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Fig. 13.5: Detail of the effects of a 50 and 5
s
on a single GPi neuron of a Parkinson's patient as observed experimentally and
reported by Wu et al. [162]. The
tallest thin vertical line
segments are the stimulus
artifacts, while the
shorter line
segments can be attributed to neuronal spike activity.
A large pulse immediately followed by an inhibitory period is observed following
the stimulus. Moreover, the smaller stimulus (5
μ
A DBS pulse of duration 150
μ
A) is followed by a short inhibitory
period (roughly 30 ms), while the larger stimulus is followed by a longer inhibitory
period (roughly 60 ms).
μ
Pulse amplitude:
0-10.5 V (in steps of 0.1 V), and assuming a 1 k
Ω
load as re-
ported, this means a 0-10.5 mA stimulation current.
1
Pulse duration:
60-450
μ
s (1,000
μ
s maximum in the case of Extrel).
Pulse frequency:
2-185 Hz in the Soletra, 2-250 Hz in the Kinetra, and 2-1,000 Hz
in the Extrel.
Pulse polarity:
both monopolar and bipolar modes are available (only bipolar in
the Extrel).
1
The amplitude used in commercial DBS units (0-10.5 mA) is obviously much larger than what is
reported in the experiments of Dostrovsky et al. [36], Hamilton et al. [60], and Lehman et al. [91],
namely 5-100
A. However, the current density turns out to be similar because of the differences
in electrode diameter. In particular, the experimental work sited uses 25
μ
m
(diameter) electrodes, while commercial devices use a 1.5-mm (length) by 1.27-mm (diameter)
electrodes.
μ
m (length) by 25-100
μ
