Testing the connections within face processing circuitry in Capgras delusion with diffusion imaging tractography

Abstract

Although Capgras delusion (CD) patients are capable of recognizing familiar faces, they present a delusional belief that some relatives have been replaced by impostors. CD has been explained as a selective disruption of a pathway processing affective values of familiar faces. To test the integrity of connections within face processing circuitry, diffusion tensor imaging was performed in a CD patient and 10 age-matched controls. Voxel-based morphometry indicated gray matter damage in right frontal areas. Tractography was used to examine two important tracts of the face processing circuitry: the inferior fronto-occipital fasciculus (IFOF) and the inferior longitudinal (ILF). The superior longitudinal fasciculus (SLF) and commissural tracts were also assessed. CD patient did not differ from controls in the commissural fibers, or the SLF. Right and left ILF, and right IFOF were also equivalent to those of controls. However, the left IFOF was significantly reduced respect to controls, also showing a significant dissociation with the ILF, which represents a selective impairment in the fiber-tract connecting occipital and frontal areas. This suggests a possible involvement of the IFOF in affective processing of faces in typical observers and in covert recognition in some cases with prosopagnosia.

Positive emotional reactions to loved names

“…The mere identification of someone that we know prompts unique emotional reactions associated with that person. Syndromes such as prosopagnosia (Bauer, ) and Capgras delusion (Bobes et al, ; Ellis & Lewis, ) confirm the strong relationship between identity recognition and emotional responses. Both central and peripheral psychophysiological measures have served as indicators of this strong relationship between the recognition process and affective modulation (Guerra, Sánchez‐Adam, Anllo‐Vento, Ramírez, & Vila, ; Guerra, Vico et al, ; Sánchez‐Adam, ; Vico, Guerra, Robles, Vila, & Anllo‐Vento, ).…”

“…The raw EMG signals were acquired at a sampling rate of 100 Hz, except for critical trials, where the sampling rate for orbicularis EMG was increased to 1,000 Hz. Startle eyeblink EMG acquisition followed the guidelines proposed by Blumenthal et al (2005).…”

Repetition priming effects for famous faces through dynamic causal modelling of latency‐corrected event‐related brain potentials

“…From the perspective of DCM, our design of network architecture for the identified sources followed a hypothesis‐driven approach (Garrido, Kilner, Kiebel, & Friston, ; Garrido, Kilner, Kiebel, Stephan, & Friston, ; Garrido et al., ) based on PADP, where each source was connected to any other source identified in previous face recognition studies providing anatomical insights (Bobes et al., ; Fox, Iaria, & Barton, ; Gschwind, Pourtois, Schwartz, Van De Ville, & Vuilleumier, ; Ishai, ; Pyles, Verstynen, Schneider, & Tarr, ). Two plausible models with multiple links between sources were outlined to emulate a possible PADP‐based architecture.…”

“…Backward connections between the sources were based on Bayesian "explaining away" (for details; see Methods). For both models, homologous sources in the two hemispheres were reciprocally connected to each other (Bobes et al, 2016;Chen, Henson, Stephan, Kilner, & Friston, 2009;Frässle et al, 2016;Geiger et al, 2016). These inter-hemispheric connections were allowed to be modulated in an incremental manner such that the models varied from having no modulations to modulations of all inter-hemispheric connections.…”

Delusional possibilities

“…But, experimental evidence shows that individuals who are diagnosed with Capgras delusion do not experience autonomic arousal when they look at familiar faces. [3][4][5] As a result, the person that one is staring at might look exactly like one's own mother, but she doesn't feel like it. Within cognitive neuropsychiatry, most theorists think that, in addition to the occurrence of a strange experience, there must be some additional cognitive or neuro biological disturbance implicated in the onset of a delusional belief.…”