Brains, Neurons and Neural Coding

Question 1

What are the three promary brain vesicles from embryonic develoment? What are the 6 major divisions of the adult CNS do we get from these?

Answer 1

Forebrain: Cerebral cortex, thalamus

Midbrain: midbrain

Hindbrain: Cerebellum, pons, medulla

Question 2

What is neural processing dependent on?

Answer 2

Neural coding are forms of patterns of electrical activity where individual action potential does not differ but coding is based on space and time

Question 3

What are the 2 neural codings?

Answer 3

Space and time

Question 4

What is neural coding in terms of space?

Answer 4

They are nerual circuits which have speciifc synaptic connections bewteen nerve cells from circuits/networks

• 86billion neurons in the human brain, up to 10,000 synaptic contacts per neuron

Question 5

What is neural coding in terms of time?

Answer 5

The time taken for spike trains

Question 6

What are the two types of time codes?

Answer 6

• Rate code: the average spike frequency | number of spikes over time
• Temporal code: the precise timing of spikes is important

Question 7

What is the conduction of spikes?

Answer 7

range: <1m`s to >100ms
majority <10ms

Question 8

What is the generation of spikes?

Answer 8

Varies with cell type and species but the fastest action potentials can take place within 1-2ms

Question 9

What are the different ways to record electrical activity of the nervous system?

Answer 9

• EEG
• ECoG
• Extracellular recording
• Intracellualr recording

Question 10

How do EEGs work?

Answer 10

• Electrodes are used to amplify and record small voltage changes from the surface of the head
• Can be done prior to neurosurgery

Question 11

How do ECoGs work?

Answer 11

Electrodes attached directly on cortical surface and records local fields potentials due to summed neural activity

Invasive!!

Question 12

How does extracellular recording work?

Answer 12

Microelectrodes are inserted into extracellular space. APs in nearby neurons generate small extracellular currents that can be amplified and picked up as spikes.

Question 13

How does intracellular recording work?

Answer 13

Microelectrodes are inserted through the cell membrane and records voltage difference between intra and extracellular space

Question 14

Which of the 4 methods of recording has highest resolution?

Answer 14

Intracellular recording, then extra, then ECoG and EEG has lowest resolution

Question 15

What is Event Related Potentials (ERP)?

Answer 15

Using EEGs to study responses to sensory stimuli

since the signal from a single electrode due to acticity of thousands to millions of neurons, any response which is lost in noise may be unrelated to the stimulus

• If stimulus is repeated multiple times and averaged random activity cancels out so the activity observed is due to the stimulus.