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Abstract:
The main aims of this research were to determine whether
memory and learning difficulties occur concurrently with
morphological changes in neuroanatomical components of two brain
subsystems, a functionally later developing single-trial memory
(STM) and earlier developing multitrial learning (MTL), and whether
these two subsystems are anatomically and functionally dissociable.
Volumetric measures from magnetic resonance images of the brain of
the mamillary bodies (MB), components of the
cortico-limbo-diencephalic subsystem subserving STM, bilateral
heads of caudate nuclei (CN), components of the cortico-striatal
subsystem subserving MTL, and bilateral dorsolateral prefrontal
cortices (DLPFC), involved in STM and MTL, and neuropsychological
measures of memory and learning, were obtained for children treated
with neurotoxic chemotherapy for acute lymphoblastic leukemia (ALL)
and matched controls. The ALL group manifested significant
reductions in volume of MBs, but nonsignificant reductions in CN,
concurrent with significant reductions in prefrontal cortical
volume, consistent mild-to-moderate difficulties in visual and
verbal single-trial memory, with sparing of verbal but not
visual-spatial multitrial learning. Multiple regression model
results suggested that neurotoxic chemotherapy for ALL may affect
the structures and functions of single-trial memory and multitrial
learning subsystems selectively, with partial dissociation as well
as connectivity between the subsystems. These results also suggest
that over the course of development, greater CN involvement may
compensate for inefficiency of diencephalic and prefrontal
involvement in single-trial memory performance in children.
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