The list below exemplifies some of the different instruments used over the years. Algesiometers and algometers. Audiometer. Colorimeter. Electroencephalography. Simultaneous video and EEG recording of two guitarists improvising.
Electroencephalography (EEG) is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus on the spectral content of EEG, that is, the type of neural oscillations that can be observed in EEG signals. EEG is most often used to diagnose epilepsy, which causes obvious abnormalities in EEG readings. It is also used to diagnose sleep disorders, coma, encephalopathies, and brain death. History Hans Berger In 1934, Fisher and Lowenback first demonstrated epileptiform spikes. In 1947, The American EEG Society was founded and the first International EEG congress was held.
Functional magnetic resonance imaging. Researcher checking fMRI images Functional magnetic resonance imaging or functional MRI (fMRI) is a functional neuroimaging procedure using MRI technology that measures brain activity by detecting associated changes in blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled.
When an area of the brain is in use, blood flow to that region also increases. The primary form of fMRI uses the Blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. The procedure is similar to MRI but uses the change in magnetization between oxygen-rich and oxygen-poor blood as its basic measure. Galvanometer. D'Arsonval/Weston galvanometer movement - with the moving coil shown in orange.
A galvanometer is a type of sensitive ammeter: an instrument for detecting electric current. It is an analog electromechanical actuator that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. Galvanometers were the first instruments used to detect and measure electric currents. Sensitive galvanometers were used to detect signals from long submarine cables, and to discover the electrical activity of the heart and brain.
Some galvanometers use a solid pointer on a scale to show measurements, other very sensitive types use a miniature mirror and a beam of light to provide mechanical amplification of low level signals. History The deflection of a magnetic compass needle by current in a wire was first described by Hans Oersted in 1820. Operation D'Arsonval/Weston galvanometer movement (ca. 1900). Types Theory Hipp chronoscope / chronograph.
Kymograph. Mazes. Olfactometer. Photokymograph. Positron emission tomography. PET/CT-System with 16-slice CT; the ceiling mounted device is an injection pump for CT contrast agent Whole-body PET scan using 18F-FDG Positron emission tomography (PET) is a nuclear medicine, functional imaging technique that produces a three-dimensional image of functional processes in the body.
The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. Three-dimensional images of tracer concentration within the body are then constructed by computer analysis. Stereoscope. Old Zeiss pocket stereoscope with original test image A stereoscope is a device for viewing a stereoscopic pair of separate images, depicting left-eye and right-eye views of the same scene, as a single three-dimensional image.
A typical stereoscope provides each eye with a lens that makes the image seen through it appear larger and more distant and usually also shifts its apparent horizontal position, so that for a person with normal binocular depth perception the edges of the two images seemingly fuse into one "stereo window". In current practice, the images are prepared so that the scene appears to be beyond this virtual window, through which objects are sometimes allowed to protrude, but this was not always the custom.
A divider or other view-limiting feature is usually provided to prevent each eye from being distracted by also seeing the image intended for the other eye. History Wheatstone mirror stereoscope.