Asymmetrical distractibility of global and focal visuospatial attention during segmental and total compound line bisections.

BACKGROUND/OBJECTIVES: Compound horizontal lines are composed of 2 segments of unequal length and width. Line bisection requires that the participants attend to the entire line (global attention). The longer segment often distracts participants, suggesting that attention directed to this segment (focal attention) disrupts the allocation of global attention. This study attempted to learn whether the allocation of focal attention to a line segment is distracted by global attention allocated to the entire line and whether there are right-left distraction asymmetries when allocating focal or global attention. METHOD: Twenty-four healthy adults (12 > 65 years old) attempted to bisect horizontal lines composed of 2 segments of unequal length, with the larger segment placed to the right or left. They were also asked to bisect the longer segment of these lines. RESULTS: When allocating focal attention to the larger segment, healthy participants were more distracted when the smaller segment was on the left than on the right. In contrast, when attempting to allocate global attention to the entire line, participants were more distracted when the larger segment was on the right side. There were no significant differences between older and younger participants. CONCLUSIONS: The asymmetrical global distraction during segment bisection might be related to the right hemisphere's dominance in mediating global attention and allocating attention leftward. In contrast, the asymmetrical focal distraction during full-line bisection might be related to the left hemisphere's dominance in mediating focal attention and allocating attention toward the right. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Background distraction during vertical solid and character line bisections.

Background-objectives: When vertical lines are positioned above or below the center of the page, line bisection deviates toward the center of the page, suggesting that the edges of the page distract the allocation of attention to the line. A letter-character line (LCL) bisection requires both global and focal attention, to identify the target letter closest to the line's center. If more focal and less global attention is allocated to a LCL, more global attentional resources may be available and inadvertently allocated to the page. Alternatively, if the allocation of focal attention to a LCL inhibits global attentional processing, there may be less distraction by the page. METHOD: Twenty-four healthy adults (12 older) bisected vertical solid and character lines centered, or positioned closer to the top or bottom of the page. RESULTS: There was no difference between bisection of solid and character lines centered on the page. Page-related deviations were greater with character lines than solid line bisections, and greater for lines positioned toward the top than the bottom of the page. With lines positioned toward the top, the older participants' attempted bisections were higher than those of the younger participants. CONCLUSIONS: These results suggest that the allocation of focal attention increases global attentional distractibility and that global-background attentional distraction is greater when the vertical lines are placed in the upper part of the page. Older participants appeared to be less distracted when lines were placed toward the top of the page, but the reason for this age difference requires further research.

The aging brain: Movement speed and spatial control.

BACKGROUND/OBJECTIVES: With aging, people commonly develop motor slowing (bradykinesia). Although this slowness with aging may be entirely related to degradation of the cerebral networks important in motor programing, it is possible that, at least in part, it may be a learned procedure for enhancing the accuracy and/or precision of movements. The goal of this study is to test these contradictory hypotheses. METHODS: Twenty-four healthy adults, 12 younger than age 26 and 12 older than age 65 were asked to make alternative marks with a pen between a card centered in front of them and a series of circles distributed across a page. Performance was timed, and participants were instructed to complete the task as quickly as possible while not sacrificing accuracy for speed. The circle sizes and hand used varied by trial. RESULTS: The older adults performed the task more slowly for all target circle diameters. As the circles decreased in size, the younger adults performed the task more rapidly than did the older participants, but the younger participants also had a greater decline in accuracy. CONCLUSIONS: During this aiming task, healthy older adults were less likely than younger adults to sacrifice accuracy for speed. Thus, at least in part, their slowing may be a learned adaptive strategy.

The relationship between semantic knowledge and conceptual apraxia in Alzheimer disease.

BACKGROUND: Conceptual apraxia (CA), a feature of Alzheimer disease (AD), can be detected by asking participants to identify the correct tool to act on an object. Assessment can be based on either learned associations (a tool selection test) or the mechanical properties that the tool needs to alter the target object (an alternative tool selection test). OBJECTIVES: We wanted to determine whether knowledge of semantic taxonomic relations (intrinsic properties shared by items) correlated with performance on tests for CA in people with AD or amnestic mild cognitive impairment (aMCI). METHODS: We tested 10 participants with AD, 12 with aMCI, and 18 healthy older adults for CA using an alternative tool selection test, a tool selection test, and a test of taxonomic relations. RESULTS: The aMCI group did not differ from the control group on the CA tests. The patients with AD were impaired on all tests except tool selection; their performance on the alternative tool selection test correlated significantly with their performance on the taxonomic relations test. CONCLUSIONS: The correlation between performances on the alternative tool selection test and the taxonomic relations test in AD suggests a common pathophysiologic substrate, either impairment in accessing conceptual-semantic representations or a degradation of these representations.