Any applicant or other interested person may, within twenty (20) days after the publication of notice of the decision, move the board for a rehearing of the matter by filing an application in the form of a letter addressed to the board containing a brief statement of the grounds relied upon. If the motion is granted by the board, it shall fix a date for rehearing and shall require the moving party to give notice to all persons who participated in the original hearing or hearings, upon such terms as the board may deem adequate. The board may grant a rehearing on its own motion when unusual circumstances so require in the interest of justice.