EPrime Day 1

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E-Prime Day 1

• August 17, 2001

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Lets run an E Experiment

• Double click
• IFIS_Experiments\Cognitive\Cognitive.es

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IFIS vs. E

• E-prime is the development software
• IFIS lets E-prime communicate with the scanner.
• What do you get from IFIS?
• Button response units (BRUs)
• Feedback to experimenters on subject performance
• Scanner can trigger start of experiment
• Better control of timing (Periods / Blocks to
  keep your experiments on time

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What you will learn

• How to navigate the E GUI (graphical user
  interface)
• How to build an experiment from scratch in the
  GUI
• How to build an IFIS experiment
• How to add some functionality (that you couldnt
  otherwise get) with scripting
• Key tips on what to do and what not to do.

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The Most Important Slide

• Start with fMRI_Base
• Use the OLD SYSTEM (e beta5 and IFIS R1.0.9.0)
• Pay attention to cumulative vs. event timing
• Set the BRUs to Unique if you use both hands
• Use the Period / Block functionality in IFIS to
  keep timing accurate
• In Beta5, make short experiments or different
  files for each run (some scripts are too long to
  compile).
• Re-use the same objects in your script (drag from
  one procedure to another) if you can.
• Save multiple copies of your script at different
  points
• Check the experiment and data file before running
  for real

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Lets run another E Experiment

• Double click
• IFIS_Experiments\FMRIBase\FMRIbase.es
• IFIS_Experiments\FMRIBase\tor_FMRIbase.es

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E-Prime
This is a diagram of E-Primes core system
components.
E-Studio
E-Basic
E-Run
Real-Time Experiment Generator
Graphical Design Environment
Full Scripting Language
E-Merge
Data Merging Utility
E-DataAid
Spreadsheet Application for E-Prime Data
Files
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E-Studio - Interface
The E-Studio interface has four major
components 1.Toolbox 2. Structure View 3.
Properties Window 4. Workspace
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1
4
3
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E-Studio - Interface
The Toolbox contains objects that are dragged to
procedural timelines. These objects are the
basic building blocks of your E-Studio
experiments.
1
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E-Studio - Interface
The TextDisplay allows you to specify text, such
as instructions, that the subject will see during
the experiment.
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E-Studio - Interface
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The Structure View is an outline or hierarchical
representation of your experiment. This window
features a tree view similar to that in Windows
Explorer.
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E-Studio - Interface
The Properties Window lists the properties for
selected objects and displays their current
settings. This feature is similar to that in
Visual Basic.
3
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E-Studio - Interface
The Workspace contains the window representations
of your experiment objects. An object is opened
in the Workspace by double clicking the object on
a procedural timeline or in the Structure View.
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E-Run
The Run button on the E-Studio toolbar allows you
to compile and execute an opened experiment in
E-Studio.
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E-Basic
This is the finished script in E-Studios Script
Window. The Script Window is displayed via the
Script command under E-Studios View menu.
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Structure of an IFIS Experiment
Session
Run
Block
Block
Period
Trial
Event
Event
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Three Ways to Build an IFIS Experiment

• Use IFIS Wizard to generate an experiment
  status Need IFIS machine with new ISM server
• Use one of the fMRI standard experiments and
  extend it
• fMRIBase, Retinal Mapping, Language Mapping,
  Motor Mapping, Emotional Images, Retinal Event
  Use fMRIBase
• Structure an experiment at the Block, Trial and
  Event level and add the IFIS objects Problems
  doing this in Beta5 Start with fMRIBase

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Tutorial IWell start by building a simple
e-prime experiment.
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Exercise 1 Conceptualize and implement the core
experimental procedure
Sample Abstract The experiment will measure the
time to make a lexical decision. The independent
variable is whether a letter string is a word or
non-word. The stimuli will be text strings of
words and non-words, presented in random order in
black text on a white background. The subject
will be presented with a fixation () displayed
in the center of the screen for one second. Then
a probe display will present a letter string
stimulus in the center of the screen for up to 2
seconds. The stimulus display will terminate
when the subject responds. Subjects are to
respond as quickly as possible as to whether the
stimulus was a word or a non-word by pressing the
1 or 2 key respectively. The dependent
measures are the response (i.e., key pressed),
response time, and response accuracy of the probe
display.
Design
Structure
Displays
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Implementing Lexical Decision

• 1. Open E-Studio
• 2. Choose the Blank Experiment
• 3. Drag and drop a List to the session procedure
  in the structure View, Rename with F2 to
  DesignList

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Specify Stimuli and Trial Events

• 4. Add Attributes of Condition, Stimulus and
  CorrectResponse to DesignList
• 5. Fill in TrialProc, Condition (Word/NonWord),
  stimulus (cat,jop), correct response (1,2)
• 6. Put events into a TrialProc
• 7. Set Fixation text to and Probe to
  Stimulus

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Set Response Processing

• 8. Set the Duration/Input Properties of the
  Probe to
• Duration 2000
• Data Logging Standard
• Add Input Keyboard
• Allowable Input 12
• Correct Input CorrectResponse
• Input Action Terminate

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Running and Saving

• 9. Save file as Lex1
• Save it in
• \My Experiments directory
• 10. Run Lexical Decision
• 11. Run 2 trials

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CHECK Lexical Decision
Specified Structure of experiment Specified a
List with Procedure, Condition, Stimulus and
Correct Response Set display text to
Stimulus Set Duration/Input
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Run Lexical Decision

• Verify that the trial procedure ran as expected
• Could you at this point?
• Increase the number of words/non-words?
• Change the sampling method to random?
• Could you change to a mouse response?
• Change the duration of the display to 4 seconds?
• Change the font color and size?

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Optional Add Feedback

• 1. Add Feedback object after Probe, and open
• 2. Set InputObjectName to Probe
• 2. Click on border
• 3. Select properties
• 4. Enter Probe

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2
1
4
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Run experiment with feedback

• Make both correct and incorrect responses
• Check to be sure you get both reaction and
  accuracy feedback
• At this point, could you
• Change the text of the correct message
• Delete the average percent correct display

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Tutorial II

• IFIS_Experiments\Tutorials\Tutorial2.pdf

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IFIS Paradigm Timing Parameters
RunDuration (ms) (computed value)
NrOfPreTaskVolumes (auto NrOfDiscardedVolumes
NrOfVolumesToSkip)
NrOfPostTaskVolumes
Block(s)
IFIS Intervals
Stimuli
Scanner
VolumeDuration (computed value)
NrOfDiscardedVolumes (recommend zero)
NrOfVolumesToSkip
NrOfVolumes
Scanner Data
fMRI Data to be Analyzed
BlockEnd
RunBegin
RunEnd
Start of Session
BlockBegin
RFP.LastPulseTime ms
RFP.StartTime ms
Revision 12 08/08/02
Zero Time in TDAT File
RFP.Total ms
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Advanced E-Prime and IFIS
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Timing in E-Prime
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E-Prime Timing Precision
Executive Summary of E-Prime Timing E-Prime can
provide millisecond precision timing (see
operational definition) on machines above 120 MHz
class. E-Prime uses a microsecond precision
clock for all time assessment. The most serious
problem with maintaining millisecond precision is
that the operating system will take over control
of the computer occasionally blocking E-Prime
(and any other program) from reading the clock.
E-Prime minimizes the quantity and duration of
such events by running at high priority and
structuring of the program to minimize
interruptions and virtual memory swaps. With a
well a configured system the probability of
missing a millisecond tick of the clock is small
(typically less than 0.05). Rare short duration
(lt5 ms) missed clock ticks have negligible impact
in most experiments (e.g., equal to running 1
extra trial per 22,500 trials). E-Prime provides
data logging to identify errors and if desired
the researcher can exclude those trials from
analysis.
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Testing your computers timing precision
We provide a test program to assess timing
precision on your specific computer.
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Technique 1 Utilizing Pre-release Time
Pre-release, allow the next command to prepare
the stimulus while the current command is being
displayed.
Stimulus Onset Time Sequential
Stimulus 1 2 3 4 Expected time 0
preparation 0 100 200 300 Time with
preparation 30 160 290 420 Time with
pre-release preparation 30 130 230 330
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Technique 3 Event Cumulative Mode Timing
Event Mode Timing make the timing from stimulus
onset to offset to be the specified duration
allowing interstimulus interval and cumulative
error to increase. Cumulative Mode Timing Time
from onset to next onset is maintained and
duration is reduced if necessary.
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Technique 4 Logging millisecond time-stamp of
all actions
OnsetTime milliseconds since the start of the
experiment when the event occurred OnsetDelay
milliseconds from the intended time to the actual
time of the start of the event DurationError
difference of the intended duration relative to
the actual duration before the command
ended ActionTime Time of completion of action
The Onset Time is used to communicate with the
IFIS data stream the actual time of the event, to
allow time synching of the behavioral and imaging
data streams.
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Technique 6 Rescaling Clocks To Match Precision
Typically crystal clocks are accurate to 99.9.
However, in an fMRI experiment a 0.1 difference
between the behavioral computer and the imaging
computer can cause cumulative errors in timing
(e.g., 360 ms after 6 minutes of
scanning). E-Prime allows rescaling of the
clock such that E-Prime can rescale to the
scanner clock with 15 digits of precision. This
is done by comparing the timing of the recorded
RF pulses to the observed pulses and rescaling
the clock
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Technique 7 Caching images to speed execution
By preloading images, displays can be altered on
single refreshes. This allows rapid change
display experiments (e.g., rotating
checkerboards).
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Writing Code in E-Prime
E-Basic is a full programming language with over
300 standard Visual Basic for Applications (VBA)
commands and over 100 special commands for
behavioral research experimentation. The
majority of programs can be written with little
or no user written code (e.g., typically less
than 2). However, the ability to add a little
code allows users to extend the system to cover a
wider range of complex experiments. To learn
VBA for E-Prime, read the Using E-Basic chapter,
use the E-Basic help functions, and perhaps read
some of the standard E-Basic books available For
the novice user who has little to no programming
experience and for those new to VBA type
languages VBA for Dummies, Steve Cummings, IDG
Books Worldwide, Inc., Foster City, CA, 1998. For
more advanced users with substantial programming
experience VBA Developer's Handbook, Ken Getz
Mike Gilbert, Sybex Inc., San Francisco, CA, 1997
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Use of VB Online Help
Locating a command
Sample Online Help
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Code Example 1 Use of Code to Set a Property
Simple example of adding code to display the
stimuli in a random circle.
Load in the example CodeExample to illustrate
each of these points.
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Code Example 2. Use of Code to Set the Stimulus
Conditional on a List Attribute
This example uses the Condition variable to set
the Stim variable to a random number and the
Resp variable to the expected key. Note the
Case Else to catch experimenter coding errors.
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Code Example 3. Use of code to provide cumulative
data about the trial number to the subject
Code that maintains static variables typically
must be declared in the User script, initiated in
the beginning of the experiment, and updated
during the trial procedure.
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Tutorial III

• Walkthrough and debugging
• IFIS_Experiments\FMRIBase\tor_FMRIBase.es

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Instructions For Use

• These instructions specify how to generate slides
  from PowerPoint for use in E-Prime.
• Design the slides using a screen size of 8.89
  wide by 6.67 inches for 640x480 displays.
• PowerPoint outputs slides to bitmaps at 72 points
  per inch and this gives the correct bitmap size.
• Save the PowerPoint File
• Select Save As from the File menu
• Set the File Type to be Save as Device
  Independent Bitmap (.bmp)
• Choose a name for your slide set, e.g. German
• When asked to save every slide as a separate file
  say yes
• Slides will be saved in the folder you specified
  in order as Slide1.bmp, Slide2.bmp, Slide3.bmp,
  , SlideN.bmp
• After generation you may need to rename your
  image files to match the filenames used within
  the associated paradigm.

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The Most Important Slide

• Start with fMRI_Base
• Use the OLD SYSTEM (e beta5 and IFIS R1.0.9.0)
• Pay attention to cumulative vs. event timing
• Set the BRUs to Unique if you use both hands
• Use the Period / Block functionality in IFIS to
  keep timing accurate
• In Beta5, make short experiments or different
  files for each run (some scripts are too long to
  compile).
• Re-use the same objects in your script (drag from
  one procedure to another) if you can.
• Save multiple copies of your script at different
  points
• Check the experiment and data file before running
  for real

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Thank you!