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dependent on dorsolateral prefrontal-striatal circuitry,
potentially disrupted following damage to the SVZ.
Motor speed was assessed using Purdue Pegboard
which measures the time it takes to place pegs into a
board with 25 parallel holes. The 2-Hand trial was ana-
lyzed for the present study. Measures of motor speed are
considered to be dependent on frontostriatal circuitry in-
volving the motor circuit including the putamen, which
may be disrupted secondary to damage to the SVZ.
Visual perception required the participants to
match 2-dimensional line drawings to a model.
Performance on the visual perception test has been
shown to be associated with temporal lobe volumes
Data Analysis
Linear mixed effect (LME) regression analyses were used
to examine differences in neuropsychological test scores
between patients and controls (“group”), withmoderating
variables including age at the time of the baseline visit
(“age0”) and time since baseline (“time”). Main effects
and their 2- and 3-way interactions were used in the anal-
yses of the raw scores of the neuropsychological tests.
Two-way interaction terms included Age0 × Time,
which examined the change in test score with age over
time; Group × Age0, which examined differences in test
scores with age between the groups; and Group × Time,
which examined differences in test scores with time
between the groups. A 3-way interaction term (Group ×
Age0 × Time) was used to examine whether the neuropsy-
chological scores changed differently with age and over
time between patients and controls. For LME analyses
showing a significant term “time,” a general linear
model ANOVA with Fisher’s least significant difference
was used as a post-hoc test to evaluate the differences in
neuropsychological performance between patients and
controls at individual time points (visits 1–4).
In patients, LME analyses were also used to evaluate
the overall relationship between the raw scores of the
neuropsychological tests and regional radiation doses
(“dose”) to SVZ, hippocampus, temporal lobes, and
cerebrum. The analyses controlled for age at the time
of irradiation (ageRT) and for the presence or absence
of concurrent chemotherapy. For presentation of the
results in the Figures, Z -scores were used to account for
the effect of age on neuropsychological performance.
Because we hypothesized that higher radiation doses to
specific brain regions in patients would result in a more
pronounced impairment on specific neuropsychological
tests, no corrections for multiple comparisons were
performed. Statistical significance was set to P , .05.
Fig. 1. Representative contours of the hippocampus on an axial (top image) T1-weighted MRI postgadolinium contrast and on the sagittal
(bottom left) and coronal reconstructions (bottom right). The T1 postgadolinium and FLAIR-sequence MRIs were fused to the RT-planning
CT scan to allow calculation of the doses to contoured structures.
Redmond et al.: Radiation to neural progenitor niches and neurocognitive outcomes
362 NEURO-ONCOLOGY † M A R C H 2 0 1 3
at Universitaet Leipzig, Institut fuer Informatik/URZ, Bibliothek on August 25, 2014
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