Dataset Information

Electrophysiological correlates of default-mode processing in macaque posterior cingulate cortex.

ABSTRACT: During the course of daily activity, our level of engagement with the world varies on a moment-to-moment basis. Although these fluctuations in vigilance have critical consequences for our thoughts and actions, almost nothing is known about the neuronal substrates governing such dynamic variations in task engagement. We investigated the hypothesis that the posterior cingulate cortex (CGp), a region linked to default-mode processing by hemodynamic and metabolic measures, controls such variations. We recorded the activity of single neurons in CGp in 2 macaque monkeys performing simple tasks in which their behavior varied from vigilant to inattentive. We found that firing rates were reliably suppressed during task performance and returned to a higher resting baseline between trials. Importantly, higher firing rates predicted errors and slow behavioral responses, and were also observed during cued rest periods when monkeys were temporarily liberated from exteroceptive vigilance. These patterns of activity were not observed in the lateral intraparietal area, an area linked to the frontoparietal attention network. Our findings provide physiological confirmation that CGp mediates exteroceptive vigilance and are consistent with the idea that CGp is part of the "default network" of brain areas associated with control of task engagement.

SUBMITTER: Hayden BY

PROVIDER: S-EPMC2667004 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Publications

Electrophysiological correlates of default-mode processing in macaque posterior cingulate cortex.

Hayden Benjamin Y BY Smith David V DV Platt Michael L ML

Proceedings of the National Academy of Sciences of the United States of America 20090317 14

During the course of daily activity, our level of engagement with the world varies on a moment-to-moment basis. Although these fluctuations in vigilance have critical consequences for our thoughts and actions, almost nothing is known about the neuronal substrates governing such dynamic variations in task engagement. We investigated the hypothesis that the posterior cingulate cortex (CGp), a region linked to default-mode processing by hemodynamic and metabolic measures, controls such variations. ...[more]

PMID: 19293382

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Project description:The intrinsic connectivity of the default mode network has been associated with the level of consciousness in patients with severe brain injury. Especially medial parietal regions are considered to be highly involved in impaired consciousness. To better understand what aspect of this intrinsic architecture is linked to consciousness, we applied spectral dynamic causal modeling to assess effective connectivity within the default mode network in patients with disorders of consciousness. We included 12 controls, 12 patients in minimally conscious state and 13 in vegetative state in this study. For each subject, we first defined the four key regions of the default mode network employing a subject-specific independent component analysis approach. The resulting regions were then included as nodes in a spectral dynamic causal modeling analysis in order to assess how the causal interactions across these regions as well as the characteristics of neuronal fluctuations change with the level of consciousness. The resulting pattern of interaction in controls identified the posterior cingulate cortex as the main driven hub with positive afferent but negative efferent connections. In patients, this pattern appears to be disrupted. Moreover, the vegetative state patients exhibit significantly reduced self-inhibition and increased oscillations in the posterior cingulate cortex compared to minimally conscious state and controls. Finally, the degree of self-inhibition and strength of oscillation in this region is correlated with the level of consciousness. These findings indicate that the equilibrium between excitatory connectivity towards posterior cingulate cortex and its feedback projections is a key aspect of the relationship between alterations in consciousness after severe brain injury and the intrinsic functional architecture of the default mode network. This impairment might be principally due to the disruption of the mechanisms underlying self-inhibition and neuronal oscillations in the posterior cingulate cortex.

Project description:Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of toxic misfolded proteins, which are believed to have propagated from disease-specific epicenters through their corresponding large-scale structural networks in the brain. Although previous cross-sectional studies have identified potential AD-associated epicenters and corresponding brain networks, it is unclear whether these networks are associated with disease progression. Hence, this study aims to identify the most vulnerable epicenters and corresponding large-scale structural networks involved in the early stages of AD and to evaluate its associations with multiple cognitive domains using longitudinal study design. Annual neuropsychological and MRI assessments were obtained from 23 patients with AD, 37 patients with amnestic mild cognitive impairment (MCI), and 33 healthy controls (HC) for 3 years. Candidate epicenters were identified as regions with faster decline rate in the gray matter volume (GMV) in patients with MCI who progressed to AD as compared to those regions in patients without progression. These epicenters were then further used as pre-defined regions of interest to map the synchronized degeneration network (SDN) in HCs. Spatial similarity, network preference and clinical association analyses were used to evaluate the specific roles of the identified SDNs. Our results demonstrated that the hippocampus and posterior cingulate cortex (PCC) were the most vulnerable AD-associated epicenters. The corresponding PCC-SDN showed significant spatial association with the patterns of GMV atrophy rate in each patient group and the overlap of these patterns was more evident in the advanced stages of the disease. Furthermore, individuals with a higher GMV atrophy rate of the PCC-SDN also showed faster decline in multiple cognitive domains. In conclusion, our findings suggest the PCC and hippocampus are two vulnerable regions involved early in AD pathophysiology. However, the PCC-SDN, but not hippocampus-SDN, was more closely associated with AD progression. These results may provide insight into the pathophysiology of AD from large-scale network perspective.

Dataset Information

Electrophysiological correlates of default-mode processing in macaque posterior cingulate cortex.

Publications

Electrophysiological correlates of default-mode processing in macaque posterior cingulate cortex.

Similar Datasets

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