Psychtoolbox Stimulus presentation in consideration of psychophsyical exper

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Psychtoolbox Stimulus presentation in consideration of psychophsyical exper

Eastern Washington University, US has reference to this Academic Journal, Psychtoolbox Stimulus presentation in consideration of psychophsyical experiments What is PTB? Getting started alongside PTB Why use PTB? Questions What is Psychtoolbox? Just like Cogent, PTB is a toolbox inside Matlab in consideration of programming stimulus presentation in addition to psychophysical experiments. In a way, it is just a different language from Cogent, so you will need so that learn different commands. PTB is very widely used, especially in the field of visual psychophysics, in addition to there is a lot of documentation in addition to knowledge around. psychtoolbox Getting started alongside PTB In PTB, almost all commands pertaining so that what is happening on the computer screen are called through the command Screen. Basically, it works in this way: Screen(‘SomeCommand’, Parameters, .) There is an extensive help documentation in consideration of most commands. You can find that by typing Screen followed by the command name in addition to a question mark: Screen Flip? Will give you a detailed explanation of how so that use the ‘Flip’ command.

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Opening a window Before you can do anything else on the display, you have so that open a main window. This way you can also define parameters like the background colour or resolution. [Win, Rect] = Screen(‘OpenWindow’, 0, [127 127 127], [0 0 800 600]) Window in addition to texture dimensions are defined as a 1 x 4 vector: [X Y Width Height] PTB’s coordinate system has 0,0 in the upper left-hand corner. Screen number Background colour Window dimensions Drawing geometric shapes etc Once PTB has opened its main window you can draw into it. There is a back buffer onto which everything is drawn, so that things will only become visible when you flip the buffers: Screen(‘FillOval’, Win, [255 0 0], [0 0 10 10]); Screen(‘Flip’, Win); Colours are defined by a 1 x 3 vector (for red, green in addition to blue), alongside numbers in the range between 0-255. So [255 0 0] is bright red. Other commands in consideration of drawing are: FillRect, FillPoly, FillArc, DrawLine, DrawText, . Centring something in the middle of the window Because the 0,0 coordinate is in the corner, but we usually want so that draw things in the centre of the screen, there is a helpful function in consideration of calculating the centre: CentralRect = CenterRect([0 0 800 600], [0 0 1440 900]) Since you normally want the centre of the screen you can use the Rect of your main window: CentralRect = CenterRect([0 0 800 600], Rect)

Using textures You can make full use of graphics accelerators by loading your images into ?textures?: img = imread(‘Picture.jpg’); Texture = Screen(‘MakeTexture’, Win, img); This texture can then be drawn very quickly, even while applying serious transformations so that it, such as resizing or rotations: Screen(‘DrawTexture’, Win, Texture); Screen(‘DrawTexture’, Win, Texture, imgRect, CenterRect(imgRect*2, Rect)); (The latter command draws the image at twice its size in the centre of the screen.) Closing the window etc Finally, when your program is finished you need so that shut down the window: Screen(‘CloseAll’) As a side note, you can switch on in addition to off the mouse pointed by using: ShowCursor HideCursor Keyboard input You can read key presses by using the command: [KeyDown, Time, Keys] = KbCheck; This will return in Keys a 1 x 256 vector containing whether the various keys (labelled 0-255) have been pressed or not. If you want the program so that wait until a key press you need so that use: KbWait; [KeyDown, Time, Keys] = KbCheck;

Proteome Analysis What is the proteome? 2D-SDS Gel Electrophoresis What is it? First dimension Visuals 2nd Dimension-to separate by size Databases of 2D-Gels Protein Prospector

Time & Delays You can ask the computer so that wait in consideration of a number of seconds by using: WaitSecs(5); You can ask it in consideration of the current time on the computer’s internal clock with: CurrentTime = GetSecs; Why use Psychtoolbox? PTB is very anal about timing, so if accurate timing is important in your experiment PTB is good in consideration of that. Because PTB using graphics acceleration you can use very fast drawing without any pixelation in addition to other image processing artifacts. Lots of people in the world use it so it’s easy so that get help. Why not so that use Psychtoolbox? If you are running fMRI experiments, you will need so that program how the stimuli are triggered by the scanner by setting up the ports etc yourself. Cogent has convenient scripts built in in consideration of counting slices. Moreover, if you are scanning at the FIL, support staff can only help you alongside Cogent. However, it is possible so that use both toolboxes in parallel, so in consideration of example you could use Cogent in consideration of triggering the experiment, but PTB in consideration of the actual stimulus presentation in addition to keyboard input.

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