Short-term memory in the in situ canine myocardium

1984 ◽  
Vol 247 (1) ◽  
pp. H8-H16
Author(s):  
O. Nwasokwa ◽  
K. Sagawa ◽  
H. Suga

We studied the effect of intracycle (short-term) mechanical history on canine myocardial performance. Intracycle muscle force and/or length history was varied, and the resultant changes in end-systolic force-length relationship were analyzed. Antecedent isotonic shortening impaired, whereas isometric force development enhanced end-systolic myocardial performance. A history of shortening concurrent with force development produced an intermediate effect. We conclude that decreasing force or length impairs whereas increasing length or force enhances performance in the same cycle. Different combinations of antecedent force and length changes affect end-systolic performance by algebraic summation (superposition) of their disparate effects. Time measurements established that 1) total systolic time varied little with altered history, 2) isotonic shortening took longer than isometric contraction in reaching a point P in the force-length plane, and 3) less time was therefore available for contraction after P with antecedent isotonic shortening than with antecedent isometric force development. This history-dependent time differential accounts for the corresponding differential in performance.

1987 ◽  
Vol 253 (3) ◽  
pp. H645-H653
Author(s):  
O. N. Nwasokwa

Canine papillary muscle force-length-time relation (F-L-t) was investigated under pentobarbital sodium anesthesia. The time intervals taken from end diastole to any point (P) on the force-length plane was determined for isometric (t1) and isotonic (t2) systole and corrected for excitation contraction coupling duration. The ratio t1/t2, designated km, was approximately constant for widely scattered positions of P chosen systematically. The km in the 10 dogs ranged from 0.36 to 0.94 with means +/- SD of 0.66 +/- 0.16; km correlated negatively with muscle average cross-sectional area (r = -0.82; P less than 0.005). Assuming constancy of km, a general relationship was derived between (delta F/delta t)t1L, the rate of isometric force development at P; (delta L/delta t)t2F, the velocity of isotonic shortening at P; (delta F/delta L)(t1,t2)t, the stiffness; and (delta L/delta F)(t1,t2)t, the compliance of the myocardium (all taken at P) as follows (delta F/delta L)t1,t2t = -km(delta F/delta t)t1L/(delta L/delta t)t2F and (delta L/delta F)t1,t2t = -km-1(delta L/delta t)t2F/(delta F/delta t)t1t. The ratio of (delta F/delta t)t1L to (delta L/delta t)t2F defines functional proclivity and measures the differential propensity to force development relative to shortening. Thus myocardial stiffness or compliance determines functional proclivity by acting as an impedance-matching transformer that steps up or steps down force development of shortening as warranted by the loading conditions.


2021 ◽  
Vol 14 (1) ◽  
pp. e237398
Author(s):  
Jonathan E Attwood ◽  
Saniya Naseer ◽  
Sophia Michael ◽  
Josie Riley

An 83-year-old woman was referred to hospital with a 2-week history of short-lived episodic unpleasant sensations in her head and running down her body. This was accompanied by new short-term memory impairment and arm spasms. Initial investigations including blood tests and brain imaging did not reveal the diagnosis. The patient developed an increasing frequency of abnormal movements of her face and arm. These were clinically recognised as faciobrachial dystonic seizures (FBDS). FBDS are pathognomonic of an autoimmune encephalitis caused by an antibody directed against leucine-rich glioma-inactivated 1 (LGI1). The clinical diagnosis resulted in treatment with immunotherapy, leading to cessation of seizures and rapid cognitive recovery. Later, the predicted serology was confirmed. This reversible and under-recognised cause of cognitive impairment, typically affecting elderly patients, can be diagnosed clinically to enable early and effective treatment.


2019 ◽  
Vol 10 (1) ◽  
pp. 69 ◽  
Author(s):  
Peyman Sheikholharam Mashhadi ◽  
Sławomir Nowaczyk ◽  
Sepideh Pashami

Predictive Maintenance (PM) is a proactive maintenance strategy that tries to minimize a system’s downtime by predicting failures before they happen. It uses data from sensors to measure the component’s state of health and make forecasts about its future degradation. However, existing PM methods typically focus on individual measurements. While it is natural to assume that a history of measurements carries more information than a single one. This paper aims at incorporating such information into PM models. In practice, especially in the automotive domain, diagnostic models have low performance, due to a large amount of noise in the data and limited sensing capability. To address this issue, this paper proposes to use a specific type of ensemble learning known as Stacked Ensemble. The idea is to aggregate predictions of multiple models—consisting of Long Short-Term Memory (LSTM) and Convolutional-LSTM—via a meta model, in order to boost performance. Stacked Ensemble model performs well when its base models are as diverse as possible. To this end, each such model is trained using a specific combination of the following three aspects: feature subsets, past dependency horizon, and model architectures. Experimental results demonstrate benefits of the proposed approach on a case study of heavy-duty truck turbochargers.


1989 ◽  
Vol 41 (3) ◽  
pp. 471-487 ◽  
Author(s):  
Elaine Funnell ◽  
Margaret Davison

We report a case of a 35-year-old teacher, Louise, with a history of learning difficulties and current evidence of developmental phonological dyslexia and dysgraphia. Her reading, spelling, and remembering of novel stimuli written in conventional alphabetic script was poor, but she performed significantly better when the same items were written in the International Phonetic Alphabet, a system that she learned when studying linguistics. Her impaired performance in tasks of phonemic segmentation and short-term memory, which are generally associated with impaired reading and spelling of unfamiliar material, could not account for her specific difficulty with alphabetic stimuli. Instead, her problems appear to result from a lexical strategy, which we have called “lexical capture”.


Philosophies ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 26 ◽  
Author(s):  
Frank Broz ◽  
Chrystopher L. Nehaniv ◽  
Hatice Kose ◽  
Kerstin Dautenhahn

In this article, an enactive architecture is described that allows a humanoid robot to learn to compose simple actions into turn-taking behaviours while playing interaction games with a human partner. The robot’s action choices are reinforced by social feedback from the human in the form of visual attention and measures of behavioural synchronisation. We demonstrate that the system can acquire and switch between behaviours learned through interaction based on social feedback from the human partner. The role of reinforcement based on a short-term memory of the interaction was experimentally investigated. Results indicate that feedback based only on the immediate experience was insufficient to learn longer, more complex turn-taking behaviours. Therefore, some history of the interaction must be considered in the acquisition of turn-taking, which can be efficiently handled through the use of short-term memory.


2000 ◽  
Vol 88 (6) ◽  
pp. 2246-2250 ◽  
Author(s):  
Lu Wang ◽  
Peter D. Paré ◽  
Chun Y. Seow

It has been shown that deep inspiration (DI) taken before application of bronchoconstricting stimuli causes a reduction in the subsequent bronchoconstriction; a fast DI has a greater inhibitory effect than a slow DI. We hypothesize that periodic length changes imposed on a relaxed airway smooth muscle (ASM) would attenuate subsequent bronchoconstriction by disrupting the organization of the contractile apparatus, and this could be an important mechanism for the observed bronchoprotective effect of DI and tidal breathing. Length oscillations of different amplitude, frequency, and duration were applied to a relaxed muscle. The effects of such perturbations on force development were then assessed. Results show that oscillations reduce the subsequent force generation and that the magnitude of force reduction is proportional to amplitude and duration of the length oscillation. After the oscillation, isometric force recovered to the preoscillation level in a series of isometric contractions, and the rate of recovery was facilitated by frequent stimulation. The in vitro behavior of ASM found in this study could account for the observed temporary reduction in bronchoconstriction subsequent to a DI.


Author(s):  
Georgina Papadopoulos-Nydam ◽  
Jana Maureen Rieger ◽  
Gabriela Constantinescu

Purpose The objective of this study was to evaluate the usability of a mobile health (mHealth) system designed for dysphagia exercise in persons with a history of stroke. Method Five participants with a history of stroke were recruited from a tertiary health center and assessed for their ability to use and interact with the system. After being introduced to the technology, participants were asked to independently complete five tasks, one at a time. Assistance was available when required or requested. Usability was evaluated with respect to effectiveness, efficiency, and user satisfaction when completing the prespecified goals. Results Four men and one woman between the ages of 50 and 83 years ( M = 65.4) completed the usability testing. Time from stroke onset varied from 1 month to 2.5 years. Additional poststroke challenges related to the usability of the mHealth system included reduced range of motion or mobility, vision, and short-term memory difficulties. Independent success (system effectiveness) varied in this user subgroup, and the research clinician or the family member was required to adjust the level and type of support they provided (system efficiency). All participants reported satisfaction with the use of the system. Conclusion Usability of and satisfaction with this mHealth system and others like it can be achieved in individuals who have had a stroke, either as an independent user or as a patient–caregiver dyad.


Circulation ◽  
2017 ◽  
Vol 135 (suppl_1) ◽  
Author(s):  
Julio Fernandez-Mendoza ◽  
Fan He ◽  
Alexandros N Vgontzas ◽  
Duanping Liao ◽  
Edward O Bixler

Background: Cardiovascular disease (CVD) and cerebrovascular disease (CBV) have been associated with short sleep duration and mortality. Furthermore, short sleep duration has been associated with impaired cognition. Most studies have been limited by using self-report measures and treating sleep duration as a sole, independent predictor, thus, its role in predicting mortality is still not well-established. Hypothesis: We hypothesized that 1) short sleep duration increases the impact of CVD and CBV on mortality and 2) cognitive impairment mediates the association of short sleep duration with mortality in those with CVD or CBV. Methods: We addressed this question in the Penn State Adult Cohort, a random, general population sample of 1,741 men and women (48.7 ± 13.5 years) who were studied in the sleep laboratory and followed-up for 16.7 ± 4.6 years. CVD was defined by a history of heart disease, including hypertension or diabetes, and CBV by a history of stroke. Polysomnographic (PSG) total sleep time was classified as normal (≥ 6 hours) and short (< 6 hours) sleep duration based on the median of the cohort. All individuals underwent a comprehensive neuropsychological evaluation, including Symbol Digit Modalities Test, Trail Making Test, Benton Visual Retention Test, Thurstone Word Fluency Test, and Mini-Mental State Examination. We tested the interaction between CVD, CBV and PSG sleep duration on mortality using Cox proportional hazard models controlling for multiple potential confounders. Results: The hazard ratios (95%CI) of mortality associated with CVD and CBV were 0.9 (0.6-1.3) and 1.3 (0.5-3.1) for individuals with normal sleep duration and 1.8 (1.3-2.5) and 2.4 (1.3-4.4) for individuals with short sleep duration (P-interaction < .05). In individuals with CVD or CBV, short sleep duration was associated with impaired processing speed, executive attention, and short-term memory (all Ps < .05). Cognitive impairment significantly mediated the impact of short sleep duration on mortality in those with CVD or CBV [proportion of mediation effects were 6.5% (1.4%-18.6%), 4.5% (0.4%-14.2%), and 6.2% (1.0%-18.4%) for processing speed, executive attention and short-term memory, respectively]. Conclusions: The risk of mortality associated with CVD and CBV is significantly increased in those with short sleep duration. Although cognitive impairment significantly mediated this association, its modest effect suggests that future studies should examine other underlying mechanisms linking short sleep duration with mortality in individuals with CVD or CBV.


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