I'd go with a week of 'tempo', it takes more than 4 weeks to really lose a solid base and then build on some intensity again. For me personally I find it harder to get my head back into shape after a crash, especially if it was a nasty one - the fear of crashing again in a race can have more effect on your performance than physical fitness - depends on yopur mental make-up I guess.
I'd recommend low intensity rides (zones 2 and 3 if you have a Heart Rate Monitor) whilst at the same time concentrating on improving your technique on the bike. Are you pedelling in circles? Is your pedal stroke even? Are you keeping a good even cadence?
Focusing on the above will help in getting your head back into cycling and off the negative thoughts of the crash!