Influence of moving background on line bisection performance in the normal elderly versus patients with hemispatial neglect.
OBJECTIVE
Previous studies have shown that when healthy young participants bisect stationary lines on a moving background (MB) or optokinetic stimulation, they perceive the stationary line moving in the opposite direction of the MB (illusory motion [IM]), and they displace their bisection mark in the direction of the IM. This study attempted to learn whether IM also influences attentional biases of the healthy elderly and patients with hemispatial neglect.


METHODS
In experiment 1, healthy elderly participants and patients with neglect bisected lines in conditions where IM was absent or present. To better understand the MB dichotomy between the healthy elderly and neglect patients, in experiment 2, participants' eye movements were recorded using an infrared eye tracker.


RESULTS
In experiment 1, healthy elderly participants' biases occurred in the opposite direction of MB when IM was present but in the same direction of MB when IM was absent. In contrast, neglect patients' biases occurred in the same direction of MB regardless of conditions. Eye movements reflect the spatial direction of attention. In experiment 2, the healthy elderly participants were able to selectively attend to the line, whereas neglect patients were impaired in that they fixated on the line.


CONCLUSIONS
These results suggest that the healthy elderly can selectively fixate on a line, and with MB, they perceive the stationary line moving, resulting in a bisection bias in the direction of the IM. In contrast, when there is an MB, the patients with neglect are impaired in that they fixate on the line. Thus, they do not perceive IM; instead, they are primarily influenced by the MB.
Choi
Kyung Mook
KM
Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, and Myongji Hospital, Gyeonggi, Korea.
Lee
Byung Hwa
BH
Lee
Sang Chan
SC
Ku
Bon D
BD
Kim
Eun-Joo
EJ
Suh
Mee Kyung
MK
Jeong
Yong
Y
Heilman
Kenneth M
KM
Na
Duk L
DL
D000368:Aged; D000369:Aged, 80 and over; D002544:Cerebral Infarction / Q000150:complications* / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D017120:Nystagmus, Optokinetic / Q000502:physiology*; D009903:Optical Illusions / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology; D010468:Perceptual Disorders / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D013028:Space Perception / Q000502:physiology; D014057:Tomography, X-Ray Computed