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Home » Archives for Adolf Pfefferbaum
Adolf Pfefferbaum

Adolf Pfefferbaum

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Publications

Biomedical sciences publications August 1, 2015 Article

Cognitive Demands During Quiet Standing Elicit Truncal Tremor in Two Frequency Bands: Differential Relations to Tissue Integrity of Corticospinal Tracts and Cortical Targets

SRI International, Natalie Zahr, Adolf Pfefferbaum

The ability to stand quietly is disturbed by degradation of cerebellar systems. Given the complexity of sensorimotor integration invoked to maintain upright posture, the integrity of supratentorial brain structures may also contribute to quiet standing and consequently be vulnerable to interference from cognitive challenges. As cerebellar system disruption is a common concomitant of alcoholism, we examined 46 alcoholics and 43 controls with a force platform to derive physiological indices of quiet standing during cognitive (solving simple, mental arithmetic problems) and visual (eyes closed) challenges. Also tested were relations between tremor velocity and regional gray matter and white matter tissue quality measured with the diffusion tensor imaging (DTI) metric of mean diffusivity (MD), indexing disorganized microstructure. Spectral analysis of sway revealed greater tremor in alcoholic men than alcoholic women or controls. Cognitive dual-tasking elicited excessive tremor in two frequency bands, each related to DTI signs of degradation in separate brain systems: tremor velocity at a low frequency (2-5 Hz/0-2 Hz) correlated with higher MD in the cerebellar hemispheres and superior cingulate bundles, whereas tremor velocity at a higher frequency (5-7 Hz) correlated with higher MD in the motor cortex and internal capsule. These brain sites may represent “tremorgenic networks” that, when disturbed by disease and exacerbated by cognitive dual-tasking, contribute to postural instability, putting affected individuals at heightened risk for falling.

Biomedical sciences publications April 1, 2015 Article

Dynamic Responses of Selective Brain White Matter Fiber Tracts to Binge Alcohol and Recovery in the Rat

Adolf Pfefferbaum, Natalie Zahr

To determine the dynamics of white matter vulnerability to excessive alcohol consumption, diffusion tensor imaging (DTI) was used in an animal model of alcohol exposure.

Biomedical sciences publications January 1, 2015

Quantitative Susceptibility Mapping by Inversion of a Perturbation Field Model: Correlation with Brain Iron in Normal Aging

Adolf Pfefferbaum

We present a method for quantifying susceptibility by inversion of a perturbation model, or “QSIP.” The perturbation model relates phase to susceptibility using a kernel calculated in the spatial domain, in contrast to previous Fourier-based techniques.

Biomedical sciences publications December 1, 2014

Compromised Frontocerebellar Circuitry Contributes to Nonplanning Impulsivity in Recovering Alcoholics

Tilman Schulte, Adolf Pfefferbaum

We tested the hypothesis that alcoholic patients would demonstrate compromised dorsal anterior cingulate cortex (dACC) -cerebellar functional connectivity when adjusting their strategies to accommodate uncertain conditions and would recruit compensatory brain regions to overcome ineffective response patterns.

Biomedical sciences publications November 1, 2014

Interhemispheric Functional Connectivity Change Is Linked to Callosal Fiber Integrity Change over a 1-Year Follow-up in Chronic Alcoholics

Adolf Pfefferbaum, Tilman Schulte

We tested whether microstructural fiber changes relate to resting-state functional connectivity changes in alcoholics who have maintained sobriety during a one-year interval, and whether these changes are beyond those potentially exhibited by controls.

Biomedical sciences publications November 1, 2014

Imaging Neuroinflammation? A Perspective from MR Spectroscopy

SRI International, Natalie Zahr, Adolf Pfefferbaum

The present MRS study was conducted in four groups: alcohol dependent, HIV-infected, alcohol dependent + HIV infected and healthy control individuals to determine whether metabolites would change in a pattern reflecting neuroinflammation.

Biomedical sciences publications June 1, 2014 Conference Paper

In Vivo Diffusion Tensor Imaging Evidence for Reversible White Matter Microstructural Integrity Disruption: Effects of Abstinence in Rat and Man

SRI International, Natalie Zahr, Adolf Pfefferbaum

SRI Authors: Natalie Zahr, Adolf Pfefferbaum

Biomedical sciences publications June 1, 2014 Conference Paper

Brain Connectivity Changes over Time in Alcoholism

SRI International, Adolf Pfefferbaum, Tilman Schulte

SRI Authors: Adolf Pfefferbaum, Tilman Schulte

Biomedical sciences publications May 1, 2014 Article

Dissociation of Preparatory Attention and Response Monitoring Maturation During Adolescence

Adolf Pfefferbaum, Fiona C Baker

Objective
Substantial brain development occurs during adolescence providing the foundation for functional advancement from stimulus-bound “bottom-up” to more mature executive-driven “top-down” processing strategies. The objective was to assess development of EEG markers of these strategies and their role in both preparatory attention (contingent negative variation, CNV) and response monitoring (Error Related Negativity, ERN, and Correct Related Negativity, CRN).
Methods
CNV, ERN and CRN were assessed in 38 adolescents (18 girls), age 11–18 years, using a variation of a letter discrimination task.
Results
Accuracy increased with age and developmental stage. Younger adolescents used a posterior attention network involved in inhibiting irrelevant information. Activity in this juvenile network, as indexed by a posteriorly-biased CNV and CRN decreased with age and advancing pubertal development. Although enhanced frontal CNV, known to be predictive of accuracy in adults, was not detected even in the older adolescents, top-down medial frontal response monitoring processes (ERN) showed evidence of development within the age-range studied.
Conclusions
The data revealed a dissociation of developmental progress, marked by relatively delayed onset of frontal preparatory attention relative to error monitoring.
Significance
This dissociation may render adolescents vulnerable to excessive risk-taking and disinhibited behavior imposed by asynchronous development of component cognitive control processes.

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