Hi,
It looks like your highpass filter is too aggressive and is causing
this problem. Make your cut-off period (in seconds) longer and
it should avoid this problem. You should be able to see this
effect when you look at your EVs in the design matrix.
All the best,
Mark
On 25 Oct 2010, at 21:05, Jeremy Smith wrote:
> Not sure if this list accepts attachments, so please let me know if
> I need to do it another way.
>
> The green trace in the [hopefully-]attached screenshot should be a
> unitary "lump," rather than two cusps and a "valley."
>
> Regards,
> JLS
>
>
>
>> Hi - I've never seen this and can't think what this might be - can
>> you
>> send in an example?
>> Cheers.
>>
>>
>> On 22 Oct 2010, at 17:17, Jeremy Smith wrote:
>>
>>> I searched the FSL Archives for this, but came up empty-handed.
>>>
>>> We're convolving a simple boxcar vector with a gamma function to
>> create an EV model in first-level FEAT. In the FEAT report, however,
>> the convolved waveform appears to "clip" at the top of the y-axis,
>> such
>> that the peak and a few time points around it get inverted... so
>> instead of a nice "hill" we get two cusps and a "valley." Is this
>> merely a graphing issue, or will it affect our analysis? What can be
>> done about it?
> <Screenshot.png>
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