Koç, Mert
Functional electrical stimulation (FES) has been used to remedy neurological or physiological ailments for many years. Several methods for functional electrical stimulation exist, among which constant current stimulation is adopted by many devices thanks to its safety and charge control. One of the most successful among these devices is the cochlear implant. More than 120.000 people use them to improve the quality of their lives. In the last decade or so, the amount of research done to fully implant these cochlear implants has increased dramatically. To comply with the requirements of such a fully implanted device, rigorous specifications are necessary. One of the most important among these specifications is related to power consumption. Due to weight and volume restrictions the device must operate with ultra-low power. This, however, is quite difficult due to the necessity of high voltage compliance that is required for constant current stimulation. The high voltage must be generated with a converter circuit, which further degrades the efficiency of the system. To alleviate these issues an adaptive converter is designed in this thesis. The system tracks the voltages of an 8- channel stimulation electrode array. Accordingly, with the utilization of a 3-stage charge pump, the necessary supply voltage for the stimulator ranging from 1.8 V to 5.5 V is generated. This way up to 35% power dissipation reduction is observed within the neural stimulator compared to when the converter is operating in its constant 5.5 V configuration, resulting in a much more efficient overall system.


A direct relationship between oscillatory subthalamic nucleus-cortex coupling and rest tremor in Parkinson's disease
Hirschmann, Jan; Hartmann, Christian J.; Butz, Markus; Hoogenboom, Nienke; Özkurt, Tolga Esat; Elben, Saskia; Vesper, Jan; Wojtecki, Lars; Schnitzler, Alfons (2013-12-01)
Electrophysiological studies suggest that rest tremor in Parkinson's disease is associated with an alteration of oscillatory activity. Although it is well known that tremor depends on cortico-muscular coupling, it is unclear whether synchronization within and between brain areas is specifically related to the presence and severity of tremor. To tackle this longstanding issue, we took advantage of naturally occurring spontaneous tremor fluctuations and investigated cerebral synchronization in the presence an...
Unilateral deep brain stimulation suppresses alpha and beta oscillations in sensorimotor cortices
Abbasi, Omid; Hirschmann, Jan; Storzer, Lena; Özkurt, Tolga Esat; Elben, Saskia; Vesper, Jan; Wojtecki, Lars; Schmitz, Georg; Schnitzler, Alfons; Butz, Markus (2018-07-01)
Deep brain stimulation (DBS) is an established therapy to treat motor symptoms in movement disorders such as Parkinson's disease (PD). The mechanisms leading to the high therapeutic effectiveness of DBS are poorly understood so far, but modulation of oscillatory activity is likely to play an important role. Thus, investigating the effect of DBS on cortical oscillatory activity can help clarifying the neurophysiological mechanisms of DBS. Here, we aimed at scrutinizing changes of cortical oscillatory activit...
Investigating pain perception in somatosensory cortex for healthy and fibromyalgia patient populations by using fNIRS
Eken, Aykut; Gökçay, Didem; Kara, Murat; Department of Medical Informatics (2016)
In this study, we investigated the difference in hemodynamic responses between fibromyalgia (FM) and healthy controls via functional near infrared spectroscopy (fNIRS) during application of painful stimulus and transcutaneous electrical nerve stimulation (TENS). We collected several clinical data (pain threshold, Beck Depression Inventory (BDI) score, Fibromyalgia Impact Questionnaire (FIQ) score, pain ratings) before and during the experiment. After data collection, we analyzed it using general linear mode...
Differential efficiency of transcutaneous electrical nerve stimulation in dominant versus nondominant hands in fibromyalgia: placebo-controlled functional near-infrared spectroscopy study
EKEN, AYKUT; KARA, MURAT; BASKAK, BORA; Baltaci, Aysegul; Gökçay, Didem (2018-01-01)
Using functional near-infrared spectroscopy (fNIRS), modulation of hemodynamic responses by transcutaneous electrical nerve stimulation (TENS) during delivery of nociceptive stimulation was investigated in fibromyalgia (FM) patients and healthy controls for both hands. Two experiments were conducted: (1) median nerve stimulation with TENS and (2) painful stimulation using electronic von Frey filaments with TENS/placebo TENS. Mean Delta HbO(2) brain activity was compared across groups and conditions using fa...
Differential modulation of STN-cortical and cortico-muscular coherence by movement and levodopa in Parkinson's disease
Hirschmann, J.; Özkurt, Tolga Esat; Butz, M.; Homburger, M.; Elben, S.; Hartmann, C. J.; Vesper, J.; Wojtecki, L.; Schnitzler, A. (2013-03-01)
Previous research suggests that oscillatory coupling between cortex, basal ganglia and muscles plays an important role in motor behavior. Furthermore, there is evidence that oscillatory coupling is altered in patients with movement disorders such as Parkinson's disease (PD).
Citation Formats
M. Koç, “AN ADAPTIVE CONVERTER FOR CONSTANT CURRENT STIMULATORS,” M.S. - Master of Science, Middle East Technical University, 2021.