Prospective Memory in HIV-1 Infection

Abstract

The cognitive deficits associated with HIV-1 infection are thought to primarily reflect neuropathophysiology within the fronto-striato-thalamo-cortical circuits. Prospective memory (ProM) is a cognitive function that is largely dependent on prefronto-striatal circuits, but has not previously been examined in an HIV-1 sample. A form of episodic memory, ProM involves the complex processes of forming, monitoring, and executing future intentions vis-à-vis ongoing distractions. The current study examined ProM in 42 participants with HIV-1 infection and 29 demographically similar seronegative healthy comparison (HC) subjects. The HIV-1 sample demonstrated deficits in time-and event-based ProM, as well as more frequent 24-hour delay ProM failures and task substitution errors relative to the HC group. In contrast, there were no significant differences in recognition performance, indicating that the HIV-1 group was able to accurately retain and recognize the ProM intention when retrieval demands were minimized. Secondary analyses revealed that ProM performance correlated with validated clinical measures of executive functions, episodic memory (free recall), and verbal working memory, but not with tests of semantic memory, retention, or recognition discrimination. Taken together, these findings indicate that HIV-1 infection is associated with ProM impairment that is primarily driven by a breakdown in the strategic (i.e., executive) aspects of retrieving future intentions, which is consistent with a prefronto-striatal circuit neuropathogenesis.HIV-1 infiltrates the brain during the initial phases of systemic infection where it promotes neuronal and glial injury (e.g., dendritic simplification) (Petito, 2004). Prevalent throughout the neocortex and white matter tracts, HIV-1-associated neuropathology is perhaps most

Neuropsychological substrates and everyday functioning implications of prospective memory impairment in schizophrenia

“…Consistent with the findings of Shum et al (2004), our results showed a modest correlation between ProM and executive functions; however, ProM performance was also associated with performance in several neuropsychological domains, including attention, working memory, processing speed, and learning. Such associations are commensurate with conceptual models suggesting that optimal ProM functioning relies on multiple cognitive substrates (e.g., Carey et al, 2006). Interestingly, learning, but not delayed recall, uniquely predicted variance in ProM performance.…”

“…Cognitive measures assessed the domains of information processing speed (Trail Making Test, Part A [Reitan and Wolfson, 1993], Symbol Search and Digit Symbol subtests of the WAIS-III [Wechsler, 1997a]); attention (Continuous Performance Test-Identical Pairs d-prime [Cornblatt et al, 1989], Digit Span Forward subtest of the WAIS-III [Wechsler, 1997a], Digit Span Distractibility distracted and non-distracted total scores [Oltmanns and Neale, 1975]); working memory (Letter Number Sequencing and Digit Span Backward subtests of the WAIS-III [Wechsler, 1997a]); learning (total immediate recall scores from the Hopkins Verbal Learning Test-Revised [Benedict et al, 1998], Logical Memory from the Wechsler Memory Scale-Third Edition [Wechsler, 1997b], and Brief Visuospatial Memory Test-Revised [Benedict, 1997]); memory (percent retention at delay for each of the learning tests); and executive functioning (Trail Making Test, Part B minus Part A [Reitan and Wolfson, 1993], Wisconsin Card Sorting Test-64 card version total correct [Kongs et al, 2000], Stroop Color-Word Interference Test interference measure [Golden, 1978], Controlled Oral Word Association Test FAS total correct [Benton and Hamsher, 1989] Raskin, 2004), which is a standardized, 30-minute task whose psychometric properties (Woods et al, in pressb) and construct validity are well supported (e.g., Carey et al, 2006;Woods et al, 2007a,b, Woods et al, in press-b). The MIST includes eight ProM tasks counterbalanced for 1) length of delay (2 or 15 minutes); 2) response type (verbal or action); and 3) cue type (time-based, e.g., "In 2 minutes, ask me what time this session ends," or event-based, e.g., "When I hand you a postcard, self-address it").…”

“…A 24-hour delay task (leaving a telephone message for the examiner the following day) was also administered. The following variables were calculated from the MIST: 1) summary score (6 points are possible for each of the 8 items, for a maximum score of 48); 2) time-based scale (8 points possible); 3) event-based scale (8 points possible); 4) recognition total (8 points possible); 5) a retrieval index (i.e., recognition hits -free recall; see Carey et al, 2006); 6) 24-hr delay (2 points possible); and 7) four error types, including No Response, Task Substitutions (i.e., performance of the wrong task), Loss of Content (i.e., remembering that an intention should be performed, but forgetting the content of the intention), and Loss of Time errors (i.e., executing a correct intention that is ±15% of the target time).…”

“…However, ProM has been relatively understudied in schizophrenia, particularly in comparison to retrospective memory. ProM is a multi-step cognitive process conceptualized to function in four stages (Carey et al, 2006;Einstein and McDaniel, 1990;Knight, 1998): (1) Intention formation involves encoding the intention and its corresponding action, requiring both organizational and planning skills. (2) The delay maintenance interval requires retaining the intention during unrelated activities, and may require time monitoring to respond to time cues.…”

“…(4) Intention execution involves performing the intended task. Given the inherent complexity of this model, ProM is purported to depend upon the integrity of multiple cognitive abilities associated with frontostriatal and temporolimbic systems (Simons et al, 2006), including executive functions, working memory, episodic retrospective memory, and information processing speed (e.g., Carey et al, 2006).…”