Methods in detail
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Evoked potentials:
Standardised visual,auditory or somatosensory signals
are applied and event related evoked potentials are recorded from the vertex
EEG and evaluated (amplitudes and latencies) as a measure of the `specific`
vigilance- and pain-related responses (due to specific afferent CNS information
processing). The method is not subject to no or minor habituation. Attention
is kept stable by a simultaneous tracking task.
Standard and provocation EEG or EEG brain mapping:
The resting, vigilance-controlled and task-related EEG is recorded and its spectral power analysed for the evaluation of `non-specific` vigilance responses (spontaneous fluctuations of vigilance). Provocation methods - as photic stimulation, hyperventilation and sleep deprivation - can be applied to detect epileptic/ hyper-excitatory tendencies in subjects (spike and wave s/w detection). Up to 32 EEG-channels can be evaluated simultaneously.
Oculodynamic test (ODT):
Saccadic eye movements to fixed positioned, randomly
presented targets are recorded. The latency (polysynaptic retino-ponto muscular
reflex time), the angular velocity (efferent and myogenic components) and the
time to fixation (retinal, neuronal and central components) are evaluated. These
parameters of vigilance are not influenced by motivation and learning and are
not subject to habituation.
Complex choice reaction task (CRT):
This test is normally combined with the ODT. The subject
uses an ergometrically designed key board for the identification and coding
of light signals of different type. The mean number of correctly identified
signs (1/ min) reflects the quality of attentional information processing and
psychomotor components of performance. The mean reaction time is a speed oriented
measure of performance (afferent and efferent pathway of CNS-processing).
Electroretinogram (ERG):
The Institute has developed a very subject comfortable
method of recording the ERG with skin electrodes only. The retina is the only
extra cranial organ which contains functional glial cells (Müller cells).The
ATP dependent K-pump system of the retina, depending on the function of these
cells is the basis of the most important electrophysiological signal of the
eye. As the retina, and thus the ERG, is extremely sensitive to hypoxia, the
ERG can be used to detect drug effects which restore hypoxia induced functional
deficits by either affecting the local concentrations of neurotransmitters and
the sensitivity of their receptors or by influencing the metabolism of essential
substrates (O2, glucose, ATP).
Pursuit tracking test (PTT):
The subject follows a moving target on a video screen
with a pursuer signal by means of a joy stick. Adaptation of the task difficulty
to the subject's ability by immediate feedback of performance keeps a constant
stress level. The error vectors between target and pursuer are evaluated. They
reveal information of the steering capabilities as needed for car driving (eye-hand
coordination).
Computer assisted calculation test (CCT):
Calculation tasks are displayed on a screen. The volunteer uses a special ergonomically designed key board. Reaction time and errors are monitored as dependent variables. The level of difficulty can be kept constant or can be gradually or linearly increased by aid of a computer programme. This makes it possible to determine standard preset levels and to measure influences on the subject's arithmetic abilities (combining intellectual functions) with low inter-individual variation.
Memory tests:
We can carry out the Sternberg Memory Scanning Test
(SMST) and use the Coloured Word List(CW) measuring short and medium term memory
performance (immediate and delayed recall).
Evaluation of questionnaires and visual analogue scales with computer scanning (Form Scan):
Multiple choice questionnaires (e.g. psychiatric scales)
visual analogue scales and coded experimental and clinical pd-parameters (BP,
HR, temperature etc.) are automatically evaluated by aid of a computer.
Handwriting test:
The volunteer creates and follows a continuous series
of letters. The deviation vectors of velocity and acceleration are recorded
and evaluated, thus displaying changes in sensu-motor coordination (e.g. under
hypoxia).
Visual analogue scales:
Bipolar 100 mm paper and pencil (p&P) scales are used for the subjective rating of sedation/ excitation and anxiety/ calmness, pain and other relevant items.