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