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While monkeys performed spatial working memory tasks, cue- (C), delay- (D), and response-period (R) activities or their combinations (CD, CR, DR, CDR) were observed in prefrontal neurons. In the present study, we tried to understand information flow during spatial working memory performances and how each task-related neuron contributed to this process. We first characterized each neuron based on which...
Previous studies of dual-task performance have demonstrated that encoding and retrieval processes are differentially affected by the simultaneous performance of a secondary task. Whilst dual task demands during encoding have a detrimental effect on memory performance, dual task demands during retrieval have a detrimental effect on secondary task performance. However, dual task effects on memory during...
Previous research has indicated that patients with semantic short-term memory (STM) deficits demonstrate unusual intrusions of previously presented material during serial recall tasks (Martin and Lesch, 1996). These intrusions suggest excessive proactive interference (PI) from previous lists. Here, we explore one such patient's susceptibility to PI. Experiment 1 demonstrated patient M.L.'s extreme...
Primate prefrontal delay neurons are involved in retaining task-relevant cognitive information in working memory (WM). Recent studies have also revealed primate prefrontal delay neurons that are related to reward/omission-of-reward expectancy. Such reward-related delay activities might constitute “affective WM” (Davidson, 2002). “Affective” and “cognitive” WM are both concerned with representing not...
Functional magnetic resonance imaging (fMRI) has shown that brain activation during performance of working memory (WM) tasks under high memory loads is altered in adults with severe traumatic brain injury (TBI) relative to uninjured subjects (Perlstein et al., 2004; Scheibel et al., 2003). Our study attempted to equate TBI patients and orthopedically injured (OI) subjects on performance of an N-Back...
Common activations in prefrontal cortex (PFC) during episodic and semantic long-term memory (LTM) tasks have been hypothesized to reflect functional overlap in terms of working memory (WM) and cognitive control. To evaluate a WM account of LTM-general activations, the present study took into consideration that cognitive task performance depends on the dynamic operation of multiple component processes,...
Prefrontal cortex (PFC) supports the maintenance of currently relevant information in working memory (WM). How the PFC is organized for the maintenance of disparate information, how this information is conjoined into a unified whole, and how the representation may change with task demands is still debated. The pattern of neural activity during maintenance of either abstract visual patterns, locations,...
Neuroimaging studies exploring the neural substrates of executive functioning have only rarely investigated whether the non-executive characteristics of the experimental executive tasks could contribute to the observed brain activations. The aim of this study was to determine cerebral activity in three different tasks involving the updating executive function. The experimental updating tasks required...
We used event-related functional magnetic resonance imaging (fMRI) to measure prefrontal cortex (PFC) activity while younger and older adults performed an item-recognition task in which the memory-set size varied between 1 and 8 letters. Each trial was composed of a 4-sec encoding period in which subjects viewed random letter strings, a 12-sec retention period and a 2-sec retrieval period in which...
Executive functions include processes by which important information (e.g., words, objects, task goals, contextual information) generated via perception or thought can be foregrounded and thereby influence current and subsequent processing. One simple executive process that has the effect of foregrounding information is refreshing – thinking briefly of a just-activated representation. Previous studies...
Visual working memory (WM) is a limited capacity system which maintains information about objects in the immediate visual environment. Recent neurophysiological and neuroimaging studies have identified sustained memory-item specific activity during the retention period of WM tasks, and this activity may be a physiological substrate of maintaining representations in WM. In the present study, we present...
The assumption that ignoring irrelevant sound in a serial recall situation is identical to ignoring a non-target channel in dichotic listening is challenged. Dichotic listening is open to moderating effects of working memory capacity (Conway et al., 2001) whereas irrelevant sound effects (ISE) are not (Beaman, 2004). A right ear processing bias is apparent in dichotic listening, whereas the bias is...
Clinical research on facial emotions has focused primarily on differences between right and left hemiface. Social psychology, however, has suggested that differences between upper versus lower facial displays may be more important, especially during social interactions. We demonstrated previously that upper facial displays are perceived preferentially by the right hemisphere, while lower facial displays...
We report a 55 year-old right-handed man who presented with topographical disorientation following left retrosplenial hemorrhage. His directional information about familiar places, encoded by previous navigation, was severely impaired, and he could not learn the direction to new places in large-scale spaces beyond the range of visual surveillance. By contrast, he had no difficulties with directional...
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