Background: The putative neural bases of affected episodic memory and emotional recognition in early Alzheimer’s disease are suspected to be limbic and paralimbic pathological processes. The uncinate fasciculus (UF) is especially considered to be a critical structure. In the present study, we investigated microstructural UF pathology by diffusion tensor imaging in the subjects with amnestic mild cognitive impairment (aMCI), and its association with memory and emotional processing impairment. Methods: Subjects included 16 patients with aMCI and 16 healthy individuals. Diffusion tensor images were acquired and the fractional anisotropy (FA) of the UF was calculated. In addition, its association with verbal memory and emotional facial recognition was investigated. Results: The FA values of the left UF were significantly lower in aMCI, and strongly correlated with episodic memory performance in aMCI. For the emotional recognition task, the aMCI subjects performed worse in negative emotion recognitions. The FA values of the left UF were correlated with the performance of fearful facial expression recognition in aMCI. Conclusion: These results indicated that microstructural alterations of the UF had already occurred in aMCI. In addition, these alterations could be one of the causes of memory and emotional processing impairment in aMCI.

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The anterior cingulate gyrus (ACG) is a critical structure for social cognitive processing; the pathology of this structure might be a major source of social dysfunction in schizophrenia. Multiple structural abnormalities of the ACG have been demonstrated in schizophrenia including changes in gray matter volume, white matter microstructures and macroscopic sulcal morphology. However, the interrelationships among these different abnormalities have not been investigated. Thus, the relationship between structural abnormalities in the ACG and social cognition in schizophrenia remains to be elucidated. Magnetic resonance imaging data were acquired at 3.0 T from 26 schizophrenic patients and 20 healthy participants. We performed anterior cingulate cortex (ACC) volumetry, evaluated diffusion tensor imaging of the anterior cingulum, analyzed paracingulate/cingulate sulcus (PCS/CS) morphology and investigated the interrelationships among these measures. We also investigated the association between ACG structural abnormalities and psychopathology, and the social cognition ability of schizophrenic patients as estimated by emotion attribution tasks. Compared with healthy subjects, schizophrenic patients exhibited reduced ACC volume, decreased fractional anisotropy in the anterior cingulum bilaterally and a poorly developed PCS/CS in the left hemisphere. No interrelationship was identified among these measures in the schizophrenic group. Schizophrenic patients performed poorly on emotion attribution tasks. Importantly, clinical symptoms and performance on emotion attribution subtasks were associated with ACC volumes and left PCS/CS variation in different ways. These results suggested that pathology of the ACC, anterior cingulum and PCS/CS is, at least partially, independent and has differential impacts on psychopathology and social cognitive impairment in schizophrenia.

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