Spatial bias in natural, implicit tasks such as reaching and grasping may manifest differently from that in arbitrary laboratory-experiment line bisection tasks. Because spatial processing in everyday activities is difficult to quantify, it is important to study spatial behavior in an implicit laboratory task. Drawing tasks of copying lines or objects integrate spatial perceptual-attentional (“where”) input and motor-intentional (“aiming”) output, and may be more implicit than line bisection because participants are unaware that the placement of their drawings will be assessed.
We examined whether it is possible to distinguish “where” and “aiming” spatial biases in a line-copying task. We examined changes in “where” and “aiming” biases in response to bottom-up versus top-down cues (hemispace presentation and drawing direction).
In 13 healthy adults, we collected copied-line displacements and lengths in both the natural (left-right congruency) and reversed (left-right incongruency) viewing conditions, to distinguish “where” and “aiming” biases.
Participants displaced lines leftward (P=0.01) as they copied, displaying primarily a “where” bias. They displaced lines in the drawing direction irrespective of viewing condition, a finding consistent with induced “aiming” effects (P=0.291). Presenting lines on participants' right or left side did not affect the “where” spatial bias. Cues did not affect copied-line lengths.
We showed that an implicit laboratory-experiment task of copying lines can discern complex stages of spatial processing in healthy adults. Further evaluation of this task will greatly contribute to the understanding of mechanisms of human spatial cognition.
*Stroke Rehabilitation Research Laboratory, Department of Physical Medicine and Rehabilitation, Kessler Foundation Research Center, West Orange, NJ
†Graduate School of Biomedical Sciences
§Department of Neurology and Neurosciences, University of Medicine and Dentistry of New Jersey, Newark, NJ
‡Department of Neurology, Penn State College of Medicine, Hershey, PA
1Present address: Keith O. Gonzalez, MD, Department of Neurology, The University of Arizona Medical Center-South Campus, Tucson, AZ.
This research was started at the Penn State College of Medicine, and continued at the Kessler Foundation.
Supported by the Kessler Foundation, National Institute of Neurological Disorders and Stroke (R01 NS055808-01-A2, K08 NS002085, and K02 NS47099), National Center for Medical Rehabilitation Research (K24 HD062647-01), Departments of Medicine and Neurology at Penn State College of Medicine, and General Research Center at the Penn State College of Medicine (NIH/NCRR C06 RR016499 and M01 RR010732).
Presented in preliminary form at the 53rd Annual Meeting of the American Academy of Neurology (Neurology. 2001;56 [8 Suppl 3]:A187, P03.071).
The authors declare no conflicts of interest.
Reprints: Priyanka P. Shah, MS, Stroke Rehabilitation Research Laboratory, Kessler Foundation Research Center, 1199 Pleasant Valley Way, West Orange, NJ 07052 (e-mail: email@example.com).
Received August 10, 2011
Accepted February 22, 2012