More than 60% of intensive care unit (ICU) patients are adults ages 60 and older, who are at high risk for ICU-acquired cognitive impairment. After ICU discharge, ICU survivors often experience sleep disturbances and inactivity, and almost 80% of ICU patients experience disturbances in circadian rhythm, which may affect cognitive function. Understanding the optimal, chronotherapeutic timing of cognitive interventions is crucial to promote circadian realignment and cognitive function, and may improve intervention feasibility, acceptability, and efficacy. Specific Aim 1 will determine feasibility, acceptability, and preliminary effect sizes for: 1) a morning session of a computerized cognitive training intervention \[COG\]; and 2) a late afternoon/early evening session of the COG intervention; compared to 3) standard inpatient care/usual care \[UC\]. Specific Aim 2 will examine circadian rhythm parameters to determine the optimal timing of the daily COG intervention. Exploratory Aim 3 will explore if the effects of the COG intervention on cognitive function are mediated by daytime activity, and explore if selected biological and clinical factors moderate intervention effects on cognitive function.