Dissociation of Storage and Rehearsal in Verbal Working Memory: Evidence From Positron Emission Tomography

1996 ◽  
Vol 7 (1) ◽  
pp. 25-31 ◽  
Author(s):  
Edward Awh ◽  
John Jonides ◽  
Edward E. Smith ◽  
Eric H. Schumacher ◽  
Robert A. Koeppe ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Working Memory ◽  
Memory Task ◽  
Recognition Task ◽  
Verbal Working Memory ◽  
Brain Regions ◽  
Emission Tomography ◽  
Positron Emission ◽  
Rehearsal Strategy ◽  
Phonological Store

Current cognitive models of verbal working memory include two components a phonological store and a rehearsal mechanism that refreshes the contents of this store We present research using positron emission tomography (PET) to provide further evidence for this functional division In Experiment 1, subjects performed a variant of Sternberg's (1966) item recognition task Experiment 2 used a continuous memory task with control conditions designed to separate the brain regions underlying storage and rehearsal The results show that independent brain regions mediate storage and rehearsal In Experiment 3, a dual-task procedure supported the assumption that these memory tasks elicited a rehearsal strategy

Verbal working memory and solvent exposure: A positron emission tomography study.

2000 ◽  
Vol 14 (4) ◽  
pp. 551-558 ◽  
Author(s):  
Marc W. Haut ◽  
Sharon Leach ◽  
Hiroto Kuwabara ◽  
Shannon Whyte ◽  
Ty Callahan ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Working Memory ◽  
Verbal Working Memory ◽  
Emission Tomography ◽  
Positron Emission Tomography Study ◽  
Solvent Exposure ◽  
Positron Emission

scholarly journals Validating Age-Related Functional Imaging Changes in Verbal Working Memory with Acute Stroke

2011 ◽  
Vol 24 (3) ◽  
pp. 187-199 ◽  
Author(s):  
Timothy B. Meier ◽  
Lin Naing ◽  
Lisa E. Thomas ◽  
Veena A. Nair ◽  
Argye E. Hillis ◽  
...  
Keyword(s):  
Older Adults ◽  
Working Memory ◽  
Acute Stroke ◽  
Functional Imaging ◽  
Memory Task ◽  
Recognition Task ◽  
Verbal Working Memory ◽  
Brain Regions ◽  
Stroke Patients ◽  
Younger Adults

Functional imaging studies consistently find that older adults recruit bilateral brain regions in cognitive tasks that are strongly lateralized in younger adults, a characterization known as the Hemispheric Asymmetry Reduction in Older Adults model. While functional imaging displays what brain areas are active during tasks, it cannot demonstrate what brain regions are necessary for task performance. We used behavioral data from acute stroke patients to test the hypothesis that older adults need both hemispheres for a verbal working memory task that is predominantly left-lateralized in younger adults. Right-handed younger (age ≥ 50,n= 7) and older adults (age > 50,n= 21) with acute unilateral stroke, as well as younger (n= 6) and older (n= 13) transient ischemic attack (TIA) patients, performed a self-paced verbal item-recognition task. Older patients with stroke to either hemisphere had a higher frequency of deficits in the verbal working memory task compared to older TIA patients. Additionally, the deficits in older stroke patients were mainly in retrieval time while the deficits in younger stroke patients were mainly in accuracy. These data suggest that bihemispheric activity is necessary for older adults to successfully perform a verbal working memory task.

The Effect of Divided Attention on Encoding and Retrieval in Episodic Memory Revealed by Positron Emission Tomography

2000 ◽  
Vol 12 (2) ◽  
pp. 267-280 ◽  
Author(s):  
Tetsuya Iidaka ◽  
Nicole D. Anderson ◽  
Shitij Kapur ◽  
Roberto Cabez ◽  
Fergus I. M. Craik
Keyword(s):  
Positron Emission Tomography ◽  
Prefrontal Cortex ◽  
Episodic Memory ◽  
Divided Attention ◽  
Memory Performance ◽  
Memory Task ◽  
Anterior Cingulate ◽  
Emission Tomography ◽  
Positron Emission ◽  
Encoding And Retrieval

The effects of divided attention (DA) on episodic memory encoding and retrieval were investigated in 12 normal young subjects by positron emission tomography (PET). Cerebral blood flow was measured while subjects were concurrently performing a memory task (encoding and retrieval of visually presented word pairs) and an auditory tone-discrimination task. The PET data were analyzed using multivariate Partial Least Squares (PLS), and the results revealed three sets of neural correlates related to specific task contrasts. Brain activity, relatively greater under conditions of full attention (FA) than DA, was identified in the occipital-temporal, medial, and ventral-frontal areas, whereas areas showing relatively more activity under DA than FA were found in the cerebellum, temporo-parietal, left anterior-cingulate gyrus, and bilateral dorsolateral-prefrontal areas. Regions more active during encoding than during retrieval were located in the hippocampus, temporal and the prefrontal cortex of the left hemisphere, and regions more active during retrieval than during encoding included areas in the medial and right-prefrontal cortex, basal ganglia, thalamus, and cuneus. DA at encoding was associated with specific decreases in rCBF in the left-prefrontal areas, whereas DA at retrieval was associated with decreased rCBF in a relatively small region in the right-prefrontal cortex. These different patterns of activity are related to the behavioral results, which showed a substantial decrease in memory performance when the DA task was performed at encoding, but no change in memory levels when the DA task was performed at retrieval.

scholarly journals Quantification of PET infusion studies without true equilibrium: A tissue clearance correction

2019 ◽  
Vol 40 (4) ◽  
pp. 860-874
Author(s):  
Ansel T Hillmer ◽  
Richard E Carson
Keyword(s):  
Positron Emission Tomography ◽  
Data Analysis ◽  
Brain Regions ◽  
Distribution Volume ◽  
Emission Tomography ◽  
Constant Infusion ◽  
Scanning Time ◽  
Positron Emission ◽  
Study Population ◽  
True Equilibrium

In some positron emission tomography (PET) studies, a reversibly binding radioligand is administered as a constant infusion to establish true equilibrium for quantification. This approach reduces scanning time and simplifies data analysis, but assumes similar behavior of the radioligand in plasma across the study population to establish true equilibrium in all subjects. Bias in outcome measurements can result if this assumption is not met. This work developed and validated a correction that reduces bias in total distribution volume ( VT) estimates when true equilibrium is not present. This correction, termed tissue clearance correction (TCC), took the form [Formula: see text], where β is the radioligand clearance rate in tissue, γ is a radiotracer-specific constant, and VT(A) is the apparent VT. Simulations characterized the robustness of TCC across imperfect values of γ and β and demonstrated reduction to false positive rates. This approach was validated with human infusion data for three radiotracers: [18F]FPEB, (−)-[18F]flubatine, and [11C]UCB-J. TCC reduced bias in VT estimates for all radiotracers and significantly reduced intersubject variance in VT for [18F]FPEB data in some brain regions. Thus, TCC improves quantification of data acquired from PET infusion studies.

29 POSITRON EMISSION TOMOGRAPHY IMAGING OF BRAIN METABOLISM AND DOPAMINERGIC NEURON DESTRUCTION IN PARKINSON'S DISEASE MODEL PIG

2017 ◽  
Vol 29 (1) ◽  
pp. 122
Author(s):  
H. J. Oh ◽  
J. Moon ◽  
G. A. Kim ◽  
S. Lee ◽  
S. H. Paek ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Dopaminergic Neuron ◽  
Brain Metabolism ◽  
Brain Research ◽  
Brain Regions ◽  
Emission Tomography ◽  
Positron Emission ◽  
Significant Difference ◽  
And Control ◽  
The Brain

Due to similarities between human and porcine, pigs have been proposed as an excellent experimental animal for human medical research. Especially in paediatric brain research, piglets share similarities with human infants in the extent of peak brain growth at the time of birth and the growth pattern of brain. Thus, these findings have supported the wider use of pigs rather than rodents in neuroscience research. Previously, we reported the production of porcine model of Parkinson's disease (PD) by nuclear transfer using donor cell that had been stably infected with lentivirus containing the human α-synuclein gene. The purpose of this study was to determine the alternation of brain metabolism and dopaminergic neuron destruction using noninvasive method in a 2-yr-old PD model and a control pig. The positron emission tomography (PET) scan was done using Biograph TruePoint40 with a TrueV (Siemens, Munich, Germany). The [18F]N-(3-fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (FP-CIT) was administrated via the ear vein. Static images of the brain for 15 min were acquired from 2 h after injection. The 18F-fluorodeoxy-D-glucose PET (18F-FDG PET) images of the brain were obtained for 15 min at 45 min post-injection. Computed tomography (CT) scan and magnetic resonance imaging (MRI) were performed at the same location of the brain. In both MRI and CT images, there was no difference in brain regions between PD model and control pigs. However, administration of [18F]FP-CIT was markedly decreased in the bilateral putamen of the PD model pig compared with the control pigs. Moreover, [18F]FP-CIT administration was asymmetrical in the PD model pig but it was symmetrical in control pigs. Regional brain metabolism was also assessed and there was no significant difference in cortical metabolism of PD model and control pigs. We demonstrated that PET imaging could provide a foundation for translational Parkinson neuroimaging in transgenic pigs. In the present study, a 2-yr-old PD model pig showed dopaminergic neuron destruction in brain regions. Therefore, PD model pig expressing human α-synuclein gene would be an efficient model for human PD patients. This study was supported by Korea IPET (#311011–05–5-SB010), Research Institute for Veterinary Science, TS Corporation and the BK21 plus program.

scholarly journals Medial Orbitofrontal Cortex Is Associated with Fatigue Sensation

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Seiki Tajima ◽  
Shigeyuki Yamamoto ◽  
Masaaki Tanaka ◽  
Yosky Kataoka ◽  
Masao Iwase ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Orbitofrontal Cortex ◽  
Brain Region ◽  
Statistical Parametric Mapping ◽  
Brain Regions ◽  
Mapping Method ◽  
Emission Tomography ◽  
Neural Basis ◽  
Positron Emission ◽  
The Brain

Fatigue is an indispensable bioalarm to avoid exhaustive state caused by overwork or stresses. It is necessary to elucidate the neural mechanism of fatigue sensation for managing fatigue properly. We performedH2O  15positron emission tomography scans to indicate neural activations while subjects were performing 35-min fatigue-inducing task trials twice. During the positron emission tomography experiment, subjects performed advanced trail-making tests, touching the target circles in sequence located on the display of a touch-panel screen. In order to identify the brain regions associated with fatigue sensation, correlation analysis was performed using statistical parametric mapping method. The brain region exhibiting a positive correlation in activity with subjective sensation of fatigue, measured immediately after each positron emission tomography scan, was located in medial orbitofrontal cortex (Brodmann's area 10/11). Hence, the medial orbitofrontal cortex is a brain region associated with mental fatigue sensation. Our findings provide a new perspective on the neural basis of fatigue.

scholarly journals Network Diffusion Modeling Explains Longitudinal Tau PET Data

2020 ◽  
Vol 14 ◽  
Author(s):  
Amelie Schäfer ◽  
Elizabeth C. Mormino ◽  
Ellen Kuhl
Keyword(s):  
Positron Emission Tomography ◽  
Clinical Symptoms ◽  
Dynamic Network ◽  
Network Models ◽  
Brain Regions ◽  
Brain Network ◽  
Emission Tomography ◽  
Model Parameters ◽  
Positron Emission ◽  
Network Diffusion

Alzheimer's disease is associated with the cerebral accumulation of neurofibrillary tangles of hyperphosphorylated tau protein. The progressive occurrence of tau aggregates in different brain regions is closely related to neurodegeneration and cognitive impairment. However, our current understanding of tau propagation relies almost exclusively on postmortem histopathology, and the precise propagation dynamics of misfolded tau in the living brain remain poorly understood. Here we combine longitudinal positron emission tomography and dynamic network modeling to test the hypothesis that misfolded tau propagates preferably along neuronal connections. We follow 46 subjects for three or four annual positron emission tomography scans and compare their pathological tau profiles against brain network models of intracellular and extracellular spreading. For each subject, we identify a personalized set of model parameters that characterizes the individual progression of pathological tau. Across all subjects, the mean protein production rate was 0.21 ± 0.15 and the intracellular diffusion coefficient was 0.34 ± 0.43. Our network diffusion model can serve as a tool to detect non-clinical symptoms at an earlier stage and make informed predictions about the timeline of neurodegeneration on an individual personalized basis.

scholarly journals Measurement of Benzodiazepine Receptor Number and Affinity in Humans Using Tracer Kinetic Modeling, Positron Emission Tomography, and [11C]Flumazenil

1993 ◽  
Vol 13 (4) ◽  
pp. 656-667 ◽  
Author(s):  
Julie C. Price ◽  
Helen S. Mayberg ◽  
Robert F. Dannals ◽  
Alan A. Wilson ◽  
Hayden T. Ravert ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Specific Activity ◽  
Free Fraction ◽  
Benzodiazepine Receptor ◽  
Occipital Cortex ◽  
Compartment Model ◽  
Brain Regions ◽  
Emission Tomography ◽  
Positron Emission ◽  
Convergence Problems

Kinetic methods were used to obtain regional estimates of benzodiazepine receptor concentration ( Bmax) and equilibrium dissociation constant ( Kd) from high and low specific activity (SA) [11C]flumazenil ([11C] Ro 15-1788) positron emission tomography studies of five normal volunteers. The high and low SA data were simultaneously fit to linear and nonlinear three-compartment models, respectively. An additional inhibition study (pretreatment with 0.15 mg/kg of flumazenil) was performed on one of the volunteers, which resulted in an average gray matter K1/ k2 estimate of 0.68 ± 0.08 ml/ml (linear three-compartment model, nine brain regions). The free fraction of flumazenil in plasma ( f1) was determined for each study (high SA f1: 0.50 ± 0.03; low SA f1: 0.48 ± 0.05). The free fraction in brain ( f2) was calculated using the inhibition K1/ k2 ratio and each volunteer's mean f1 value ( f2 across volunteers = 0.72 ± 0.03 ml/ml). Three methods (Methods I–III) were examined. Method I determined five kinetic parameters simultaneously [ K1, k2, k3 (= kon f2 Bmax), k4, and kon f2/SA] with no a priori constraints. An average kon value of 0.030 ± 0.003 n M−1 min−1 was estimated for receptor-rich regions using Method I. In Methods II and III, the kon f2/SA parameter was specifically constrained using the Method I value of kon and the volunteer's values of f2 and low SA (Ci/μmol). Four parameters were determined simultaneously using Method II. In Method III, K1/ k2 was fixed to the inhibition value and only three parameters were estimated. Method I provided the most variable results and convergence problems for regions with low receptor binding. Method II provided results that were less variable but very similar to the Method I results, without convergence problems. However, the K1/ k2 ratios obtained by Method II ranged from 1.07 in the occipital cortex to 0.61 in the thalamus. Fixing the K1/ k2 ratio in Method III provided a method that was physiologically consistent with the fixed value of f2 and resulted in parameters with considerably lower variability. The average Bmax values obtained using Method III were 100 ± 25 n M in the occipital cortex, 64 ±18 n M in the cerebellum, and 38 ± 5.5 n M in the thalamus; the average Kd was 8.9 ± 1.0 n M (five brain regions).

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