  Functional neuroimaging reveals both relative increases (task-positive) and
decreases (task-negative) in neural activation with many tasks. There are
strong spatial similarities between many frequently reported task-negative
brain networks, which are often termed the default mode network. The default
mode network is typically assumed to be a spatially-fixed network; however,
when defined by task-induced deactivation, its spatial distribution it varies
depending on what specific task is being performed. Many studies have revealed
a strong temporal relationship between task-positive and task-negative networks
that are important for efficient cognitive functioning and here. Here, using
data from four different cognitive tasks taken from two independent datasets,
we test the hypothesis that there is also a fundamental spatial relationship
between them. Specifically, it is hypothesized that the distance between task
positive and negative-voxels is preserved despite different spatial patterns of
activation and deactivation being evoked by different cognitive tasks. Here, we
show that there is lower variability in the distance between task-positive and
task-negative voxels across four different sensory, motor and cognitive tasks
than would be expected by chance - implying that deactivation patterns are
spatially dependent on activation patterns (and vice versa) and that both are
modulated by specific task demands. We propose that this spatial relationship
may be the macroscopic analogue of microscopic neuronal organization reported
in sensory cortical systems, and we speculate why this spatial organization may
be important for efficient sensorimotor and cognitive functioning.
