Contemporary issues in working memory research

Transcription

1 1 st Workshop of The International Research Training Group Adaptive Minds Neural and Environmental Constraints on Learning and Memory Topic: Contemporary issues in working memory research Department of Psychology, Saarland University, Building A 2 4, Room Nr Saarbrücken, Organized by Hubert D. Zimmer & Katja Umla-Runge

2 Program Thursday (11.12.): Methodological Course A, Combined fmri + ERP (Conference language: German) ERP and fmri studies on visual working memory Part 1 Christoph Bledowski Medical Psychology, Goethe University, Frankfurt/Main Coffee Break ERP and fmri studies on visual working memory Part 2 Christoph Bledowski Medical Psychology, Goethe University, Frankfurt/Main Dinner (active participants) Da Toni, Mainzerstraße 3, Saarbrücken

3 Friday (12.12.): Research Presentations (Conference language: German and English) Age differences in working memory capacity and selectivity across the lifespan Markus Werkle-Bergner, Myriam Sander & Ulman Lindenberger Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin Limits and costs of storage in visual working memory Hubert D. Zimmer & Anna M. Arend IRTG Adaptive Minds, Brain & Cognition Unit, Saarland University, Saarbrücken Coffee Break Short-term maintenance of action information in the dorsal stream Katja Fiehler & Frank Rösler Experimental & Biological Psychology, Philipps-University, Marburg Working and long term memory processes involve the same action-related neural substrates Katja Umla-Runge & Hubert D. Zimmer IRTG Adaptive Minds, Brain & Cognition Unit, Saarland University, Saarbrücken Lunch break Trägt Aufrechterhaltung im Arbeitsgedächtnis zur Speicherung im Langzeitgedächtnis bei? Patrick Khader Allgemeine & Biologische Psychologie, Philipps-Universität, Marburg Contributions of modality-specific brain regions to working memory and long-term memory processes Thorsten A. Brinkmann & Hubert D. Zimmer Brain & Cognition Unit, Saarland University, Saarbrücken Coffee break The sketchpad: Visual or visuospatial? Boris Suchan Institute of Cognitive Neuroscience, Neuropsychology, Ruhr University, Bochum Dinner Oishii Restaurant, Berliner Promenade 17-19, Saarbrücken

4 Saturday (13.12.): Methodological Course B, Phase Locking (Conference language: German) It s swinging in the brain: Phase synchronization in the EEG Part 1 Paul Sauseng Physiological Psychology, University of Salzburg Coffee break It s swinging in the brain: Phase synchronization in the EEG Part 2 Paul Sauseng Physiological Psychology, University of Salzburg

5 Abstracts ERP and fmri Studies on Visual Working Memory Christoph Bledowski Medizinische Psychologie, Goethe Universität Frankfurt/Main In my talk I will present three studies on different aspects of visual working memory (WM) which used neuroimaging techniques such as EEG and fmri and their combination. I will start with an ERP study which took advantage of the method's fine temporal resolution providing evidence for different time courses for the processing of match, similar and dissimilar probes during short-term recognition. Next, I will show how rapid event-related fmri helps to reveal spatially distinct neuronal patterns associated with selection and updating of information held active in working memory. Finally, I will present data from a published study (*) which combined ERP and fmri signals to overcome the limitations of EEG and fmri, when these techniques are used separately. Using the study data as an example, I will show how fmriconstrained source analysis integrates ERP and fmri data to elucidate sequences of activity in various brain areas underlying working memory retrieval. (*) Bledowski et al. (2006). Mental chronometry of working memory retrieval: A combined fmri and ERP approach. Journal of Neuroscience, 26,

6 Contributions of modality-specific brain regions to working memory and longterm memory processes Thorsten A. Brinkmann & Hubert D. Zimmer Brain & Cognition Unit, Saarland University, Saarbrücken In the present studies we investigated whether brain regions specialized in the processing of visual or auditory information contribute to working memory (WM) as well as long-term memory (LTM) processes. Recent studies using EEG-recordings have shown that during both tasks, processing of different types of information (e.g. spatial or object information) can be dissociated according to the scalp topography of slow-wave potentials. Additionally, fmri studies revealed an overlap of activation during working memory and long-term memory tasks, suggesting that WM and LTM representations were provided by the same neuronal networks. Therefore, we hypothesized that working memory (maintenance and target) and long-term memory (retrieval and target) processes recruit the same modality-specific brain regions (primary visual and auditory cortex), indicated by identical topographies of slow-wave potentials (ERPs) and overlapping activations (fmri). Activations during auditory information processing should be obtained in the auditory cortex and leading to a more frontally distributed topography of ERP slow wave potentials. The processing of visual information should reveal activations in the visual cortex and slow potentials should be observed at parietal electrode sides. Furthermore, by using a working memory task as the encoding phase of a long-term memory task, we were able to directly compare modality-specific processes in both types of tasks.

7 Short-term maintenance of action information in the dorsal stream Katja Fiehler & Frank Rösler Experimental and Biological Psychology, Philipps-University Marburg There is wide agreement that the dorsal action stream projecting from primary visual areas to the posterior parietal cortex processes visual information for online action control, i.e., a crude, fast and automatic visuomotor transformation process. Delayed motor acts, however, are assumed to be processed by the ventral perception stream which projects from primary visual areas to the inferotemporal cortex. In contrast, research in non-human primates suggests that the posterior parietal cortex is also engaged in memory-guided actions. Using a delayed hand manipulation task, the anterior intraparietal area of the monkey elicited sustained activity during the delay period. Using functional magnetic resonance imaging (fmri), we investigated the neural correlates of short-term maintenance of action-related information. The results showed significant activation in the left anterior intraparietal sulcus which systematically varied with memory load. We propose that the action-representation system of the dorsal stream is utilized not only for immediate action control but also for working-memory maintenance of action information.

8 Trägt Aufrechterhaltung im Arbeitsgedächtnis zur Speicherung im Langzeitgedächtnis bei? Patrick Khader Allgemeine und Biologische Psychologie, Philipps-Universität Marburg In einer EEG-Studie untersuchten wir die Beziehung zwischen der Aufrechterhaltung von Informationen im Arbeitsgedächtnis (AG) und deren Einspeicherung ins Langzeitgedächtnis (LZG). Hierbei wurde eine delayed-matching-to-sample - Aufgabe (DMTS) mit verbalen und bildhaften Reizen durchgeführt, der ein unerwarteter Wiedererkennungstest folgte. Während des Verzögerungsintervalls der DMTS-Aufgabe differenzierten langsame ereigniskorrelierte Potentiale generell zwischen den Reizarten, mit negativeren Potentialen über dem linken präfrontalen Kortex für verbale Reize und über dem okzipitalen Kortex für Objektreize. Darüber hinaus waren die Potentiale an diesen Orten jeweils negativer für später erinnerte im Vergleich zu vergessenen Reizen, was dafür spricht, dass Erstere einen erhöhten Aktivierungsgrad in materialspezifischen AG-Speichern aufweisen. Aber ist eine verstärkte AG-Mehrbelastung ausreichend für eine erfolgreiche Speicherung im LZG? Dieser Frage gingen wir in mehreren Verhaltensstudien nach, in denen Wortreihen während des Verzögerungsintervalls einer DMTS-Aufgabe entweder aufrechterhalten oder in ihrer Reihenfolge vertauscht werden sollten. Das Verzögerungsintervall wurde hierbei so kurz gewählt, dass eine semantische Elaboration der Reize nicht möglich war. Es zeigte sich, dass die transformierten Wörter nur wenig besser erinnert wurden (3-6%) als die aufrechterhaltenen Wörter, was gegen eine bedeutende Rolle der AG-Belastung für die Speicherung im LZG spricht.

9 Its swinging in the brain: Phase synchronization in the EEG Paul Sauseng Physiological Psychology, University of Salzburg Due to its excellent temporal resolution phase dynamics in the EEG are often superior to the rather slow amplitude dynamics of human electroencephalography. Three different kinds of phase synchronization will be discussed: (i) phase coupling between brain sites, (ii) phase synchronization across frequencies, and (iii) phaselocking to external events. Techniques how to gain phase information and how to estimate phase synchronization are presented. Moreover, interpretation (and misinterpretation!) of phase synchronization estimates will be dealt with. Empirical examples for the different kinds of EEG phase dynamics will be presented.

10 The sketch pad: Visual or visuospatial? Boris Suchan Institute of Cognitive Neuroscience, Department of Neuropsychology, Ruhr University Bochum Based on Baddeley and Hitchs (1974) classical working memory model, Smith and Jonides (1999) published an influential modified model which integrated results from functional imaging studies of the recent years. The present talk will critically discuss the model suggested by Smith and Jonides and will present some result from functional imaging studies which further modify this model. The focus will be on the functional neuroanatomy of visual and visuospatial processes in working memory as well as executive functions and prefrontal cortex organisation. Results of the presented studies suggest that visual and visuospatial working memory relies on separable neural circuits including also the prefrontal cortices which might converge under specific demands. This phenomenon supports results from cognitive psychology (Cornoldi and Vecchi; 2000) and also functional neuroanatomy (Petrides; 2000). Additionally, evidence for an amodal visual and auditory object working memory will be discussed as well as hippocampal and thalamic activation pattern which in general are associated with long term memory functions.

11 Working and long term memory processes involve the same action-related neural substrates Katja Umla-Runge & Hubert D. Zimmer IRTG Adaptive Minds, Brain & Cognition Unit, Saarland University, Saarbrücken We hypothesize that working and long term memory are represented by the same content-specific neural structures (e.g. visual sensory, auditory sensory, motor). A previous study has demonstrated that the retention of actions in working memory selectively activates an action-specific processing network consisting of left inferior frontal and inferior parietal cortices (Mecklinger et al., 2004). Our experiment aimed at elucidating the overlap of an action processing network during retention in working memory and retrieval from long term memory. Sixteen healthy subjects participated in an fmri study using an S1-cue-S2 paradigm. First, participants were to retain either action or size information about visually presented everyday objects. Second, they performed a long term source memory task. Whole brain analyses revealed a jointly activated left hemispheric action-specific network comprising inferior frontal, inferior parietal and STS regions for action information, and a right hemispheric network comprising early visual areas in occipital cortex and medial parietal cortex for size information. It can be concluded that information-specific configurations exist pertaining to both working and long term memory. This is in line with a theoretical framework which posits domain-specific sets of representations which can be used for multiple purposes.

12 Age Differences in Working Memory Capacity and Selectivity across the Lifespan Markus Werkle-Bergner, Myriam Sander, & Ulman Lindenberger Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin The capacity of visual working memory (WM) is commonly assumed to be limited to about 4 items. However, recent studies provide evidence for large age-related, interindividual, and even intra-individual differences in WM capacity. Furthermore, given limited capacity, the selection of information to be encoded and held in WM seems to be crucial for an individual s range of effective performance. Both functions, WM capacity and attentional selection, are subject of tremendous changes across the lifespan. However, the neuronal mechanisms and age-dependent changes therein are only vaguely understood. We present first pilot-results from a behavioral lifespan study that investigates the influence of perceptual processing time on WM capacity and information selection abilities in groups of children (10-11 years), younger (20-25 years), and older adults (70-75 years). Our data suggests that increasing encoding time increases WM capacity. This effect is differentially expressed in the three age groups. Furthermore, we currently develop an adaptive testing algorithm that allows to individually determine the optimal presentation time to yield a given WM capacity between 3 to 4 items. The individual adjustment of presentation times and performance range will facilitate an age-fair and process-pure comparison of neuronal mechanisms limiting WM capacity as measured with EEG.

13 Limits and costs of storage in visual working memory Hubert D. Zimmer & Anna M. Arend IRTG Adaptive Minds, Brain & Cognition Unit, Saarland University, Saarbrücken It is often postulated that the capacity of visual working memory is limited to four objects and that this capacity is independent of qualities of features that are stored. We investigated the influence of the visual appearance of items on memory capacity using behavioral and electrophysiological methods. We only found partial support of feature independence. An increase of complexity reduced memory performance, but only for novel items (Exp. 1). Memorizing conjunctions within the same feature domain caused strong memory costs compared to features only but this had only a weak impact on slow potentials (delay activity) during maintenance (Exp. 2). In contrast (Exp. 3), with complex colored nonsense shapes the amplitudes of delay activity went more positive if either complexity or the number of items increased (additive effects). However, in the conjunction block - now the conjunction of shape and color had to be memorized -, delay activity was even lower than in the feature block. We discuss the results in the context of Vogel's trade-off model between the number and resolution of objects, of memory distinctiveness, and of the difficulty of feature comparison.