Efficiency of Sensorimotor Networks: Posture and Gait in Young and Older Adults.

Background/Study context: Posture and gait are complex sensorimotor functions affected by age. These difficulties are particularly apparent when performing cognitively demanding tasks. Characterizing the functional organization of brain networks involved in these associations remains a challenge because of the incompatibility of brain imagery techniques with gross body movements. The present study aimed at testing whether resting-state functional connectivity of sensorimotor networks is associated with posture and gait performance recorded offline, in young and older adults. METHODS: Young (n = 12, mean = 24.1 y/o) and older (n = 14, mean = 65.6 y/o) healthy adults were tested for stability of their posture and gait. Four hours later, anatomical and functional brain imaging data were collected with Magnetic Resonance Imaging (MRI). Bilateral precentral and postcentral gyri were used as seeds in a graph theory analysis focused on global and local efficiency. The possible association between these data and posture and gait performance was examined. RESULTS: Both samples presented similar sensorimotor graphs, but with different global and local efficiencies (small world properties). The association between the networks' graph measures and posture and gait performance also differed across groups: local efficiency was correlated with gait stability in challenging conditions in older adults, but not in young adults. CONCLUSION: This exploratory study suggests that combining analyses of functional networks and offline body movement may provide important information about motor function. In older adults, the association between graph properties of the sensorimotor network and gait performance in challenging conditions may be indicative of compensatory processes. Prospective studies involving more subjects with a larger age range are warranted.

Frailty and Brain-Muscle Correlates in Older People With Type 2 Diabetes: A structural-MRI Explorative Study.

OBJECTIVES: Muscle alterations, mainly functional alterations are frequently observed in older people with type 2 diabetes (T2DM). Sarcopenia may be one mechanism of transition to frailty in these people. Thus, we aim to explore the characteristics of muscle and its association with cerebral grey matter volumes within this group. METHODS: Single center study nested within the international MID-Frail (a randomized clinical trial to evaluate the effectiveness of a multi-modal intervention in older people with T2DM on frailty and quality of life) trial participants underwent both brain and muscle T1 MRI, nutritional and functional assessments. Muscle areas were measured in rectus femoris (RF). Relationships between MRI grey matter volumes and muscle areas or function tests were described using positive and negative regressions. RESULTS: Twenty-six subjects (7 female, mean age 78.2 y, SD 5.0), 6 frail and 20 pre-frail were explored in this sub-study. Frail subjects had lower Mini Nutritional Assessment (MNA), Short Physical Performance Battery (SPPB), hip flexor strength than pre-frail ones but similar BMI and balance. Total SPPB was positively related with hip flexor strength and maximal RF area. Balance SPPB sub-score was unrelated to strength or RF area. MNA score was correlated with hip flexor strength and to global grey matter but not to SPPB. Hip flexor strength was correlated with grey matter areas involved in motor control. Walking time was negatively and rising chair sub-score was positively associated with grey matter volumes of motor areas. CONCLUSIONS: Sarcopenia features were more frequent in frail than prefrail subjects and were associated with decrease in grey matter volumes involved in motor control.