diff --git a/projects/project_face_selectivity/Makefile b/projects/project_face_selectivity/Makefile new file mode 100644 index 0000000..a7b3726 --- /dev/null +++ b/projects/project_face_selectivity/Makefile @@ -0,0 +1,3 @@ +ZIPFILES= + +include ../project.mk diff --git a/projects/project_face_selectivity/auto/face_selectivity.el b/projects/project_face_selectivity/auto/face_selectivity.el new file mode 100644 index 0000000..0e5be37 --- /dev/null +++ b/projects/project_face_selectivity/auto/face_selectivity.el @@ -0,0 +1,15 @@ +(TeX-add-style-hook + "face_selectivity" + (lambda () + (TeX-add-to-alist 'LaTeX-provided-class-options + '(("exam" "a4paper" "12pt" "pdftex"))) + (TeX-run-style-hooks + "latex2e" + "../header" + "../instructions" + "exam" + "exam12") + (TeX-add-symbols + "ptitle")) + :latex) + diff --git a/projects/project_face_selectivity/face_selectivity.tex b/projects/project_face_selectivity/face_selectivity.tex new file mode 100644 index 0000000..b6ff677 --- /dev/null +++ b/projects/project_face_selectivity/face_selectivity.tex @@ -0,0 +1,127 @@ +\documentclass[a4paper,12pt,pdftex]{exam} + +\newcommand{\ptitle}{Face-selectivity index} +\input{../header.tex} +\firstpagefooter{Supervisor: Marius G\"orner}{}% +{email: marius.goerner@uni-tuebingen.de} + +\begin{document} + +\input{../instructions.tex} + + +%%%%%%%%%%%%%% Questions %%%%%%%%%%%%%%%%%%%%%%%%% +\section{Estimating the face-selectivity index (FSI) of neurons} + + + +In the temporal lobe of primates you can find neurons that respond +selectively to a certain type of object category. You may have heard +stories about the famous grandmother neurons which are supposed to +respond exclusively when the subject perceives a particular +person. Even though the existence of a grandmother neuron in the +strict sense is implausible, the concept exemplifies the observation +that sensory neurons within the ventral visual stream are tuned to +certain stimuli types. One of the most important and first visual +stimulus the newborn typically perceives is the mother's face. It is +believed that the early ubiquity of faces and their importance for +social interactions triggers the development of the so called +face-patch system within the temporal lobe of primates.\par +Your task here will be to estimate the \textit{selectivity index} +($SI$) of neurons that were recorded in the superior temporal sulcus +of a rhesus monkey during the visual presentation of objects of different +categories. + + +\begin{questions} +\question + In the accompanying datasets you find the + \texttt{spiketimes} of 184 neurons that were recorded during the visual + presentation of non-face like stimuli (tools, fruits, hands and + bodies) and averted and directed faces of humans and rhesus + monkeys. Each \texttt{.mat}-file contains the data of one neuron + which was recorded during multiple trials. Spike times are given in + ms relative to trial onset. Each trial consists of 400 ms of + baseline recording (presentation of white noise) followed by 400 ms + of stimulus presentation. Each trial belongs to one object category, + trial identities can be found in the \texttt{*\_trials}-fields + (9 fields). + + \begin{parts} + \part + Illustrate the spiking activity of all neurons, sorted by object + category, in a raster plot. As a result you should get one plot + for each neuron subdevided in subplots for the different + categories. Mind that there are four categories that contain faces + (\texttt{averted\_human}, \texttt{face} (straight human face), + \texttt{monkey} (straight monkey face) and \texttt{gaze\_monkey}), + you may want to analyze them separately as well combined. Add also + a marker where the stimulus starts. + + \part + Estimate the time-resolved firing rate of each neuron for each + object category. Use at least two different methods + (e.g. instantaneous firing rate based on interspike intervals, + spike counting within bins (PSTH), kernel density estimation). Do + this individually for each trial and average afterwards in order + to obtain the standard deviation of the firing rates. Plot the + firing rates and their standard deviations on top of the raster + plots. Which of the methods appears to be a better representation + of the spike rasters? + + \part + Generate figures that show for each neuron the firing rates + belonging to each object category. Don't forget to add an + appropriate legend. + + \part + Next step is to examine the obtained firing rates for significant + modulations. + % First, normalize each response to baseline activity + % (first 400 ms). Why is the normalization useful? + % \par + Now, determine the periods within which the neurons activity + deviates from the baseline activity at least by $2*\sigma$. Do + this for each object category and mark the periods in the plots in + an appropriate way. Are there also inhibitory responses? \par + Describe qualitatively the response properties (phasic, tonic, are + there differences between neurons and/or stimulus categories?). + + \part + The $SI$ gives an estimate of how strong a neuron is tuned to the + chosen object categories. It is given by the neurons response + during the presentation of the one category compared to the other + category. + \begin{equation} + SI = \frac{ \mu_{\text{Response to category A}} - \mu_{ \text{Response + to category B}} } { \mu_{\text{Response to category A}} + \mu_{ \text{Response + to category B} } } + \end{equation} + $SI$ can take values between -1 and 1 which indicates tuning to + the one or to the other category. There are different + possibilities of how it can be estimated. The easiest way would be + to average the spike count during the whole time of stimulus + presentation. However, if responses are phasic you will + underestimate the $SI$. Therefor, you should limit the estimate to + periods of significant modulations. Use the periods determined in + (d). Store all obtained $SI$s within one variable. We are mainly + interested to identify face-selective neurons but feel free to test + the neurons for selectivity to other categories, as well. + + \part + Plot the distribution of $SI$ values and describe it + qualitatively. Does it indicate a continuum or a distinct + population of face-selective neurons. \par + Think about a statistical test that tells you whether a given + neuron is significantly modulated by one or the other category + (try different combinations of categories). List cells that show + significant modulation to faces and non-faces. Which is the + minimum SI that reaches significance when choosing + $\alpha = 0.05$? Is it an all or nothing selectivity? + + \end{parts} +\end{questions} + + + +\end{document}