AI is a wide field that goes far beyond machine learning, deep learning, neural networks, etc. In some of these fields, the programming language does not matter at all (except for speed issues), so LISP would certainly not be a topic there.
In search or AI planning, for instance, standard languages like C++ and Java are often the first choice, because they are fast (in particular C++) and because many software projects like planning systems are open source, so using a standard language is important (or at least wise in case one appreciates feedback or extensions). I am only aware of one single planner that is written in LISP. Just to give some impression about the role of the choice of the programming language in this field of AI, I'll give a list of some of the best-known and therefore most-important planners:
description: the probably best-known classical planning system
language: C++, parts (preprocessing) are in Python
description: together with Fast-Downward the classical planning system everyone knows
description: one of the best-known partial-order causal link (POCL) planning systems
SHOP and SHOP2:
description: the best-known HTN (hierarchical) planning system
language: there are two versions of SHOP and SHOP2. The original versions have been written in LISP. Newer versions (called JSHOP and JSHOP2) have been written in Java. Pyshop is a further SHOP variant written in Python.
description: another well-known HTN (and hybrid) planning system
language: there are different versions of the planner: PANDA1 and PANDA2 are written in Java, PANDA3 is written primarily in Java with some parts being in Scala.
These were just some of the best-known planning systems that came to my mind. More recent ones can be retrieved from the International Planning Competitions (IPCs, http://www.icaps-conference.org/index.php/Main/Competitions), which take place every two years. The competing planners' codes are published open source (for a few years).