neurons and neural codes

Question 1

state the three primary sensory types we have and their modalities

Answer 1

Electromagnetic- vision
Mechanical- touch, hearing
Chemical- smell, taste

Question 2

define inter-neurons

Answer 2

between sensory and muscle efferents- most of the processing in the brain.

Question 3

compare and contrast graded potentials with AP

Answer 3

In a non repropergated AP (a graded response)
Cannot be used over a long distance because of leaky membrane hence signal has range and degrades.
AP
Infinite distance
Strength cannot be used for encoding.

Question 4

what is Muller’s law

Answer 4

Each sensory nerve gives rise to its own characteristic sensation regardless of how its stimulated.

Question 5

how is TMS used to reaserch brain areas

Answer 5

Modern technique TMS high strength/ pulse rate inactivates brain region lower levels stimulate the brain area.

Question 6

Disadvantages/ criticisms of frequency coding

Answer 6

Maximum rate is limited by refractory period
Visual system variance 1*10^1012 too great for linear corelation
Spike rate is relative to log range of values
It takes time to decode rate of a signal.
Latency of fusiform face areas response is 80-100ms with number of neurons used not possible to use rate coding synapse time ect…

Question 7

define and criticize place coding model sensory representation

Answer 7

Place coding using multiple distinct neurons for different intensities
Metabolically expensive because of number of neurons that need to be involved
Hence tradeoff between speed and metabolic cost.