A display device for biomedical signals

The design of a 20-segment LED display device is presented. The display visually indicates peak levels of slowly changing biomedical data. Its fullscale indication is adjustable from +0.5 to +12.5 volts. The segments can be activated in either a dot or a bar mode, and upper-limit sensing can be indicated by an audio tone and/or a flashing display.     

Microcomputer analysis and display of canine small intestinal electrical activity

A system combining analogue filtering and digital counting was used to study the canine intestinal EMG. Recordings were made in conscious dogs from electrodes previously sutured to the serosa of the small intestine at operation under halothane/nitrous oxide anaesthesia. Signals recorded on cassette tape were replayed 60 times faster than the recording speed. After filtering the output was half-wave rectified and passed to Schmitt triggers with variable gain for adjustment of the input voltage. This triggered a monostable multivibrator which produced a 1 ms output pulse. The pulses were taken to three flag switches of the Apple lle Games Controller An Assembler program read the value at the flag locations every millisecond, incremented a temporary store and transferred the contents of the counter into a memory location when an interrupt was received every second by a clock. The data were displayed to show patterns of EMG activity and used for quantification of the results. This system provides a low-cost, flexible method of analysing intestinal EMG which avoids analogue-to-digital conversion.     

纯氧及LED阵列光动力复合治疗设备的研制

基于变压吸附制氧原理产生纯氧,并采用微透镜阵列多光谱LED发光器件与二次透镜阵列相结合构成光动力治疗辐照器,研制一种纯氧及LED阵列光动力复合治疗设备。其辐照器输出纯氧浓度大于90%,照射光包括波长625 nm红光、465 nm蓝光和520 nm绿光,应用光排序辐照技术实现纯氧及多光谱光动力复合治疗。通过辐照器上纯氧和照射光同步输出等多种外源性给氧保持光动力治疗区域的富氧状态,解决由于乏氧影响光动力疗效的问题。辐照器光学系统解决现有技术采用LED阵列排布替代激光器作为光动力治疗光源时存在的光能利用率低、光功率密度分布不均匀、不同波长光束在目标靶面光功率密度分布曲面差异大等缺陷。     

A device to display moving objects for visual stimulation in the early development: with numerical control of a pulse motor

In order to observe oculomotor responses to moving objects in infants and the profoundly retarded, a control system of moving objects was developed. The system consists of two parts, the one is to control movement, while the other is to display stimuli. The movement control part is made of a microcomputer, a pulse motor, and a rail, which guides a stimulus carrier with slight friction. The pulse motor rotates 1.8 degrees, according to the input of one pulse. Therefore, the microcomputer can control the velocity of movement of a heavy object exactly. The microcomputer detects the position of a stimulus carrier, counting the number of pulses and receiving signals from switches attached to the rail. The stimuli displaying part controls lighting with respect to the position of a stimulus carrier. Applying this system to a profoundly retarded subject, whose DA was three months, smooth pursuit oculomotor responses at the same velocity as the stimulus were observed in EOG recordings. Measurement of duration of those responses was achieved.     

A noninvasive stimulus onset device for use in gustatory research

A simple device for precise, noninvasive measurement of stimulus onset time in gustatory research is described. This device utilizes an ultrafast, self-heated, micro-thermistor to sense the cooling effect of the fluid stream that bathes the tongue.     

ERP effects of spatial attention and display search with unilateral and bilateral stimulus displays

Two experiments were performed in which the effects of selective spatial attention on the ERPs elicited by unilateral and bilateral stimulus arrays were compared. In Experiment 1, subjects received a series of grating patterns. In the unilateral condition these gratings were presented one at a time, randomly to the right or left of fixation. In the bilateral condition, gratings were presented in pairs, one to each side of fixation. In the unilateral condition standard ERP effects of visual spatial attention were observed. However, in the bilateral condition we failed to observe an attention related posterior contralateral positivity (overlapping the P1 and N1 components, latency interval about 100–250 ms), as reported in several previous studies. In Experiment 2, we investigated whether attention related ERP lateralizations are affected by the task requirement to search among multiple objects in the visual field. We employed a task paradigm identical to that used by Luck et al. (Luck, S.J., Heinze, H.J., Mangun, G.R., Hillyard, S.A., 1990. Visual event-related potentials index focused attention within bilateral stimulus arrays. II. Functional dissociation of P1 and N1 components. Electroencephalogr. Clin. Neurophysiol. 75, 528–542). Four letters were presented to a visual hemifield, simultaneously to both the attended and unattended hemifields in the bilateral conditions, and to one hemifield only in the unilateral conditions. In a focused attention condition, subjects searched for a target letter at a fixed position, whereas they searched for the target letter among all four letters in the divided attention condition (as in the experiment of Luck et al., 1990). In the bilateral focused attention condition, only the contralateral P1 was enhanced. In the bilateral divided attention condition a prolonged posterior positivity was observed over the hemisphere contralateral to the attended hemifield, comparable to the results of Luck et al. (1990). A comparison of the ERPs elicited in the focused and divided attention conditions revealed a prolonged ‘search related negativity’. We discuss possible interactions between this negativity and attention related lateralizations. The display search negativity consisted of two phases, one phase comprised a midline occipital negativity, developing first over the ipsilateral scalp, while the second phase involved two symmetrical occipitotemporal negativities, strongly resembling the N1 in their topography. The display search effect could be modelled with a dipole in a medial occipital (possibly striate) region and two symmetrical dipoles in occipitotemporal brain areas. We hypothesize that this effect reflects a process of rechecking the decaying information of iconic memory in the occipitotemporal object recognition pathway.     

Optimum control of the Hemopump as a left-ventricular assist device

A general framework for designing an optimum control strategy for the Hemopump is described. An objective function was defined that includes four membership functions, each constructed based on the desired values of one of the four members: stroke volume, mean left atrial pressure, aortic diastolic pressure and mean pump rotation speed. The Hemopump was allowed to operate either at a constant speed or at two different speeds during a cardiac cycle. The goal was to maximise the objective function by varying the magnitude and timing of the pump speed. Using a canine circulatory model, it was demonstrated that, in general, different cardiac conditions or different clinical objectives require different operation parameters. For example, when a left ventricle with minor ischaemia was simulated, and the main objective was to increase stoke volume, the objective function was maximised, from a value of 0.877 when the pump was off, to 0.946 when the pump was operated at speed 2 (18 500-revolutions min⁻¹). On the other hand, for a severely ischaemic heart, the optimum pump speed became speed 3 (20 000 revolutions min⁻¹), which maximized the objective function to 0.943 (from 0.707 when the pump was off). The results also suggest that it is more beneficial to operate the Hemopump at two different speeds during a cardiac cycle (a higher speed during systole and early diastole, and a lower speed during late diastole) than to maintain a constant speed throughout the cardiac cycle.     

Gustatory stimulus control and reversal learning in rats

Behavioral indices of taste discrimination have been used to study gustatory physiology and psychophysics though they are often biased by taste and position preferences and offer limited stimulus control. In the present experiment five rats were trained to discriminate distilled water from 0.9% NaCl using a discretetrials go-no go procedure. When two rats were further trained on a series of 0.1% saccharin/NaCl discrimination reversals, correct responding occurred more rapidly following saccharin presentations independent of its stimulus property (S^D or S^Δ). The results are discussed in the context of experimental methods and the usefulness of the present technique for studies of gustatory physiology.     

Microcomputer control of canine heart rate through chronotropic drug infusion

Cardiovascular changes principally take two forms: (a) inotropic or pressure-related changes, and (b) chronotropic or rate-related changes. Although the two are not mutually exclusive in the biofeedback of a normally functioning animal, this work was concerned principally with affecting the heart rate of a dog by infusing a rate-altering drug. The purpose of this project was to design an external heart-rate control system which consisted of a dog, an infusion pump containing a chronotropic drug and an infusion-pump/heart-rate controller. Input to the system was a target heart rate. The feedback element and the system output was the dog's actual heart rate, ideally being driven to that target heart rate by the controller. A microcomputer-based system was used with proportional derivative control to accommodate the inherent plant delay. Through the use of an inline solid-state relay, on/off control was chosen because of (i) the capability to use any type of infusion pump, and (ii) the simplicity of design due to slow animal response. The experimental results have demonstrated success at overriding the dog's own biological feedback network and driving its heart rate to some artificially chosen target.     

Influence of stimulus color on the control of reaching-grasping movements

This kinematic study aimed to determine whether color is a stimulus property involved in the control of reaching-grasping movements. Subjects reached and grasped a target-object, located either on the right or on the left of the subject's midline. A distractor, placed along the subject's midline, could be randomly presented. The colors, i.e., both chromaticity (red and green stimuli were presented) and lightness, of the target and distractor were varied in experiment 1. Only stimulus lightness and only stimulus chromaticity were varied in experiments 2 and 3, respectively. In experiment 4 subjects matched with their thumb and index finger the size of the target-stimuli presented in experiment 1. Chromaticity (experiments 1 and 3) of the target and distractor influenced grasp, but not reach. Maximal finger aperture was larger during grasping the red than the green target. Data collected in the matching task (experiment 4) confirmed a trend to overestimate the red target and to underestimate the green one. During grasp, hand shaping was influenced by distractor chromaticity when it was different from target chromaticity. Distractor lightness affected reach, but not grasp (experiments 1 and 2). Reach was slower when the distractor was lighter and arm trajectory veered away from it. The results of the present study suggest that color, that is the ensemble of chromaticity and lightness, is a stimulus property involved in the control of reaching-grasping. The different effects of target color on reach and grasp support the notion that intrinsic object properties, such as color, affect grasp more than reach. In addition, the different effects of distractor chromaticity and lightness on reach and grasp confirm that target-objects are visually extracted from surrounding cues by means of different processes, according to the required motor response.     

灯光显示浅静脉模拟穿刺装置的制作与应用

正静脉穿刺术是临床上应用最广泛的操作之一,熟练的穿刺手法能提高穿刺成功率,减轻患者痛苦,保证治疗质量。在实践教学中,一般采用塑胶模型进行模拟操作,但它造价昂贵,据此,在以往的工作基础上~([1]),使用人体解剖实验中常用的福尔马林防腐固定标本,选择常用部位设计制作了灯光显示浅静脉模拟     

Time acts as a conditioned stimulus to control behavioral sensitization to amphetamine in rats

Repeated exposure to the psychostimulant drug, amphetamine, results in a persistent increase in the ability of the drug to elicit behavioral activation.(14,19) The development of sensitized responses to amphetamine involves long-lasting neuroadaptations within defined circuitry.(3,6,12,15,23) The behavioral expression of sensitization, however, can come under the control of specific environmental cues. Thus, the sensitized locomotor response to a challenge injection of amphetamine is greater if the drug is given in the environment previously associated with intermittent injections than if given in a different environmental context.(2,13,16,18,20,21) Contrary to the wealth of information on the significance of contextual cues, little is known about the importance of time cues in the expression of sensitized responding to amphetamine.In the present study we, therefore, asked whether time of injection might influence the expression of amphetamine sensitization. We found that time can readily act as a conditioned stimulus to control the expression of behavioral sensitization to amphetamine in rats. This finding is important for understanding the mechanisms underlying sensitization to psychostimulant drugs and its impact on behavior.     

Overshadowing effects in the stimulus control of morphine analgesic tolerance

This study attempted to replicate previous demonstrations of classical conditioning of morphine analgesic tolerance, with the additional aim of determining whether stimulus overshadowing effects might explain previous conflicting findings. Eight groups of rats received a series of 10 morphine (5 mg/kg) and/or saline injections, differing only with respect to the contingency between a compound visual-auditory conditioned stimulus (CS) and the substance injected. When tested for analgesic responding to morphine in the presence of the compound CS, only those groups for which the CS and morphine injections were paired during the acquisition sequence evidenced tolerance. In a second experiment, tolerant animals were tested in the presence of one component of the compound CS. When a loud (85 dB) tone was used in the compound, less analgesic tolerance was elicited later by the weaker visual stimulus alone. This differential stimulus control of the analgesic response suggests that overshadowing may contribute to failures to replicate conditioned morphine tolerance. That internal morphine-produced stimuli might overshadow external cues is considered.     

A comparison of two methods for assessing the performance of the display system of a clinical radioisotope imaging device

Two ways of measuring the performance of the display system of a clinical radioisotope imaging device are considered: (i) using the method of constant stimuli; and (ii) using signal detection theory. The adjustment of a rectilinear scanner with multicolour, equal bandwidth, linear ribbon for better abnormality detection is discussed. A comparison was made between setting the maximum counts at the edge and at the middle of a colour band using the two methods. It was found that setting up the maximum counts at the middle of the band rather than at the edge favours easy detection by both methods independently.     

Direct cardiac potential trigger for chronic control of a ventricular assist device

As a new trigger method for chronic drive control of a ventricular assist device (VAD), a direct cardiac potential trigger was assessed under various conditions in a chronic experimental model. A pneumatic pulsatile VAD was implanted as circulatory support between the left ventricular apex and the ascending aorta in 12 adult pigs. Hemodynamic parameters and pump output were continuously monitored. Two tips of a bipolar electrode were set on the RV anterior wall and the LV posterior wall for recording direct cardiac potential. Counterpulsation drive of the VAD was applied by using the R wave in a standard electrocardiogram (ECG) or the direct cardiac potential as an ECG trigger. As special conditions, various artifacts on ECG, electromusculogram, arrhythmia, irregular ventilation, and passive vibration (simulation of exercise) were set for assessing the ECG trigger modes. Artifacts of irregular ventilation and passive vibration made the drive control poor using a standard ECG trigger. In contrast, the direct cardiac potential trigger maintained the counterpulsation control of the VAD well in all conditions of this study, and was a safe and reliable support for the native heart. It also supported animals for up to 48 hours after operation. The above results suggested that the direct cardiac potential trigger might be useful for monitoring native heart beats and adjusting the support cycle to the native heart cycle as a chronic control method for various VADs.     

Modeling and control of a brushless DC axial flow ventricular assist device

This article presents an integrated model of the human circulatory system that incorporates circulatory support by a brushless DC axial flow ventricular assist device (VAD), and a feedback VAD controller designed to maintain physiologically sufficient perfusion. The developed integrated model combines a network type model of the circulatory system with a nonlinear dynamic model of the brushless DC pump We show that maintaining a reference differential pressure between the left ventricle and aorta leads to adequate perfusion for different pathologic cases, ranging from normal heart to left heart asystole, and widely varying physical activity scenarios from rest to exercise.