A rightward shift in the visuospatial attention vector with healthy aging

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.

Adult developmental trajectories of pseudoneglect in the tactile, visual and auditory modalities and the influence of starting position and stimulus length

“…The present results for visual bisection are at odds with some published data which has suggested that older adults show reduced pseudoneglect (Fujii et al, 1995;Stam & Bakker, 1990;Benwell et al, 2014b;Schmitz & Peigneux, 2011;Barrett & Craver-Lemley, 2008;Goedert et al, 2010), so it is necessary to consider why this may be. One speculative candidate may be method: Benwell et al (2014b) and Schmitz & Peigneux (2011) both used variants of the 'Landmark' task, in which judgements are made about a pre-bisected presented line: it may be that this task requires more fine grained perceptual evaluation, and thus elicits higher levels of real or perceived difficulty, , and that this causes additional recruitment of areas in the contralateral hemisphere, which is a clear possibility under the CRUNCH model of aging (Reuter-Lorenz and Cappell, 2008) and may also be so under the HAROLD model (Cabeza, 2002;Cabeza, et al, 1997;2002).…”

“…The observation of consistent lateral bias in representational tasks like mental number line and tactile bisection are especially problematic under the HAROLD model with its focus on decreasing hemispheric asymmetry over age especially in prefrontal cortex, given the role Running Head: ADULT DEVELOPMENTAL TRAJECTORIES 26 prefrontal cortex is known to play in spatial memory (Courtney et al, 1998). For similar reasons, our findings are not in line with the right hemi-ageing model (Dolcos et al, 2002;Prodan et al, 2007) nor with findings indicating rightward biases for older adults (Benwell et al, 2014b).…”

“…There is now additional research to draw upon. Reduced or reversed rightward biases have been reported on visuo-spatial line bisection or landmark tasks (where participants classify pre-bisected line stimuli: Barrett & Craver-Lemley, 2008;Benwell, Thut, Grant & Harvey, 2014b;Schmitz & Peigneux, 2011;Goedert, LeBlanc, Tsai & Barrett, 2010; see also Schmitz, Dehon & Peigneux, 2013). There is also evidence that males and females may produce differential patterns of pseudoneglect over aging, with older females exhibiting more consistent left biases, whilst older males may exhibit a drift into rightward bias with age (Varnava & Halligan, 2007;Chen, Goedert, Murray, Kelly, Ahmeti, Barrett, 2011).…”

“…One speculative candidate may be method: Benwell et al (2014b) and Schmitz & Peigneux (2011) both used variants of the 'Landmark' task, in which judgements are made about a pre-bisected presented line: it may be that this task requires more fine grained perceptual evaluation, and thus elicits higher levels of real or perceived difficulty, , and that this causes additional recruitment of areas in the contralateral hemisphere, which is a clear possibility under the CRUNCH model of aging (Reuter-Lorenz and Cappell, 2008) and may also be so under the HAROLD model (Cabeza, 2002;Cabeza, et al, 1997;2002). However, the other studies listed have used more traditional line bisection, so this cannot be the sole explanation.…”

An investigation of the mechanisms underlying the effects of viewing distance and stimulus length on attentional asymmetries during line bisection

“…Results have shown that line length and fatigue have additive effects, suggesting that the bisection asymmetries for short and long lines are governed by a common set of processes. A similar additive effect was observed by Benwell, Thut, Grant, and Harvey (2014) for the effect of ageing, which is also known to reduce right hemisphere activity.…”