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Biomedical subjects

Michael Rose

Publications and source records attributed to Michael Rose.

At least 19 recordsLinked to original sources
PubMed2007

Associative symmetry versus independent associations in the memory for object-location associations.

The formation of associations between objects and locations is a vital aspect of episodic memory. More specifically, remembering the location where one experienced an object and, vice versa, the object one encountered at a specific location are both important elements for the memory of an event. Whether episodic associations are holistic representations of individual components or whether there are unidirectional, separately modifiable connections between them has been investigated nearly exclusively using verbal stimuli. A preliminary conclusion concerning this controversy is that verbal associations are, at least, highly correlated (M. J. Kahana, 2002). This theoretical debate, which in the past has undergone a major empirical effort, is still of relevance for the concurrent global matching models of associative memory (S. E. Clark & S. D. Gronlund, 1996). The authors used variations of a novel object-location learning paradigm to complement the accumulated evidence regarding the nature of episodic associations.

Adolescent↗
PubMed2006

Dissociable parietal systems for primacy and subsequent memory effects.

The frequently observed superior memory for the first items on a list is referred to as primacy. The aetiology of this effect in terms of cognitive processes and their neural substrate is subject to an ongoing debate. However, the brain areas generally involved in successful encoding are well described by subsequent memory studies in which activity during encoding is correlated with memory performance. We employed an object-location association paradigm to differentiate the neural correlate of the primacy from the subsequent memory effect. Activity in the intraparietal sulcus predicted memory performance across all encoding positions. Increased activity in the inferior parietal lobe and angular gyrus resulted exclusively in a more efficient encoding of the first item presented. These areas are part of the ventral frontoparietal network involved in stimulus driven attention. Our results implicate the relatively elevated attention to the first item probably due to its contextual distinctiveness, as a major contributor to the primacy effect.

Adult↗
PubMed2006

Precursors of insight in event-related brain potentials.

Event-related potentials (ERPs) were investigated to find precursors of insightful behavior. Participants had to process successive pairs in strings of digits to obtain a final response in each trial. Within the sequence of five responses required in each trial, the last two responses mirrored the two preceding ones. This hidden regularity, allowing for shortcutting each trial from five to two responses, was discovered by 6 out of 26 participants. Both groups, solvers and nonsolvers, implicitly learned the regularity, reflected by faster responses to the repeated, predictable responses, but this differential effect was larger in solvers, whereas nonsolvers became unspecifically faster with all responses. Several ERP components were larger in solvers than in nonsolvers from the outset: slow positive wave, frontocentral P3a, anterior N1 to those digits that triggered the critical repeating responses, and P3b to the digit that evoked the immediately repeating response. Being already present in the first block, these effects were early precursors of insightful behavior. This early occurrence suggests that participants who will gain insight may be distinguished beforehand by their individual characteristics.

Adult↗
PubMed2005

Integration of local features to a global percept by neural coupling.

The integration of different visual attributes into the percept of a single global shape is a central aspect of object processing. In hierarchically organized stimuli with local and global levels, the attentional focus largely determines which level is processed. Here we tested the hypothesis that object processing during attention to the global aspect of the stimulus is characterized by an increased neural coupling between visual areas reflecting the integration of local features. In the present experiment, we used global letters that were constructed by smaller local letters, and a cue signaled which spatial level should be identified. On the local level, only 1 relevant letter was presented laterally in 1 visual hemifield. In contrast, the global letter extended into both hemifields, and the integration of information from both hemispheres was necessary to identify the global stimulus. Therefore, we expected an increased functional coupling between hemispheres during global processing. This hypothesis was investigated using electroencephalographic recordings and an analysis of phase locking and coherence. The results show that stimulus-locked neural coupling within the gamma band (30-40 Hz) across hemispheres in visual cortex increased for global processing after stimulus presentation and could therefore reflect the integration of local visual information.

Adult↗
PubMed2005

Neural coupling binds visual tokens to moving stimuli.

Spatially separated visual objects that appear in alternating sequence can be perceived as a single moving object. This phenomenon of apparent motion enables us to perceive sequentially presented images as a motion picture. How does the visual system bind together single visual tokens to one moving object? Here we report a series of experiments investigating apparent motion with electroencephalographic recordings showing that gamma-band oscillatory coupling in the visual cortex is crucial for this phenomenon. We used an ambiguous stimulus that could be perceived as moving either vertically or horizontally. Because visual information from the right and left visual hemifields is routed to the contralateral early visual cortex, in the case of perceived horizontal movement, information from both hemispheres has to be integrated. In accord with this assumption, our data show stronger oscillatory coupling between right and left visual cortices during perception of horizontal motion compared with vertical motion.

Adult↗
PubMed2005

Dissociable contributions within the medial temporal lobe to encoding of object-location associations.

The crucial role of the medial temporal lobe (MTL) in episodic memory is well established. Although there is little doubt that its anatomical subregions-the hippocampus, peri-, entorhinal and parahippocampal cortex (PHC)-contribute differentially to mnemonic processes, their specific functions in episodic memory are under debate. Data from animal, human lesion, and neuroimaging studies suggest somewhat contradictory perspectives on this functional specialization: a general participation in declarative memory, an exclusive involvement in associative mnemonic processes, and a specific contribution to spatial memory are reported for the hippocampus, adjacent cortices, and the PHC. A functional lateralization in humans dependent on the verbalizability of the material is also discussed herein. To further elucidate the differential contributions of the various MTL subregions to encoding, we employed an object-location association memory paradigm. The memory for each of the studied associations was tested twice: by the object, and by the location serving as retrieval cue. The memory accuracy in response to both cue types was also assessed parametrically. Brain activity during encoding which leads to different degrees of subsequent memory accuracy under the two retrieval conditions was compared. We found the bilateral posterior PHC to participate in encoding of both the object associated with a location and the location associated with an object. In contrast, activity in an area in the left anterior PHC and the right anterior MTL was only correlated with the memory for the location associated with an object.

Adult↗
PubMed2005

Low molecular weight glycosaminoglycan C3 attenuates AF64A-stimulated, low-affinity nerve growth factor receptor-immunoreactive axonal varicosities in the rat septum.

Glycosaminoglycans (GAGs) play a pivotal role in the pathogenesis of Alzheimer's disease (AD). Although, as we have shown earlier, a low molecular weight GAG, C3, protects against ethylcholine aziridinium (AF64A)-induced cholinergic damage, and against A(beta)-induced tau-2-immunoreactivity (IR), the mechanism of the neuroprotective effect of GAGs is not yet known. Several clues exist. Previous studies in rats revealed that continuous NGF infusion (icv) after AF64A injection increases septal ChAT and AChE activities. Moreover, C3 increases axonal outgrowth in the rat hippocampus, raising the possibility of a NGF-receptor mediated neuroprotection. Furthermore, it has been reported that NGF expression is increased in the septum following AF64A administration. To study the question regarding the mechanism of neuroprotective action of GAGs, AF64A, a selective cholinotoxin, was administered stereotaxically, bilaterally, into the lateral ventricles of Fischer albino male rats (1 nmol/2 microl/side). In order to establish the effect of C3 on the expression of the NGF receptor-IR elements, C3 was administered orally (25 mg/kg, once a day), by gavage, 7 days before, and 7 days after the AF64A injection. NGF receptor immunohistochemistry revealed that AF64A induced the appearance of NGF-receptor-IR axonal varicosities in the rat medial septum. These varicose fibers were attenuated by 14 days' administration of C3. The possible explanation of our data may be that C3 increases NGF synthesis in the lateral septum. The increased level of NGF could suppress the increased, AF64A-induced NGF receptor expression in the medial septal nucleus. These results further accentuate our earlier observations that C3 may have potential as a therapeutic agent in AD and other neurodegenerative disorders.

Animals↗
PubMed2005

Pathological gambling is linked to reduced activation of the mesolimbic reward system.

By analogy to drug dependence, it has been speculated that the underlying pathology in pathological gambling is a reduction in the sensitivity of the reward system. Studying pathological gamblers and controls during a guessing game using functional magnetic resonance imaging, we observed a reduction of ventral striatal and ventromedial prefrontal activation in the pathological gamblers that was negatively correlated with gambling severity, linking hypoactivation of these areas to disease severity.

Adult↗
PubMed2005

Contributions of occipital, parietal and parahippocampal cortex to encoding of object-location associations.

Events are stored in our episodic memory in varying degrees of accessibility for conscious retrieval and combined with varying amounts of associated information. A crucial aspect of episodic memory is to bind information together, e.g. linking an object to a certain location. Spontaneous or experimenter-induced variance in the allocation of attentional resources during encoding critically determines the strength of the resulting memory trace especially for associative information as measured in subsequent memory tests. The neural correlates of associative memory encoding were investigated by lesion, PET- and fMRI-studies. So far no study aimed to assess the memory for associative information in a non-categorical way. Such a parametric assessment opens the possibility for a closer inspection of the relationship between brain activity and memory trace formation. We established a novel associative object-location memory paradigm, together with a parametric assessment of subsequent memory performance for spatial location which allows: (i) to determine if associative information is retrieved in a continuous or discontinuous manner during recognition and (ii) to investigate the relationship between activity during encoding and the resulting memory trace. Such correlations were observed in the occipital, parietal and the parahippocampal cortex, areas known to be involved in processing either objects and/or locations. The analysis of response functions revealed for the majority of areas involved in encoding a continuous relationship between brain activity during encoding and the confidence in a subsequent memory test.

Adult↗
PubMed2005

Automation of the glycerolization of red blood cells with the high-separation bowl in the Haemonetics ACP 215 instrument.

BACKGROUND: The FDA has approved a closed-system red blood cell (RBC) glycerolization procedure with the ACP 215 (Haemonetics), which requires a centrifuge to prepare RBCs before and after glycerolization. In the study reported here, the Haemonetics high-separation bowl was evaluated in an attempt to automate these two concentration steps. STUDY DESIGN AND METHODS: Ten units of nonleukoreduced citrate phosphate dextrose (CPD)-anticoagulated whole blood were stored at 4 degrees C for 2 to 6 days before glycerolization and freezing as nonrejuvenated RBCs. Twenty-five units of nonleukoreduced CPD whole blood were stored at 4 degrees C for 2 to 8 days and then biochemically treated with a solution containing pyruvate, inosine, phosphate, and adenine (PIPA) before glycerolization and freezing as indated-rejuvenated RBC. Twenty units of leukoreduced CPD and AS-1 RBCs were stored at 4 degrees C for a mean of 48 days and treated with PIPA solution before glycerolization and freezing as outdated-rejuvenated RBCs. The glycerolized RBCs were frozen for at least 2 weeks at -80 degrees C, deglycerolized in the Haemonetics ACP 215 with the 325-mL bowl, and stored in AS-3 at 4 degrees C for 21 days. RESULTS: It took approximately 50 minutes to glycerolize the nonrejuvenated and rejuvenated RBCs. After freezing, deglycerolization, and postwash storage at 4 degrees C in AS-3 for 2 weeks, the quality was similar to that of RBCs processed by the current FDA-approved method. CONCLUSION: Processing time and need for technical expertise were significantly reduced with the completely automated functionally closed glycerolization procedure with the high-separation bowl in the Haemonetics ACP 215 instrument.

2,3-Diphosphoglycerate↗
PubMed2005

Unconscious detection of implicit expectancies.

The detection of unexpected events is a fundamental process of learning. Theories of cognitive control and previous imaging results indicate a prominent role of the prefrontal cortex in the evaluation of the congruency between expected and actual outcome. In most cases, this attributed function is based on results where the person is consciously aware of the discrepancy. In this functional magnetic imaging (fMRI) study, we examined violations of predicted outcomes that did not enter conscious awareness. Two groups were trained with nearly identical material and the effects of new stimuli were assessed after learning. For the first group, the material was arranged with a hidden regularity. In this incidental learning situation, volunteers acquired implicit knowledge about structural response regularities as was demonstrated by an increase in reaction time when introducing new stimuli that violated the learned relations. To differentiate the detection process of stimuli that deviate from learned expectations from more unspecific effects generated by novel, unfamiliar stimuli, the second group was trained with rearranged material without a hidden regularity. No behavioral effects were found for the introduction of new stimuli in the group without implicit learning. Comparing the two groups, specific fMRI effects concerning the violation of implicitly learned expectations were found in the ventral prefrontal cortex and in the medialtemporal lobe. In accord with theories of learning, the results show a direct influence of the detection of prediction errors on the neuronal activity in learning related structures even in the absence of conscious knowledge about the predictions or their violations.

Adult↗
PubMed2004

The functional and temporal characteristics of top-down modulation in visual selection.

Perceptual load of an attended task influences the processing of irrelevant background stimuli. In a series of behavioral, functional magnetic resonance (fMRI) and electroencephalography (EEG) experiments we examined the influence of working memory (WM) load related to a relevant visual stimulus on the processing of irrelevant backgrounds. We further addressed two open questions about the mechanism of load-dependent modulation: (i) is this modulation dependent on regional activity (i.e. phasic)? (ii) At what processing stage does this modulation take place? Load was manipulated by a WM task and concurrently the processing of irrelevant visual objects was assessed with fMRI and EEG. To examine the dependency of this modulation on intrinsic activity, we varied the activity level of visual areas by presenting objects with different levels of degradation. Activity in the lateral occipital complex (LOC) increased with object visibility and was phasically modulated by WM load. Event related potentials revealed that this phasic modulation occurred approximately 170 ms after stimulus onset, indicative of an early selection under high load. The results indicate a phasic modulatory effect of WM load on visual object processing in the LOC that is comparable to the effects found for perceptual load manipulations.

Adult↗
PubMed2004

Are boreal ecosystems susceptible to alien plant invasion? Evidence from protected areas.

Although biological invasion by alien species is a major contributor to loss of indigenous biological diversity, few studies have examined the susceptibility of the boreal biome to invasion. Based on studies of other ecosystems, we hypothesized that alien plants will be restricted to disturbed areas near human activity and will not be found in natural areas of boreal ecosystems in Gros Morne National Park (Canada), a protected area experiencing a wide range of disturbance regimes. The distribution of alien plants in the region was evaluated using surveys, and study sites were established in naturally and anthropogenically disturbed habitats that had been invaded. Within study sites, randomization tests evaluated the importance of disturbance to alien plant invasion by examining changes in environmental conditions and species abundance within various disturbance regimes, while the importance of site characteristics limiting the distribution of alien plants were examined using Canonical Correspondence Analysis. Consistent with studies in a variety of biomes, areas of high disturbance and human activity had the greatest abundance of resources and the highest percentage of alien species. However, contrary to our hypothesis, natural areas of boreal ecosystems were found susceptible to alien plant invasion. Vegetation types vulnerable to invasion include forests, riparian areas, fens, and alpine meadows. Natural disturbance occurring in these vegetation types caused increases in bare ground and/or light availability facilitating alien plant invasion. Although high soil pH was associated with alien plants in these areas, disturbance was not found to cause changes in soil pH, suggesting susceptibility to invasion is pre-determined by bedrock geology or other factors influencing soil pH. Moose (Alces alces), a non-native herbivore, acts as the primary conduit for alien plant invasion in GMNP by dispersing propagules and creating or prolonging disturbance by trampling and browsing vegetation. The recurrent nature of disturbance within the boreal biome and its interaction with site conditions and herbivores enables alien plants to persist away from areas of high human activity. Managers of natural lands should monitor such interactions to decrease the invasion potential of alien plants.

Analysis of Variance↗
PubMed2004

Perioperative hypertension due to undiagnosed aortic coarctation: are current standards of care adequate?

A 12-year-old male presented for a superficial parotidectomy for chronic parotitis. The patient had an unremarkable past medical history and was admitted on the day of surgery for his procedure without further anaesthetic or surgical review. During the patient's intraoperative course, higher than expected blood pressures were noted and treated with clonidine. After further high blood pressure readings in the postoperative care unit, close surveillance of blood pressures for the following 24 h was arranged. The hypertension was ongoing, and further examination and investigation confirmed the diagnosis of coarctation of the aorta. We examine the possible reasons for failure to diagnose this patient's hypertension preoperatively and suggest that there is a need for greater surveillance of blood pressures in the paediatric population presenting for surgery. A discussion of the significance of hypertension in paediatrics and recommendations for minimum standards of care to address shortcomings in the diagnosis and treatment of paediatric hypertension are proposed.

Aortic Coarctation↗
PubMed2004

Extended storage of AS-1 and AS-3 leukoreduced red blood cells for 15 days after deglycerolization and resuspension in AS-3 using an automated closed system.

BACKGROUND: The utilization of cryopreserved red blood cell (RBC) units had been limited by a maximum postdeglycerolization storage of 24 hours at 1 to 6 degrees C until the recent development of a closed system for the glycerolization and deglycerolization process. STUDY DESIGN AND METHODS: Sixty leukoreduced additive solution (AS), AS-1 (n = 30) and AS-3 (n = 30) RBC units from 500-mL whole blood (WB) collections were stored for 6 days, glycerolized, frozen at -70 +/- 5 degrees C for at least 14 days, thawed, deglycerolized, and stored for 15 days at 1 to 6 degrees C. Glycerolization and deglycerolization were performed with the ACP 215. In-vitro variables were tested before glycerolization, on Day 0, and Day 15 after deglycerolization storage. Forty donors were assessed for double-label 24-hour percent recovery, and T1/2 survival time was measured for 20 donors. RESULTS: Postdeglycerolization mean +/- standard deviation in-vitro RBC mass recoveries were 93 +/- 5 percent for AS-1 and 95 +/- 4 percent for AS-3. Mean hemoglobin +/- standard deviation after deglycerolization was 50.5 +/- 5.5g for AS-1 and 50.1 +/- 3.5g for AS-3. Mean hemolysis (Day 15) was 0.36 +/- 0.11 percent for AS-1 and 0.38 +/- 0.13 percent for AS-3. Double-label 24-hour in-vivo recoveries were 82.5 +/- 7.8 percent for AS-1 and 81.4 +/- 7.1 percent for AS-3. The 51Cr T1/2 value was 41.8 +/- 3.97 for AS-1 and 40.6 +/- 7.11 for AS-3. Other in-vitro variables were as expected. CONCLUSION: Leukoreduced AS-1 and AS-3 RBCs after frozen storage at -70 +/- 5 degrees C can be stored for up to 14 days when processing is performed with the ACP 215 system with resuspension of deglycerolized RBCs in AS-3.

Adenine↗
PubMed2003

Dose-dependent effect of cholinotoxin AF64A on the cholinergic elements of the cingulum bundle in rat.

Previous studies revealed that cholinergic neurons possessing long axons are extremely sensitive to ethylcholine aziridinium ion (AF64A) administration [Neuropharmacology 31 (1992) 397]. In the present paper we examined the effect of AF64A on the cholinergic elements of the cingulum bundle. Seven days after AF64A administration choline acetyltransferase (ChAT)-immunoreactive fibers were extensively damaged on the dorsal part of cingulum bundle. These findings are the first reporting damage by AF64A to this brain region.

Animals↗