Biomedical subjects

Jöran Lepsien

Publications and source records attributed to Jöran Lepsien.

6 recordsLinked to original sources

PubMed2006

Attentional modulation of object representations in working memory.

We investigated the role of object-based attention in modulating the maintenance of faces and scenes held online in working memory (WM). Participants had to remember a face and a scene, while cues presented during the delay instructed them to orient their attention to one or the other item. Event-related functional magnetic resonance imaging revealed that orienting attention in WM modulated the activity in fusiform and parahippocampal gyri, involved in maintaining representations of faces and scenes respectively. Measures from complementary behavioral studies indicated that this increase in activity corresponded to improved WM performance. The results show that directed attention can modulate maintenance of specific representations in WM, and help define the interplay between the domains of attention and WM.

Adult↗

PubMed2006

Cognitive control of attention in the human brain: insights from orienting attention to mental representations.

In this review, we summarize a new line of experimentation showing that attentional orienting can bias information processing in the working memory domain as well as in the perceptual domain to optimize goal-directed behavior. A new experimental paradigm was developed, which revealed that spatial orienting cues that appear after perceptual events (retro-cues), when these have been internalized into working memory representations, can retrospectively enhance performance to a similar degree as spatial precues appearing before perceptual events. As part of their facilitatory action, retro-cues diminish the costs of retrieving items from increasing loads within working memory. Hemodynamic and electrophysiological brain imaging experiments show a high degree of overlap between brain areas and dynamics involved in spatial orienting in the working memory domain compared to the perceptual domain. In addition, functional magnetic resonance imaging points to the selective involvement of frontal areas during spatial orienting in the working memory domain. The roles of different frontal areas remain to be clarified but may include both early roles in guiding spatial shifts occurring within a mnemonic context as well as selection of memorized targets amidst distracting stimuli. Experiments have also begun to reveal the ability to orient attention selectively to object-based representations in working memory and suggest that the neural representations of objects in working memory can be directly modulated by this process. The findings bolster contemporary notions of a strong theoretical relationship between attentional orienting and working memory, suggesting that these two cognitive functions interact in more ways and directions than previously considered.

Attention↗

PubMed2006

Orienting attention based on long-term memory experience.

Attentional orienting and memory are intrinsically bound, but their interaction has rarely been investigated. Here we introduce an experimental paradigm using naturalistic scenes to investigate how long-term memory can guide spatial attention and thereby enhance identification of events in the perceptual domain. In the task, stable memories of objects embedded within complex scenes guide spatial orienting. We compared the behavioral effects and neural systems of memory-guided orienting with those in a more traditional attention-orienting task in which transient spatial cues guide attention. Memory-guided attention operated within surprisingly short intervals and conferred reliable and sizeable advantages for detection of objects embedded in scenes. Event-related functional magnetic resonance imaging showed that memory-guided attention involves the interaction between brain areas participating in retrieval of memories for spatial context with the parietal-frontal network for visual spatial orienting. Activity in the hippocampus was specifically engaged in memory-guided spatial attention and correlated with the ensuing behavioral advantage.

Adult↗

PubMed2005

Task-order coordination in dual-task performance and the lateral prefrontal cortex: an event-related fMRI study.

A crucial demand in dual tasks suffering from a capacity limited processing mechanism is task-order scheduling, i.e. the control of the order in which the two component tasks are processed by this limited processing mechanism. The present study aims to test whether the lateral prefrontal cortex (LPFC) is associated with this demand. For this, 15 participants performed a psychological refractory paradigm (PRP) type dual task in an event-related functional magnetic resonance (fMRI) experiment. In detail, two choice reaction tasks, a visual (response with right hand) and an auditory (response with left hand), were presented with a temporal offset of 200 ms, while the participants were required to respond to the tasks in the order of their presentation. Importantly, the presentation order of the tasks changed randomly. Based on previous evidence, we argue that trials in which the present task order changed as compared to the previous trial (different-order trials) impose higher demands on task coordination than same-order trials do. The analyses showed that cortical areas along the posterior part of the left inferior frontal sulcus as well as the right posterior middle frontal gyrus were more strongly activated in different-order than in same-order trials, thus supporting the conclusion that one function of the LPFC for dual-task performance is the temporal coordination of two tasks. Furthermore, it is discussed that the present findings favour the active scheduling over the passive queuing hypothesis of dual-task processing.

Adult↗

PubMed2005

Directing spatial attention in mental representations: Interactions between attentional orienting and working-memory load.

Orienting spatial attention to locations in the extrapersonal world has been intensively investigated during the past decades. Recently, it was demonstrated that it is also possible to shift attention to locations within mental representations held in working memory. This is an important issue, since the allocation of our attention is not only guided by external stimuli, but also by their internal representations and the expectations we build upon them. The present experiment used behavioural measures and event-related functional magnetic resonance imaging to investigate whether spatial orienting to mental representations can modulate the search and retrieval of information from working memory, and to identify the neural systems involved, respectively. Participants viewed an array of coloured crosses. Seconds after its disappearance, they were cued to locations in the array with valid or neutral cues. Subsequently, they decided whether a probe stimulus was presented in the array. The behavioural results indicated that orienting of spatial attention within working memory attenuates the well-known effect of decreasing performance when memory load is increased. So "internal" spatial orienting seems to highlight information or facilitate search within working memory, which leads to advantages in retrieval. Imaging enabled the separation of brain areas supporting spatial orienting functions from those sensitive to working-memory load. Orienting of spatial attention to the contents of working memory activated posterior parietal cortex bilaterally, the insula, and lateral and medial frontal cortices.

Adult↗

PubMed2002

Covert reorienting and inhibition of return: an event-related fMRI study.

Using event-related fMRI, we analyzed the functional neuroanatomy of covert reorienting and inhibition of return (IOR). Covert reorienting to a target appearing within 250 msec after an invalid contralateral location cue elicited increased activation in the left fronto-polar cortex (LFPC), right anterior and left posterior middle frontal gyrus, and right cerebellum, areas that have previously been associated with attentional processes, specifically attentional change. In contrast, IOR, which leads to prolonged response times to targets that appear at the cued location at a stimulus-onset-asynchrony (SOA)>250 msec, was accompanied by increased activation in brain areas involved in oculomotor programming, such as the right medial frontal gyrus (supplementary eye field; SEF) and the right inferior precentral sulcus (frontal eye field; FEF), supporting the oculomotor bias theory of IOR. Pre-SEF and pre-FEF areas were involved both in covert reorienting and IOR. The supramarginal gyri were bilaterally involved in IOR, with the right supramarginal gyrus additionally involved in covert reorienting.

Adult↗