specgram of EEG data

Hi John (and others),

I'm working with EEG data and want to use a specgram similar to what you
have in the example at the bottom of


I'm working with data sampled at 500Hz but as you would know we're more
interested in the 0-50Hz range. Is the some way to get the specgram()
function to only show up a particular frequency range rather than
downsampling the data to a lower sampling rate? I'm currently plotting

    specgram(data, Fs=500)

but I'm not too sure where to go from here to achieve my aims.

Thanks in advance and for putting together an amazingly useful package.

Tim Leslie