Visuospatial temporal order memory deficits in older adults with HIV infection

Abstract

Objective: To compare temporal order memory in older adults with and without human immunodeficiency virus (HIV) infection.

Background: The frontal and temporal lobes play a key role in temporal order memory for items in a sequence. HIV-associated episodic memory deficits correlate with damage to neocortical interneurons in the fronto-striato-thalamo-cortical pathway and with atypical activation of the medial temporal lobes. Therefore, temporal order memory may be sensitive to neuropathological changes in individuals with HIV.

Methods: In this study, 50 HIV-seropositive individuals aged ≥ 50 years and 50 seronegative controls performed a computerized visuospatial temporal order memory task. During the sample phase of each trial, participants were shown circles presented 1 at a time in a random sequence at the end of each of the 8 arms of a radial maze. During the choice phase, they were shown the maze with a circle at the ends of 2 of the arms and asked which circle had appeared earlier than the other in the original sequence.

Results: Performance in both groups improved as a function of greater temporal separation between circle presentations. However, the HIV group had significantly worse memory impairment across all temporal separations, and the impairment was independently associated with clinical deficits in executive function and delayed retrospective memory.

Conclusions: Our results extend prior findings that HIV is associated with deficits in strategic aspects of memory encoding and retrieval. The neural mechanisms warrant further research, as do potential impacts on everyday function, eg, adherence to antiretroviral drug regimens.

FIGURE 1

Schematic of our visuospatial temporal order memory task. Panel A: Sample phase: Participants are shown 1 circle at a time at the end of an arm of an 8-arm radial maze, and are asked to remember the sequence in which the circles appeared. This panel shows a random sequence of the presentation of circles from the 1st through the 8th arms. Panel B: Choice phase: Participants are shown 2 circles at once and are asked which of the 2 circles had appeared earlier than the other during the sample phase. This panel shows examples of 0-, 2-, 4-, and 6-lag temporal separations. A lag is defined as the number of circles presented between the 2 circles shown. (Adapted from Tolentino et al, 2012. Used by permission of Cold Spring Harbor Laboratory Press.)

FIGURE 2

Performance by the HIV-seropositive (HIV+) group and the seronegative (HIV−) control group on the temporal order memory task as a function of temporal separation lag. The percentages of correct answers are shown as mean ± standard error.