<?php if(is_category("collections")) : ?>

/* CONTENT FOR PARENT COLLECTION */

<?php endif; ?>

<?php if(is_category("collections")) : ?>

/* CONTENT FOR PARENT COLLECTION */

<?php elseif(is_category("author")) : ?>

/* CONTENT FOR PARENT AUTHOR */

<?php elseif (*is_children_category_of*("collections")) ?>

/* CONTENT FOR CHILDREN COLLECTIONS */

<?php elseif (*is_children_category_of*("author")) ?>

/* CONTENT FOR CHILDREN AUTHORS */

<?php endif; ?>