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Damage to the frontal lobes can affect a person's ability to 'stay on the job'

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  • Ian Pitchford
    Public release date: 3-Oct-2003 Contact: Kelly Connelly kconnelly@baycrest.org 416-785-2432 Baycrest Center for Geriatric Care Damage to the frontal lobes can
    Message 1 of 1 , Oct 4, 2003
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      Public release date: 3-Oct-2003
      Contact: Kelly Connelly
      Baycrest Center for Geriatric Care

      Damage to the frontal lobes can affect a person's ability to 'stay on the job'

      Study may influence how clinical assessments of brain injury are conducted in

      Toronto, CANADA -- A new study sheds light on why brain injury patients have
      difficulty performing tasks consistently -- a necessary requirement for holding
      a job. The findings may influence how clinical assessments of brain injury are
      conducted in future, encouraging doctors to pay closer attention to
      'variability' of performance as a marker for impairment.
      The study is published in the November issue of the journal BRAIN. It was led
      by Dr. Donald Stuss, Director of The Rotman Research Institute at Baycrest
      Centre for Geriatric Care, with Dr. Michael Alexander, Associate Clinical
      Professor, Neurology, Harvard Medical School in Cambridge, Mass.

      "Our study has shown that damaging certain areas of the frontal lobes can
      impair our ability to perform consistently -- a key requisite for holding a
      job," says Dr. Stuss. "Many people who suffer brain injuries from an accident,
      tumor, or stroke for example, may make considerable progress in their
      rehabilitation, but somehow have difficulty in daily life. The one area that
      may give them trouble -- performing consistently on tasks, both within a task
      and at different times -- may be the most difficult and nuanced for doctors to
      pick up on with a 'single' clinical assessment. The patient may need to be
      assessed more than once over a period of time. Inconsistency over repeated
      assessments is an important measure of impairment."

      The inspiration for this frontal lobe study came about 15 years ago when Dr.
      Stuss and his colleagues were testing brain injury patients in studies. They
      discovered that some patients would perform normally on the first test, but
      then one week later perform poorly on the same test. Because the data was not
      replicable over the short interval, it was assumed to be statistical "noise" --
      that is, scientifically unimportant. The results had to be rejected due to
      inability to replicate the findings. Fortunately, a parallel study in mild head
      injury patients who were tested not twice but five times over several weeks on
      the same test, revealed similar variability in performance.

      "What we came to realize was that what we had been taught for years as the
      death knell of an experiment -- the lack of replicable findings -- in certain
      circumstances is the finding itself. The "noise" in the data was the data! It
      was the source of considerable information for us," says Dr. Stuss. This
      realization became the basis for developing the study that is now published in

      Since the earlier publications, numerous studies have confirmed reduced
      consistency in patients with traumatic brain injury at all levels of severity,
      with or without focal frontal lesions. Performance variability has also been
      reported in dementing illness, attention deficit disorder and schizophrenia.
      However, there has been no direct experiment to determine if lesions in 'any'
      focal region of the frontal lobes are critical for performance variability. Dr.
      Stuss wanted to investigate whether different frontal lobe lesions were
      particularly important in impairing sustained attention and task performance.
      The importance of this study is that it addresses the mechanisms underlying the
      observation, a necessary step in developing targeted rehabilitation.

      Thirty-six patients who had suffered brain injuries as a result of trauma,
      stroke, hemorrhage or removal of a benign tumor, were part of the study. The
      patients were divided into five groups depending on the location of their
      primary lesion. Eleven patients had lesions located in nonfrontal regions. The
      other 25 patients had focal frontal lesions and were divided into four groups
      based on the location of their primary lesions -- left dorsolateral frontal,
      right dorsolateral frontal, inferior medial, and superior medial. The five
      patient groups were compared to 12 normal, control subjects.

      The subjects completed four different reaction time computer tasks that ranged
      from simple to increasingly more complex; the latter supposedly demanding more
      involvement from the executive functions located in the frontal regions of the
      brain. Each task required the subject to press a button with their dominant
      hand when they saw a particular target image that they were told to watch for.
      There were four primary image shapes -- circle, square, triangle and cross.
      They were alerted to a particular target to watch for that had specific
      characteristics of shape, color and internal texture -- for example a red
      circle with horizontal lines. Subjects were instructed to respond as quickly
      and as accurately as possible when they saw this target. If they saw a
      non-target image, they were to press the other button that was in their
      non-dominant hand. This testing session was repeated on two additional
      occasions, each a week apart. Researchers focused on two major measures: a) the
      variability while doing a task over time at one sitting; and b) "consistency of
      performance" -- the ability of an individual to perform comparably across
      different testing sessions. Results were correlated to task complexity as well
      as location of brain lesion.

      Study's findings:
      While there was minimal variability with nonfrontal lesions, all of the frontal
      patient groups (except the inferior medial) had some degree of inconsistency of
      performance. Those with frontal lesions in the dorsolateral (right and left)
      and superior medial areas, showed the most performance variability -- even on
      the simplest tasks. "We found that individual variability is significantly
      increased in most patients with frontal injury, but the effects are not uniform
      across all frontal regions," says Dr. Stuss. "Most importantly, we discovered
      that different frontal brain regions result in variability for different

      Investigators made four conclusions from the study: (1) Performance variability
      may be caused by damage to specific brain regions. Lesions in the frontal
      lobes, in particular, impair stability of behavior; (2) These fluctuations of
      performance in an individual are not simply statistical noise but an important
      measure of impairment; (3) Different types of variablity are affected by damage
      in different brain regions; (4) Task factors have important effects on
      demonstration of variability.

      These results provide a means for investigating why some patients seem to
      recover fully, yet are not able to hold down a job. Understanding that
      different brain regions result in variability of performance for different
      reasons is the first step in treating these disorders. Dr. Stuss says future
      research should look more closely at the interaction of frontal lesion
      involvement, specific task demands and task complexity.

      Funding for the study was provided by the Canadian Institutes of Health
      Research. Dr. Stuss's team included Dr. Michael Alexander, Harvard Medical
      School; and statistician Malcolm Binns and post-doctoral student Kelly Murphy,
      both with The Rotman Research Institute at Baycrest.

      Dr. Stuss is available for interviews between now and Oct. 19th. For more
      information on this release or to set up an interview, please contact:
      Kelly Connelly, Media Relations
      The Rotman Research Institute
      Baycrest Centre for Geriatric Care

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