Behavioral Variability: Implications for Rehabilitation

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Behavioral VariabilityImplications for
Rehabilitation

• John Whyte, MD, PhD
• Moss Rehabilitation Research Institute
• Thomas Jefferson University

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Clinical Case Examples

• Minimally conscious state
• High variability in response rate and accuracy
  rate in command following and yes/no
  communication
• Occasional dramatic cases of variability
• Apraxia of speech
• The patient does not lack the absolute capacity
  to produce specific speech sounds they lack the
  ability to do so reliably

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Treatment Implications

• How much assessment does it take to characterize
  a patients current status or response to
  treatment?
• How much safe performance guarantees safety after
  discharge?
• Are there ways to work on consistency of
  performance other than working on overall quality
  of performance?

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Research Examples

• In our attention studies, central tendency of RT
  is strongly correlated with measures of
  dispersion in both patients and controls.
• Transformations that are intended to eliminate
  this intrinsic correlation work poorly (either a
  positive correlation remains or becomes
  negative).
• Weve found it difficult to isolate a variability
  parameter and be confident it was not a
  statistical artifact.

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Big Question 1

• Are we sure there is an independent phenomenon of
  a variability deficit vs. an intrinsic
  relationship between variability and central
  tendency?

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Big Question 2

• What would constitute evidence for a separable
  impairment in behavioral consistency?
• Ability to match subjects on central tendency (a
  thorny issue in itself) but find differences in
  variability?
• Different neuroanatomic correlates for central
  tendency and variability?
• Differential treatment responsiveness?