Abstract
The study of lateralized visuospatial attention bias in non-clinical samples has revealed a systematic group-level leftward bias (pseudoneglect), possibly as a consequence of right hemisphere (RH) dominance for visuospatial attention. Pseudoneglect appears to be modulated by age, with a reduced or even reversed bias typically present in elderly participants. It has been suggested that this shift in bias may arise due to disproportionate aging of the RH and/or an increase in complementary functional recruitment of the left hemisphere (LH) for visuospatial processing. In this study, we report rightward shifts in subjective midpoint judgment relative to healthy young participants whilst elderly participants performed a computerized version of the landmark task (in which they had to judge whether a transection mark appeared closer to the right or left end of a line) on three different line lengths. This manipulation of stimulus properties led to a similar behavioral pattern in both the young and the elderly: a rightward shift in subjective midpoint with decreasing line length, which even resulted in a systematic rightward bias in elderly participants for the shortest line length (1.98° of visual angle, VA). Overall performance precision for the task was lower in the elderly participants regardless of line length, suggesting reduced landmark task discrimination sensitivity with healthy aging. This rightward shift in the attentional vector with healthy aging is likely to result from a reduction in RH resources/dominance for attentional processing in elderly participants. The significant rightward bias in the elderly for short lines may even suggest a reversal of hemisphere dominance in favor of the LH/right visual field under specific conditions.
Highlights
Studies of lateralized visuospatial attention in non-clinical samples have consistently revealed a slight but systematic group-level bias favoring the left visual field in young adults, a phenomenon termed “pseudoneglect”
For the first time, how the established line bisection bias modulator of line length interacts with healthy aging to influence lateralized visuospatial bias as displayed during landmark task performance
Young participants displayed a group-level systematic leftward bias during long line landmark task performance. This leftward bias was reduced for the medium length lines and no systematic bias was observed for performance of the task with short lines, confirming the previously reported line-length effect (McCourt and Jewell, 1999; Rueckert et al, 2002; Rueckert and McFadden, 2004; Heber et al, 2010; Thomas et al, 2012; Benwell et al, 2013a, 2014)
Summary
Studies of lateralized visuospatial attention in non-clinical samples have consistently revealed a slight but systematic group-level bias favoring the left visual field in young adults, a phenomenon termed “pseudoneglect” (see Voyer et al, 2012; Brooks et al, 2014 and Jewell and McCourt, 2000 for reviews). In order to minimize the influence of motor factors on bisection decisions, Schmitz and Peigneux (2011) recently employed the Landmark Task (a non-manual, perceptual variant of line bisection) to investigate age-related changes in pseudoneglect In this task participants are asked to estimate which of two segments of a pre-bisected line is shortest or longest (Milner et al, 1992, 1993; Harvey et al, 1995; Milner and Harvey, 1995). They found that young participants perceived the left side of bisected lines to be longer than the right side (typical of pseudoneglect), Frontiers in Aging Neuroscience www.frontiersin.org
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