Engrams, Mnemons, Praxicons, and The Hunting of the Snark: A Conceptual Analysis

The conception of the engram as "the enduring though primarily latent modification of the irritable substance produced by a stimulus" dates back over 100 years to the work of Richard Semon. This conception initiated experimental investigations for the structural embodiment of the engram, most notably pursued by Karl Lashley, as well as formulation of related conceptions, such as mnemons and praxicons. In the past decade, an increasing number of empirical studies have attempted to identify the neural substrates of the engram. However, no conceptual analysis of the coherence of this term has been undertaken hitherto. The authors provide a conceptual analysis of the engram terminology that shows that the conceptual framework is incoherent, and they recommend the abandonment of this terminology.