Subcortical Ischemic Vascular Cognitive Impairment: Insights from Reaction Time Measures

Abstract

In this study, reaction time (RT), intraindividual variability (IIV), and errors, and the effects of practice and processing load upon such function, were compared in patients with subcortical ischemic vascular cognitive impairment (SIVCI) [n = 27] and cognitively healthy older adults (CH) [n = 26]. Compared to CH aging, SIVCI was characterized by a profile of significantly slowed RT, raised IIV, and higher error levels, particularly in the presence of distracting stimuli, indicating that the integrity and/or accessibility of the additional functions required to support high processing load, serial search strategies, are reduced in SIVCI. Furthermore, although practice speeded RT in SIVCI, unlike CH, practice did not lead to an improvement in IIV. This indicates that improvement in RT in SIVCI can in fact mask an abnormally high degree of IIV. Because IIV appears more related to disease, function, and health than RT, its status and potential for change may represent a particularly meaningful, and relevant, disease characteristic of SIVCI. Finally, a high level of within-group variation in the above measures was another characteristic of SIVCI, with such processing heterogeneity in patients with ostensibly the same diagnosis, possibly related to individual variation in pathological load. Detailed measurement of RT, IIV, errors, and practice effects therefore reveal a degree of functional impairment in brain processing not apparent by measuring RT in isolation.

Reaction Time and Visible White Matter Lesions in Subcortical Ischemic Vascular Cognitive Impairment

“…Although this test revealed significantly slower RT in SIVCI compared to CH, RT did not vary significantly with respect to whether the level of periventricular white matter change in SIVCI was mild or moderate/severe [27]. We [26] suggested this lack of significance could be the consequence of relatively low numbers of patients within each subgroup (mild, n = 15, versus moderate/severe, n = 12). There was, however, a high degree of variability in RT within each subgroup, i.e., in those ostensibly with the same disease level, together with considerable RT overlap between those classified as having mild and moderate/severe levels of disease.…”

“…Trails B revealed a significantly slowed RT in SIVCI compared to CH, with a Cohen's effect size of 1.26. It is clear that for the same participants, Trails B RT appears similarly sensitive to that evoked by the visual search test, particularly when the target was surrounded by distracting information, which resulted in a Cohen's effect size of 1.19 [26]. Both tests therefore provide robust evidence of significant RT slowing in SIVCI compared to CH.…”

“…In a recent study [26], we examined RT in SIVCI using a multi-trial, computer-based visual search test. Although this test revealed significantly slower RT in SIVCI compared to CH, RT did not vary significantly with respect to whether the level of periventricular white matter change in SIVCI was mild or moderate/severe [27].…”

“…In the first part of this study [26], RT was examined using a multi-trial, computer-based visual search test, typically used in research. Participants were instructed to respond to whether a pre-defined target was pointing to the left or right, when it appeared in isolation and when it was surrounded by distracting stimuli.…”

“…In this study, we examine RT using Trails B of the Trail Making Test (TMT) [28,29] in the same participants who took part in the visual search RT study [26]. Trails B was examined because it represents a typical clinical test of RT and we wanted to examine whether it provided RT results comparable to those resulting from the use of a research-based test of such function.…”