Advances Toward Closed-Loop Deep Brain Stimulation - Computational Neuroscience - page 233

Fig. 13.4: Effects of DBS pulses on neural activity in the GPi as observed experi-
mentally and reported by Dostrovsky et al. [36]. The larger vertical line segments
are stimulus artifacts while the shorter line segments can be attributed to neuronal
spike activity. A quiescent or inhibitory period during which there is no neuronal
activity can be observed after each stimulus.

DBS are the “Itrel II Soletra,” “Kinetra,” and “Extrel” units (with Extrel used less
frequently than the former two). Moreover, the specifications of the apparatus have
been described in a number of publications [59, 101, 5, 89, 152]. Specifically, a
1.27 mm diameter probe with four 1.5 mm long contacts spaced 0.5 mm or 1.5 mm
apart (depending on the version) is in contact with the target area of the brain and
secured to the cranium at its base. Furthermore, a subcutaneous lead connects the
base of the probe to a 53 10 mm 3 neurostimulator implanted in the chest area

under the collarbone of the patient [101].
The Extrel unit differs from the Soletra and Kinetra units in that an external stim-
ulus generator communicates with the implant. In particular, the external apparatus
generates the pulse waveform and then modulates it using a carrier frequency in the
RF range. In turn, an implanted receiver demodulates the signal using passive circuit
components including a capacitor [89, 137, 102].

× 60 ×

13.5.3 Stimulus Specifications

The DBS units are capable of applying stimulus waveforms that consist of a train of
pulses with the following specifications [152, 101]: