Healthy aging is accompanied by a decline in spatial working memory that is related to functional cerebral changes within the spatial working memory network. In the last decade, important findings were presented concerning the location (e.g., prefrontal), kind (e.g., 'underactivation,' 'overactivation'), and meaning (e.g., functional deficits, compensation) of these changes. Less is known about how functional connections between specific brain regions are affected by age and how these changes are related to behavioral performance. To address these issues, we used functional magnetic resonance imaging to examine retrieval-related brain activation and functional connectivity in 18 younger individuals and 18 older individuals. We assessed working memory with a modified version of the Corsi Block-Tapping test, which requires the storage and reproduction of spatial target sequences. Analyses of group differences in brain activation and functional connectivity included comparisons between younger individuals, older individuals, older high-performers, and older low-performers. In addition, we conducted a functional connectivity analysis by using a seed region approach. In comparison to younger individuals, older individuals showed lower right-hemispheric dorsolateral prefrontal activation and lower functional connectivity between the right dorsolateral prefrontal cortex and the bilateral orbitofrontal cortex. Older high-performers showed higher right dorsolateral and anterior prefrontal cortex activation than older low-performers, as well as higher functional connectivity between these brain regions. The present results suggest age-related reductions of prefrontal activation during spatial working memory retrieval. Moreover, task-related functional connectivity appears to be lower in older adults. Performance accuracy in older adults is associated with right dorsolateral and anterior prefrontal cortex activation, and with the functional connection between these regions.
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http://dx.doi.org/10.1016/j.neuropsychologia.2014.04.020 | DOI Listing |
Neural Comput
January 2025
Department of Psychological and Brain Sciences, Indiana University Bloomington, Bloomington, IN 47405, U.S.A.
How episodic memories are formed in the brain is a continuing puzzle for the neuroscience community. The brain areas that are critical for episodic learning (e.g.
View Article and Find Full Text PDFChaos
January 2025
Departamento de Física, Universidad Nacional de Colombia, Bogotá, Colombia.
We consider a discrete-time Markovian random walk with resets on a connected undirected network. The resets, in which the walker is relocated to randomly chosen nodes, are governed by an independent discrete-time renewal process. Some nodes of the network are target nodes, and we focus on the statistics of first hitting of these nodes.
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Department of Orthopaedic Surgery, Kyoto City Hospital, Kyoto, Japan.
Case: We present 3 cases demonstrating radiographic posterior subluxation in lateral functional radiographs taken in the flexed-seated position. Two of the patients were asymptomatic, and 2 showed the posterior translation of the femoral head, which is almost a dislocation, with spontaneous reduction. The subluxation can occur not only in patients after lumbar fusion surgery but also in patients with relatively normal lumbar spine due to excessive hip flexion.
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January 2025
Department of Orthopaedic Surgery, University of Tennessee Health Science Center College of Medicine Chattanooga, Chattanooga, Tennessee.
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Morristown Medical Center, Morristown, New Jersey.
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