Upper bound on activity creation date in SOAP API?

http://developers.marketo.com/documentation/soap/getleadchanges/ supports a filtering for activties created after a certain date using activityCreatedAt. Is there a way to filter for activiites created before a certain date?

I believe it is possilbe to filter both after and before creation time for leads using latestCreatedAt and oldestCreatedAt.

Thanks!