diff --git a/spike_trains/exercises/psth.tex b/spike_trains/exercises/psth.tex
index a4c3804..a662af7 100644
--- a/spike_trains/exercises/psth.tex
+++ b/spike_trains/exercises/psth.tex
@@ -14,7 +14,7 @@
 %%%%% text size %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \usepackage[left=20mm,right=20mm,top=25mm,bottom=25mm]{geometry}
 \pagestyle{headandfoot} \header{{\bfseries\large Exercise
-    }}{{\bfseries\large Time-dependent firing rate}}{{\bfseries\large December, 04, 2018}}
+    }}{{\bfseries\large Time-dependent firing rate}}{{\bfseries\large January, 14, 2020}}
 \firstpagefooter{Dr. Jan Grewe}{Phone: 29 74588}{Email:
   jan.grewe@uni-tuebingen.de} \runningfooter{}{\thepage}{}
 
@@ -38,23 +38,23 @@
 
 \begin{questions}
   \question Plot the time-dependent firing rate of a neuron. Calculate
-  the firing rate from the instantaneous firing rate (based on the
+  the firing rate from the \emph{instantaneous firing rate} (based on the
   interspike interval). Use the \code{lifoustim.mat}. The dataset
   contains three variables. 1st the spike times in different trials,
-  2nd the stimulus, and 3rd the temporal resolution. The total
+  2nd the stimulus, and 3rd the temporal resolution of the recording. The total
   duration of each trial is 30 seconds.
 
   \begin{parts}
     \part{} Write a function that takes three arguments: the spike
     times of a single trial, the trial duration and the temporal
-    resolution.  The function should return the time values and the
-    firing rate in $Hz$.
+    resolution. The function should return two variables: the time axis and the
+    time-dependent firing rate.
     \part{} Write a script that applies the above function to estimate
-    the firing rate of each trial. Plot a single individual responses
-    and the average response as a function of time into the same plot.
-    \part{} Extend your program that it saves the figure with the width of 8.5\,cm using a fontsize of 10\,pt for labels.
-    See Chapter 3 in the script, or browse the Matlab help for information.
-    \part{} Store the figure in pdf format.
+    the time-dependent firing rate of each trial. Plot the firing rates of the individual responses
+    and the average response as a function of time into the same graph.
+    \part{} Extend your program that it saves the figure with the width and height of 8.5\,cm using a fontsize of 10\,pt for labels.
+    See Chapter 3 in the script, or browse the Matlab help for more
+    information. Store the figure in pdf format.
   \end{parts}
 
   \question{} As before but use the binning method.
@@ -65,11 +65,11 @@
 
   \question{} Some trials are different than the others.
   \begin{parts}
-    \part{} Use the rasterplot to identify them. In which sense
+    \part{} Use a rasterplot to identify them. In which sense
     are they different? Save the rasterplot in pdf
-    format. Use the same size as above and make sure it is properly labeled.
-    \part{} Identify the trials in which the spike count
-    deviates more than $2\sigma$ from the average.
+    format. Use the same figure specifications as above and make sure it is properly labeled.
+    \part{} Identify those trials in which the spike count
+    deviates more than $2\sigma$ (twice the standard deviation) from the average.
   \end{parts}
 \end{questions}