scholarly journals Metabolic Impairment in Human Amnesia: A PET Study of Memory Networks

1992 ◽  
Vol 12 (3) ◽  
pp. 353-358 ◽  
Author(s):  
Ferruccio Fazio ◽  
Daniela Perani ◽  
Maria Carla Gilardi ◽  
Fabio Colombo ◽  
Stefano F. Cappa ◽  
...  
Keyword(s):  
Hippocampal Formation ◽  
Cerebral Metabolism ◽  
Human Memory ◽  
Clinical Syndrome ◽  
Long Term Memory ◽  
Positron Emission ◽  
New Information ◽  
Magnetic Resonance Imaging Mri

Human amnesia is a clinical syndrome exhibiting the failure to recall past events and to learn new information. Its “pure” form, characterized by a selective impairment of long-term memory without any disorder of general intelligence or other cognitive functions, has been associated with lesions localized within Papez's circuit and some connected areas. Thus, amnesia could be due to a functional disconnection between components of this or other neural structures involved in long-term learning and retention. To test this hypothesis, we measured regional cerebral metabolism with 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) and positron emission tomography (PET) in 11 patients with “pure” amnesia. A significant bilateral reduction in metabolism in a number of interconnected cerebral regions (hippocampal formation, thalamus, cingulate gyrus, and frontal basal cortex) was found in the amnesic patients in comparison with normal controls. The metabolic impairment did not correspond to alterations in structural anatomy as assessed by magnetic resonance imaging (MRI). These results are the first in vivo evidence for the role of a functional network as a basis of human memory.

scholarly journals Visual working memory buffers information retrieved from visual long-term memory

2017 ◽  
Vol 114 (20) ◽  
pp. 5306-5311 ◽  
Author(s):  
Keisuke Fukuda ◽  
Geoffrey F. Woodman
Keyword(s):  
Working Memory ◽  
Human Memory ◽  
Long Term Memory ◽  
High Temporal Resolution ◽  
Term Memory ◽  
Long Term Storage ◽  
New Information ◽  
Neurophysiological Activity ◽  
Term Storage

Human memory is thought to consist of long-term storage and short-term storage mechanisms, the latter known as working memory. Although it has long been assumed that information retrieved from long-term memory is represented in working memory, we lack neural evidence for this and need neural measures that allow us to watch this retrieval into working memory unfold with high temporal resolution. Here, we show that human electrophysiology can be used to track information as it is brought back into working memory during retrieval from long-term memory. Specifically, we found that the retrieval of information from long-term memory was limited to just a few simple objects’ worth of information at once, and elicited a pattern of neurophysiological activity similar to that observed when people encode new information into working memory. Our findings suggest that working memory is where information is buffered when being retrieved from long-term memory and reconcile current theories of memory retrieval with classic notions about the memory mechanisms involved.

scholarly journals B cell–intrinsic TLR signals amplify but are not required for humoral immunity

2007 ◽  
Vol 204 (13) ◽  
pp. 3095-3101 ◽  
Author(s):  
Almut Meyer-Bahlburg ◽  
Socheath Khim ◽  
David J. Rawlings
Keyword(s):  
B Cells ◽  
B Cell ◽  
Long Term Memory ◽  
Altered Expression ◽  
Intrinsic Signals ◽  
Antibody Titers ◽  
Specific Igg ◽  
B Cell Subsets

Although innate signals driven by Toll-like receptors (TLRs) play a crucial role in T-dependent immune responses and serological memory, the precise cellular and time-dependent requirements for such signals remain poorly defined. To directly address the role for B cell–intrinsic TLR signals in these events, we compared the TLR response profile of germinal center (GC) versus naive mature B cell subsets. TLR responsiveness was markedly up-regulated during the GC reaction, and this change correlated with altered expression of the key adaptors MyD88, Mal, and IRAK-M. To assess the role for B cell–intrinsic signals in vivo, we transferred MyD88 wild-type or knockout B cells into B cell–deficient μMT mice and immunized recipient animals with 4-hydroxy-3-nitrophenylacetyl (NP) chicken gamma globulin. All recipients exhibited similar increases in NP-specific antibody titers during primary, secondary, and long-term memory responses. The addition of lipopolysaccharide to the immunogen enhanced B cell-intrinsic, MyD88-dependent NP-specific immunoglobulin (Ig)M production, whereas NP-specific IgG increased independently of TLR signaling in B cells. Our data demonstrate that B cell–intrinsic TLR responses are up-regulated during the GC reaction, and that this change significantly promotes antigen-specific IgM production in association with TLR ligands. However, B cell–intrinsic TLR signals are not required for antibody production or maintenance.

scholarly journals Repeated social defeat induces transient glial activation and brain hypometabolism: A positron emission tomography imaging study

2017 ◽  
Vol 39 (3) ◽  
pp. 439-453 ◽  
Author(s):  
Paula Kopschina Feltes ◽  
Erik FJ de Vries ◽  
Luis E Juarez-Orozco ◽  
Ewelina Kurtys ◽  
Rudi AJO Dierckx ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Positron Emission Tomography Imaging ◽  
Imaging Study ◽  
Social Defeat ◽  
Glial Activation ◽  
Emission Tomography ◽  
Biochemical Alterations ◽  
Positron Emission

Psychosocial stress is a risk factor for the development of depression. Recent evidence suggests that glial activation could contribute to the development of depressive-like behaviour. This study aimed to evaluate in vivo whether repeated social defeat (RSD) induces short- and long-term inflammatory and metabolic alterations in the brain through positron emission tomography (PET). Male Wistar rats ( n = 40) were exposed to RSD by dominant Long-Evans rats on five consecutive days. Behavioural and biochemical alterations were assessed at baseline, day 5/6 and day 24/25 after the RSD protocol. Glial activation (11C-PK11195 PET) and changes in brain metabolism (18F-FDG PET) were evaluated on day 6, 11 and 25 (short-term), and at 3 and 6 months (long-term). Defeated rats showed transient depressive- and anxiety-like behaviour, increased corticosterone and brain IL-1β levels, as well as glial activation and brain hypometabolism in the first month after RSD. During the third- and six-month follow-up, no between-group differences in any investigated parameter were found. Therefore, non-invasive PET imaging demonstrated that RSD induces transient glial activation and reduces brain glucose metabolism in rats. These imaging findings were associated with stress-induced behavioural changes and support the hypothesis that neuroinflammation could be a contributing factor in the development of depression.

scholarly journals Long-Term Test–Retest Reliability of Striatal and Extrastriatal Dopamine D2/3 Receptor Binding: Study with [11C]Raclopride and High-Resolution PET

2015 ◽  
Vol 35 (7) ◽  
pp. 1199-1205 ◽  
Author(s):  
Kati Alakurtti ◽  
Jarkko J Johansson ◽  
Juho Joutsa ◽  
Matti Laine ◽  
Lars Bäckman ◽  
...  
Keyword(s):  
High Resolution ◽  
Intraclass Correlation ◽  
Binding Potential ◽  
Reference Tissue ◽  
Retest Reliability ◽  
Positron Emission ◽  
Simplified Reference Tissue Model ◽  
Test Retest Reliability

We measured the long-term test–retest reliability of [11C]raclopride binding in striatal subregions, the thalamus and the cortex using the bolus-plus-infusion method and a high-resolution positron emission scanner. Seven healthy male volunteers underwent two positron emission tomography (PET) [11C]raclopride assessments, with a 5-week retest interval. D2/3 receptor availability was quantified as binding potential using the simplified reference tissue model. Absolute variability (VAR) and intraclass correlation coefficient (ICC) values indicated very good reproducibility for the striatum and were 4.5%/0.82, 3.9%/0.83, and 3.9%/0.82, for the caudate nucleus, putamen, and ventral striatum, respectively. Thalamic reliability was also very good, with VAR of 3.7% and ICC of 0.92. Test-retest data for cortical areas showed good to moderate reproducibility (6.1% to 13.1%). Our results are in line with previous test–retest studies of [11C]raclopride binding in the striatum. A novel finding is the relatively low variability of [11C]raclopride binding, providing suggestive evidence that extrastriatal D2/3 binding can be studied in vivo with [11C]raclopride PET to be verified in future studies.

Cerebral Metabolism during Propofol Anesthesia in Humans Studied with Positron Emission Tomography 

1995 ◽  
Vol 82 (2) ◽  
pp. 393-403 ◽  
Author(s):  
Michael T. Alkire ◽  
Richard J. Haier ◽  
Steven J. Barker ◽  
Nitin K. Shah ◽  
Joseph C. Wu ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Animal Studies ◽  
Cerebral Metabolism ◽  
Anterior Cingulate ◽  
Emission Tomography ◽  
Whole Brain ◽  
Metabolic Pattern ◽  
Positron Emission ◽  
Cortical Regions

Background Although the effects of propofol on cerebral metabolism have been studied in animals, these effects have yet to be directly examined in humans. Consequently, we used positron emission tomography (PET) to demonstrate in vivo the regional cerebral metabolic changes that occur in humans during propofol anesthesia. Methods Six volunteers each underwent two PET scans; one scan assessed awake-baseline metabolism, and the other assessed metabolism during anesthesia with a propofol infusion titrated to the point of unresponsiveness (mean rate +/- SD = 7.8 +/- 1.5 mg.kg-1.h-1). Scans were obtained using the 18fluorodeoxyglucose technique. Results Awake whole-brain glucose metabolic rates (GMR) averaged 29 +/- 8 mumoles.100 g-1.min-1 (mean +/- SD). Anesthetized whole-brain GMR averaged 13 +/- 4 mumoles.100 g-1.min-1 (paired t test, P < or = 0.007). GMR decreased in all measured areas during anesthesia. However, the decrease in GMR was not uniform. Cortical metabolism was depressed 58%, whereas subcortical metabolism was depressed 48% (P < or = 0.001). Marked differences within cortical regions also occurred. In the medial and subcortical regions, the largest percent decreases occurred in the left anterior cingulate and the inferior colliculus. Conclusion Propofol produced a global metabolic depression on the human central nervous system. The metabolic pattern evident during anesthesia was reproducible and differed from that seen in the awake condition. These findings are consistent with those from previous animal studies and suggest PET may be useful for investigating the mechanisms of anesthesia in humans.

scholarly journals Biased Competition during Long-term Memory Formation

2016 ◽  
Vol 28 (1) ◽  
pp. 187-197 ◽  
Author(s):  
J. Benjamin Hutchinson ◽  
Sarah S. Pak ◽  
Nicholas B. Turk-Browne
Keyword(s):  
Prior Experience ◽  
Temporal Cortex ◽  
Memory Systems ◽  
Long Term Memory ◽  
The Novel ◽  
Complete Representation ◽  
New Information ◽  
Ventral Temporal Cortex ◽  
Spatial Locations

A key task for the brain is to determine which pieces of information are worth storing in memory. To build a more complete representation of the environment, memory systems may prioritize new information that has not already been stored. Here, we propose a mechanism that supports this preferential encoding of new information, whereby prior experience attenuates neural activity for old information that is competing for processing. We evaluated this hypothesis with fMRI by presenting a series of novel stimuli concurrently with repeated stimuli at different spatial locations in Experiment 1 and from different visual categories (i.e., faces and scenes) in Experiment 2. Subsequent memory for the novel stimuli could be predicted from the reduction in activity in ventral temporal cortex for the accompanying repeated stimuli. This relationship was eliminated in control conditions where the competition during encoding came from another novel stimulus. These findings reveal how prior experience adaptively guides learning toward new aspects of the environment.

Safety of Hybrid Electrodes for Single-Neuron Recordings in Humans

Neurosurgery ◽  
2013 ◽  
Vol 73 (1) ◽  
pp. 78-85 ◽  
Author(s):  
Stefan Hefft ◽  
Armin Brandt ◽  
Stefan Zwick ◽  
Dominik von Elverfeldt ◽  
Irina Mader ◽  
...  
Keyword(s):  
Single Neuron ◽  
Electrode Implantation ◽  
Intraoperative Computed Tomography ◽  
Postoperative Mri ◽  
Depth Electrodes ◽  
Magnetic Resonance Imaging Mri ◽  
Clinical Mri

Abstract BACKGROUND: Intracranial in vivo recordings of individual neurons in humans are increasingly performed for a better understanding of the mechanisms of epileptogenesis and of the neurobiological basis of cognition. So far, information about the safety of stereotactic implantations and of magnetic resonance imaging (MRI) with hybrid depth electrodes is scarce. OBJECTIVE: The aim of this study was to assess neurosurgical safety of implantations, recordings, and imaging using hybrid electrodes in humans. METHODS: Perioperative and long-term safety of implantation of a total of 88 hybrid depth electrodes with integrated microwires was assessed retrospectively in 25 consecutive epilepsy patients who underwent implantation of electrodes from 2007 to 2011 based on electronically stored charts. Safety aspects of MRI are reported from both in vitro and in vivo investigations. Precision of electrode implantation is evaluated based on intraoperative computed tomography and pre- and postoperative MRI. RESULTS: There was no clinically relevant morbidity associated with the use of hybrid electrodes in any of the patients. Precision of recordings from the targets aimed at was similar to that of standard depth electrodes. In vitro studies demonstrated the absence of relevant heating of hybrid electrodes with newly designed connectors with MRI at 1.5 T, corresponding to well-tolerated clinical MRI in patients. CONCLUSION: Given the technical approach described here, precise targeting and safe use are possible with hybrid electrodes containing microwires for in vivo recording of human neuronal units.

scholarly journals Imaging of microglial activation in MS using PET: Research use and potential future clinical application

2016 ◽  
Vol 23 (4) ◽  
pp. 496-504 ◽  
Author(s):  
Laura Airas ◽  
Eero Rissanen ◽  
Juha Rinne
Keyword(s):  
Complex Disease ◽  
Treatment Options ◽  
Quantitative Information ◽  
Imaging Biomarkers ◽  
In Vivo Evaluation ◽  
Non Invasive ◽  
Positron Emission ◽  
Magnetic Resonance Imaging Mri

Multiple sclerosis (MS) is a complex disease, where several processes can be selected as a target for positron emission topography (PET) imaging. Unlike magnetic resonance imaging (MRI), PET provides specific and quantitative information, and unlike neuropathology, it can be non-invasively applied to living patients, which enables longitudinal follow-up of the MS pathology. In the study of MS, PET can be useful for in vivo evaluation of specific pathological characteristics at various stages of the disease. Increased understanding of the progressive MS pathology will enhance the treatment options of this undertreated condition. The ultimate goal of developing and expanding PET in the study of MS is to have clinical non-invasive in vivo imaging biomarkers of neuroinflammation that will help to establish prognosis and accurately measure response to therapeutics. This topical review provides an overview of the promises and challenges of the use of PET in MS.

Ich denke, also übersetze ich: die Relevanz einer bewussten Reflexion über die Verstehensprozesse beim literarischen Übersetzen mit Beispielen aus der Übersetzung des Briefromans La Tesis de Nancy (1962) von Ramón J. Sender ins Deutsche

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Mona Helmchen
Keyword(s):  
Present Article ◽  
Cognitive Linguistics ◽  
Long Term Memory ◽  
The Novel ◽  
Term Memory ◽  
Metaphorical Thinking ◽  
New Information ◽  
Theoretical Frame ◽  
Professional Translator

AbstractIn the present article and in a theoretical frame based in cognitive linguistics, we will justify and analyse some of the translational processes that have taken place during the translation of the novel “La Tesis de Nancy” (1962). The human being constantly perceives a multitude of impressions which operate as mental impulses and which activate parts of the long-term memory to facilitate the understanding of new information. Apart from the development of mental spaces, the metaphorical thinking plays an important role in the creation of meaning and in the understanding of reality. A professional translator has to consider that an awareness of such processes can be an inspirational source for a creative and functional translation.

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