Mild cognitive impairment (MCI) is the prodromal stage of Alzheimer’s Disease (AD). Prior research shows that females are more impacted by MCI than males. On average females have a greater incidence rate of any dementia and current evidence suggests that they suffer greater cognitive deterioration than males in the same disease stage. Recent research has linked these sex differences to neuroimaging markers of brain pathology, such as hippocampal volumes. Specifically, the rate of hippocampal atrophy affects the progression of AD in females more than males. This study was designed to extend our understanding of the sex-related differences in the brain of participants with MCI. Specifically, we investigated the difference in the hippocampal connectivity to different areas of the brain. The Resting State fMRI and T2 MRI of cognitively normal individuals (n = 40, female = 20) and individuals with MCI (n = 40, female = 20) from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) were analyzed using the Functional Connectivity Toolbox (CONN). Our results demonstrate that connectivity of hippocampus to the precuneus cortex and brain stem was significantly stronger in males than in females. These results improve our current understanding of the role of hippocampus-precuneus cortex and hippocampus-brainstem connectivity in sex differences in MCI. Understanding the contribution of impaired functional connectivity sex differences may aid in the development of sex specific precision medicine to manipulate hippocampal-precuneus cortex and hippocampal-brainstem connectivity to decrease the progression of MCI to AD.
The cortical motor system can be reorganized following a stroke, with increased recruitment of the contralesional hemisphere. However, it is unknown whether a similar hemispheric shift occurs in the somatosensory system to adapt to this motor change, and whether this is related to movement impairments. This proof-of-concept study assessed somatosensory evoked potentials (SEPs), P50 and N100, in hemiparetic stroke participants and age-matched controls using high-density electroencephalograph (EEG) recordings during tactile finger stimulation. The laterality index was calculated to determine the hemispheric dominance of the SEP and re-confirmed with source localization. The study found that latencies of P50 and N100 were significantly delayed in stroke brains when stimulating the paretic hand. The amplitude of P50 in the contralateral (to stimulated hand) hemisphere was negatively correlated with the Fügl–Meyer upper extremity motor score in stroke. Bilateral cortical responses were detected in stroke, while only contralateral cortical responses were shown in controls, resulting in a significant difference in the laterality index. These results suggested that somatosensory reorganization after stroke involves increased recruitment of ipsilateral cortical regions, especially for the N100 SEP component. This reorganization delays the latency of somatosensory processing after a stroke. This research provided new insights related to the somatosensory reorganization after stroke, which could enrich future hypothesis-driven therapeutic rehabilitation strategies from a sensory or sensory-motor perspective.
Introduction: Stroke is the leading cause of serious, long-term disability. Previous neuroimaging studies have demonstrated that the cortical motor system might be reorganized following a stroke, with an increasing recruitment of the contralesional hemisphere. The control of movement requires sensory feedback; however, it is unknown if there is a similar hemispheric shift in the somatosensory system to adapt to the change in the motor system and if this is related to the impairment. Hypothesis: Cortical somatosensory reorganization occurs post stroke and is related to sensory and motor impairment. Methods: This proof-of-concept study assessed early phase cortical somatosensory processing in chronic hemiparetic stroke participants (n=9) using electroencephalograph (EEG). Components P50 and N100 of sensory evoked potentials (SEPs) were extracted and compared to motor and sensory impairments. Results: Pearson correlation analysis found that the amplitude of SEP component P50 is negatively correlated with Fugl-Meyer Upper Extremity (FM-UE) Motor Score in stroke (R=-0.630, P=0.047) and the amplitude of SEP component N100 is positively correlated with the Erasmus modifications to the Nottingham Sensory Assessment (EmNSA) (R=0.705, p=0.025). Conclusion: This information potentially helps predict the severity of motor and sensory impairments based on SEP measures. This is clinically significant, because if an assessment for sensorimotor impairments could be done from a “pure” sensory perspective using SEP, this would improve assessments in those with severe impairments or after an acute stroke in those with limited functional movements. Additionally, it may provide clinicians with enhanced sensory feedback-based interventions for rehabilitation post stroke.
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