= Stimulus delivery in the CBU Tim Trio = == Stimulus delivery computers == There are three stimulus delivery computers. All have identical software and receive the scanner trigger pulse and button box responses. '''Software''' The machines run Windows XP. Installed software is Matlab 7, Eprime, Visual Basic, Cogent, DMDX. '''Synchronising with scanner''' DMDX will recognise the signal from the Keithly I/O card. However, since the trigger pulse is of duration 6ms (rather than 50ms as before), you will need to use the keyword in the topline of your script to ensure that DMDX detects trigger pulses reliably. There are more notes on using DMDX [http://www.mrc-cbu.cam.ac.uk/~mattd/fmri_dmdx.html here]. From other environments (Eprime/Matlab/VB), you may use the [http://www.mrc-cbu.cam.ac.uk/~rhodri/vb ScannerSync] library. This allows you to synchronise, and to collect button box responses. == Mimic machine == In the CBU computer user room there is a "CBU mimic" configured exactly as the stimulus delivery machines, and with a pulse generator to simulator the scanner trigger, and a response box. '''You must test your programs thoroughly on the mimic before running any experiment.''' == Pre-testing machine == There is another mimic machine in the imaging centre, which you may use for pre-testing in experiments that require a training session just before the scan. You'll then need to have two experiments attend. '''Visual presentation:''''''''Christie video projector''''' == Visual presentation: Christie video projector == '''Recommended resolution''' 1024x768 '''Refresh rate 60 Hz.''' Please ''do not'' change this parameter. Although the projector will accept inputs up to 100 Hz, it will not actually produce output at these higher rates, but instead, sub-sample down to a rate just above 60 Hz. '''Latency:''' There is a fixed temporal delay between computer refresh and actual display of a little less than 20 ms. If you don't account for this, your RTs are probably around 20 ms shorter than you think they are. '''Size:''' Distance between MRI screen and mid-point of mirror = 823mm Approx distance between eyes and mid-point of mirror ~ 90mm Width of full-screen display on MRI screen = 268mm Width of mirror = 108mm, so the width of a full screen display in the mirror image can be calculated to be 43.5mm. This agrees wih direct measurements of the display image. Given a viewing distance of 90mm and screen resolution of 1024 pixels, 1 degree of visual angle = 37 pixels. == Using DMDX == All machines should contain a small DMDX testscript, which should be used to check the proper functioning of the button box, the headphones and the projection system. There are three video modes available for DMDX: || 1024 * 768 || 16 bit || 0 Hz || || 1024 * 768 || 16 bit || 60 Hz || || 1024 * 768 || 32 bit || 60 Hz || The first mode is only installed for compatibility. It should not be used. The 0 Hz indicates that the 'default' refresh rate is used, which is usually the refresh rate that is set for Windows. This will always be 60 Hz too, so identical to the second mode. But it is still better to explicitly set the refresh rate. People have had trouble with this before, when someone changed the Windows display settings. People do fiddle. The second mode is the one that has always been recommended for most users. The third one will give better colour, so should be used when pictures are being presented. It also has the advantage that it is completely identical to the Windows settings, meaning that there will be no mode switching, which could prevent problems, certainly with flat screens and projectors. So, to summarise, the best mode to use is the last one, which should be specified in your DMDX script like this: {{{ }}} or {{{ }}} Additionally, I would like to repeat the need to use QPIO12 with the current setup, instead of PIO12. {{{ }}} or {{{ }}} == Auditory presentation == === Option 1: Siemens tube phones === For many experiments in the scanner that require sound, but not too much audio fidelity, the built-in Siemens tube phones are sufficient. '''Frequency response''' Sound level set to max on PC and 9 bars on the scanner. Tones at various frequencies were then presented. The levels (in dB SPL) of the primary (H1) and first and second harmonics were: ||'''Freq (Hz)'''||<28%>'''H1'''||<25%>'''H2'''||<28%>'''H3'''|| ||<19%>250||<28%>92.97||<25%>73.86||<28%>74.39|| ||<19%>500||<28%>98.07||<25%>74.34||<28%>65.58|| ||<19%>1000||<28%>98.10||<25%>59.20||<28%>27.16|| ||<19%>2000||<28%>68.61||<25%>32.10||<28%>9.38|| ||<19%>3000||<28%>47.24||<25%>5.0||<28%>15.82|| ||<19%>4000||<28%>49.99||<25%>5.05||<28%>13.53|| ||<19%>6000||<28%>27.88||<25%>11.57||<28%>7.97|| ||<19%>8000||<28%>23.03||<25%>8.50||<28%>7.78|| The full frequency response as measured using periodic noise from a spectrum analyzer: http://www.mrc-cbu.cam.ac.uk/Imaging/siemens_headphones.jpg '''Headphone simulator/pre-emphasis tool ''' Here is a tool that allows you to do two things: (1) approximately simulate what your stimuli will sound like in the scanner (2) pre-emphasise your stimuli, boosting the frequencies that will be reduced by the presentation system ''A new tool for pre-emphasis has been produced by Christopher Long, which does not produce a subtle ringing artefact produced by the previous tool. This is [http://www.mrc-cbu.cam.ac.uk/~chrisl/compfilter.html described here] '' The old tool is described on [http://www.mrc-cbu.cam.ac.uk/~rhodri/headphonesim.htm this page]: === Option 2: Etymotic ER3 === This alternative pneumatic tube presentation system offers higher quality. It is being installed in Mar 2006. '''Frequency response''' Gary Chandler kindly made these measurements: || ||<^ 11% height="20px"> ||<^ 11% height="20px">'''LEFT''' ||<^ 11% height="20px"> ||<^ 11% height="20px"> ||<^ 11% height="20px"> ||<^ 11% height="20px"> ||<^ 11% height="20px">'''RIGHT''' ||<^ 11% height="20px"> || ||<^ 11% height="19px"> ||||<^ 22% height="19px">Amplitude dB SPL ||<^ 11% height="19px"> ||<^ 11% height="19px"> ||<^ 11% height="19px"> ||||<^ 22% height="19px">Amplitude dB SPL ||<^ 11% height="19px"> || ||<^ 11% height="20px">Freq (Hz) ||<^ 11% height="20px">H1 ||<^ 11% height="20px">H2 ||<^ 11% height="20px">H3 ||<^ 11% height="20px"> ||<^ 11% height="20px">Freq (Hz) ||<^ 11% height="20px">H1 ||<^ 11% height="20px">H2 ||<^ 11% height="20px">H3 || ||<^ 11% height="20px">'''250''' ||<^ 11% height="20px">107.42 ||<^ 11% height="20px">32.60 ||<^ 11% height="20px">55.82 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''250''' ||<^ 11% height="20px">106.34 ||<^ 11% height="20px">44.63 ||<^ 11% height="20px">57.80 || ||<^ 11% height="20px">'''500''' ||<^ 11% height="20px">101.45 ||<^ 11% height="20px">47.69 ||<^ 11% height="20px">61.46 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''500''' ||<^ 11% height="20px">100.60 ||<^ 11% height="20px">48.40 ||<^ 11% height="20px">62.30 || ||<^ 11% height="20px">'''1000''' ||<^ 11% height="20px">102.99 ||<^ 11% height="20px">56.90 ||<^ 11% height="20px">53.20 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''1000''' ||<^ 11% height="20px">101.78 ||<^ 11% height="20px">57.40 ||<^ 11% height="20px">53.25 || ||<^ 11% height="20px">'''2000''' ||<^ 11% height="20px">94.66 ||<^ 11% height="20px">61.65 ||<^ 11% height="20px">25.43 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''2000''' ||<^ 11% height="20px">94.20 ||<^ 11% height="20px">61.10 ||<^ 11% height="20px">26.60 || ||<^ 11% height="20px">'''3000''' ||<^ 11% height="20px">90.59 ||<^ 11% height="20px">50.25 ||<^ 11% height="20px">20.10 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''3000''' ||<^ 11% height="20px">90.30 ||<^ 11% height="20px">51.20 ||<^ 11% height="20px">22.95 || ||<^ 11% height="20px">'''4000''' ||<^ 11% height="20px">85.30 ||<^ 11% height="20px">30.40 ||<^ 11% height="20px">2.38 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''4000''' ||<^ 11% height="20px">85.06 ||<^ 11% height="20px">33.50 ||<^ 11% height="20px">2.79 || ||<^ 11% height="20px">'''6000''' ||<^ 11% height="20px">62.82 ||<^ 11% height="20px">20.54 ||<^ 11% height="20px">0.30 ||<^ 11% height="20px"> ||<^ 11% height="20px">'''6000''' ||<^ 11% height="20px">62.27 ||<^ 11% height="20px">18.24 ||<^ 11% height="20px">2.41 || ||<^ 11% height="21px">'''8000''' ||<^ 11% height="21px">45.28 ||<^ 11% height="21px">6.53 ||<^ 11% height="21px">5.90 ||<^ 11% height="21px"> ||<^ 11% height="21px">'''8000''' ||<^ 11% height="21px">47.40 ||<^ 11% height="21px">5.45 ||<^ 11% height="21px">5.04 || '''Headphone simulator/pre-emphasis tool ''' I have made a tool that allows you to do two things: (1) approximately simulate what your stimuli will sound like in the scanner (2) pre-emphasise your stimuli, boosting the frequencies that will be reduced by the presentation system This tool is described on [http://www.mrc-cbu.cam.ac.uk/~rhodri/headphonesim.htm this page] === Option 3: NNL Electrostatic Headphones === If the previous two airtube systems will not satisfy your requirements, there is one other option available, a high quality electrostatic system from Nordic Neuro Labs. This has now passed safety evaluation and is available for use. This system provides high-quality stimulus delivery and is therefore only intended for studies in which optimal presentation of auditory stimuli is essential. Since optimal audio reproduction is not compatible with the use of ear-plugs, the NNL headphones will not attenuate scanner noise as effectively as using the etymotic system in combination with ear defenders. Although using the NNL headphone without earplugs is acceptable it would generally be better to use these with sparse imaging. == Button box == The default box has four buttons designed to be used from one hand or two. == Microphone == We have a Phonar optical noise cancelling microphone that allows clear recordings of spoken responses without much interference from the scanner noise. '''Future plans''' == Future plans == '''Goggles & eye tracking:''' We are investigating a combined goggle presentation system and eye tracker from Nordic Neuro Labs. The current release date for this is July 2006. '''Physiological measurements:''' When required software is installed on our system, we should be able to record cardiac and respiritory information. '''Points of contact''' == Points of contact == Gary Chandler, who set up almost all of this equipment, is the best person to ask if you'd like an update on any changes to the system, or if something doesn't work. If there is a piece of equipment you'd like to see added, please contact Rhodri Cusack or Gary Chandler. If you would like access to the facility to install your programs or test the equipment, please contact Lucille Murby or the radiographers. ''Last updated by Rhodri Cusack and Gary Chandler Feb 2006''