Flight Simulation Control (2 Frogs); Laboratory Baseline Controls
Key Flight Hardware
Frog Otolith Experiment Package (FOEP); FOEP Life Support System (LSS)
Objectives/Hypothesis
During the OFO-A data analysis it appeared evident that the technique initially
used for data reduction, based on visual appraisal of spikes and voltage level
clipping, was completely inadequate and impossibly time consuming. Moreover,
it was evident that some information was lost, such as smaller spikes in the
data stream. This study was to further the investigation of frog vestibular
function in microgravity by development of automatic analysis of the spike train
data and recognition of secondary spikes. Analysis of the additional, smaller
action potentials constantly appearing in telemetry channels would noticeably
increase the amount of information obtained by the orbital experiment.
Approach or Method
A technique capable of automatic analysis of the rough multispike train
data was developed, based on spike shape discrimination and taking into account
the mini- mum number of amplitude and temporal parameters of each spike. A three-
channel apparatus was built which allowed the simultaneous reading of three
different spike potentials from the same electrode. The minimum number of amplitude
and temporal parameters necessary to unequivocally recognize the spike potential
was determined, and a "mask" is built by defining the voltage level and time
difference between the minimum and maximum of the spike. To analyze a given
spike, its shape is displayed on a storage scope through the mask corresponding
to the spike potential preset in one channel of the spike discrim- inator. Values
are set by potentiometers, and output is only obtained when the input signal
fits the preset values within a predetermined tolerance. A delay line is added
to allow analysis of the spike shape before the signal proceeds through the
automatic discriminator system.
Results
One additional spike was clearly recognized and analyzed as a result of data
reduction; the unit was determined to be a statoreceptor, of approximately the
same size and characteristics as the one identified in initial data reduction.
Results suggest that even units of the same nerve are independently affected
by weightlessness, although the direction of the change is similar. Responses
to the centrifuge spin cycle also followed the same variation pattern. Final
conclusions reveal an increase in magnitude of fluctuation of impulse rate up
to twenty times larger than on the ground, and a gradual return to normal by
four to five days, with activity at rest producing about the same magnitudes
as activity from ground controls. A change of gain and mode of responses to
centrifuge spin cycles was observed. This apparently random change in the mode
of operation of otolith cells from phasic to tonic and vice versa, involving
both tonic and phasic stato- receptors, was still present after six days of
weightlessness, contrary to the behavior of the spontaneous firing activity.
Publications
Experiment Reference Number: OFO-1.2
Bracchi, F. et al.: Multi-day Recordings from the Primary Neurons of the Statoreceptors
of the Labyrinth of the Bullfrog: the Effect of an Extended Period of Weightlessness
on the rate of Firing at Rest and in Response to Stimulation by Brief Periods
of Centrifugation (OFO-A Orbiting Experiment). Acta Ototlaryng, supl. 334, 1975,
pp. 1-26.
Gualtierotti, T. et al.: Automatic Analysis of Spike Train Data and Recognition
of Secondary Spikes. OFO-A Conclusive Report, Contract NAS 250/2-7699, 1977,
pp. 3-9.
Gualtierotti, T. et al.: Orbiting Frog Otolith Experiment (OFO). BIOSPEX: Biological
Space Experiments, NASA TM-58217, 1979, p. 108.
¥ = publication of related ground-based study