Worked on pointprocess exercises
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@ -103,6 +103,7 @@ jan.benda@uni-tuebingen.de}
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\begin{solution}
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\begin{lstlisting}
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clear all
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% not so good:
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load poisson.mat
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whos
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poissonspikes = spikes;
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@ -111,6 +112,14 @@ jan.benda@uni-tuebingen.de}
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load lifadapt.mat;
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lifadaptspikes = spikes;
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clear spikes;
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% better:
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clear all
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x = load( 'poisson.mat' );
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poissonspikes = x.spikes;
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x = load( pifou.mat' );
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pifouspikes = x.spikes;
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x = load( 'lifadapt.mat' );
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lifadaptspikes = x.spikes;
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\end{lstlisting}
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\end{solution}
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@ -11,11 +11,11 @@
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\usepackage[left=20mm,right=20mm,top=25mm,bottom=25mm]{geometry}
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\pagestyle{headandfoot}
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\ifprintanswers
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\newcommand{\stitle}{: L\"osungen}
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\newcommand{\stitle}{L\"osungen}
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\else
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\newcommand{\stitle}{}
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\newcommand{\stitle}{\"Ubung}
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\fi
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\header{{\bfseries\large \"Ubung 6\stitle}}{{\bfseries\large Statistik}}{{\bfseries\large 27. Oktober, 2015}}
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\header{{\bfseries\large \stitle}}{{\bfseries\large Punktprozesse 2}}{{\bfseries\large 27. Oktober, 2015}}
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\firstpagefooter{Prof. Dr. Jan Benda}{Phone: 29 74573}{Email:
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jan.benda@uni-tuebingen.de}
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\runningfooter{}{\thepage}{}
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@ -89,26 +89,27 @@ jan.benda@uni-tuebingen.de}
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\begin{questions}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\question \qt{Homogeneous Poisson process}
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We use the Poisson process to generate spike trains on which we can test and imrpove some
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standard analysis functions.
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A homogeneous Poisson process of rate $\lambda$ (measured in Hertz) is a point process
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where the probability of an event is independent of time $t$ and independent of previous events.
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The probability $P$ of an event within a bin of width $\Delta t$ is
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\question \qt{Homogener Poisson Prozess}
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Wir wollen den homogenen Poisson Prozess benutzen um Spikes zu generieren,
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mit denen wir die Analysfunktionen des vorherigen \"Ubungszettel \"uberpr\"ufen k\"onnen.
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Ein homogener Poisson Prozess mit der Rate $\lambda$ (measured in Hertz) ist ein Punktprozess,
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bei dem die Wahrschienlichkeit eines Ereignisses unabh\"angig von der Zeit $t$ und
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unabh\"angig von vorherigen Ereignissen ist.
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Die Wahrscheinlichkeit $P$ eines Ereignisses innerhalb eines Bins der Breite $\Delta t$ ist
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\[ P = \lambda \cdot \Delta t \]
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for sufficiently small $\Delta t$.
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f\"ur gen\"ugend kleine $\Delta t$.
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\begin{parts}
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\part Write a function that generates $n$ homogeneous Poisson spike trains of a given duration $T_{max}$
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with rate $\lambda$.
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\part Schreibe eine Funktion die $n$ homogene Poisson Spiketrains
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einer gegebenen Dauer $T_{max}$ mit rate $\lambda$ erzeugt.
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\begin{solution}
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\lstinputlisting{hompoissonspikes.m}
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\end{solution}
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\part Using this function, generate a few trials and display them in a raster plot.
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\part Benutze diese Funktion um einige Trials von Spikes zu erzeugen
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und plotte diese als Spikeraster.
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\begin{solution}
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\lstinputlisting{../code/spikeraster.m}
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\begin{lstlisting}
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spikes = hompoissonspikes( 10, 100.0, 0.5 );
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spikeraster( spikes )
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@ -117,41 +118,31 @@ for sufficiently small $\Delta t$.
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\colorbox{white}{\includegraphics[width=0.7\textwidth]{poissonraster100hz}}
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\end{solution}
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\part Write a function that extracts a single vector of interspike intervals
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from the spike times returned by the first function.
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\begin{solution}
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\lstinputlisting{../code/isis.m}
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\end{solution}
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\part Write a function that plots the interspike-interval histogram
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from a vector of interspike intervals. The function should also
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compute the mean, the standard deviation, and the CV of the intervals
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and display the values in the plot.
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\begin{solution}
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\lstinputlisting{../code/isihist.m}
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\end{solution}
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\part Compute histograms for Poisson spike trains with rate
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$\lambda=100$\,Hz. Play around with $T_{max}$ and $n$ and the bin width
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(start with 1\,ms) of the histogram.
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How many
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interspike intervals do you approximately need to get a ``nice''
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histogram? How long do you need to record from the neuron?
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\part Berechne Histogramme aus den Interspikeintervallen von $n$
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Poisson Spiketrains mit der Rate $\lambda=100$\,Hz. Ver\"andere
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\"uber die Dauer $T_{max}$ der Spiketrains und die Anzahl $n$ der
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Trials die Anzahl der Intervalle und ver\"andere auch die Binbreite
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des Histograms (fange mit 1\,ms an). Wieviele Interspikeintervalle
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werden ben\"otigt um ein ``sch\"ones'' Histogramm zu erhalten? Wie
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lange m\"usste man also von dem Neuron ableiten?
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\begin{solution}
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About 5000 intervals for 25 bins. This corresponds to a $5000 / 100\,\hertz = 50\,\second$ recording
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of a neuron firing with 100\,\hertz.
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About 5000 intervals for 25 bins. This corresponds to a $5000 /
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100\,\hertz = 50\,\second$ recording of a neuron firing with
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100\,\hertz.
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\end{solution}
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\part Compare the histogram with the true distribution of intervals $T$ of the Poisson process
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\part Vergleiche das Histogramm mit der zu erwartenden Verteilung
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der Intervalle $T$ des Poisson Prozesses
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\[ p(T) = \lambda e^{-\lambda T} \]
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for various rates $\lambda$.
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mit rate $\lambda$.
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\begin{solution}
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\lstinputlisting{hompoissonisih.m}
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\colorbox{white}{\includegraphics[width=0.48\textwidth]{poissonisih100hz}}
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\colorbox{white}{\includegraphics[width=0.48\textwidth]{poissonisih20hz}}
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\end{solution}
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\part What happens if you make the bin width of the histogram smaller than $\Delta t$
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\part \extra Was pasiert mit den Histogrammen, wenn die Binbreite der Histogramme kleiner
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als das bei der Erzeugung der $\Delta t$ der
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used for generating the Poisson spikes?
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\begin{solution}
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The bins between the discretization have zero entries. Therefore
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