growth and innovations of Grass Instrument, founded by Albert Grass
who developed the first commercially successful electroencephalograph
(EEG), may be of interest to those interested in the history of neurophysiology,
EEG and polysomnography (PSG).
The following is
a chronology of the beginnings of EEG/PSG technology, and consequently,
of Grass Instrument Company.
A small grant is awarded to Dr. Frederic Gibbs for instrumentation to
process electroencephalographic data. His goal is to apply the knowledge
gained by Hans Berger and confirmed by Lord Adrian to clinical applications.
Dr. Gibbs approaches Albert Grass, a recent graduate of MIT, to design
three devices to amplify human EEG potentials. Grass does so, defining
the foundation of Grass Instrument Company, and of EEG technology.
While working at Harvard Medical School, Grass designs moving coil galvanometers,
which enables the embryonic EEG instrumentation to accurately and reliably
record the EEG frequencies on chart paper. The addition of these new
galvanometers to his early amplifiers becomes the Grass Model I, used
by Gibbs, Lennox, Davis and others. This same amplifier design was used
by Cannon, Rosenbluth and Renshaw in early neuromuscular studies.
A two-channel Grass Model I EEG is used by Dr. Hallowell Davis to record
and report more detailed steps in the awake-sleep transition; named
the "K" complex, a high voltage diphasic slow wave associated
with a sleep spindle.
Grass Model II is developed and used by doctors to evaluate head injuries
and the condition of airplane pilots as World War II begins in Europe.
The post-war development and production of the Grass Model III begins,
which sets the standard for ease of use, sturdy design, and system safeguards,
that endures among Grass EEGs today.
Grass begins development of an electrical stimulator to aid in mapping
the human cortex.
Grass improves the design and production of electrodes and develops
a cortical electrode array for electrocorticography, still in use today.
Dr. Nathaniel Kleitman uses the Grass Model III in his ground breaking
research on REM sleep. This is the first time an accurate recording
is made of rapid eye movements in sleep.
Dr. Frederic Gibbs
& Erna Gibbs, used an eight-channel Grass Model III EEG, first emphasized
age-related differences in the sleep onset EEG and separated the adult
type from that of children.
Grass Model 5 Polygraphs are used to record a wide range of physiological
and pharmacological parameters in animal research laboratories all over
the world and they are introduced in student laboratories of major medical
schools for "hands on" teaching exercises. Grass designs an
oscilloscope kymograph recording camera that photographs the oscilloscope
traces on photosensitive film and paper, and faithfully captures fast
transient neurophysiological events.
Albert Grass establishes the Grass Foundation to promote and foster
research and education in neurophysiology. To date, the Foundation has
provided funding for the Marine Biological Laboratory (MBL) at Woods
Hole, Massachusetts and grants for over 400 MBL research fellows in
neurophysiology. One such fellow was a member of a NASA space shuttle
Dr. W.C. Dement, Dr. Nathaniel Kleitman, used Grass Model III EEG, while
reporting EEG patterns associated with REM and dreaming, redefined the
stages of sleep. They defined Stage 1 REM, associated with a high percentage
of dream recalls by the subjects, as having no essential EEG differences
from Stage 1 non-REM except for the presence of characteristic eye movements.
It was Dr. Eugene Aserinski and this group that first recorded the eye
movements using electrodes placed above and below the eye. Prior to
this, it was necessary for researchers to observe the eye lids to detect
Grass pioneers the development of computer-compatible medical devices
with the design of EEG and Polygraph systems with outputs designed for
Grass develops clinical and research EEGs with greater numbers of channels
and the capacity to interface with data processing instruments. Grass
Models 8 and 9 have the capacity to perform dual EEG and PSG functions.
Model 78 PSG sets the watermark in modern sleep studies. Clinical Sleep
Disorders recordings demand more flexibility in the recorders to accommodate
the recording of EMG, EOG, ECG, upper airway airflow and respiratory
effort, limb movements, oxygent saturation. The Grass Model 78 PSG meets
the demand by offering AC and DC amplifiers and special plug-ins for
interfacing various analyzers
In 1994, Grass
Instrument Co. is acquired by Astro-Med, Inc. The Model 15 line of digitally
controlled amplifiers is introduced. The digital EEG and digital PSG
are introduced, named the Albert Grass Heritage® to honor the founder,
along with the Heritage Portable PSG. New single-channel amplifiers
along with PolyVIEW™ and Gamma™ data acquisition software are
In 1999, Astro-Med also acquires
Telefactor Corp., adding long-term epilepsy monitoring instrumentation,
with seizure and spike analysis software to the existing line of Grass
A steady stream
of new products for research and clinical applications continue to be
issued from the Grass Technologies,
including ambulatory PSG systems
and digital video and audio software.
In 2013, Grass Technologies is acquired by Natus Neurology and is continuing its long history of providing high quality instrumentation to the neurophysiological field.