NeuroImage
-
Normal aging is accompanied by various cognitive functional declines. Recent studies have revealed disruptions in the coordination of large-scale functional brain networks such as the default mode network in advanced aging. However, organizational alterations of the structural brain network at the system level in aging are still poorly understood. ⋯ More importantly, the aging brain network exhibited reduced intra-/inter-module connectivity in modules corresponding to the executive function and the default mode network of young adults, which might be associated with the decline of cognitive functions in aging. Finally, we observed age-associated alterations in the regional characterization in terms of their intra/inter-module connectivity. Our results indicate that aging is associated with an altered modular organization in the structural brain networks and provide new evidence for disrupted integrity in the large-scale brain networks that underlie cognition.
-
Analyses of spontaneous hemodynamic fluctuations observed on functional magnetic resonance imaging (fMRI) have revealed the existence of temporal correlations in signal changes between widely separated brain regions during the resting state, termed "resting state functional connectivity." Recent studies have demonstrated that these correlations are also present in the hemodynamic signals measured by near infrared spectroscopy (NIRS). However, it is still uncertain whether frequency-specific characteristics exist in these signals. In the present study, we used multichannel NIRS to investigate the frequency dependency of functional connectivity between diverse regions in the cerebral cortex by decomposing fluctuations of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) signals into various frequency bands. ⋯ This approach demonstrated that functional connectivity based on the oxy-Hb signals between homologous cortical regions of the contralateral hemisphere (homologous connectivity) showed high coherence over a wide frequency range (0.009-0.1Hz), whereas connectivity between the prefrontal and occipital regions (fronto-posterior connectivity) showed high coherence only within a specific narrow frequency range (0.04-0.1Hz). Our findings suggest that homologous connectivity may reflect synchronization of neural activation over a wide frequency range through direct neuroanatomical connections, whereas fronto-posterior connectivity as revealed by high coherence only within a specific narrow frequency range corresponding to the time scale of typical hemodynamic response to a single event may reflect synchronization of transient neural activation among distant cortical regions. The present study demonstrated that NIRS provides a powerful tool to elucidate network properties of the cortex during resting state.
-
Observational studies investigating the association between smoking, cognitive decline and dementia have produced conflicting results. We completed this trial to determine if smoking cessation decreases the progression of cognitive decline in later life. ⋯ These results are consistent with the hypothesis that smoking causes cognitive decline and loss of gray matter tissue in the brain over time.
-
The brainstem is the part of the human brain that plays a pivotal role in the maintenance of many critical body functions. Due to the elevated level of cardiogenic noise, few fMRI studies have investigated the brainstem so far. Cardiac-gated echo-planar imaging with acquisition of two echoes per excitation (dual-echo EPI) is one method that significantly reduces cardiogenic noise and, thus, allows for fMRI measurements of the brainstem. ⋯ Five methods were found to be sensitive for activation of both nuclei. These included FSL normalization with 3mm and 4.5mm pre-smoothing as well as 3mm post-smoothing, SPM unified normalization with 3mm pre-smoothing and ABC normalization with 4.5mm pre-smoothing. All these methods can be recommended for normalization and smoothing when analyzing fMRI data of the brainstem acquired by cardiac-gated dual-echo EPI.
-
Skilled performance requires the ability to monitor ongoing behavior, detect errors in advance and modify the performance accordingly. The acquisition of fast predictive mechanisms might be possible due to the extensive training characterizing expertise performance. Recent EEG studies on piano performance reported a negative event-related potential (ERP) triggered in the ACC 70 ms before performance errors (pitch errors due to incorrect keypress). ⋯ In healthy pianists, the main outcomes were increased pre-error theta and beta band oscillations over the pFMC and 13-15 Hz phase synchronization, between the pFMC and the right lateral prefrontal cortex, which predicted corrective mechanisms. In MD patients, the pattern of phase synchronization appeared in a different frequency band (6-8 Hz) and correlated with the severity of the disorder. The present findings shed new light on the neural mechanisms, which might implement motor prediction by means of forward control processes, as they function in healthy pianists and in their altered form in patients with MD.