neurohw6 - Neuro Homework-1. For reasonable Iapp ranges...

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Unformatted text preview: Neuro Homework-1. For reasonable Iapp ranges between 0 and 50 the model works well for correctly choosing a cell to fire. Significantly out side of this range however the model breaks down. If one of the inputs is negative the opposite result of cell firing occurs (cell 5 when iapp1 is negative, even though a negative number is smaller than the non negative and non zero iapp2). Also for extremely large Iapp values cell 5 will always fire, even when iapp2 is smaller than iapp1. 2. the 2 connections that need to finely tuned are the recurrent connections for the two integrators cells. If these are not correctly tuned than the saved/held value by these neurons will change the threshold level without stimulus effecting the threshold change. Additionally these need to be more finally tuned because they are recurrent, and have a continuous effect throughout the simulation, thus a small error in tuning has a long time to mess up the rate of the integrators. Both of the graphs have Iapp1 = 12 and Iap2 =14 so cell 5 (magenta) should fire. However when cell 3 has an integrator overtuned by 5% 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 10 20 30 40 50 60 70 80 90 100 time,t rate,r This graph results showing that cell 3 quickly pushes up to maximum rate and prevents anything from firing (the second Iapp cannot be higher than the enlarging value in cell 3, but it is not lower than Iapp1 so it will not trigger cell 6 to fire) When the same Iapp values are used but the cell 4 reccurent connection is undertuned by 5% the following graph results. 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 10 20 30 40 50 60 70 80 90 100 time,t rate,r This occurs because cell 4 has no stored value after enough time and the second value will always cause enough excitation in cell 2 to cause cell 6 to fire. 3. For this and all following graphs the Iapp1 value is fixed at 12 and Iapp2 varies. Probability of cell 5 firing is on the y axis and the Iapp2 value is on the x axis. Here the sigma is 0.05. 10 10.5 11 11.5 12 12.5 13 13.5 14 0.2 0.4 0.6 0.8 1 1.2 1.4 Here the probability forms a linear relationship with the difference in value between Iapp1 and Iapp2. As Iapp2 gets larger the probability of having cell 5 fire grows larger....
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neurohw6 - Neuro Homework-1. For reasonable Iapp ranges...

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