brain: module-like. Amygdala/insula – fear/disgust

The primate brain: non-modular. But: mirror neurons.

Mirror neurons: neurons that respond to both self-behavior and other-behavior. Thought to serve observational learning. Are not tightly localized to one region.

Conclusion: the social brain might be a mixed mode of modularity.

Psychological methods in which we can measure behavioral and cognitive measures

Subjective measures

• Emotional experience (interview or POMS)
• Personality questionaires (e.g. STAI/STAS)
• Use it for:
  
  • Control variable
  • Correlation with other measure
  • To compare different studies

Observational measures

• What will the participant do?
• But also eye tracking

Performance measures

• Speed and accuracy
• IQ tests
• Recognition tests
• Selective attention

Phychophysiology --> controlled by the brain through the spinal cord. ((Para)sympathetic nervous systems). 

Physiological methods

• Skin conductance (sweat gland activity)
• Heart rate, respiration (preparation for fight/flight
• Electromyography (EMG; muscle activity)

Skin conductance (SCR)

• You measure sweat gland activity
• Peak between 1-5s

Heart rate

• Deceleration: preparing for danger
• Acceleration: active escape or attack
• Heart rate variability (HRV)
  
  • More variability = rest = parasympathetic
  • Less = concentration, enhanced attention = sympathetic

Electromyography (EMG)

• Measures potential between pairs of close elektrodes
• Muscle activity
• Application:
  
  • Mimicking facial expressions (affective empathy)
  • Startle potentiation

Brain imaging methods

1. Electrophysiology

• Single-cell recordings
• Electroencephalography (EEG)
  
  • Possible to the column-like organization of the cortex (therefore also limited to the cortex)
  • Frequency bands approach
    
    • Delta-waves (1-4 Hz): motivational system (bottom-up drive)
    • Beta-waves (12-30 Hz): cortex: top-down modulation
  • Event-related potentials approach: EEG signal that is averaged over many trials. The resulting ERP is a series of positive and negatieve peaks.
    
    • Tells you something about location, amplitude, and timing in response to the event
    • Advantage: has an excellent temporal resolution

Disadvantage: poor spatial resolution (derived from multiple

sources in the brain)

2. Structural imaging

Magnetic resonance imaging

• Relies on alignment of water molecules, aligned in a strong magnet

The strength of the realignment signal is different for different types of tissue. So you can tell the tissue type and structure.

Diffusion tensor imaging (DTI)

• Used to map the white matter microstructure
• You measure the communication bundles of the brain
• Uses the diffusion of water molecules
• You emit a radio signal and then measure the direction of the realignment of the water molecules. The directions are more limited in myelinated areas than in grey matter.
• Is also MRI, but from multiple angles and time-points

3. Functional imaging

Functional MRI

• Relies on the hemodynamic method: neural activity consumes oxygen, thus needs blood.
• Measures blood oxygenation
  
  • Oxygen slows re-alignment of water molecules
  • Non-invasive (unlike PET)
• A region is active if it shows a greater response in one condition RELATIVE to another
• Good spatial resolution! Voxel-size can be as low as 1 mm3. But bad temporal resolution because of the hemodynamic response function (BOLD response): the signal is a few seconds late.

4. Lesion methods

Reversed engineering: infer the function of a region by removing it and measuring the effect on the rest of the system

Human models:

• Accidents
• Stroke
• Lobectomy
• Genetic disorders

TMS

• Coil --> the magnetic field will evoke action potentials in the brain
• Will disrupt the cognitive function
• Advantage: the fake lesion is focal, but no deep brain regions. It’s reversible and moveable. You can investigate the time-course of cognition
• Disadvantages: there is not a good placebo condition. Solutions (partly):
  
  • Different time windows act as control conditions
  • Different spatial locations act as control conditions
  • Different task used as control
  • Different stimuli used as a control

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