Does the capacity of visual short-term memory (VSTM) depend on the complexity of the objects represented in memory? Although some previous findings indicated lower capacity for more complex stimuli, other results suggest that complexity effects arise during retrieval (due to errors in the comparison process with what is in memory) that is not related to storage limitations of VSTM, per se. We used ERPs to track neuronal activity specifically related to retention in VSTM by measuring the sustained posterior contralateral negativity during a change detection task (which required detecting if an item was changed between a memory and a test array). The sustained posterior contralateral negativity, during the retention interval, was larger for complex objects than for simple objects, suggesting that neurons mediating VSTM needed to work harder to maintain more complex objects. This, in turn, is consistent with the view that VSTM capacity depends on complexity.

In three experiments, we examined the effects of old age on the reaction time (RT) decrement associated with task alternation. Old age was associated with increased mixing-cost, which is the RT difference between two conditions: mixed-task, where trials involving two tasks were intermixed, and single-task, where all the trials involved the same task. Old age was also associated with an increased switching-cost, which is the RT difference between trials in which the task was just changed and trials in which it was repeated. There was also indication of a slowed passive dissipation of task set adopted in the preceding trial. In contrast to these impairments, old age was also associated with an almost intact ability to prepare for an upcoming task switch. This ability was indicated by a normal reduction in switching-cost due to an increase in the time allowed to prepare for the switch. We discuss the implications of the results in relation to theories of task-switching and to the underlying brain mechanisms, especially with respect to the effect of old age on the prefrontal cortex.

The goal of the present investigation was to discover whether visual working memory maintenance for faces is modulated by facial expression using event-related potentials (ERPs). Each trial consisted of two sequential arrays, a memory array and a test array, each including either two or four faces with neutral or fearful expressions. The faces were displayed to the left and to the right of a central fixation cross. Two central arrows cued participants to encode one face or two faces displayed on one side of the memory array. The sustained posterior contralateral negativity (SPCN) component of the ERP time-locked to the onset of the memory array was used as an index of visual working memory maintenance. Visual working memory performance was quantified using indexes of memory capacity (Cowan's K and K-iterative), a standard index of sensitivity (d'), and reaction times (RTs). Relative to neutral faces, superior memory and longer change-detection RTs to fearful face identities were observed when two faces were displayed on the cued side of the memory array. Fearful faces elicited an enhanced SPCN relative to neutral faces, especially when only one face was displayed on the cued side of the memory array. These findings suggest increased maintenance in visual working memory of faces with a fearful expression relative to faces with a neutral expression and that the representational format in which fearful faces are stored in memory may be characterized by enhanced resolution relative to that subtended in the maintenance of neutral faces.

Acitretin does not appear to cause significant long-term side effects at low doses; the implications for thousands of patients are that use of this medication can be continued for long periods of time with routine monitoring.

Studies have shown that task sets could be configured endogenously (i.e., on the basis of memory) according to an explicit sequence or exogenously according to a task cue. In two experiments, we examined whether an implicitly learned sequence could facilitate task set configuration without participants' intention. These experiments led to opposite conclusions regarding this question, but their methodology made it impossible to distinguish between the interpretations. We alteredthe task-switching paradigm by embedding a hidden task sequence, while randomizing all other aspects, including perceptual (i.e., task cues) and motor elements. We found that a sequence of tasks, proper, was learned implicitly and that the memory of that sequence endogenously facilitatedtask decision processes without the participants' explicit knowledge.