Anatomical connections underlying personally-familiar face processing

Abstract

Familiar face processing involves face specific regions (the core face system) as well as other non-specific areas related to processing of person-related information (the extended face system). The connections between core and extended face system areas must be critical for face recognition. Some studies have explored the connectivity pattern of unfamiliar face responding area, but none have explored those areas related to face familiarity processing in the extended system. To study these connections, diffusion weighted imaging with probabilistic tractography was used to estimate the white-matter pathways between core and extended system regions, which were defined from functional magnetic resonance imaging responses to personally-familiar faces. Strong white matter connections were found between occipitotemporal face areas (OFA/FFA) with superior temporal sulcus and insula suggesting the possible existence of direct anatomical connections from face-specific areas to frontal nodes that could underlay the processing of emotional information associated to familiar faces.

Fig 1

Functional activation identified by the contrasts: A) faces > houses and B) familiar faces > unknown faces. Maps were overlaid on the average inflated cortical surface of the SPM. The figure depicts voxels surviving p< 0.001 and p < 0.01 uncorrected, respectively. Color indicates the t-values.

Fig 2

Regions of interest extracted from activation clusters in left and right view (L and R) and ventral view (A: anterior and P: posterior region).

Fig 3. Connectivity path among the functional seeds obtained using probabilistic tractography.

The average of count of visits is drawn in each voxel. Color indicates the number of visits.

Fig 4. Averaged connectivity matrix across the subjects of cumulated count of visits in each ROI.

Fig 5. Averaged connectivity matrix across the sample from human connectome project´s subjects of cumulated count of visits in each ROI and considering Occipital Face Area (OFA) and Fusiform Face Area (FFA) as independent seeds.

Fig 6. Circular graph of the sum of count of visits from and to each ROI.

Line width is normalized to the maximum number of count of visits.

Fig 7. Connectivity probability among regions of interest (ROI) that belong to face processing system.

Histograms represent the normalized number of streamlines leaving each seed region towards the target regions. Core system areas: A) Occipital face area-Fusiform face area (OFA/FFA) and B) posterior Superior Temporal Sulcus (STSp); Extended system areas: C) Insula (Ins), D) medial Orbito-frontal cortex/Anterior cingulate (mOF/AC), E) medial cingulate (MC), F) posterior cingulate (PC) and G) Visual cortex (Vis). L: Left hemisphere (blue), R: right hemisphere (red).