(a) The Secretary may pay the expenses (other than membership fees) of persons described in sections 7306 and 7401(1) of this title (including persons in positions described in section 7401(1) of this title who are appointed on a temporary full-time basis or a part-time basis under section 7405 of this title) who are detailed by the Under Secretary for Health to attend meetings of associations for the promotion of medical and related science.

(b)

(1) The Secretary may prescribe regulations establishing conditions under which officers and employees of the Administration who are nationally recognized principal investigators in medical research may be permitted to accept payment, in cash or in kind, from non-Federal agencies, organizations, and individuals for travel and such reasonable subsistence expenses as are approved by the Secretary pursuant to such regulations—

(A) in connection with their attendance at meetings or in performing advisory services concerned with the functions or activities of the Department; or

(B) in connection with acceptance of significant awards or with activity related thereto concerned with functions or activities of the Department.

(2) Any such payment may be retained by such officers and employees to cover the cost of such expenses or shall be deposited to the credit of the appropriation from which the cost of such expenses is paid, as may be provided in such regulations.