function stimulus = Spatial_Contrast_Adaptation_Stimulus(seed, numframes,switchframe, Nrepeats, meanIntensity)
%
%
%%% Spatial_Contrast_Adaptation_Stimulus %%%
%
%
% This function generate the stimulus that was used to study spatial contrast
% adaptation accompanying dataset of Khani and Gollisch (2017). The dataset is available at:
% https://gin.g-node.org/gollischlab/Khani_and_Gollisch_2017_RGC_spiketrains_for_spatial_contrast_adaptation
%
%
% ===============================Inputs====================================
%
%   seed            :   starting seed for generating random number sequences.
%   numframes       :   number of displayed stimulus frames.
%   switchframe     :   time point of contrast change from high to low and vice versa.
%   Nrepeats        :   number of stimulus trials.
%   meanIntensity   :   mean intensity during the experiment (between 0-1, usually 0.5).
%
%================================Output====================================
%
%   stimulus         :   high and low contrast stimulus sequences for locations X and Y.


% first get the sequence of random numbers
screenstimulus = ran1(seed,2*numframes);    % 2 times number of frame for locations X and Y
% convert the values to binary.
% values > meanintensity are set to 1 (100% contrast).
% values < meanintensity are set to -1 (-100% contrast).
screenstimulus = 2*single(screenstimulus>meanIntensity)-1;
% reshape to separate the values for locations X and Y.
screenstimulus = reshape(screenstimulus,2,[]);

% get screen stimulus per trial
stim_locX = reshape(screenstimulus(1,:),switchframe,Nrepeats)';
stim_locY = reshape(screenstimulus(2,:),switchframe,Nrepeats)';    % location Y is the second seed series

% separate high and low contrast for locations X and Y
stimulus.locX_high      =   stim_locX(2:2:end,:);   % location X, high contrast
stimulus.locX_low       =   stim_locX(1:2:end,:);   % location X, low contrast
stimulus.locY_high      =   stim_locY(2:2:end,:);   % location Y, high contrast
stimulus.locY_low       =   stim_locY(1:2:end,:);   % location Y, low contrast

% match the stimuli sizes
s = min([size(stimulus.locX_high,1),size(stimulus.locX_low,1),size(stimulus.locY_high,1),size(stimulus.locY_low,1)]); 

stimulus.locX_high      =   stimulus.locX_high(1:s,:);
stimulus.locX_low       =   stimulus.locX_low(1:s,:);
stimulus.locY_high      =   stimulus.locY_high(1:s,:);
stimulus.locY_low       =   stimulus.locY_low(1:s,:);

end