q.15 of week 8 assignment

[Nudrat Jahan]

i ticked a and c. but the answers are b and d. how? please explain

[Vignesh Sompur (Teaching Assistant)]

Hello Nudrat

The answers to question 15 of Assignment 8 are b and c (not b & d) which are 

"Parallel fiber system is responsible for the encoding of amplitude or the extent of events"

"Climbing fiber system is responsible for the temporal encoding of events"

The Purkinje neurons receive input from both Mossy - Parallel fiber system as well as from Climbing fibers. These two inputs are of different types. The parallel fibers produce regular action potentials (AP) where as climbing fibers produce "Complex spikes" which are a combination of a very high amplitude signal and high frequency low amplitude signal. Also, the activity of these 2 inputs are different at both rest condition as well as during activity/event.

The climbing fibers produce ~1 to 3 complex spikes per second whereas the parallel fibers produce ~100 regular spikes per second at rest. Now during activity/event, the climbing fibers produce complex spikes in such a manner so as to indicate the presence or absence of the event (i.e like a ON/OFF switch) whereas the parallel fibers produce several hundreds of regular spikes per second during an event. This number is higher as the amplitude of the event increases.

Hence we can say that

Climbing fiber activity informs the presence or absence of the event i.e Temporally codes the event             whereas

Parallel fibers activity informs about the amplitude of the event or the extent to which the event has occurred.

Vignesh