Although developmental dyslexia is often defined as a language-based reading impairment not attributable to low intelligence or educational
or socioeconomic limitations, the behavioral manifestations of dyslexia are not restricted to the realm of language. Functional
brain imaging studies have shed light on physiological differences associated with poor reading both inside and outside the classical language
areas of the brain. Concurrently, clinically useful tests that elicit these nonlinguistic deficits are few. Specifically, the integrity of
the dorsal visual pathway, which predominantly projects to the parietal cortex, remains underinvestigated, lacking easily administered
tests. Here we present the Clock Drawing Test (CDT), used to test the visuoconstructive ability of children with and without dyslexia
and garden-variety poor readers. Compared to typically reading children, many children with dyslexia and some garden-variety poor
readers showed significant left neglect, as measured by the distribution of figures drawn on the left clock face. In the poor readers with
dyslexia, we observed spatial construction deficits like those of patients with acquired right-hemisphere lesions. The results suggest that
in some children with dyslexia, right-hemisphere dysfunction may compound the phonological processing deficits attributed to the left
hemisphere. The CDT provides an easy opportunity to assess skills known to be associated with right-hemisphere parietal function. This
test can be easily administered to children for both clinical and research purposes.
The clock-drawing test is used for screening for
cognitive impairment and dementia and as a measure
of spatial dysfunction and neglect. It was originally
used to assess visuo-constructive abilities but we know
that abnormal clock drawing occurs in other cognitive
impairments. Doing the test requires verbal understanding,
memory and spatially coded knowledge in
addition to constructive skills [1]. Education, age and
mood can influence the test results, with subjects of
low education, advanced age and depression performing
more poorly [2 - 4].
