هذیان: یک مورد مناسب برای تصویربرداری؟

This review is intended to outline the need/opportunities for imaging research in the area of delusions. In particular, delusions of misidentification are offered as possible examples of how both spatial and temporal brain imaging may throw light upon the theoretical, parallel processes of identification and emotional arousal occurring when a familiar face is encountered. Other types of Delusional Misidentifications are also briefly explored. The review then turns to related phenomena, including the ways imaging may help elucidate different types of covert face recognition; and also further explain the distinctive (but not entirely independent) processes underlying face, voice and object recognition. Throughout the review the aim is to emphasise the potential value to cognitive neuropsychiatry of good imaging techniques.

The title to this paper includes an obvious rhetorical question. Delusions (or at least some forms of them) are eminent candidates for imaging analysis. Indeed, some success in this regard has recently been claimed, for example, by Blackwood et al. (2004) who, in a fMRI study, found that, compared with matched controls, people diagnosed with schizophrenia with persecutory delusions, when asked about the self-relevance of certain either ambiguous or non-ambiguous threat statements, revealed a significant absence of rostral-ventral anterior cingulate activation combined with an increase in activation within the posterior cingulate gyrus. Compared with the efforts that have gone into analysing many other cognitive phenomena, however, the use of techniques such as SPECT, PET, MRI, fMRI and MEG to explore the structures underlying delusions (and, by implication, beliefs in general) has been limited. The field is clearly ready for a more systematic approach, and in this paper I shall endeavour both to outline some reasons for doing so and to add the stricture that imaging research must be based upon good models of information processing. In order to do this I shall focus on a particular set of monothematic delusions, each of which involves inappropriate beliefs about the identity of other people or objects, that have already received extensive analysis using cognitive neuropsychiatric principles (Ellis, 1998).

Green and Gazzaniga (2001) have made a persuasive case for linking neuroimaging and cognitive neuropsychiatry – especially for the study of schizophrenia – yet imaging delusions of belief have yet to be fully embraced by the imaging community. The area of delusions in general and delusions of misidentification in particular are ideal candidates for imaging analyses — both spatial and temporal. These would not only help us to understand how these anomalous states occur but also cast important light on how beliefs develop and, specifically from studies of DMS, either validate and extend the model in Fig. 3 or, if the analyses prove not to be consistent with it, suggest new ways of understanding face processing. What will be essential is that imaging studies are informed by the data on normal information processing gathered over the last 50 years, together with the theoretical insights they have generated. All too often sophisticated imaging studies have been limited by their failing to be firmly grounded upon good cognitive models. Future imaging studies of delusions and belief should not make the same mistake.