Recording Of Electrical Signals Research Articles

Field-effect transistor array for monitoring electrical activity from mammalian neurons in culture

A field-effect transistor (FET) array has been fabricated and used for recording of electrical signals from neural cells. The array consists of p-channel FETs with non-metallized gates. The size of the gates of the 16 FETs are from 28×12 μm 2 down to 10×4 μm 2 and are arranged in a 4×4 matrix on 200 μm centers. For the device fabrication process we have especially focused on high sensitivity, good long-term stability in physiological conditions, and sufficient reduced signal-to-noise ratio. Special care was taken on the encapsulation technique of the device to allow surface modification based on the self-assembly technique. It can be shown that the microelectronic device surface can be modified with a synthetic peptide linked to the surface. Tailoring of the surface composition using this method allows hippocampal neurons to adhere and grow for days. More importantly, these cells develop typical electrical characteristics when cultured on this artificial surface. Using this approach neuron-FET couplings were recorded.

Non-invasive multielectrode array for high resolution sampling of scalp-recorded potential fields.

A new non-invasive electrode array has been devised to record electrical signals on the scalp. The electrodes are arranged every 10 mm in a 4 x 8 grid, thus totalling 32. Electrical coupling is assured by a column of conductor gel with a diameter of 2 mm. The electrode array has been used to record multichannel scalp potentials evoked by stimulation of the median nerve at the wrist. It was positioned on the parietal region with the midline corresponding to the external acoustic meatus. The high spatial resolution of this device allows a detailed spatial sampling of the scalp potential field where the electrical activity arising from the parietal and premotor cortex is predominant. Scalp potentials with the system are compared with those with the 10/20 system. The improved spatial resolution allows more precise localization of minimum and maximum of the potential field, though the overall distortion introduced by aliasing in the 10/20 system is not striking. Instead, the amplitudes of the fields are considerably affected by insufficient spatial sampling.

Shadows of Thoughts Revealed

W hat do thoughts look like in the human brain? Does every mental sentence, every intention, every little decision explode in a telltale pattern of neurochemical activity? If so, might a brain scan someday provide a printout of a person's most intimate thoughts? As of 1990, neither scientists nor philosophers have gained sufficient insight into the nature of cognition to peruse the private diaries nestled within the brain's convoluted folds. But researchers using new technology have now developed the first pictures of what they call shadows of Their approach can't detect the contents of thoughts. However, it clearly differentiates among many of the electrochemical fireworks that underlie specific acts of cognition. The technique's developers say the high-resolution images they obtain may soon provide a wealth of practical benefits ranging from improved assessment of brain injury to reduced incidence of fatigue-related industrial accidents. Moreover, the work offers intriguing new clues about how the brain perceives and constantly updates its sense of the world and its sense of self. Generations of neuroscientists have dreamed about having a movie camera for observing thinking in the says Alan Gevins, director of EEG Systems Laboratory, a private brain-research center in San Francisco. Revolutionary advances in computers are now making this possible. A space-age electroencephalography (EEG) device, worn like a soft helmet, is the heart of Gevins' mind-camera. Unlike old-fashioned EEG machines, which record electrical signals at 19 points on the scalp and enable clinicians to detect gross brain-wave abnormalities, Gevins' device records electrical activity at 124 points. Computers monitor the skullbound electrical squalls we call thought and map their shifting locations within a three-dimensional image of the monitored brain, created by a magnetic resonance imager (MRI). The EEG-MRI combo -called the mental activity network scanner, or MANSCAN snaps a fresh picture of brain activity every 4 milliseconds, providing far more images per minute than positron emission tomography (PET), another popular brain-imaging technique (SN: 2/25/89, p.116). Together, the string of snapshots provides a movie of neuronal bursts, tracing peaks and troughs of brain activity while the monitored person performs specific mental tasks. Speaking in St. Louis last week at the *~ :

A 500 MHz CCD Serial Analog Memory

The design of a GaAs charge coupled device as a solution to transient recording of electrical signals is discussed. The requirements of Experiment 787 and others require the analysis of signals with a 250 MHz bandwidth. Some initial results of the work are presented.

Holographic Techniques for Recording of Electrical Signals on Moving Storage Media

Three different approaches to record electrical signals by holographic techniques on moving data carriers are discussed. It is shown that, besides the well-known redundancy of holography and the possibility of attaining high storage densities, it is the flexibility of the holographic principle itself that makes holography an attractive recording method. Holographic parameters can be varied widely to meet specific boundary conditions imposed by the design of the data carrier or the storage medium. So, by using the "hy-brid" recording technique, holograms may be recorded which are invariant to hologram translations in two directions per-pendicular to one preferred axis, but with respect to this axis their sensitivity to displacements is increased by a factor of two. This hybrid technique combines the advantage of an increased linear storage density with drastically reduced precision requirements for guiding the data carrier and is thus very well suited for a holographic tape recorder.

Electric Control of Fluid Jets and Its Application to Recording Devices

A new method for the intensity modulation of ink jets used for recording of electrical signals is described. It uses the fact that a liquid jet ejected from a fine nozzle towards a recording paper is dispersed into a spray if an electric field is established near the nozzle. This allows the intensity modulation of the recording trace with frequencies exceeding 100 kHz. The use of this method in facsimile recording, graphic data displays, and alphanumeric printing devices is described briefly as well as results showing the capacity of the method.

A New Method of Transverse-Stroke Recording of Electrical Signals on Magnetic Tape

A New Method of Transverse-Stroke Recording of Electrical Signals on Magnetic Tape

Equipment of instrumental accuracy for recording and reproduction of electrical signals, using cinematographic film

Equipment has been made for the recording of electrical signals and their reproduction or play-back, providing an accuracy comparable with that of typical electrical instruments. The errors are about ±1% over most of the range, but increase at the maximum amplitude and frequency; the frequency range is 0–1 kc/s. The equipment is primarily intended for the recording of experiments of short duration or a non-repetitive nature and their subsequent reproduction for study or analysis; a particular feature is the facility for reproduction on a changed time scale, which may be faster or slower than real time.It is thought that the apparatus offers a significant addition to experimental technique, particularly when used in conjunction with an electronic analogue computer.Cinematographic methods are employed. A simple film-traversing mechanism is used, with a variable-speed drive. Appropriate optical units are attached to it for recording or reproduction. One type of recording unit gives variable-density tracks on the film; it uses variable-intensity discharge lamps the outputs of which are monitored by photocells, to provide negative feedback to the amplifier. Precision photographic processing methods have been evolved for this application. An alternative optical unit gives variable-width tracks, using modified Duddell oscillographs and being based on standard cinematographic practices, including processing. This unit was made to determine the relative suitability in use of the two techniques, and practical experience shows that it gives significantly greater accuracy, constancy of calibration and reliability in operation. Subsidiary equipment provides for recording on film, mechanical signals, data transcribed from other recording apparatus or numerical data applied manually; this is of value for certain types of analysis using the analogue computer. The importance of making the equipment suitable for use by non-specialist operators has been recognized during the design period.On reproduction from the records, the light transmitted through each track is measured with a photocell, the outputs from the equipment being presented as voltages; the film provides two tracks carrying independent information of high accuracy, and a third track for timing marks or a reference frequency.A thorough discussion is given of the considerations underlying the design of the equipment, and results of experiments are presented to show the performance attainable and the types of error which occur.In Appendix 11.2 a summary is given of the major features of the cinematographic, magnetic tape and disc methods of recording, when used for this application. It is concluded that a comprehensive installation might include equipment of more than one type.

Magnetic tape recorder for very low frequency phenomena.

An apparatus is described for the recording of electrical signals of frequencies below 100 cycles per second on magnetic tape for subsequent playback. A system of wide deviation frequency modulation of an audio frequency carrier has been employed to eliminate the difficulties normally encountered in the direct recording of low frequency and d.c. signals.