69 lines
3.0 KiB
TeX
69 lines
3.0 KiB
TeX
\documentclass[a4paper,12pt,pdftex]{exam}
|
|
|
|
\newcommand{\ptitle}{Photoreceptor activity}
|
|
\input{../header.tex}
|
|
\firstpagefooter{Supervisor: Jan Grewe}{phone: 29 74588}%
|
|
{email: jan.grewe@uni-tuebingen.de}
|
|
|
|
\begin{document}
|
|
|
|
\input{../instructions.tex}
|
|
|
|
|
|
%%%%%%%%%%%%%% Questions %%%%%%%%%%%%%%%%%%%%%%%%%
|
|
\section*{Light responses of an insect photoreceptor.}
|
|
Fly R\,1--6 photoreceptors respond to light-on stimuli with graded membrane
|
|
potential changes. In the acompanying datasets you find the membrane
|
|
potential of a single R\,1-6 photoreceptor that was recorded while the receptor was
|
|
stimulated with a light stimulus of different amplitudes.
|
|
|
|
\begin{questions}
|
|
\question{} The accompanying dataset (photoreceptor\_data.zip)
|
|
contains seven mat files. Each of these holds the data from one
|
|
stimulus intensity and contains three variables. (i)
|
|
\textit{voltage} a matrix with the recorded membrane potential from
|
|
10 consecutive trials, (ii) \textit{time} a matrix with the
|
|
time-axis for each trial, and (iii) \textit{trace\_meta} a structure
|
|
that stores several metadata including the \emph{amplitude} value
|
|
that is the voltage used to drive the light stimulus. (Note that
|
|
this voltage is only a proxy for the true light intensity. Twice the
|
|
voltage does not lead to twice the light intensity. Within this
|
|
project, however, you can treat it as if it was the intensity.)
|
|
|
|
\begin{parts}
|
|
\part Create a plot of the raw data. For each light intensity plot
|
|
the individual responses as a function of time.
|
|
|
|
\part Intracellular recordings often suffer from drifts in the resting
|
|
potential. This leads to a large variability in the responses which has technical reasons and is not a cellular
|
|
property. To compensate for such drifts trials usually are aligned to the
|
|
resting potential before stimulus onset.
|
|
Replot the data but with the compensation for the drifts.
|
|
|
|
\part Instead of plotting individual responses plot the average response.
|
|
This plot should also depict the across-trial variability in an appropriate way.
|
|
|
|
\part You will notice that the responses have three main parts, (i) a
|
|
pre-stimulus phase, (ii) the phase in which the light was on, and (iii)
|
|
a post-stimulus phase. The light-on phase can further be devided into two parts, the onset, and the "steady state" response part. Create an characteristic curve that
|
|
plots the response strength as a function of the stimulus
|
|
intensity for ``onset'' and ``steady state''
|
|
phases of the light response.
|
|
|
|
\part The light switches on at time zero. Estimate the delay
|
|
between stimulus and response.
|
|
|
|
\part Analyze the across trial variability in the ``onset'' and
|
|
``steady state''. Check for statistically significant differences.
|
|
|
|
\part The membrane potential shows some fluctuations (noise)
|
|
compare the noise before stimulus onset and in the steady state
|
|
phase of the response.
|
|
|
|
\part (optional) You may also analyze the post-stimulus response
|
|
in some more detail.
|
|
\end{parts}
|
|
\end{questions}
|
|
|
|
\end{document}
|