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At least 631 records · Page 35Linked to original sources
PubMed1994

Functional magnetic resonance imaging of human prefrontal cortex activation during a spatial working memory task.

High-speed magnetic resonance (MR) imaging was used to detect activation in the human prefrontal cortex induced by a spatial working memory task modeled on those used to elucidate neuronal circuits in nonhuman primates. Subjects were required to judge whether the location occupied by the current stimulus had been occupied previously over a sequence of 14 or 15 stimuli presented in various locations. Control tasks were similar in all essential respects, except that the subject's task was to detect when one of the stimuli presented was colored red (color detection) or when a dot briefly appeared within the stimulus (dot detection). In all tasks, two to three target events occurred randomly. The MR signal increased in an area of the middle frontal gyrus corresponding to Brodmann's area 46 in all eight subjects performing the spatial working memory task. Right hemisphere activation was greater and more consistent than left. The MR signal change occurred within 6-9 sec of task onset and declined within a similar period after task completion. An increase in MR signal was also noted in the control tasks, but the magnitude of change was less than that recorded in the working memory task. These differences were replicated when testing was repeated in five of the original subjects. The localization of spatial working memory function in humans to a circumscribed area of the middle frontal gyrus supports the compartmentalization of working memory functions in the human prefrontal cortex and the localization of spatial memory processes to comparable areas in humans and nonhuman primates.

Color Perception↗
PubMed2002

Effects of intrahippocampal CT105, a carboxyl terminal fragment of beta-amyloid precursor protein, alone/with inflammatory cytokines on working memory in rats.

In this study, we examined the effects of a 105 amino acid carboxyl terminal fragment of beta-amyloid precursor protein (CT105) and inflammatory cytokines on working memory in rats, by using a three-panel runway set-up. CT105 at 10 nmol/side significantly impaired working memory when it was administered bilaterally into the hippocampus. Furthermore, to elucidate the interaction of CT105 with inflammatory cytokines, we co-administered tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in combination with CT105. Concurrent injections of CT105 (1.0 nmol/side) and TNF-alpha (100 ng/side) produced a synergistic deficit of working memory, whereas IL-1beta (100 ng/side) combined with CT105 (1.0 nmol/side) did not affect the working memory performance. These results indicate that the CT105-induced impairment of working memory is strongly aggravated by an increase in the level of the inflammatory cytokine TNF-alpha, which may occur in the brains of patients with Alzheimer's disease.

Alzheimer Disease↗
PubMed1998

Rehearsal in spatial working memory.

This article reports 3 experiments that tested a hypothesis regarding the nature of rehearsal in spatial working memory, one in which discrete shifts of spatial selective attention mediate the maintenance of location-specific representations. Experiment 1 demonstrated increases in visual processing efficiency for locations held in working memory, which suggested that attention was oriented toward these locations. Experiment 2 eliminated key alternative explanations for Experiment 1 by using an identical stimulus display with a nonspatial memory task, and little or no facilitation of processing at memorized locations was found under these conditions. Finally, Experiment 3 showed that spatial working memory was impaired when participants were hindered in their ability to attend to memorized locations. It is argued that these results implicate selective spatial attention as a rehearsal mechanism for spatial working memory.

Attention↗
PubMed2004

The basolateral amygdala interacts with the medial prefrontal cortex in regulating glucocorticoid effects on working memory impairment.

Previous findings indicate that the basolateral complex of the amygdala (BLA) interacts with other brain regions in regulating stress hormone effects on memory functions. Lesions of the BLA or infusions of a beta-adrenoceptor antagonist into the BLA block glucocorticoid effects on both memory consolidation and retrieval when administered either systemically or directly into the hippocampus. The present experiments examined BLA and beta-adrenoceptor involvement in regulating glucocorticoid effects on spatial working memory, a task that depends on the medial prefrontal cortex (mPFC). Male Sprague Dawley rats with bilateral sham- or NMDA-induced lesions of the BLA received either corticosterone (1.0 or 3.0 mg/kg, i.p.) systemically or the specific glucocorticoid receptor agonist 11beta,17beta-dihydroxy-6,21-dimethyl-17alpha-pregna-4,6-trien-20yn-3-one (RU 28362; 3.0 or 10.0 ng in 0.5 microl) into the mPFC shortly before testing on a delayed alternation task in a T-maze. Both glucocorticoid treatments induced comparable impairments in working memory performance in sham-lesioned controls. Although lesions of the BLA alone did not affect working memory, BLA lesions blocked the impairment induced by either corticosterone or RU 28362. Likewise, systemic injections of the centrally acting beta-adrenoceptor antagonist propranolol (2.0 mg/kg, i.p.) given before testing prevented corticosterone-induced working memory impairment. These findings indicate that BLA activity is essential for enabling glucocorticoid effects in the mPFC on working memory and suggest that stress hormone-induced modulation of working memory involves noradrenergic activation.

Adrenergic beta-Agonists↗
PubMed2005

Fatty acid amide hydrolase (-/-) mice exhibit an increased sensitivity to the disruptive effects of anandamide or oleamide in a working memory water maze task.

Although recent evidence suggests that fatty acid amide hydrolase (FAAH) may represent a potential therapeutic target, few published studies have investigated FAAH or its fatty acid amide substrates (FAAs) in animal models of learning and memory. Therefore, our primary goal was to determine whether FAAH (-/-) mice, which possess elevated levels of anandamide and other FAAs, would display altered performance in four Morris water maze tasks: acquisition of a hidden fixed platform, reversal learning, working memory, and probe trials. FAAH (-/-) mice failed to exhibit deficits in any task; in fact, they initially acquired the working memory task more rapidly than FAAH (+/+) mice. The second goal of this study was to investigate whether the FAAH inhibitor OL-135 (1-oxo-1[5-(2-pyridyl)-2-yl]-7-phenylheptane), anandamide, other FAAs, and methanandamide would affect working memory in both genotypes. FAAH (-/-), but not (+/+), mice displayed working memory impairments following exogenous administration of anandamide (ED(50) = 6 mg/kg) or oleamide (50 mg/kg). However, the central cannabinoid receptor (CB(1)) receptor antagonist SR141716 [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl] only blocked the disruptive effects of anandamide. Methanandamide, which is not metabolized by FAAH, disrupted working memory performance in both genotypes (ED(50) = 10 mg/kg), suggesting that CB(1) receptor signaling is unaltered by FAAH deletion. In contrast, OL-135 and other FAAs failed to affect working memory in either genotype. These results suggest that FAAH deletion does not impair spatial learning but may enhance acquisition under certain conditions. More generally, FAAH may represent a novel therapeutic target that circumvents the undesirable cognitive side effects commonly associated with direct-acting cannabinoid agonists.

Amidohydrolases↗
PubMed2000

Chronic stress induces impairment of spatial working memory because of prefrontal dopaminergic dysfunction.

Although the mechanism responsible for cognitive deficits in stress-related neuropsychiatric disorders has been obscure, prefrontal cortical (PFC) dopaminergic dysfunction is thought to be involved. In animals, the mesoprefrontal dopaminergic system is particularly vulnerable to stress, and chronic stress induces working memory impairment. However, the relation between the working memory impairment and altered dopaminergic activity in chronically stressed rats is unclear. Furthermore, the change of dopaminergic activity in the PFC induced by stress is thought to express as a stress response, not as a disorder of organic function. We have previously reported that chronic stress administered by water immersion and restraint for 4 weeks induces a organic disorder such as hippocampal neuronal degeneration. We therefore examined whether chronically stressed (4 weeks) and recovered (10 d) rats show a working memory impairment caused by reduced dopamine (DA) transmission in the PFC, as suspected in the neuropsychiatric disorders. The stress impaired the spatial working memory evaluated by T-maze task and induced a marked reduction of DA transmission concomitant with an increase in DA D1 receptor density in the PFC. This memory impairment was sufficiently ameliorated by intra-PFC infusion of 10 ng SKF 81297, a D1 receptor-specific agonist. Pretreatment with intraperitoneal injection of 20 microgram/kg SCH 23390, a D1 receptor antagonist, reversed the SKF 81297 response. These results indicate that chronic stress induces working memory impairment through a D1 receptor-mediated hypodopaminergic mechanism in the PFC. These findings provide important information for understanding of the mechanisms underlying PFC dysfunction in stress-related neuropsychiatric disorders.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1984

The effects of visual and spatial interference on spatial working memory.

Baddeley and Lieberman (1980) have shown that processing within spatial working memory is disrupted by a spatial secondary task, but not significantly by a visual processing secondary task. In the present study their experiment was replicated under broadly similar circumstances. The spatial and verbal primary tasks involved remembering descriptions of spatially arranged or nonsense sequences of digits, respectively. The secondary visual and spatial tasks involved either judging the level of brightness or pressing an unseen matrix of buttons in a predetermined sequence. In contrast to the finding of Baddeley and Lieberman, both the visual and spatial secondary tasks significantly impaired spatial working memory. Neither of these secondary tasks significantly interfered with concurrent verbal processing. The present findings suggest that spatial working memory draws from resources from both visual and spatial quarters.

Adult↗
PubMed2002

The impact of moderate sleep loss on neurophysiologic signals during working-memory task performance.

STUDY OBJECTIVES: This study examined how sleep loss affects neurophysiologic signals related to attention and working memory. DESIGN: Subjective sleepiness, resting-state electroencephalogram, and behavior and electroencephalogram during performance of working-memory tasks were recorded in a within-subject, repeated-measures design. SETTING: Data collection occurred in a computerized laboratory setting. PARTICIPANTS: Sixteen healthy adults (mean age, 26 years; 8 female) INTERVENTIONS: Data from alert daytime baseline tests were compared with data from tests during a late-night, extended-wakefulness session that spanned up to 21 hours of sleep deprivation. MEASUREMENTS AND RESULTS: Alertness measured both subjectively and electrophysiologically decreased monotonically with increasing sleep deprivation. A lack of alertness-related changes in electroencephalographic measures of the overall mental effort exerted during task execution indicated that participants attempted to maintain high levels of performance throughout the late-night tests. Despite such continued effort, responses became slower, more variable, and more error prone within 1 hour after participants' normal time of sleep onset. This behavior failure was accompanied by significant degradation of event-related brain potentials related to the transient focusing of attention. CONCLUSIONS: Moderate sleep loss compromises the function of neural circuits critical to subsecond attention allocation during working-memory tasks, even when an effort is made to maintain wakefulness and performance. Multivariate analyses indicate that combinations of working-memory-related behavior and neurophysiologic measures can be sensitive enough to permit reliable detection of such effects of sleep loss in individuals. Similar methods might prove useful for assessment of functional alertness in patients with sleep disorders.

Adult↗
PubMed2004

High level estradiol impairs and low level estradiol facilitates non-spatial working memory.

The present study investigated the effect of different doses of estradiol treatment on performance in the non-spatial delayed alternation T-maze a task in which performance is mediated by the integrity of the prefrontal cortex (PFC). Ovariectomized (OVX) female rats were injected with estradiol benzoate (0.3 microg/0.1 ml sesame oil (EB0.3), 5 microg/0.1 ml sesame oil (EB5) or 10 microg/0.1 ml sesame oil (EB 10)) or vehicle (sesame oil, 0.1 ml). Approximately 2 h after each injection, animals were trained daily on the T-maze with an initial delay of 10 s (short delay). Following a month with no treatment animals were re-trained at a 40 s delay (long delay). Days to reach criterion (one error per day for three consecutive days), mean total errors, errors across days, change in performance across training (short subtracted from long delay), and latency to reach goal arm, were scored. At the short delay, there was a weak effect for the low dose of estradiol (EB0.3 low-to-medium physiological) to significantly decrease the number of working memory errors compared to controls. However at the longer delay the higher doses of estradiol EB5 (high physiological) and to a lesser extent EB10 (suupraphysiological) significantly increased the number of working memory errors compared to controls. These data demonstrate the differential effect of estradiol during short and long delays on prefrontal cortex dependent working memory. High levels of estradiol impair PFC-dependent working memory at longer delays, while low level estradiol weakly facilitates PFC-dependent working memory at a shorter delay. These data suggest that estradiol's facilitatory effects on working memory may not be mediated through the PFC, while estradiols inhibitory effects on working memory may be mediated at least in part through the PFC.

Animals↗
PubMed2001

Involvement of cholinergic and glutamatergic functions in working memory impairment induced by interleukin-1beta in rats.

Interleukin-1beta at doses of 32 and 100 ng/side, injected bilaterally into the dorsal hippocampus of rats, significantly increased the working memory errors in a three-panel runway setup, whereas interleukin-1beta at doses affecting working memory errors had no effect on the number of errors in the first trial or the latency. The increase in working memory errors induced by intrahippocampal administration of 100 ng/side interleukin-1beta was significantly decreased by concurrent injection (300 ng/side) of the interleukin-1 receptor antagonist. The cholinesterase inhibitor physostigmine at a dose of 3.2 microg/side and D-cycloserine (1.0 and 10 microg/side), which is a partial agonist acting at the glycine binding site of the NMDA receptor/channel complex, reduced the increase in working memory errors induced by 100 ng/side interleukin-1beta. These results suggest that interleukin-1beta causes disruptions of septohippocampal cholinergic and glutamatergic transmission via its high-affinity receptor, which underlie the impairment of working memory.

Analysis of Variance↗
PubMed2006

Are early grammatical and phonological working memory abilities affected by preterm birth?

UNLABELLED: There have been few investigations of the effects of very immature preterm birth on specific linguistic competencies and phonological working memory at preschool age. Study 1 aimed to investigate early grammatical abilities in very immature healthy preterms, taking into account their cognitive development and biological and social factors. The linguistic and cognitive differences found between preterms and fullterms led to investigate in Study 2 the role of phonological working memory on preterms' grammatical development. Very immature preterm birth resulted to affect grammatical, cognitive and phonological working memory abilities until 3.5 years leading to persisting difficulties in comparison with fullterms, albeit not severe deficits. Tight relations between phonological working memory and grammar were found both in preterms and fullterms, that highlights the reciprocal support of these abilities in development. A partial compensatory effect by the maternal level of education on preterms' grammatical and cognitive abilities was also found. LEARNING OUTCOMES: The reader will become familiar with the relations between grammatical and phonological working memory abilities in typical and preterm 3.5-year-old children.

Articulation Disorders↗
PubMed2001

What limits children's working memory span? Theoretical accounts and applications for scholastic development.

Explanations of working memory span in children were studied in a longitudinal follow-up of J. N. Towse, G. J. Hitch, and U. Hutton (1998). Reading span and operation span were lower when within-task retention intervals were lengthened. For each task, variation in span between test waves and age cohorts was systematically related to changes in processing speed. The two spans explained substantial shared variance in both reading and arithmetic scores, with some evidence for domain specificity. Combined span scores predicted unique variance in scholastic attainment over a 1-year interval. The authors concluded that working memory span is constrained by rapid loss of active codes and is not simply a measure of capacity for resource sharing. Working memory is also implicated in scholastic development.

Child↗
PubMed1993

The effects of background noise and working memory capacity on speechreading performance.

The present study was conducted to investigate the effects of background noise and working memory capacity on speechreading performance. The results displayed no differences in speechreading performance (i.e. on a word-test and on a sentence-test) due to background noise. When working memory capacity was correlated with speechreading, only one of the two tests of working memory capacity (i.e. the reading span task) was found to be related to speechreading performance. This relationship applies to both speechreading tests, but only to one specific background noise condition in the tests: meaningful noise. The results are discussed with respect to the demands of simultaneous storage and processing in working memory and how these demands apply to speech-based noise distractors. It was also concluded that although performance was similar across different background noise conditions, they apparently engage different components of the individual's cognitive system.

Adult↗
PubMed2006

Decreased activation of anterior cingulate cortex in the working memory of the elderly.

We examined aging effects on activation in the anterior cingulate cortex during a verbal working memory using functional magnetic resonance imaging. Ten young (mean age 25 years) and 10 elderly (mean age 69 years) healthy adults performed the reading span test in which performance reflects individual differences in verbal working memory. We found an age-related difference in executive function in the prefrontal cortex; younger participants showed significant anterior cingulate cortex activation whereas the elderly did not. We found that the anterior cingulate cortex plays a critical role in executive function related to working memory. We found that behavioral deficits in verbal working memory because of aging result from the deterioration of cognitive control owing to decreased activation of the anterior cingulate cortex.

Adult↗
PubMed2004

Modulation of effective connectivity inside the working memory network in patients at the earliest stage of multiple sclerosis.

fMRI and structural equation modeling (SEM) were used to study effective connectivity inside the working memory network in patients at the earliest stage of multiple sclerosis (MS), while performing paced auditory serial addition test (PASAT), a sensitive task to reveal subtle cognitive impairments related to working memory and information speed processing. The path model used for SEM included bilateral connections between left and right BA 46, left and right BA 40, left and right anterior cingulate cortex (ACC), left BA 44 and left BA 40, right BA 44 and right BA 40, and unidirectional ipsilateral connections from BA 46 to BA 44, from ACC to BA 46, and from ACC to BA 44. Experimental data from the two groups fit accurately the working memory model, in patients [chi20(2) = 13, P = 0.877] as well as in controls [chi20(2) = 13.54, P = 0.853]. The omnibus test indicated a significant difference of model fits in patients and in controls [chi40(2) = 160.07, P < 0.0001]. Connectivity strengths from right BA 46 to left BA 46, from left ACC to left BA 46 were lower in patients than in controls, and higher from right ACC to right BA 46, from left to right and from right to left ACC (stacked model). Effective connectivity inside the working memory network appears altered in patients at the earliest stage of MS. Modulation of effective connectivity is present in patients inside the executive subsystems of working memory, and could be related to adaptive cognitive control processes that may limit the clinical manifestation of MS.

Acoustic Stimulation↗
PubMed2003

Individual differences in rCBF correlates of syntactic processing in sentence comprehension: effects of working memory and speed of processing.

Positron emission tomography (PET) was used to determine the effect of working memory and speed of sentence processing on regional cerebral blood flow (rCBF) during syntactic processing in sentence comprehension. PET activity associated with making plausibility judgments about syntactically more complex subject-object (SO) sentences (e.g., The juice that the child spilled stained the rug) was compared to that associated with making judgments about synonymous syntactically simpler object-subject (OS) sentences (e.g., The child spilled the juice that stained the rug). Two groups of nine subjects differing in working memory and matched for speed of sentence processing both showed increases in rCBF in lateral posteroinferior frontal lobe bilaterally. The subjects were reclassified to form two groups of eight subjects who were matched for working memory but who differed in speed of sentence processing. Fast-performing subjects activated lateral posteroinferior frontal lobe bilaterally and slow-performing subjects showed activation of left superior temporal lobe. The results indicate that rCBF responses to syntactic comprehension tasks vary as a function of speed of sentence processing but not as a function of working memory.

Adult↗
PubMed2003

Perceptual organization influences visual working memory.

Previous studies have demonstrated that top-down factors can bias the storage of information in visual working memory. However, relatively little is known about the role that bottom-up stimulus characteristics play in visual working memory storage. In the present study, subjects performed a change detection task in which the to-be-remembered objects were organized in accordance with Gestalt grouping principles. When an attention-capturing cue was presented at the location of one object, other objects that were perceptually grouped with the cued object were more likely to be stored in working memory than were objects that were not grouped with the cued object. Thus, objects that are grouped together tend to be stored together, indicating that bottom-up perceptual organization influences the storage of information in visual working memory.

Adult↗
PubMed2006

Working memory for conjunctions relies on the medial temporal lobe.

A prominent theory of hippocampal function proposes that the hippocampus is importantly involved in relating or binding together separate pieces of information to form an episodic representation. This hypothesis has only been applied to studies of long-term memory because the paradigmatic view of the hippocampus is that it is not critical for short-term forms of memory. However, relational processing is important in many working memory tasks, especially tasks using visual stimuli. Here, we test the hypothesis that the medial temporal lobes are important for relational memory even over short delays. The task required patients with medial temporal lobe amnesia and controls to remember three objects, locations, or object-location conjunctions over 1 or 8 s delays. The results show that working memory for objects and locations was at normal levels, but that memory for conjunctions was severely impaired at 8 s delays. Additional analyses suggest that the hippocampus per se is critical for accurate conjunction working memory. We propose that the hippocampus is critically involved in memory for conjunctions at both short and long delays.

Aged↗