  title="" class="an ">&ensp;</span>which <span  title="" class="an ">&ensp;</span>underlie <span  title="" class="an ">&ensp;</span>persistent <span  title="" class="an ">&ensp;</span>oscillatory <span  title="" class="an ">&ensp;</span>activity <span  title="" class="an ">&ensp;</span>of <span  title="" class="an ">&ensp;</span>the <span  title="" class="an ">&ensp;</span>respiratory <span  title="" class="an ">&ensp;</span>network <span  title="" class="an ">&ensp;</span>are <span  title="" class="an ">&