Abstract
The hippocampus has exhibited navigation-related changes in volume and activity after visual deprivation; however, the resting-state functional connectivity (rsFC) changes of the hippocampus in the blind remains unknown. In this study, we focused on sub-region-specific rsFC changes of the hippocampus and their association with the onset age of blindness. The rsFC patterns of the hippocampal sub-regions (head, body and tail) were compared among 20 congenitally blind (CB), 42 late blind (LB), and 50 sighted controls (SC). Compared with the SC, both the CB and the LB showed increased hippocampal rsFCs with the posterior cingulate cortex, angular gyrus, parieto-occpital sulcus, middle occipito-temporal conjunction, inferior temporal gyrus, orbital frontal cortex, and middle frontal gyrus. In the blind subjects, the hippocampal tail had more extensive rsFC changes than the anterior hippocampus (body and head). The CB and the LB had similar changes in hippocampal rsFC. These altered rsFCs of the hippocampal sub-regions were neither correlated with onset age in the LB nor the duration of blindness in CB or LB subjects. The increased coupling of the hippocampal intrinsic functional network may reflect enhanced loading of the hippocampal-related networks for non-visual memory processing. Furthermore, the similar changes of hippocampal rsFCs between the CB and the LB suggests an experience-dependent rather than a developmental-dependent plasticity of the hippocampal intrinsic functional network.
Highlights
Sighted people mainly depend on the visual system to locate objects and to navigate through their environment
The hippocampal tails had relatively weaker resting-state functional connectivity (rsFC) than the hippocampal heads and bodies, these three hippocampal sub-regions were all strongly connected with the medial (MTL) and lateral temporal lobes (LTL), thalamus, posterior cingulate cortex (PCC) and middle cingulate cortex (MCC), medial prefrontal cortex (MPFC), and occipito-temporal conjunction
Altered rsFCs were present between the left hippocampal tail and the bilateral angular gyrus (AG), PCC, parieto-occpital sulcus (POS), bilateral middle occipito-temporal conjunction (MOT), right inferior temporal gyrus (ITG), right lateral orbital frontal cortex (OFC) and right middle frontal gyrus (MFG), between the right hippocampal tail and the left AG, PCC, bilateral MOT, and right ITG, between the left hippocampal head and the PCC, between the right hippocampal body and the right MOT, and between the right hippocampal head and the right MOT and right ITG
Summary
Sighted people mainly depend on the visual system to locate objects and to navigate through their environment. Blind subjects usually exhibit comparable or even superior non-visual spatial abilities compared to sighted subjects, including sound localization (Lessard et al, 1998; Gougoux et al, 2005), tactile orientation (Van Boven et al, 2000; Norman and Bartholomew, 2011), and navigation (Fortin et al, 2008; Kupers et al, 2010), some studies report an impaired performance (Zwiers et al, 2001; Gori et al, 2014). The cross-modal activation of the occipital cortex has been associated with the superior non-visual spatial abilities in the EB (Gougoux et al, 2005; Simon-Dack et al, 2008). The reorganization of the hippocampus, a structure for spatial mapping and navigation, in the blind is seldom considered
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