Parietal Involvement in Constructional Apraxia as Measured Using the Pentagon Copying Task

Abstract

Deficits in copying (“constructional apraxia”) is generally defined as a multifaceted deficit. The exact neural correlates of the different types of copying errors are unknown. To assess whether the different categories of errors on the pentagon drawing relate to different neural correlates, we examined the pentagon drawings of the MMSE in persons with subjective cognitive complaints, mild cognitive impairment, or early dementia due to Alzheimer’s disease. We adopted a qualitative scoring method for the pentagon copy test (QSPT) which categorizes different possible errors in copying rather than the dichotomous categories “correct” or “incorrect.” We correlated (regional) gray matter volumes with performance on the different categories of the QSPT. Results showed that the total score of the QSPT was specifically associated with parietal gray matter volume and not with frontal, temporal, and occipital gray matter volume. A more fine-grained analysis of the errors reveals that the intersection score and the number of angles share their underlying neural correlates and are associated with specific subregions of the parietal cortex. These results are in line with the idea that constructional apraxia can be attributed to the failure to integrate visual information correctly from one fixation to the next, a process called spatial remapping.

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“…Deficits in the well-known Pentagon Copying Task were related to GM volumes of the total parietal (for total score) and specific sub-regions of the parietal cortex (such as the posterior cingulate cortex and supramarginal gyrus, for intersection and the number of angle scores) in AD, MCI and SCD cases, conceptualizing the constructional apraxia as a failure in the integration of visual information from one fixation point to the next. 80 …”

“…Deficits in the well-known Pentagon Copying Task were related to GM volumes of the total parietal (for total score) and specific sub-regions of the parietal cortex (such as the posterior cingulate cortex and supramarginal gyrus, for intersection and the number of angle scores) in AD, MCI and SCD cases, conceptualizing the constructional apraxia as a failure in the integration of visual information from one fixation point to the next. 80 Different studies are also targeting executive and frontal-lobe functioning in MCI, AD and healthy controls. [81][82][83] Authors of a multimodal MRI study in healthy adults showed that low deactivation of the DMN, high activation of the executive-control network and high WMH burden were the most accurate predictors of executive functioning at baseline.…”

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“…Copying tasks require several complex cognitive functions, including visuospatial and executive functions. 21 The parietal lobe may be involved in copying tasks since it is bilaterally activated during drawing tasks; 22 moreover, patients with a parietal lobe stroke often present with constructional apraxia. 23 Additionally, a recent study reported a negative correlation between parietal gray matter volumes and qualitative scoring on the pentagon copy test.…”

“… 23 Additionally, a recent study reported a negative correlation between parietal gray matter volumes and qualitative scoring on the pentagon copy test. 21 Visual information travels through two pathways: the “what pathway” in the ventral route for perceiving objects and the “where pathway” in the dorsal route for recognizing object positions. 24 …”

“…23 Additionally, a recent study reported a negative correlation between parietal gray matter volumes and qualitative scoring on the pentagon copy test. 21 Visual information travels through two pathways: the "what pathway" in the ventral route for perceiving objects and the "where pathway" in the dorsal route for recognizing object positions. 24 Since the parietal lobe is mainly involved in the visuospatial "where pathway," patients with a low score on the pentagon copying test might present with parietal lobe deficits.…”