My explanation of Depersonalisation Disorder (DPD) argued that the characteristic experience is shared by people who suffer from the Cotard Delusion (CD). The difference between the two conditions is that the person with DPD does not develop a delusional response to her experience of de-affectualisation. She simply reports is as it is: “I feel as if my experiences do not belong to me”. The person with Cotard, however develops an explanation of that feeling and identifies with it “I no longer exist”. In commenting on this proposal Ying-Tung Lin opens up a range of new possibilities for cognitive theorizing. The first is that the predictive coding approach provides a new framework for cognitive theorizing which improves on “second factor” approaches to delusion. The second is that attention to the predictive nature of the processes which generate experience might suggest an important difference between the two conditions: namely the role of the Anterior Insular Cortex (AIC).
One way to approach the phenomenon would be to ask why the person with DPD seems to be able to understand that her experience is not veridical while the person with CD does not (modulo all the caveats about the epistemic status of delusional attitudes). The CD patient for example does not say “It feels as if I don’t exist” she says “I don’t exist”. This way of approaching the problem fits with a now standard approach to delusion, that argues that there are (at least) two stages of cognitive processing involved in delusion formation. The first generates an anomalous experience and the second generates a delusional response to that experience.
Ying-Tung Lin however, following Hohwy and Clark, explains delusion in terms of the attempt by higher order control systems to account for surprisal in a predictive coding hierarchy. The radical aspect of these ideas is that neither the precipitating experience nor the delusional response need be conceived of as the result of cognitive malfunction. Because there is no intrinsic connection between error minimization and malfunction “certain misrepresentations can lead to error minimization; furthermore, it is possible for misrepresentation rather than veridical representation to lead to a generative model ”(Lin this collection, p. 8).
Ying-Tung Lin’s commentary applies these ideas to the Cotard delusion, arguing that it is a model that mimimises the prediction error represented by depersonalisation experience. Her target is to describe a
cognitive architecture [that] could, in principle, explain CD in terms of its development from depersonalization, and what exactly are the underlying differences between patients suffering from the Cotard delusion and those suffering from depersonalization disorder (DPD) but free from the Cotard delusion? (Lin this collection, p. 2)