Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

Thirty years of brain imaging research has converged to define the brain’s default network—a novel and only recently appreciated brain system that participates in internal modes of cognition Here we synthesize past observations to provide strong evidence that the default network is a specific, anatomically defined brain system preferentially active when individuals are not focused on the external environment Analysis of connectional anatomy in the monkey supports the presence of an interconnected brain system Providing insight into function, the default network is active when individuals are engaged in internally focused tasks including autobiographical memory retrieval, envisioning the future, and conceiving the perspectives of others Probing the functional anatomy of the network in detail reveals that it is best understood as multiple interacting subsystems The medial temporal lobe subsystem provides information from prior experiences in the form of memories and associations that are the building blocks of mental simulation The medial prefrontal subsystem facilitates the flexible use of this information during the construction of self-relevant mental simulations These two subsystems converge on important nodes of integration including the posterior cingulate cortex The implications of these functional and anatomical observations are discussed in relation to possible adaptive roles of the default network for using past experiences to plan for the future, navigate social interactions, and maximize the utility of moments when we are not otherwise engaged by the external world We conclude by discussing the relevance of the default network for understanding mental disorders including autism, schizophrenia, and Alzheimer’s disease

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The Brain's Default Network Anatomy, Function, and Relevance to Disease

http://findlab.stanford.edu/Publications/Biol%20Psych_in%20press.pdf

Resting-State Functional Connectivity in Major Depression: Abnormally Increased Contributions from Subgenual Cingulate Cortex and Thalamus

Alzheimer's disease (AD) and antecedent factors associated with AD were explored using amyloid imaging and unbiased measures of longitudinal atrophy in combination with reanalysis of previous metabolic and functional studies. In total, data from 764 participants were compared across five in vivo imaging methods. Convergence of effects was seen in posterior cortical regions, including posterior cingulate, retrosplenial, and lateral parietal cortex. These regions were active in default states in young adults and also showed amyloid deposition in older adults with AD. At early stages of AD progression, prominent atrophy and metabolic abnormalities emerged in these posterior cortical regions; atrophy in medial temporal regions was also observed. Event-related functional magnetic resonance imaging studies further revealed that these cortical regions are active during successful memory retrieval in young adults. One possibility is that lifetime cerebral metabolism associated with regionally specific default activity predisposes cortical regions to AD-related changes, including amyloid deposition, metabolic disruption, and atrophy. These cortical regions may be part of a network with the medial temporal lobe whose disruption contributes to memory impairment.

https://www.jneurosci.org/content/jneuro/25/34/7709.full.pdf

Molecular, Structural, and Functional Characterization of Alzheimer's Disease: Evidence for a Relationship between Default Activity, Amyloid, and Memory

Structural imaging based on magnetic resonance is an integral part of the clinical assessment of patients with suspected Alzheimer dementia. Prospective data on the natural history of change in structural markers from preclinical to overt stages of Alzheimer disease are radically changing how the disease is conceptualized, and will influence its future diagnosis and treatment. Atrophy of medial temporal structures is now considered to be a valid diagnostic marker at the mild cognitive impairment stage. Structural imaging is also included in diagnostic criteria for the most prevalent non-Alzheimer dementias, reflecting its value in differential diagnosis. In addition, rates of whole-brain and hippocampal atrophy are sensitive markers of neurodegeneration, and are increasingly used as outcome measures in trials of potentially disease-modifying therapies. Large multicenter studies are currently investigating the value of other imaging and nonimaging markers as adjuncts to clinical assessment in diagnosis and monitoring of progression. The utility of structural imaging and other markers will be increased by standardization of acquisition and analysis methods, and by development of robust algorithms for automated assessment.

http://users.loni.usc.edu/~thompson/PDF/FrisoniNRN-09.pdf

The clinical use of structural MRI in Alzheimer disease

Discrimination between Alzheimer dementia and controls by automated analysis of multicenter FDG PET

In vivo study of acetylcholine esterase in basal forebrain, amygdala, and cortex in mild to moderate Alzheimer disease.

Department of Psychiatry and Psychotherapy, Dresden University of Technology, Dresden, Germany. vjera.holthoff@mailbox.tu-dresden.deOBJECTIVE: Functional brain correlates of remission in patients with major depressive disorder (MDD) are measured with positron emission tomography (PET) and 18F-fluorodeoxyglucose. METHOD: Glucose metabolism was measured in patients (n = 41) with moderate to severe MDD during acute depression and in the remitted state defined as a period of asymptomatic condition over 12 weeks. Data analyses used a region-of-interest (ROI) approach and statistical parametric mapping (SPM). RESULTS: There were significant decreases in metabolism upon remission with respect to the baseline scan in left prefrontal, anterior temporal and anterior cingulate cortex and bilateral thalamus (SPM analysis) and bilateral putamen and cerebellum (SPM and ROI analyses). There was a significant asymmetry in prefrontal and anterior cingulate cortex metabolism with lower metabolism in the left hemisphere that persisted despite clinical remission. CONCLUSION: These findings support the hypothesis that selective monoamine reuptake inhibition leads to an attenuation of a brain circuit that mediates depressive symptomatology.PMID: 15283738 [PubMed - indexed for MEDLINE]

Gerhard Zündorf

Papers

Discrimination between Alzheimer dementia and controls by automated analysis of multicenter FDG PET

In vivo study of acetylcholine esterase in basal forebrain, amygdala, and cortex in mild to moderate Alzheimer disease.

Changes in brain metabolism associated with remission in unipolar major depression.

Measuring cerebral acetylcholine esterase activity in Alzheimer dementia by PET functional parametric imaging.