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At least 235 records · Page 13Linked to original sources

PubMed2005

An information-processing model of three cortical regions: evidence in episodic memory retrieval.

ACT-R (Anderson, J.R., et al., 2003. An information-processing model of the BOLD response in symbol manipulation tasks. Psychon. Bull. Rev. 10, 241-261) relates the inferior dorso-lateral prefrontal cortex to a retrieval buffer that holds information retrieved from memory and the posterior parietal cortex to an imaginal buffer that holds problem representations. Because the number of changes in a problem representation is not necessarily correlated with retrieval difficulties, it is possible to dissociate prefrontal-parietal activations. In two fMRI experiments, we examined this dissociation using the fan effect paradigm. Experiment 1 compared a recognition task, in which representation requirement remains the same regardless of retrieval difficulty, with a recall task, in which both representation and retrieval loads increase with retrieval difficulty. In the recognition task, the prefrontal activation revealed a fan effect but not the parietal activation. In the recall task, both regions revealed fan effects. In Experiment 2, we compared visually presented stimuli and aurally presented stimuli using the recognition task. While only the prefrontal region revealed the fan effect, the activation patterns in the prefrontal and the parietal region did not differ by stimulus presentation modality. In general, these results provide support for the prefrontal-parietal dissociation in terms of retrieval and representation and the modality-independent nature of the information processed by these regions. Using ACT-R, we also provide computational models that explain patterns of fMRI responses in these two areas during recognition and recall.

Adolescent↗

PubMed2006

Reactivation of medial temporal lobe and occipital lobe during the retrieval of color information: A positron emission tomography study.

It is widely accepted that memory traces of an event include various types of information about the content of the event and about the circumstances in which the individual experienced it. However, how these various types of information are stored and later retrieved is poorly understood. One hypothesis postulates that the retrieval of specific event information reactivates regions that were active during the encoding of this information, with the aid of binding functions of the medial temporal lobe (MTL) structures. We used positron emission tomography to identify the brain regions related to the encoding and retrieval of color information. Specifically, we assessed whether overlapping activity was found in both the MTL structures and color-related cortical regions during the encoding and retrieval of color information attached with meaningless shapes. During the study, subjects were asked to encode colored (red or green) and achromatic random shapes. At subsequent testing, subjects were presented with only achromatic shapes, which had been presented with or without colors during encoding, and were engaged in retrieval tasks of shapes and colors. Overlapping activity was found in the MTL and occipital lobe (the lingual and inferior occipital gyri) in the right hemisphere during the encoding and retrieval of meaningless shapes with color information compared with those without color information. Although there are some limitations to be considered, the present findings seem to support the view that the retrieval of specific event information is associated with reactivation of both the MTL structures and the regions involved during encoding of the information.

Adult↗

PubMed2006

fMRI correlates of retrieval orientation.

Processes related to the cueing of memory retrieval were investigated using fMRI during a yes/no recognition memory test. Participants studied either pictures or auditory words and were subsequently tested with visual words that either corresponded to studied items (old items) or were unstudied (new items). It was expected that neural activity would differ according to the type of information participants are trying to retrieve: a manifestation of the so-called "retrieval orientation" effect. We replicated robust old/new effects in parietal, prefrontal and anterior medial temporal lobe cortices, which did not differ according to the study material. However, we did observe differential activity to test items in temporoparietal cortex and fusiform cortex as a function of the study material. More specifically, attempts to retrieve words encoded auditorily produced greater activity in auditory cortex than attempts to retrieve words encoded as pictures, whereas the converse was found in fusiform cortex. The above pattern was found for both new and old test items. These findings implicate these regions in constraining the search for specific types of encoded information and thus are in accordance with the transfer-appropriate processing framework. Further, we propose that our results can be seen as an extension of the cortical reinstatement hypothesis, in that the same material-specific cortical regions are engaged during both encoding and retrieval, and this increases the likelihood of successful recognition, or rejection, of retrieval cues in a memory test.

Acoustic Stimulation↗

PubMed1997

"How do you remember you ate...?": a Delphi technique study to identify retrieval categories from fourth-grade children.

OBJECTIVE: To develop and validate a consensus set of retrieval categories for how children remember what they have eaten, and to relate retrieval categories to accuracy of reporting items eaten during school lunch. DESIGN: A Delphi technique study was conducted using 10 psychologists. The subject matter consisted of responses transcribed from interviews conducted with 89 randomly selected fourth graders within 90 minutes of eating. Retrieval categories were evaluated for accuracy by comparing students' self-reported lunch intake with observation. STATISTICAL ANALYSES: For round 1, a centroid hierarchical cluster analysis was used to identify common sets of rating pairs to propose categories for reaching consensus. For rounds 2 and 3, percent of agreement was calculated. Accuracy was tabulated across meal items and student use by retrieval category. RESULTS: After round 3, we found that 23 "near-consensus" categories were used by at least eight raters. Six categories were used 60% of the time, 4 were used 20% of the time, and 5 were used 15% of the time. Less frequently used categories were combined with similar, more frequently used categories for a total of 16 categories. Students used a large variety of retrieval categories when accurately reporting consumption. Of the 16 categories, 12 were used similarly by both accurate and inaccurate students. Where there were differences in accuracy by retrieval category, the more accurate students used "taste/smell/texture" and "visual" in deference to "order items consumed" and "oral cue still present." APPLICATIONS: These categories provide insight into the broad range of retrieval categories that children use and provide direction for researchers to design and study specific cues to enhance the accuracy of children's self-reports of diet.

Child↗

PubMed1997

Retrieval by other procurement teams provides favorable lung transplantation outcome.

BACKGROUND: During the last 4 years, we have increasingly used lungs retrieved by other procurement teams. We therefore investigated whether the use of those lungs affected the outcome of lung transplantation. METHODS: We analyzed the results of 159 consecutive lung transplantations performed at our institution between July 1, 1992, and December 31, 1995. The transplants were divided into three groups: distant donor lungs retrieved by our team (DB group, n = 68); distant donor lungs retrieved by other teams (DX group, n = 46); and local donor lungs retrieved by our team (LB group, n = 44). One transplantation with a local donor lung retrieved by another team was excluded from the analysis. RESULTS: No significant differences were noted between the three groups in alveolar-arterial oxygen gradient immediately after transplantation (DB group, 359 +/- 18 mm Hg; DX group, 329 +/- 23 mm Hg; LB group, 327 +/- 20 mm Hg) and at 24 hours; days on ventilator; days in the intensive care unit; length of hospital stay; 30-day mortality; and actuarial 1-year survival (DB group, 81%; DX group, 87%; LB group, 89%). CONCLUSIONS: The use of donor lungs retrieved by other teams achieves an equivalently satisfactory outcome after lung transplantation as lungs retrieved by our team.

Adult↗

PubMed1988

Timing of oocyte retrieval in cycles with a spontaneous luteinizing hormone surge in a large in vitro fertilization program.

Forty-four cycles with a spontaneous luteinizing hormone (LH) surge among 377 in vitro fertilization (IVF) patients were studied for outcome with different timing of oocyte retrieval. Mean number of preovulatory oocytes per retrieval and per transfer was significantly less in these cycles than in controls. Mean number of preovulatory oocytes per retrieval and per transfer was significantly higher when the human chorionic gonadotropin (hCG)-retrieval interval was greater than 35 hours, compared with less than 24 hours. In cycles with an hCG-retrieval interval of less than 24 hours, percentage of preovulatory oocytes was higher when serum estradiol (E2) decreased by greater than 15% on the morning after hCG administration compared with a plateau or an increase in serum E2. Timing oocyte retrieval after spontaneous LH surge should consider the hCG-retrieval interval and changes in E2 levels after hCG administration; this may avoid cancellation for many patients.

Adult↗

PubMed2001

Remembering familiar people: the posterior cingulate cortex and autobiographical memory retrieval.

Most functional imaging studies of memory retrieval investigate memory for standardized laboratory stimuli. However, naturally acquired autobiographical memories differ from memories of standardized stimuli in important ways. Neuroimaging studies of natural memories may reveal distinctive patterns of brain activation and may have particular value in assessing clinical disorders of memory. This study used functional magnetic resonance imaging to investigate brain activation during successful retrieval of autobiographical memories elicited by name-cued recall of family members and friends. The caudal part of the left posterior cingulate cortex was the most strongly activated region and was significantly activated in all eight subjects studied. Most subjects also showed significant activation of the left anterior orbitomedial, anterior middle frontal, precuneus, cuneus, and posterior inferior parietal cortices, and the right posterior cingulate and motor cortices.Our findings are consistent with prior studies showing posterior cingulate cortex activation during autobiographical memory retrieval. This region is also consistently activated during retrieval of standardized memory stimuli when experimental designs emphasizing successful retrieval are employed. Our results support the hypothesis that the posterior cingulate cortex plays an important role in successful memory retrieval. The posterior cingulate cortex has strong reciprocal connections with entorhinal and parahippocampal cortices. Studies of early Alzheimer's disease, temporal lobectomy, and hypoxic amnesia show that hypometabolism of the posterior cingulate cortex is an early and prominent indicator of pathology in these patients. Our findings suggest that autobiographical memory retrieval tasks could be used to probe the functional status of the posterior cingulate cortex in patients with early Alzheimer's disease or at risk for that condition.

Acoustic Stimulation↗

PubMed1994

Staging of fixation and retrievability of Greenfield filters.

PURPOSE: The purpose of this study was to determine the retrievability of the Greenfield filter, to characterize fixation, and to evaluate the mechanical function of a new retrieval unit. METHODS: Stainless steel, titanium, and two prototype Greenfield filters (n = 82) were placed in 15 sheep at multiple sites and retrieved acutely, and 7, 14, and 21 days after placement. The animals were killed, and appropriate tissues were submitted for histopathologic evaluation. RESULTS: Eighty-two percent of all filters were retrieved. Two animals died during the procedure of cardiac tamponade. Retrieval was easiest immediately after placement, but it was least successful from the right atrium and associated with the highest incidence of damage. By 21 days, the intima around the filter hooks had thickened with myointimal hyperplasia and variable amounts of endothelial regeneration. Guide wire-hook modification was used to improve filter capture. CONCLUSIONS: All models of the Greenfield filter can be retrieved 14 to 21 days after placement, although there is high risk to retrieval from the right atrium and ventricle. The long-term safety of the Greenfield filter in man makes it difficult to justify removal in any but exceptional cases.

Animals↗

PubMedDate not supplied

The combination of high-accelerator epoxy resin and antigen retrieval to obtain more intense immunolabeling on epoxy sections than on LR-white sections for large proteins.

The purpose of this study was to examine how antigen retrieval affected the yield of immunogold labeling on epoxy sections based on embedding with different amounts of accelerator. The concentration of accelerator DMP-30 (tri(dimethyl amino methyl) phenol) was varied in the range of 0-8% in the processing of the tissue for epoxy embedding. Immunogold labeling was performed on epoxy sections and LR-White sections of fibrin clots and renal tissue with IgG-deposits, and the antibodies used were anti-fibrinogen anti-IgG and, respectively. For some of the sections antigen retrieval was performed by heating the sections in citrate buffer. In all cases, the yield of immunogold labeling increased following antigen retrieval. The increase (%) in the yield of immunogold labeling as a result of antigen retrieval was larger for epoxy sections than for LR-White sections. The immunolabeling on high-accelerator epoxy sections exposed to antigen retrieval was about 20% more intense than on untreated LR-White sections both for IgG and fibrinogen. In addition to breaking fixations bonds introduced by the chemical fixation, we believe that the antigen retrieval also breaks bonds between the epoxy resin and the embedded tissue. The combination of increased amount of accelerator during tissue processing for epoxy embedding and antigen retrieval by heating in citrate buffer is a potent method for increasing specific immunolabeling on epoxy sections.

Acrylic Resins↗

PubMed2003

Cholinergic modulation of the hippocampus during encoding and retrieval.

The present experiments were aimed at determining whether acetylcholine (ACh) plays a role in encoding and retrieval of spatial information using a modified Hebb-Williams maze. In addition, the present experiments tested two computational models of hippocampal function during encoding and retrieval using a maze sensitive to hippocampal disruption. Thirty male, Long-Evans rats served as subjects. Chronic cannulae were implanted bilaterally into the CA3 (n=26) and CA1 (n=5) subregions of the hippocampus. Rats were tested using a modified Hebb-Williams maze. In the first experiment, rats were injected with either saline or scopolamine hydrobromide 10 min before testing for each day. The number of errors made per day per group was used as the measure of learning. Encoding was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day I was used to assess retrieval. No deficit was found for the saline group. The scopolamine group showed a deficit in encoding, but not retrieval. In the second experiment, rats were injected with either saline or physostigmine 10 min before testing each day. In contrast to the scopolamine groups, the physostigmine group showed a deficit in retrieval, but not encoding. To test whether the retrieval deficit was due to a disruption in storage or gaining access to the information two groups of rats received either saline on Day 1 and physostigmine on Day 2 or physostigmine on Day 1 and saline on Day 2. In addition, one group received physostigmine immediately after testing on Day 1. Data indicate that physostigmine causes a disruption of retrieval by means of a disruption in consolidation process. In conclusion, the cholinergic antagonist, scopolamine, disrupts encoding in both CA3 and CA1 subregions of the hippocampus. Furthermore, the cholinesterase inhibitor, physostigmine, boosts ACh action during a time when cholinergic levels need to decline for proper consolidation.

Animals↗

PubMed2000

Retrieval processing and episodic memory.

The emergence of brain imaging has had a major impact on research into the cognitive and neural bases of human memory. An area in which this impact has been particularly strong is retrieval processing - the processes engaged when attempting to retrieve information during a memory test. Several different classes of retrieval process - such as 'mode', 'effort' and 'success' - have been invoked to account for findings from neuroimaging studies of episodic retrieval. In this article we discuss how these different kinds of process, along with a fourth kind associated with 'retrieval orientation', can be investigated in brain imaging experiments. We then review studies of retrieval processing, and assess how well their designs match up to our proposed criteria for dissociating the neural correlates of different classes of retrieval process. We conclude that few studies have used designs that permit these different kinds of process to be independently identified, and that presently there is little evidence to indicate which kinds of processing can be fractionated in terms of their neural correlates.

Journal Article↗

PubMed2003

Practice effects on two memory retrievals from a single cue.

The effects of practice on 2 retrievals from a single cue were investigated. In Experiment 1, participants were given extended single-task practice and were then tested on a dual memory retrieval task. Perfomance was consistent with a sequential retrieval model proposed by T. C. Rickard and H. Pashler (2003). In Experiment 2, participants practiced both single- and dual-retrieval tasks extensively. Initially, data from all participants indicated sequential retrieval. However, participants who grouped the 2 response outputs were eventually able to perform the dual task with a latency that approached the prediction of a parallel race model. Models that assume a transition from sequential to parallel retrieval with practice, along with other models that assume an immutable retrieval bottleneck at all practice levels, are considered.

Cues↗

PubMed1996

Activation of medial temporal structures during episodic memory retrieval.

Medial temporal lobe structures have been implicated in human episodic memory. Patients with medial temporal lesions show memory deficits, and functional neuroimaging studies have revealed activation in this region during episodic encoding and retrieval when data are averaged over a sample of subjects. The relevance of such observations for memory performance has remained unclear, however. Here we have used positron emission tomography (PET) to examine cerebral blood flow related to verbal episodic retrieval. We observed strong positive correlations between retrieval and blood flow in left medial temporal structures in individual normal human subjects. In addition, multivariate analysis showed that regions in the left medial temporal lobe were dominant components of a pattern of brain regions that distinguished a high-retrieval condition from conditions of lower retrieval. These results suggest that medial temporal activity is related to retrieval success rather than retrieval attempt, possibly by reflecting reactivation of stored patterns.

Brain Mapping↗

PubMed2006

Developmental memory capacity resources of typical children retrieving picture communication symbols using direct selection and visual linear scanning with fixed communication displays.

PURPOSE: This study examined the cognitive demands of 2 selection techniques in augmentative and alternative communication (AAC), direct selection, and visual linear scanning, by determining the memory retrieval abilities of typically developing children when presented with fixed communication displays. METHOD: One hundred twenty typical children from kindergarten, 1st, and 3rd grades were randomly assigned to either a direct selection or visual linear scanning group. Memory retrieval was assessed through word span using Picture Communication Symbols (PCSs). Participants were presented various numbers and arrays of PCSs and asked to retrieve them by placing identical graphic symbols on fixed communication displays with grid layouts. RESULTS: The results revealed that participants were able to retrieve more PCSs during direct selection than scanning. Additionally, 3rd-grade children retrieved more PCSs than kindergarten and 1st-grade children. An analysis on the type of errors during retrieval indicated that children were more successful at retrieving the correct PCSs than the designated location of those symbols on fixed communication displays. CONCLUSIONS: AAC practitioners should consider using direct selection over scanning whenever possible and account for anticipatory monitoring and pulses when scanning is used in the service delivery of children with little or no functional speech. Also, researchers should continue to investigate AAC selection techniques in relationship to working memory resources.

Analysis of Variance↗

PubMed2000

Identification of a premature stop codon in the melanocyte-stimulating hormone receptor gene (MC1R) in Labrador and Golden retrievers with yellow coat colour.

We have examined whether black/yellow coat colour in Labrador retrievers is controlled by allelic variants at the extension locus. As the gene encoding the melanocyte-stimulating hormone receptor (MC1R) has been shown to correspond to the extension locus in several species, we have determined the genomic MC1R sequence in Labrador retrievers with black and with yellow coat colour. Using primers based on the fox (Vulpes vulpes) MC1R sequence we initially isolated and sequenced the innerpart of the canine MC1R. By means of inverse PCR we succeeded in the characterization of both flanking regions of the MC1R gene (Genbank: AF064455). Comparison of the complete MC1R sequences of a yellow and a black Labrador retriever revealed a single C-->T mutation at nucleotide position 916 in the yellow dog. This transition changed the codon for arginine at position 305 into a stop codon, resulting in the elimination of the evolutionary strongly conserved 10 carboxyterminal amino acid residues. With an allele-specific-oligonucleotide (ASO) test it was shown that the mutation cosegregated with the recessively inherited yellow coat colour in the Labrador retriever. Golden retrievers also appeared to be homozygous for the mutation. Seventeen other breeds were all negative for the mutation. Since the Labrador and Golden retriever are closely related, we suggest a common founder for the yellow coat colour in Labrador and Golden retrievers.

Amino Acid Sequence↗

PubMed2002

Assessment of the physical properties of endoscopic retrieval systems.

BACKGROUND: A reliable method of retrieval of laparoscopically resected organs is required. The physical properties of three commercial systems available for clinical use (two plastic, one woven fabric) were examined. METHODS: Pig abdominal walls and gallbladders containing steel balls to represent gallstones were used to simulate organ retrieval on 60 occasions. The performance of retrieval bags was measured in terms of the temporal profile of pressure developed inside the bag, the force on the bag during withdrawal, and whether or not the bag could be retrieved intact. The force versus elongation relationship was also determined for each bag. RESULTS: Although there was a wide range of maximum pressures recorded (14-320 mmHg) with each retrieval system, the mean pressures in the plastic systems were significantly higher. The forces recorded during attempted withdrawal of both plastic bags were significantly lower than those with the fabric system (BERT bag: mean (range) 87 (25-165) N; Endocatch: 40 (7-123) N; Endopouch: 40 (14-68) N; P = 0.005 Endocatch versus BERT, P = 0.004 Endopouch versus BERT). The BERT bags tore more easily at the site of the grasper. CONCLUSION: Plastic retrieval systems were less likely to burst than fabric systems when subjected to simulated retrieval, and required less force for withdrawal. Plastic systems may therefore be associated with less tumour seeding or gallstone spillage as a consequence of bag disruption.

Animals↗

PubMed2005

Remembering one year later: role of the amygdala and the medial temporal lobe memory system in retrieving emotional memories.

The memory-enhancing effect of emotion can be powerful and long-lasting. Most studies investigating the neural bases of this phenomenon have focused on encoding and early consolidation processes, and hence little is known regarding the contribution of retrieval processes, particularly after lengthy retention intervals. To address this issue, we used event-related functional MRI to measure neural activity during the retrieval of emotional and neutral pictures after a retention interval of 1 yr. Retrieval activity for emotional and neutral pictures was separately analyzed for successfully (hits) vs. unsuccessfully (misses) retrieved items and for responses based on recollection vs. familiarity. Recognition performance was better for emotional than for neutral pictures, and this effect was found only for recollection-based responses. Successful retrieval of emotional pictures elicited greater activity than successful retrieval of neutral pictures in the amygdala, entorhinal cortex, and hippocampus. Moreover, in the amygdala and hippocampus, the emotion effect was greater for recollection than for familiarity, whereas in the entorhinal cortex, it was similar for both forms of retrieval. These findings clarify the role of the amygdala and the medial temporal lobe memory regions in recollection and familiarity of emotional memory after lengthy retention intervals.

Adult↗

PubMed1998

Function of the KKXX motif in endoplasmic reticulum retrieval of a transmembrane protein depends on the length and structure of the cytoplasmic domain.

Transmembrane glycoproteins with type 1 topology can be retrieved to the endoplasmic reticulum (ER) by a retrieval signal containing a di-lysine (KK) motif near the C terminus. To investigate the structural requirements for ER retrieval, we have constructed mutants of the simian immunodeficiency virus (SIV) envelope (Env) protein with cytoplasmic tails of different lengths and containing a KK motif at the -3 and -4 positions. Such proteins were found to be retained intracellularly when the signal was located 18 amino acids or more away from the membrane spanning domain. The retrieval signal was found to be functional even when placed at the distal end of the wild-type SIV Env protein with 164 amino acids in the cytoplasmic tail, as shown by the lack of proteolytic processing and lack of cell surface expression of the mutant proteins. However, proteins with a cytoplasmic tail length of 13 amino acids or less having the di-lysine motif at the -3 and -4 positions were not retrieved to the ER since they were found to be processed and transported to the cell surface. The surface-expressed proteins were found to be functional in inducing cell fusion, whereas the proteins retained intracellularly were defective in fusion activity. We also found that the KK motif introduced near an amphipathic helical region in the cytoplasmic tail was not functional. These results demonstrate that the ability of the KK motif to cause protein retrieval and retention in the endoplasmic reticulum depends on the length and structure of the cytoplasmic domain. The ER retrieval of the mutant proteins was found to correlate with increased intracellular binding to beta COP proteins.

Cell Line↗