Episodic memory assessment: effects of sex and age on performance and response time during a continuous recognition task.

Introduction: Continuous recognition tasks (CRTs) assess episodic memory (EM), the central functional disturbance in Alzheimer's disease and several related disorders. The online MemTrax computerized CRT provides a platform for screening and assessment that is engaging and can be repeated frequently. MemTrax presents complex visual stimuli, which require complex involvement of the lateral and medial temporal lobes and can be completed in less than 2 min. Results include number of correct recognitions (HITs), recognition failures (MISSes = 1-HITs), correct rejections (CRs), false alarms (FAs = 1-CRs), total correct (TC = HITs + CRs), and response times (RTs) for each HIT and FA. Prior analyses of MemTrax CRT data show no effects of sex but an effect of age on performance. The number of HITs corresponds to faster RT-HITs more closely than TC, and CRs do not relate to RT-HITs. RT-HITs show a typical skewed distribution, and cumulative RT-HITs fit a negative survival curve (RevEx). Thus, this study aimed to define precisely the effects of sex and age on HITS, CRs, RT-HITs, and the dynamics of RTs in an engaged population. Methods: MemTrax CRT online data on 18,255 individuals was analyzed for sex, age, and distributions of HITs, CRs, MISSes, FAs, TC, and relationships to both RT-HITs and RT-FAs. Results: HITs corresponded more closely to RT-HITs than did TC because CRs did not relate to RT-HITs. RT-FAs had a broader distribution than RT-HITs and were faster than RT-HITs in about half of the sample, slower in the other half. Performance metrics for men and women were the same. HITs declined with age as RT-HITs increased. CRs also decreased with age and RT-FAs increased, but with no correlation. The group over aged 50 years had RT-HITs distributions slower than under 50 years. For both age ranges, the RevEx model explained more than 99% of the variance in RT-HITs. Discussion: The dichotomy of HITs and CRs suggests opposing cognitive strategies: (1) less certainty about recognitions, in association with slower RT-HITs and lower HIT percentages suggests recognition difficulty, leading to more MISSes, and (2) decreased CRs (more FAs) but faster RTs to HITs and FAs, suggesting overly quick decisions leading to errors. MemTrax CRT performance provides an indication of EM (HITs and RT-HITs may relate to function of the temporal lobe), executive function (FAs may relate to function of the frontal lobe), processing speed (RTs), cognitive ability, and age-related changes. This CRT provides potential clinical screening utility for early Alzheimer's disease and other conditions affecting EM, other cognitive functions, and more accurate impairment assessment to track changes over time.

Correctness and response time distributions in the MemTrax continuous recognition task: Analysis of strategies and a reverse-exponential model.

A critical issue in addressing medical conditions is measurement. Memory measurement is difficult, especially episodic memory, which is disrupted by many conditions. On-line computer testing can precisely measure and assess several memory functions. This study analyzed memory performances from a large group of anonymous, on-line participants using a continuous recognition task (CRT) implemented at https://memtrax.com. These analyses estimated ranges of acceptable performance and average response time (RT). For 344,165 presumed unique individuals completing the CRT a total of 602,272 times, data were stored on a server, including each correct response (HIT), Correct Rejection, and RT to the thousandth of a second. Responses were analyzed, distributions and relationships of these parameters were ascertained, and mean RTs were determined for each participant across the population. From 322,996 valid first tests, analysis of correctness showed that 63% of these tests achieved at least 45 correct (90%), 92% scored at or above 40 correct (80%), and 3% scored 35 correct (70%) or less. The distribution of RTs was skewed with 1% faster than 0.62 s, a median at 0.890 s, and 1% slower than 1.57 s. The RT distribution was best explained by a novel model, the reverse-exponential (RevEx) function. Increased RT speed was most closely associated with increased HIT accuracy. The MemTrax on-line memory test readily provides valid and reliable metrics for assessing individual episodic memory function that could have practical clinical utility for precise assessment of memory dysfunction in many conditions, including improvement or deterioration over time.

Now is the Time to Improve Cognitive Screening and Assessment for Clinical and Research Advancement.

Wang et al. analyze Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment accuracy as screening tests for detecting dementia associated with Alzheimer's disease (AD). Such tests are at the center of controversy regarding recognition and treatment of AD. The continued widespread use of tools such as MMSE (1975) underscores the failure of advancing cognitive screening and assessment, which has hampered the development and evaluation of AD treatments. It is time to employ readily available, efficient computerized measures for population/mass screening, clinical assessment of dementia progression, and accurate determination of approaches for prevention and treatment of AD and related conditions.

Sedation modulates recognition of novel stimuli and adaptation to regular stimuli in critically ill adults.

BACKGROUND: Responsiveness of critically ill patients is affected by disease and by therapy. Subjective tests of responsiveness (e.g., modified Ramsay score) reflect global integrity of a response arc that includes transduction, perception, classification, and an overt response. The performance of individual components is usually not assessed. OBJECTIVE: To determine whether an association exists among sedative medications and the brain's component information processing and adaptive abilities. DESIGN: Initial observational study of a convenience sample. SETTING: A surgical intensive care unit of a university hospital. PATIENTS: A total of 22 endotracheally intubated, mechanically ventilated patients chemically sedated with narcotics and a benzodiazepine (n = 12), or narcotics and propofol (n = 10) using sedation protocols. INTERVENTIONS: None. MEASUREMENTS AND FINDINGS: Patients were presented flashes of light and pulses of sound at fixed or random intervals. Patients receiving low doses of fentanyl and propofol adapted to stimuli presented at fixed intervals and retained the response to novelty. Patients receiving higher doses of those medications did not respond to novelty and responded to stimuli presented at fixed intervals as if they were novel. Patients receiving fentanyl and benzodiazepines had generally weaker responses to all stimuli. Moreover, their responses to fixed and random stimuli were similar. At low doses, the patients retained responses to novelty and adapted to fixed, whereas at higher doses the opposite was observed: the response to novelty was lost and the patients responded to fixed stimuli as if they were novel. These observations suggest that the sedative medications generally accelerate the physiologic decay of stimuli as they engage the brain's information processing and adaptive abilities and further suggest that different sedative medications may have different effects on the brain. CONCLUSIONS: Commonly administered sedative medications may alter the brain's biophysical state and thereby modulate specific aspects of the brain's information processing and adaptive functions. These functions can be interrogated even when the patient is seemingly unresponsive. If this observation is confirmed in subsequent prospective controlled randomized trials, electrophysiologic interrogation of the brain's information processing and adaptive capacities could serve as an adjunct to clinical assessment of responsiveness and management of sedative medications.