Effects of aging and IQ on item and associative memory

The effects of aging and IQ on performance were examined in 4 memory tasks: item recognition, associative recognition, cued recall, and free recall. For item and associative recognition, accuracy and the response time (RT) distributions for correct and error responses were explained by Ratcliff's (1978) diffusion model at the level of individual participants. The values of the components of processing identified by the model for the recognition tasks, as well as accuracy for cued and free recall, were compared across levels of IQ (ranging from 85 to 140) and age (college age, 60-74 years old, and 75-90 years old). IQ had large effects on drift rate in recognition and recall performance, except for the oldest participants with some measures near floor. Drift rates in the recognition tasks, accuracy in recall, and IQ all correlated strongly. However, there was a small decline in drift rates for item recognition and a large decline for associative recognition and cued recall accuracy (70%). In contrast, there were large effects of age on boundary separation and nondecision time (which correlated across tasks) but small effects of IQ. The implications of these results for single- and dual-process models of item recognition are discussed, and it is concluded that models that deal with both RTs and accuracy are subject to many more constraints than are models that deal with only one of these measures. Overall, the results of the study show a complicated but interpretable pattern of interactions that present important targets for modeling.     

Event-related cerebral hemodynamics reveal target-specific resource allocation for both “go” and “no-go” response-based vigilance tasks

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (CBFV) in the right and left cerebral hemispheres during the performance of a 50-min visual vigilance session. Observers monitored a simulated flight of unmanned aerial vehicles for cases in which one of the vehicles was flying in an inappropriate direction relative to its cohorts. Two types of vigilance tasks were employed: a traditional task in which observers made button press (“go”) responses to critical signals, and a modification of the traditional task called the Sustained Attention to Response Task (SART) in which “go” responses acknowledged nonsignal events and response withholding (“no-go”) signified signal detection. Signal detections and global CBFV scores declined over time. In addition, fine-grained event-related analyses revealed that the detection of signals was accompanied by an elevation of CBFV that was not present with missed signals. As was the case with the global scores, the magnitude of the transient CBFV increments associated with signal detection also declined over time, and these findings were independent of task type. The results support the view of CBFV as an index of the cognitive evaluation of stimulus significance, and a resource model of vigilance in which the need for continuous attention produces a depletion of information-processing assets that are not replenished as the task progresses. Further, temporal declines in the magnitude of event-related CBFV in response to critical signals only is evidence that the decrement function in vigilance is due to attentional processing and not specific task elements such as the required response format.     

Syndrome of inappropriate antidiuretic hormone associated with escitalopram therapy

Escitalopram is the selective serotonin reuptake inhibitor (SSRI) most recently approved for use in the United States. It is structurally related to citalopram, but is felt to have a more tolerable side-effect profile than its parent compound. Side effects are not generally serious and include headache, diarrhea, and nausea. While hyponatremia and the syndrome of inappropriate antidiuretic hormone (SIADH) have been associated with treatment with other SSRIs, there has only been one case of escitalopram-induced SIADH reported in the literature to date. We now report another case of a patient who developed SIADH after being treated with escitalopram for 4 weeks. The patient's hyponatremia improved following the discontinuation of escitalopram. Clinicians should be aware of this uncommon but significant side effect of SSRIs and monitor high-risk patients for the development of SIADH.     

Aging and the revelation effect

Previous research by M. W. Prull, L. L. Light, M. E. Collett, and R. F. Kennison (1998) has shown that older adults are not susceptible to a memory illusion referred to as the revelation effect. The authors examined the robustness of Prull et al.'s findings by having participants solve a word fragment (Experiment 1) or an anagram (Experiment 2) prior to the recognition memory decision. In both experiments, younger and older adults showed a reliable revelation effect. These results simultaneously challenge both the conclusion that older adults are not vulnerable to the revelation effect and the conclusion that aging is associated with increasing susceptibility to memory illusions.