The transient electric responses of the cochlea

1. DC responses were recorded from the cochleae of pigeons, cats and guinea-pigs. In addition to the known summating potential, transients of the same polarity were observed at the onset and termination of the tonal stimulus.2. These transients were most noticeable in the pigeon, being least in the guinea-pig responses.3. They could be modified by changing the rate of rise and fall of the stimulus envelope, but not by cutting the middle ear muscles.4. Comparable effects were seen when the ear was directly driven by a mechanical stimulus.5. With stimuli of long duration the off-transient was usually masked by a slow potential of opposite polarity. This deflexion appears to be an afterpotential, rather than a mechanical transient, since it is dependent on the duration of the preceding stimulus.     

Circadian rhythms in electric waveform structure and rate in the electric fish Brachyhypopomus pinnicaudatus

Weakly electric fish have long been known to express day-night oscillations in their discharge rates, and in the amplitude and duration of individual electric organ discharges (EODs). Because these oscillations are altered by social environment and neuroendocrine interactions, electric fish are excellent organisms for exploring the social and neuroendocrine regulation of circadian rhythm expression. Previous studies asserting that these oscillations are circadian rhythms have been criticized for failing to control temperature and randomize feeding regimes, or for running the fish under constant conditions for just 2-3 days. Here we show that the day-night oscillations in the EODs of the neotropical gymnotiform fish Brachyhypopomus pinnicaudatus free-run for over a week under constant photic and thermal conditions, and randomized food provisioning. Sex differences were apparent in strength and magnitude of the circadian oscillations; male oscillations were stronger and larger. All three parameters retain a common oscillation period while differing in the persistence of oscillation strength and magnitude, a difference consistent with proposals by others that declines of behavioral circadian rhythms may result from breakdowns downstream of the central oscillator.     

On the use of electric and magnetic data to determine electric sources in a volume conductor

Methods of obtaining detailed information about electrical sources in semi-infinite and spherical volume conductors using electric and magnetic surface data are investigated. Surface data produced by various actual sources in the conductors are calculated. Using these data, a least-squares error (LSE) solution is then obtained for the dipoles in a multiple dipole assumed source and a comparison of the actual and assumed sources is made. Noise is simulated by the addition of random numbers to the data; modeling errors by the use of actual and assumed sources with different configurations. It is found that it is not possible to calculate a condition number (CN) which serves as a useful measure of the sensitivity of the LSE solutions to noise and modeling errors. It is also found that no useful information about the actual source can be obtained from LSE solutions when noise and modeling errors are present. No improvement is obtained when magnetic or a combination of electric and magnetic data are used. However, it is found that three additional solutions developed from the LSE solutions can provide some accurate information. These three solutions provide information about the general magnitude and orientation of the electrical activity of the actual source as well as the “flow” and “rotation” characteristics of the source. The most accurate flow information tends to be produced by electric or a combination of electric and magnetic data; the most accurate rotation information tends to be produced by magnetic or a combination of data. This indicates that electric and magnetic measurements can provide different information when noise and modeling errors are present. The results also show that information about the location of the actual source is provided by a comparison of differences between actual surface data and that produced by a series of LSE solutions. There are no improvements in the location information when a combination of data is used. Work supported by Public Health Service Research Fellowship (National Heart, Lung, and Blood Institute) No. 1 F32 HL05419.     

Investigation of the electric field of the isolated dog's heart

A method of investigating the electric field of the isolated perfused animal's heart in a liquid volume conductor is described. Potentials are recorded from 241 points on a spherical surface surounding the heart by a unipolar technique. The electrodes are 1–2 cm away from the surface of the heart. The leads are grouped together 6 at a time. One of them is recorded as a constituent of all groups and serves for synchronization. The method is intended for the study of various types of equivalent electrical generators of the heart.     

Hum-controlled electric wheelchair

The authors described in an earlier paper a versatile electronic control system for wheelchairs. This paper describes a plug-in conversion to the original controller so that high-level quadriplegics (c4 and above) can completely control a wheelchair by humming four notes of the musical scale. Forward-stop-reverse, right-turn and left-turn functions are provided through the use of tone decoders. The control system is designed so that the frequencies to which it respons are easily adjustable to match users' vocal characteristics.     

Precision measurement of electric organ discharge timing from freely moving weakly electric fish

Physiological measurements from an unrestrained, untethered, and freely moving animal permit analyses of neural states correlated to naturalistic behaviors of interest. Precise and reliable remote measurements remain technically challenging due to animal movement, which perturbs the relative geometries between the animal and sensors. Pulse-type electric fish generate a train of discrete and stereotyped electric organ discharges (EOD) to sense their surroundings actively, and rapid modulation of the discharge rate occurs while free swimming in Gymnotus sp. The modulation of EOD rates is a useful indicator of the fish's central state such as resting, alertness, and learning associated with exploration. However, the EOD pulse waveforms remotely observed at a pair of dipole electrodes continuously vary as the fish swims relative to the electrodes, which biases the judgment of the actual pulse timing. To measure the EOD pulse timing more accurately, reliably, and noninvasively from a free-swimming fish, we propose a novel method based on the principles of waveform reshaping and spatial averaging. Our method is implemented using envelope extraction and multichannel summation, which is more precise and reliable compared with other widely used threshold- or peak-based methods according to the tests performed under various source-detector geometries. Using the same method, we constructed a real-time electronic pulse detector performing an additional online pulse discrimination routine to enhance further the detection reliability. Our stand-alone pulse detector performed with high temporal precision (<10 μs) and reliability (error <1 per 10(6) pulses) and permits longer recording duration by storing only event time stamps (4 bytes/pulse).     

An electric thermometer for measurement of the skin temperature

Summary The author describes an electric skin thermometer furnished with a bridge circuit and a semiconductor diode D1B as a transducer. The precision of the instrument lies within the range of ±0.1°C.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 51, No. 2, pp. 115–116, February, 1961     

An atlas of the brain of the electric fish Apteronotus leptorhynchus

This atlas consists of a set of six macrophotographs illustrating the important external landmarks of the apteronotid brain, as well as 54 transverse levels through the brain stained with cresyl violet. There are 150 microns between levels and the scales have 1 mm divisions (100 microns small divisions). In general the neuroanatomy of this brain is similar to that of other teleosts except that all parts known to be concerned with electroreception are greatly hypertrophied (electrosensory lateral line lobe, nucleus praeminentialis, caudal lobe of the cerebellum, torus semicircularis dorsalis, optic tectum and nucleus electrosensorius). There are other regions of this brain which are hypertrophied or which have not been described in other teleosts, but which are not known to be directly linked to the electrosensory/electromotor system; these regions are mentioned in the accompanying text.     

The larval electric organ of the weakly electric fish Pollimyrus (Marcusenius) isidori (Mormyridae, Teleostei)

Summary The larval electric organ ofPollimyrus isidori consists of four longitudinal tubes, a dorsal and a ventral pair, which begin behind the skull, end at the beginning of the caudal peduncle and show myotomic segmentation. The elementary units are, apparently, transformed muscle fibres called electrocytes. They are shorter and thicker than muscle fibres, with long stalks and are found in the medial part of the deep lateral muscle. Electron microscopy reveals a clear difference between the anterior and posterior face of the electrocyte. Anteriorly, deep linear invaginations of the surface membrane together with many small vesicles of about 100 nm diameter can be seen. Posteriorly, many plasma membrane invaginations and vacuoles are found together with numerous cytoplasmic organelles — pleiomorphic nuclei, Golgi apparatus, oblong mitochondria and multivesicular bodies. The stalk originates at the posterior face and the nerve terminals are situated at the distal end of the stalk. In the electrocyte, myofibrils, similar to those found in muscle fibres, can be detected with clearly visible Z lines but with only a suggestion of H zones. Two bundles of myofibrils can be seen arranged orthogonally in the electrocyte. Strong acetylcholinesterase activity was found on the anterior face and on the innervated stalk. Under the given recording conditions the overall discharge amplitude of the larval electric organ reaches a maximum of about 100 mV peak to peak. The pulse duration is 1 millisecond and the main phase is head-positive.     

卡维地洛对麻醉兔希氏束电活动和心电活动的影响

目的：研究卡维地洛对麻醉兔希氏束电活动和心电活动的影响。方法：采用左心导管法记录IIBE,同步记录Ⅱ导联ECG,并与普萘洛尔进行比较。结果：卡维地洛在0．01,0.11,3,6,9mg·kg－1时分别减慢HR（%）：9．1±4．8,21．3±3．0,30．7±4．0,35.4±5．6,40．0±6．0,42．5±6.1;延长P－R间期（％）：1．8±3．0,5．4±4．9,10．0±7．4,16.8±8．4,25．7±9．3,33．6±12．4;延长A－H间或（％）：5．6±4．8,10．9±6．4,16．5±6．2,24．2±7．7,31．6±10．8,20．6±15．0延长H－V间期（％）：5．1±5．4,8．7±5．3,14．9±5．7,21．2±9．5,27．1±11．2,39．9±9．4增宽Ⅴ波（%）：2．0±42,3．8±3．9,7．8±7．1,15．6±11．0,37．0,37．0±2．4。结论：在同一累积剂量,卡维地治和普菲洛尔对心脏的抑制作用基本相同,卡维地洛可能比普蒂洛尔更适合治疗心血管系统疾病。但对已有心动过缓和心脏传导阻滞的患者,临床应用时仍应注意卡维地洛的心脏抑制作用。     

Effect of befol on the electric threshold of ventricular fibrillation

Befol (20 mg/kg) rises electric threshold of ventricular fibrillation in cats. This effect is most pronounced in ischemized myocardium. It is shown that not only tricyclic but also monocyclic antidepressants exhibit antifibrillatory activity. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 3, pp. 305–307, March, 1997