Week 1 - Intro

Question 1

What is cognitive neuroscience?

Answer 1

• Knowledge about structures, functions and mechanisms of the nervous system to describe mental processes.

Question 2

What was Rene Descartes view on the body and mind?

Answer 2

• “Evil Demon” – 1641
• We might be living in hell but think we’re living in something other than hell

Question 3

What is a braino cap?

Answer 3

• Braino cap (James Cornman & Keith Lehrer, 1968) - can produce any kind of hallucination

Question 4

What is a “brain in a jar” thought experiment (Gilbert Harman, 1973)?

Answer 4

• Brain removed from body in life-sustaining liquid
• Neurons connected by wires to a supercomputer
• Computer sends electrical impulses identical to those the brain normally receives (perception)
• Computer receives output responses from brain (motor functions)
• No brain can tell whether it is embodied or in a jar

Question 5

What is the Montreal Procedure (Penfield & Jasper, 1954)?

Answer 5

• Direct stimulation of the brain
• Used to want to help patients with severe epilepsy
• Aim - destroy nerve cells at seizure origin
• Accurate targeting of responsible areas - stimulation of brain with electrical probes while patients conscious until it triggered the same pattern that emerged whenever they had a seizure.
• Results showed an interesting phenomenon - stimulation of certain brain areas can lead to:
  
  • vivid recall of memories
  • olfactory, visual and auditory hallucinations

Question 6

What is the brain’s history?

Answer 6

1. 16th century BC - Edwin Smith Papyrus was an Egyptian battlefield surgeon. Knowledge about lateralisation of brain:
   * A head injury to the left side of the head, the right side will be affected.
2. 6^th – 4^th centuries BC – Aristotle:

• Thought intelligence was in the heart - brain is cooling mechanism
• More intellectual capacity = more heart activity, more cooling needed
• Alcmaeon of Croton & Hippocrates - mind/intelligence located in brain

1. 16^th century - Vesalius “father of modern anatomy”:
   * Focus on ventricles (cortex not detailed)
2. 19^th century - Gall and Spurzheim:

• first accurate depiction of brain
• advocates of phrenology

Question 7

What is the mind-body problem?

Answer 7

• How can the brain create our mental world?
• How can physical substance give rise to sensations, thoughts, emotions?

Question 8

What are the three approaches to solving the mind-body problem?

Answer 8

1. ​Dualism (Descartes, 1641):

• Soul and body are different “substances“, but they may interact
• Soul independent of physical substances – hard to find out about the soul
• Interaction in pineal gland

1. ​Dual-aspect theory (e.g., Spinoza, 1677):

• Mind and brain are two different levels of explanation for the same thing
• “Special” brain processes because of introspectable, mental aspect
• Analogy: photon can be wave and particle at the same time

1. Reductionism (e.g., Carnap, 1923):

• Mind-based concepts (emotions, memory, attention) are currently useful but are replaceable by biological constructs (patterns of neuronal firings, neurotransmitter release)
• Psychology will be reduced to biology (or even physics?)
• Analogy: Newton‘s law of gravity replaced by Einstein’s relativity theory

Question 9

What is phrenology and the history behind it?

Answer 9

Gall & Spurzheim (1810) – phrenology:

• Different regions of the brain perform different functions and are associated with different behaviours.
• The size of the regions in the brain produce distortions in the skull (and thus brain) related to individual differences in cognition and personality
• First systematic approach to connect cognitive functions with the brain
• Phrenology was unscientific but gave rise to notion of functional specialisation – different regions of the brain are specialised for different functions:
  
  • Local brain damage impairs speech production (Broca, 1861) or comprehension (Wernicke, 1874) independently
• Empirical observation was being used to determine the building blocks of cognition (is language a single faculty?)
• Developing models of cognition that did not make direct reference to brain (brain region irrelevant for theory)
• Gave rise to cognitive neuropsychology – the study of brain-damaged patients to inform theories of normal cognition.

Question 10

What is depth psychology?

Answer 10

• Late 19th century - less interest in neural underpinnings of the mind, more interest in consciousness, attention, personality
• Depth psychology (Freud, Jung, Bleuler):
  
  • Mind is partially conscious and partially unconscious
  • Unconscious mental states can explain behaviour and experience
• Problems:
  
  • Theory is derived with unscientific methods
  • No explanatory value (post-hoc explanations)
  • Assumptions are not falsifiable

Question 11

What is falsifiability?

Answer 11

• There is no way to show that a theory is true (David Hume)
• A theory has to be falsifiable (Karl Popper) - the capacity for some proposition, statement, theory or hypothesis to be proven wrong.

Question 12

What is psychophysics?

Answer 12

• Interested in things that are not directly observable
• Wundt, 1879 - first laboratory for psychological research
  
  • Father of experimental psychology
  • First response time experiments - how fast do people respond to visual stimuli?
  • The mind can be measured
• Gustav T. Fechner - founder of psychophysics:
  
  • Psychophysics - relationship between the psychological (experience of senses) and the material/physical world
  • “just-noticeable difference” - how large does a change of a physical measure (e.g., weight) have to be to be different from another weight to be noticeable (Fechner, 1860)
• Helmholtz:
  
  • There is a physical reality and a psychological reality (Helmholtz 1896)
  • Optical illusions can be the result of unconscious inference, e.g., “light comes from above“ we try to connect this to the physical world, e.g. Ramachandran illusion.

Question 13

What is behaviourism?

Answer 13

• Watson (1913) - introspection is not objective and thus unscientific
• Mental states cannot be examined scientifically and should remain in a ‘black box’
• Psychology should study only observable behaviour
• Methods - classical and operant conditioning
• Skinner (1963) - learning and behaviour determined by environment

Question 14

When did the cognitive revolution begin?

Answer 14

• 1950s
• Applying the scientific method to cognition:
  • Influencial paper - “The Magical Number Seven, Plus or Minus Two” (Miller, 1956); experimental test of the short-term memory capacity
  • A mental process is tested experimentally
• The computer metaphor - the brain works like a computer:
  • Inspired by computer technology emerging in 1950s
  • Broadbent (1958) - cognition is sequence of processing
• Neural Networks (Rumelhart & McClelland, 1986):
  • 1980s: Computational models possible through powerful computers
  • Computationally explicit models rather than “computer-inspired”

Question 15

What are the cognitive impairments in schizophrenia?

Answer 15

• Response times (RT) typically slower in schizophrenic patients (Gold et al., 1997):
  • Unclear which cognitive process is impaired
• Selection process is slower in schizophrenics (Luck et al., 2009):
  • Stimulus categorisation is the same for controls and schizophrenics.
  • However, response selection is slower
• EEG (event-related potentials):
  • identify which cognitive process is affected
  • pinpoint timing of cognitive process

Question 16

What are mirror neurons?

Answer 16

• Mirror neurons - similar neural pattern for observing and performing behaviour
• A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron “mirrors” the behavior of the other, as though the observer were itself acting.
• Problem:
  
  • What does the neural pattern represent?
  • Action understanding? Anticipation of food? Empathy?
  • No behavioural evidence!

Question 17

What are the methods used in cognitive neuroscience?

Answer 17

• Method types:
  
  • Stimulation – use a method to affect the brain somehow and measure the changes induced in the brain.
  • Recording – some experimental manipulation to record the effect of the manipulation.
• Invasiveness:
  • Non-invasive – skin doesn’t need to be broken.
  • Invasive – skin needs to be broken.
• Brain property:
  • Electrical activity – e.g. action potentials
  • Magnetic activity – as a result of electric activity
  • Hemodynamic – variation in the blood oxygen level due to varying brain activity

Question 18

Describe the structure of a neuron

Answer 18

• All neurons consist of a cell body (soma), dendrites and an axon:
  
  • Dendrites enable communication with other neurons. Dendrites receive information from other neurons in close proximity.
  • The axon sends information to other neurons – each neuron contains one axon (although the axon may be divided into several branches called collaterals).
• Synapse – the small gap between neurons in which neurotransmitters are released, permitting signalling between neurons:
  
  • The two neurons forming the synapse are referred to as presynaptic (before the synapse) and postsynaptic (after the synapse), reflecting the direction of information flow.
• When a presynaptic neuron is active, an electrical current (action potential) is propagated down the length of the axon. When the action potential reaches the axon terminal, chemicals are released into the synaptic cleft. These chemicals are termed neurotransmitters. Neurotransmitters bind to receptors on the dendrites or cell body of the postsynaptic neuron and create a synaptic potential. The synaptic potential is conducted passively (i.e. without creating an action potential) through the dendrites and soma of the postsynaptic neuron. If these passive currents are sufficiently strong when they reach the beginning of the axon in the postsynaptic neuron, then an action potential (an active electrical current) will be triggered in this neuron. It is important to note that each postsynaptic neuron sums together many synaptic potentials, which are generated at many different and distant dendritic sites (in contrast to a simple chain reaction between one neuron and the next).

Question 19

What are the electrical charges of a neuron?

Answer 19

• Neurons are polarised brain cells (inside more negative than the outside)
  
  • A inside of cell membrane is -70 millivolt more negative than outside
• Each neuron is surrounded by a cell membrane that acts as a barrier to the passage of certain chemicals. Within the membrane, certain protein molecules act as gatekeepers and allow particular chemicals in and out under certain conditions. These chemicals consist, among others, of charged sodium (Na + ) and potassium (K + ) ions. The balance between these ions on the inside and outside of the membrane is such that there is normally a resting potential of –70 mV across the membrane (the inside being negative relative to the outside). Voltage-gated ion channels are of particular importance in the generation of an action potential. They are found only in axons, which is why only the axon is capable of producing action potentials.

Question 20

Describe the electrochemical forces for the different elements in a neuron

Answer 20

• Electric potential determined by how many positive and negative ions there are
• Diffusion – more particles have a higher diffusion force to separate away from each other
• The resting potential of a neuron:
  
  1. Organic anions want to get to the outside of the cell because they are negatively charged, and the outside is positive. There is also more on the inside than outside so the diffusion force is strong as well. However, there are no channels for them as they are too large to leave – this is a big factor in keeping the inside of the cell negative.
  2. Potassium – opposing forces at play:
  • The diffusion force wants them out of the cell (lots on the inside and few on the outside)
  • The electrical force wants them to stay in the cell as potassium is positively charged and so is the outside of the cell (the inside is negative).
  • The electrical force is smaller though and there are channels dedicated to letting potassium ions pass through until equilibrium is reached.
  1. Sodium – mostly on the outside of the cell:
  • Diffusion force pushing them into the cell
  • Electrical force pushing them into the cell
  • Sodium struggles to get through the channels as they are quite big for them.
  1. Ion pump – exchanges two potassium ions for three sodium ions which keeps the resting potential stable.

Question 21

What is the graded potential?

Answer 21

• Graded potentials are changes in membrane potential that vary in size, as opposed to being all-or-none. The magnitude of a graded potential is determined by the strength of the stimulus:
  
  • Depolarisation - the membrane of a cell (e.g. a neuron) is polarized (negative inside). Depolarizing is when the membrane potential moves toward zero.
  • Repolarisation - repolarizing is when it moves back to negative after depolarization.
  • Hyperpolarisation - makes the cell more negative.

Question 22

What are the periods in a neuron?

Answer 22

• Ions go to the trigger zone – action potential starts which travels along the axon to the synapse which releases neurotransmitters that can trigger another action potential at the next neuron.
• Absolute refractory period – no further action potentials can be triggered as Na+ channels are activated.
• Relative refractory period – a further action potential is harder to trigger due to fewer channels where sodium can go. Also, more negative which means you need more ions to trigger the action potential.
• Myelin sheaths increase speed through saltatory conduction

Question 23

Describe action potentials

Answer 23

• Action potential - an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. When the depolarization reaches about -55 mV a neuron will fire an action potential. This is the threshold.
• The origin of all neural activity is the action potential
• All or nothing:
  
  • As soon as voltage passes threshold, AP is triggered
  • Size of AP is always roughly the same in each neuron
• Information is coded in how many APs are triggered:
  • Firing rate
  • Strong inputs will lead to higher fire rate

Question 24

What are the three ways to record neuron activity?

Answer 24

1. Intracellular single-unit recordings
2. Extracellular single-unit recordings
3. Multi-uni recordings

Question 25

What are intracellular single-unit recordings?

Answer 25

• Intracellular single-unit recordings occur within the neuron and measure the voltage change (with respect to time) across the membrane during action potentials
• Microelectrodes (~0.05 – 1 μm) are inserted inside of a neuron – need to be small to get into neuron
• Measures all stages (resting potential, graded potential etc.)
• Difficult to find cell and maintain position with electrode, cell damage
• Aim - learn about cell properties

Question 26

What are extracellular single-unit recordings?

Answer 26

• Microelectrodes (3-10 μm) inserted on the outside of a neuron – easier to achieve outside of neuron
• Can isolate activity of single neuron if close enough
• Pick up action potentials, but smaller amplitude (~0.1 mV) – because not measuring at the same level
• Aim - identify firing patterns (e.g., spike frequency)

Question 27

What are extracellular multi-unit recordings?

Answer 27

• Macroelectrodes (~100 μm) outside in large group of neurons
• An electrode may pick up on activity from multiple nearby neurons – the electrical activity of many individually recorded neurons at one or more electrodes.
• Aim: Identify response pattern of neural ensembles