When you are saving an Illustrator brush as a scatter brush you will have the options of editing how the brush behaves, from a panel that looks like the one below. The way I tend to do this is to create a circle or curve and apply the illustrator scatter brush to it, then double click on the chosen brush from the main brushes menu, and up pops this panel.

There's a preview box, if you tick that then you can see how altering the settings applies to the artwork on screen.