PhD Proposal by Matthew Wittbrodt

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  • Date/Time:
    • Thursday September 29, 2016 - Friday September 30, 2016
      11:00 am - 12:59 pm
  • Location: Room 1253 555 14th St
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Summary Sentence: Do body water deficits and exercise-heat stress affect brain structure, function, and neuromotor performance

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Doctoral Thesis Proposal


School of Biological Sciences, Georgia Institute of Technology

September 29, 2016, 11:00, Room 1253 555 14th St.


Title: Do body water deficits and exercise-heat stress affect brain structure, function, and neuromotor performance?


Student: Matthew T. Wittbrodt, M.S.


Committee Members: Mindy L. Millard-Stafford Ph.D. (advisor), Audrey L. Duarte Ph.D., J. Chris Mizelle Ph.D., Michael N. Sawka Ph.D., and Lewis A. Wheaton Ph.D.



There is reason to believe body water deficits (hypohydration) adversely impact the central nervous system

despite protective physiological mechanisms to maintain brain homeostasis. Early animal models suggested

brain volume is preserved during severe hypohydration (10% body mass loss), likely from osmolyte

production to maintain the osmotic equilibrium between intra- and extracellular compartments. Current

neuroimaging techniques (e.g., magnetic resonance imaging) allow real-time in vivo measurement of human

brain morphology and localized hemodynamic responses during a cognitive task. Of the few studies utilizing

MRI to investigate hypohydration-mediated effects on brain morphology, most suggest brain volume does

not change, but specific structures (e.g., lateral ventricles) are altered at moderate levels (2-4% body mass

loss). However, the relationship between changes in other brain structures and decrements in cognitive

function is not well-established. Most computerized tests of cognition require a motor response involving

a terminal movement (e.g., button press) via activation of the neuromotor system. Neuromotor system

processing can be divided into two major phases: motor planning (i.e., from visual perception through

the determination of a movement goal) and movement execution (i.e., pressing a button after movement

goal determination). Disruption to motor planning and/or movement execution can have potentially severe

consequences such as degraded driving performance, increased navigation errors, and elevated rate of occupational

accidents. Whether neuromotor performance is adversely impacted (e.g., slowed reaction time,

reduced accuracy) or requires additional neural resources (e.g. elevated primary motor cortex activation)

to perform a given task following hypohydration is unclear. The goal of this thesis is to investigate

whether moderate hypohydration elicited by sweat losses during exercise-heat stress alters

brain structures and if the observed changes are associated with impaired task performance

and neuromotor function. My overall hypothesis is moderate hypohydration will alter brain morphology

due to water shifts out of intracellular compartments (grey and white matter crenation) into extracellular

spaces (expanding brain ventricles, cerebrospinal fluid) eliciting elevated brain activations and degraded

neuromotor performance during repetitive upper extremity movements requiring variable levels of decision

making. Aim 1 will quantify changes in brain structures due to moderate hypohydration induced by sweat

loss during exercise-heat stress. Aim 2 will correlate these structural changes to neural resource requirements

and performance errors during rhythmically paced movements. Aim 3 will evaluate which phases

of neuromotor processing (e.g., motor planning, movement execution) are associated with performance

decrements due to moderate hypohydration.


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Phd proposal
  • Created By: Tatianna Richardson
  • Workflow Status: Draft
  • Created On: Sep 20, 2016 - 5:42am
  • Last Updated: Oct 7, 2016 - 10:19pm