Drawing objects seems like a simple task – most of us, from young to old, can copy simple pictures even if we lack artistic talent. An inability to draw simple pictures is often a symptom of a cognitive disorder or brain damage. New research looking at stroke patients has found that drawing depends on several complex cognitive processes that operate via specific neuronal networks.
The new study, just published in the Journal of Cognitive Neuroscience, assesses a large sample (358) of patients who all recently suffered a stroke. The goal was to statistically match the the drawing deficits found in these patients to changes in brain structure, observed as lesions in CT scans.
“Previous work on drawing has either been with neurologically healthy participants – fMRI and behavioral studies – or it has used relatively small samples of neuropsychological patients,” says Nele Demeyere of Oxford University, a co-author of the study. “Our work differs by using a large patient sample, by assessing the patients relatively early in the stroke recovery pathway, and by using an unselected sample.”
Patients who recently suffered strokes were asked to copy diagrams, and showed varying degrees of drawing deficits. Credit: Nele Demeyere
Among other findings, the team, led by Magdalena Chechlacz, found that overall poor performance on copying figures was associated with subcortical lesions, specifically in the basal ganglia and thalamus. Specific aspects of drawing were also linked to impairments in several cognitive mechanisms, including spatial coding, attention, motor execution, and planning.
Demeyere talked with CNS about the new work, including how the patients were selected, and the significance of the research for understanding, and ultimately treating, a host of neurological conditions.
CNS: Copying a drawing seems like a simple task but it is not. What makes it so complex?
Demeyere: Copying is a surprisingly complex task and draws on a number of cognitive processes – visual memory, visual attention to the target stimulus and to the copy, scanning of eye movements, coding of global wholes and local parts and so forth. It is the demands on multiple cognitive processes that make the task complex.
CNS: Can you describe the clinical conditions most commonly associated with drawing deficits?
Demeyere: Deficits in copying are prevalent in a number of neuropsychological syndromes. For example, it is found in forms of apraxia – where there is poor control and planning of movement even when here is no sensory loss – particularly the disorder known as constructional apraxia. However, poor copying can also be found in patients with perceptual deficits (e.g. visual agnosia) and in patients with poor control of spatial attention (e.g. unilateral neglect). Hence drawing deficits are found in several syndromes and are a relatively frequent consequence of brain damage.
CNS: Would you please describe the subjects you used in your study? Were they identified as having drawing deficits prior to the study?
Demeyere: All the patients in this study were stroke survivors, they were not selected on any cognitive measure or any particular lesion site or laterality. Instead, this was an consecutive sample of patients which we assessed with the complex figure copy task between 0 and 3 months post their stroke onset as part of a large study assessing over 800 patients with the newly developed BCoS [Birmingham Cognitive Screen].
There are several strengths in having such an unselected sample. For example, by not selecting patients on the basis of their lesion site, we avoid biasing the results of this whole brain analysis to focus on any a priori pre-specified region. Also, by not selecting patients on the basis of their behavioral deficit, we sample a large range of performance; this is important because the structural brain analyses we report involve correlation between the lesion and the behavioral performance, and for this, a range of behavioral scores are necessary.
CNS: How did you personally become interested in studying this topic?
Demeyere: In neurospsychology, there is a long history of interpreting patient drawings as they may uncover a wide range of cognitive deficits, as I just described, and drawing and copying form part of many cognitive screening tests, including the traditional Mini Mental State Examination (MMSE). Having worked with stroke survivors since my Ph.D., I have experienced drawing performance in the patients firsthand and I have appreciated the potential insights we could gain from analyzing in more detail the nature of the drawing problems.
CNS: What were you most excited to find in the study and/or surprised by?
Demeyere: The strong relation between the overall figure copy score and subcortical lesions around the basal ganglia was rather surprising to us as, traditionally, drawing deficits have been associated with parietal cortex damage. However, a rising body of evidence implicates the basal ganglia in a range of cognitive processes, including spatial working memory, while the caudate specifically has long been implicated in motor control. Our results add to this body of evidence, suggesting that damage to the basal ganglia may cause a problem in planning movement sequences, which impacts on overall performance in copying complex figures.
CNS: What’s next for this work? what do you ultimately hope to accomplish?
Demeyere: We are currently starting research of similar complex copying tasks on tablet computers in stroke patients and in patients with degenerative disorders. Our aim is to use drawing as a sensitive measure of different cognitive processes, to facilitate early diagnosis – and ultimately hopefully treatment – of neurological disorders.
-Lisa M.P. Munoz
The paper, “The Neural Substrates of Drawing: A Voxel-based Morphometry Analysis of Constructional, Hierarchical, and Spatial Representation Deficits” by Magdalena Chechlacz, Abigail Novick, Pia Rotshtein, Wai-Ling Bickerton, Glyn W. Humphreys, and
and Nele Demeyere, was published online on June 4, 2014, in the Journal of Cognitive Neuroscience.
