Home About us Contact
|
Home About us Contact | ||
|
|
||
Memory Load (memory + load)
Selected AbstractsSeven-year-olds allocate attention like adults unless working memory is overloadedDEVELOPMENTAL SCIENCE, Issue 1 2010Nelson Cowan Previous studies have indicated that visual working memory performance increases with age in childhood, but it is not clear why. One main hypothesis has been that younger children are less efficient in their attention; specifically, they are less able to exclude irrelevant items from working memory to make room for relevant items. We examined this hypothesis by measuring visual working memory capacity under a continuum of five attention conditions. A recognition advantage was found for items to be attended as opposed to ignored. The size of this attention-related effect was adult-like in young children with small arrays, suggesting that their attention processes are efficient even though their working memory capacity is smaller than that of older children and adults. With a larger working memory load, this efficiency in young children was compromised. The efficiency of attention cannot be the sole explanation for the capacity difference. [source] Oscillatory activity in parietal and dorsolateral prefrontal cortex during retention in visual short-term memory: Additive effects of spatial attention and memory loadHUMAN BRAIN MAPPING, Issue 10 2009Stéphan Grimault Abstract We used whole-head magnetoencephalography to study the representation of objects in visual short-term memory (VSTM) in the human brain. Subjects remembered the location and color of either two or four colored disks that were encoded from the left or right visual field (equal number of distractors in the other visual hemifield). The data were analyzed using time-frequency methods, which enabled us to discover a strong oscillatory activity in the 8,15 Hz band during the retention interval. The study of the alpha power variation revealed two types of responses, in different brain regions. The first was a decrease in alpha power in parietal cortex, contralateral to the stimuli, with no load effect. The second was an increase of alpha power in parietal and lateral prefrontal cortex, as memory load increased, but without interaction with the hemifield of the encoded stimuli. The absence of interaction between side of encoded stimuli and memory load suggests that these effects reflect distinct underlying mechanisms. A novel method to localize the neural generators of load-related oscillatory activity was devised, using cortically-constrained distributed source-localization methods. Some activations were found in the inferior intraparietal sulcus (IPS) and intraoccipital sulcus (IOS). Importantly, strong oscillatory activity was also found in dorsolateral prefrontal cortex (DLPFC). Alpha oscillatory activity in DLPFC was synchronized with the activity in parietal regions, suggesting that VSTM functions in the human brain may be implemented via a network that includes bilateral DLPFC and bilateral IOS/IPS as key nodes. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Cross-modal temporal order memory for auditory digits and visual locations: An fMRI studyHUMAN BRAIN MAPPING, Issue 4 2004Daren Zhang Abstract A function of working memory is to remember the temporal sequence of events, often occurring across different sensory modalities. To study the neural correlates of this function, we conducted an event-related functional magnetic resonance imaging (fMRI) experiment with a cross-modal memory task. Subjects were required to recall auditory digits and visual locations either in mixed order (cross-modality) or in separate order (within-modality). To identify the brain regions involved in the memory of cross-modal temporal order, we compared the blood oxygenation level-dependent (BOLD) response between the mixed and the separate order tasks. As a control, cortical areas sensitive to the memory load were mapped by comparing the 10-item condition with the 6-item condition in the separate order task. Results show that the bilateral prefrontal, right premotor, temporo-parietal junction (TPJ) and left superior parietal cortices had significantly more activation in the mixed task than in the separate task. Some of these areas were also sensitive to the memory load, whereas the right prefrontal cortex and TPJ were relatively more sensitive to the cross-modal order but not the memory load. Our study provides potential neural correlates for the episodic buffer, a key component of working memory as proposed previously [Baddeley. Trends Cogn Sci 2000;4:417,423]. Hum. Brain Mapping 22:280,289, 2004. © 2004 Wiley-Liss, Inc. [source] Infants' Use of Constraints to Speed Information Processing and to Anticipate EventsINFANCY, Issue 4 2002Thomas M. Dougherty Two experiments were conducted with 28-week-old infants using a modification of the Visual Expectation Paradigm. The first sought to determine whether speed of information processing (SIP) could be assessed in infants using a reaction time (RT) measure and approach that is widely used to measure SIP in adults. Infants saw a center fixation cue followed by a peripheral target that could appear in 1, 2, or 4 locations. There was a linear increase in RT of eye movements as the number of locations increased from 1 to 2 and to 4 targets, suggesting that the paradigm does measure SIP. The second experiment asked whether varying the number of cue-target pairings would augment or impair infant's SIP in the trade-off between the benefit of additional information and the liability of additional memory load. The findings showed that the presence of cue information can eliminate the difference in RT between the 1- and 2-location conditions, whereas no benefit of cue was obtained for the 4-location condition. [source] An experimental approach to executive fingerprinting in young childrenINFANT AND CHILD DEVELOPMENT, Issue 2 2002Michael Beveridge Abstract This paper presents a methodology designed to investigate the potential independence of memory and inhibition as component processes of executive function (EF) in young school age children. Two groups of 30 6- and 8-year-olds were tested on three EF tasks; a continuous performance test, a Stroop-like task, and a start/stop task. Each task had four conditions, which systematically combined two levels of memory load and two levels of inhibitory demand. This design enabled us to examine whether, within the range of memory and inhibitory loads used, the effects of memory and inhibitory demands on these tasks were additive and independent, or instead interacted with one another. Analyses of both errors and response times across the three tasks provided no positive evidence for the view that memory and inhibition are inter-dependent processes. The tasks proved sensitive to age, with the 8-year-olds generally outperforming the 6-year-olds. In addition, effects of the memory and inhibition manipulations were observed. However, there was little evidence that memory load and inhibitory demand interacted in the way that would be expected if these factors draw on a shared pool of common executive resources. Copyright © 2002 John Wiley & Sons, Ltd. [source] Practical implementation of multichannel adaptive filters based on FTF and AP algorithms for active controlINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2-3 2005Alberto González Abstract In this paper, multichannel affine projection (AP) algorithms and fast transversal filters (FTF) are introduced for active noise control. A comparative practical study of the mentioned algorithms with the filtered-X LMS (F-XLMS) and the recursive least squares (RLS) is presented for multichannel systems. This study is based on simulations using real data and is mainly focused on: their computational cost and memory load, their convergence properties, their stability and their ability to create quiet zones around listener ears. Simulations show that algorithms based on FTF exhibit a good trade-off between computational cost and convergence speed. On the other hand, those based on RLS are slightly faster but they present higher computational load and stability problems in their practical implementation. It has also been observed that algorithms based on low order AP algorithms present less computational cost than the FTF-based ones but a slightly slower convergence speed. Therefore these algorithms show a desirable behaviour and versatility for practical applications. Finally, results obtained in a real-time multichannel system validate the use of AP algorithms in practical applications as an alternative to the classical multichannel F-XLMS since they provide meaningful attenuation levels, lower convergence time and similar computational cost. Additionally, as simulations indicated, AP algorithm performance can be easily improved increasing its projection order and using fast versions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Acute Ethanol Effects on Brain Activation in Low- and High-Level Responders to AlcoholALCOHOLISM, Issue 7 2010Ryan S. Trim Background:, A low level of response (LR) to alcohol is an important endophenotype associated with an increased risk of alcoholism. However, little is known about how neural functioning may differ between individuals with low and high LRs to alcohol. This study examined whether LR group effects on neural activity varied as a function of acute alcohol consumption. Methods:, A total of 30 matched high- and low-LR pairs (N = 60 healthy young adults) were recruited from the University of California, San Diego, and administered a structured diagnostic interview and laboratory alcohol challenge followed by two functional magnetic resonance imaging (fMRI) sessions under placebo and alcohol conditions, in randomized order. Task performance and blood oxygen level-dependent response contrast to high relative to low working memory load in an event-related visual working memory (VWM) task were examined across 120 fMRI sessions. Results:, Both LR groups performed similarly on the VWM task across conditions. A significant LR group by condition interaction effect was observed in inferior frontal and cingulate regions, such that alcohol attenuated the LR group differences found under placebo (p < 0.05). The LR group by condition effect remained even after controlling for cerebral blood flow, age, and typical drinking quantity. Conclusions:, Alcohol had differential effects on brain activation for low- and high-LR individuals within frontal and cingulate regions. These findings represent an additional step in the search for physiological correlates of a low LR and identify brain regions that may be associated with the low LR response. [source] Binge Drinking Affects Attentional and Visual Working Memory Processing in Young University StudentsALCOHOLISM, Issue 11 2009Alberto Crego Background:, Binge Drinking (BD) typically involves heavy drinking over a short time, followed by a period of abstinence, and is common among young people, especially university students. Animal studies have demonstrated that this type of alcohol consumption causes brain damage, especially in the nonmature brain. The aim of the present study was to determine how BD affects brain functioning in male and female university students, during the performance of a visual working memory task. Methods:, Event-related potentials (ERPs) were recorded, with an extensive set of 32 scalp electrodes, in 95 first-year university students (age range 18 to 20 years), comprising 42 binge drinkers (BD) and 53 controls, in a visual "identical pairs" continuous performance task. Principal components analysis was used to identify and analyze the N2 (negative waveform with a latency around 200 to 300 ms related to attentional processes) and P3 (positive waveform with a latency around 300 to 600 ms related to working memory processes) components of the ERPs. Results:, In the matching condition of the task, the N2 component in central and parietal regions was significantly larger in the BD than in the control group. In the control group, the P3 component was larger in the matching than in the nonmatching condition in the frontal, central, and parietal regions, whereas the BD group did not show any significant differences between conditions in any region. Conclusions:, The results of this study confirm the presence of electrophysiological differences between young university student binge drinkers and controls during the execution of a visual task with a high working memory load. The larger N2 in the BD group suggests higher levels of attentional effort required by this group to perform the task adequately. The absence of any differences in the P3 component in the different conditions (matching and nonmatching stimuli) in the BD group suggests a deficiency in the electrophysiological differentiation between relevant and irrelevant information, which may reflect some impairment of working memory processes. [source] Does weak reading comprehension reflect an integration deficit?JOURNAL OF RESEARCH IN READING, Issue 2 2006Alice L. R. Spooner Seven- and eight-year-old skilled and less-skilled comprehenders were compared on a sentence recognition task in two conditions varying in memory load and retention interval. Integration of story information during comprehension was indexed by inflated recognition errors of foils that had been constructed by integrating information across original story sentences. Skilled comprehenders exhibited more accurate memory for sentences than less-skilled comprehenders. However, the groups did not differ in the degree to which they integrated information with minimal memory demand, or in their tendency to integrate information and retain the integrated representations with increased memory demand. These results were interpreted as evidence that integration deficits do not lie at the root of reading comprehension difficulties in mainstream children. [source] The n -back as a dual-task: P300 morphology under divided attentionPSYCHOPHYSIOLOGY, Issue 6 2001Scott Watter The n -back task was hypothesized to be a dual task, permitting the imposition of parametrically increasing attentional and working memory demands, while keeping constant the demands of an embedded matching subtask. Visual targets were presented for 200 ms every 2.2 s at pseudorandomly varying positions on a computer screen. Participants were required to remember the most recent 0, 1, 2, or 3 positions and responded with a choice button push to whether the current target position matched the position presented n items previously. P300 peak latency was constant across n -back tasks, reflecting constant perceptual and cognitive demands of the matching subtask. P300 peak amplitude decreased with increasing memory load, reflecting reallocation of attention and processing capacity away from the matching subtask to working memory activity. These data support a dual-task nature of the n -back, which should be considered when employing this paradigm. [source] The use of illustrations when learning to read: A cognitive load theory approachAPPLIED COGNITIVE PSYCHOLOGY, Issue 5 2010Susannah Torcasio Three experiments were conducted to investigate the effects of including illustrations in beginning reading materials. Experiment 1 compared reading materials consisting solely of simple prose passages with materials consisting of the same passages plus informative illustrations depicting the content of each passage. Reading proficiency improved more under the no illustrations condition. Experiment 2 compared the informative illustrations with uninformative illustrations. Reading proficiency improved more using uninformative illustrations. Experiment 3 compared uninformative illustrations with no illustrations and found no significant differences between conditions. These results were interpreted within a cognitive load theory framework. It was concluded that informative illustrations are redundant and so impose an extraneous working memory load that interferes with learning to read. Copyright © 2009 John Wiley & Sons, Ltd. This article was published online on 8th April 2009. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected [3 July 2009]. [source] Working memory interference during processing texts and pictures: Implications for the explanation of the modality effectAPPLIED COGNITIVE PSYCHOLOGY, Issue 2 2010Ralf Rummer Auditory text presentation improves learning with pictures and texts. With sequential text,picture presentation, cognitive models of multimedia learning explain this modality effect in terms of greater visuo-spatial working memory load with visual as compared to auditory texts. Visual texts are assumed to demand the same working memory subsystem as pictures, while auditory texts make use of an additional cognitive resource. We provide two alternative assumptions that relate to more basic processes: First, acoustic-sensory information causes a retention advantage for auditory over visual texts which occurs no matter if a picture is presented or not. Second, eye movements during reading hamper visuo-spatial rehearsal. Two experiments applying elementary procedures provide first evidence for these assumptions. Experiment 1 demonstrates that, regarding text recall, the auditory advantage is independent of visuo-spatial working memory load. Experiment 2 reveals worse matrix recognition performance after reading text requiring eye movements than after listening or reading without eye movements. Copyright © 2008 John Wiley & Sons, Ltd. [source] Memory demands on facial composite identificationAPPLIED COGNITIVE PSYCHOLOGY, Issue 3 2007Karl M. Oswald Face composites created with FACES 3.0 composite software were used to identify target photographs under varying conditions of memory load. Composites created while viewing a mugshot were presented concurrently with a five-photograph lineup of actual criminal suspects, immediately preceding the lineup, or with a filled delay between composite and lineup. Compared to a baseline using the mock witness technique, results demonstrated above-chance identification of target photographs from their composites in all four experiments. Identification was highest with concurrent composite-lineup presentation and lower under immediate, 30-second-delayed, and 4-minute-delayed conditions, with no significant identification differences across the three memory conditions. Confidence ratings in target selection only weakly predicted identification accuracy at best. These findings extend the limited research on computerized facial composite systems while addressing composite software use, efficacy, guidelines and limitations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Gesturing Saves Cognitive Resources When Talking About Nonpresent ObjectsCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 4 2010Raedy Ping Abstract In numerous experimental contexts, gesturing has been shown to lighten a speaker's cognitive load. However, in all of these experimental paradigms, the gestures have been directed to items in the "here-and-now." This study attempts to generalize gesture's ability to lighten cognitive load. We demonstrate here that gesturing continues to confer cognitive benefits when speakers talk about objects that are not present, and therefore cannot be directly indexed by gesture. These findings suggest that gesturing confers its benefits by more than simply tying abstract speech to the objects directly visible in the environment. Moreover, we show that the cognitive benefit conferred by gesturing is greater when novice learners produce gestures that add to the information expressed in speech than when they produce gestures that convey the same information as speech, suggesting that it is gesture's meaningfulness that gives it the ability to affect working memory load. [source] Cognitive and emotional modulation of the cardiac defense response in humansPSYCHOPHYSIOLOGY, Issue 3 2000María Nieves Pérez The cognitive and emotional modulation of the cardiac defense response was investigated in this study. One hundred forty-four participants were exposed to three presentations of an intense auditory stimulus while performing one of four attentional tasks: a control task, an external perceptual tracking task, and two internal tasks presented at either easy or difficult memory loads. State anxiety was also manipulated by requiring each group to perform either with or without the threat of shock. Heart rate and vasomotor activity were recorded. Results indicated that only the externally directed tracking task led to potentiation of the cardiac response. No predicted effects for attentional demands were obtained and the anxiety manipulation did not appear to have an effect. Differences between measures were also observed, particularly with respect to response habituation. Unlike cardiac activity, vasomotor responses displayed resistance to habituation. The results are discussed in relation to contemporary accounts of defensive responding. [source] | |||||||||||||