Hello list,
attached is my first post plus my new questions underneath every paragraph. thanks.
I'm new to optseq, and would like your help with the following issues:
- What exactly does DPSD mean? and why does the TR has to be an
integer of it?
Doug: Delta Post-Stimulus Delay. The time between samples in the FIR. Usually, it is just the TR. If you want to do sub-TR estimation, you can make it less than the TR. It has to be an integer divisor of the TR because it forms the basic "tick" of the clock.
Asaf: I'm afraid i didn't get the explanation. what is the FIR, and what
are the the samples in it ?
- My experiment design uses jitter - both ITI (i.e., between
trials) and ISI (i.e., between stimulus within a compound event). As i understood, optseq can only supply me with the ITI jitter but no the ISI jitter. is that right? do you happen to know a computerized method to introduce a jitter within a compound event?
Doug: That is right. Sorry, don't know of anything that will give you with-in event jitter.
Asaf: ok, thanks. isn't it strange though? how do researches jitter the
ISI than? manually?
- Is it true that jitter in optseq is made by inserting "NULLS",
and that the DPSD determines the "steps" of the jitter (for e.g., if DPSD equals 1, Nullmin equals 2 and Nullmax equals 4, the NULL events will be 2 3 or 4). Did i understand it right?
Doug: Yes.
Asaf: thanks.
hope all is clearer now, Asaf.
________________________________ From: Douglas N Greve greve@nmr.mgh.harvard.edu To: Asaf Kaftory asaf_kaftory@yahoo.com Cc: freesurfer@nmr.mgh.harvard.edu Sent: Tue, October 6, 2009 6:16:37 PM Subject: Re: [Freesurfer] optseq2 help: DPSD and jitter
I don't know what "two samples" refers to.
doug
Asaf Kaftory wrote:
Hey Doug - first of all, thanks for the reply. second -
- I'm afraid i didn't get the explanation. what is the FIR, and what
does it mean "two samples in the FIR" ?
- ok, thanks. isn't it strange though? how do researches jitter the
ISI than? manually?
- thanks.
*From:* Doug Greve greve@nmr.mgh.harvard.edu *To:* Asaf Kaftory asaf_kaftory@yahoo.com *Cc:* freesurfer@nmr.mgh.harvard.edu *Sent:* Saturday, September 26, 2009 7:42:43 PM *Subject:* Re: [Freesurfer] optseq2 help: DPSD and jitter
On Sat, 26 Sep 2009, Asaf Kaftory wrote:
Hello list,
I'm new to optseq, and would like your help with the following issues:
- What exactly does DPSD mean? and why does the TR has to be an
integer of it?
Delta Post-Stimulus Delay. The time between samples in the FIR. Usually, it is just the TR. If you want to do sub-TR estimation, you can make it less than the TR. It has to be an integer divisor of the TR because it forms the basic "tick" of the clock.
- My experiment design uses jitter - both ITI (i.e., between
trials) and ISI (i.e., between stimulus within a compound event). As i understood, optseq can only supply me with the ITI jitter but no the ISI jitter. is that right? do you happen to know a computerized method to introduce a jitter within a compound event?
That is right. Sorry, don't know of anything that will give you with-in event jitter.
- Is it true that jitter in optseq is made by inserting "NULLS",
and that the DPSD determines the "steps" of the jitter (for e.g., if DPSD equals 1, Nullmin equals 2 and Nullmax equals 4, the NULL events will be 2 3 or 4). Did i understand it right?
Yes.
doug
hope to hear from you soon, Asaf.
-- Douglas N. Greve, Ph.D. MGH-NMR Center greve@nmr.mgh.harvard.edu mailto:greve@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422
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