title: Somatosensory evoked potentials recorded from the human pedunculopontine nucleus region.
abstract: The pedunculopontine nucleus region (PPNR) is an integral component of the midbrain locomotor region and has widespread connections with the cortex, thalamus, brain stem, cerebellum, spinal cord, and especially, the basal ganglia. No previous study examined the somatosensory connection of the PPNR in human. We recorded somatosensory evoked potentials (SEP) from median nerve stimulation through deep brain stimulation (DBS) electrodes implanted in the PPNR in 8 patients (6 with Parkinson's disease, 2 with progressive supranuclear palsy). Monopolar recordings from the PPNR contacts showed triphasic or biphasic potentials. The latency of the largest negative peak was between 16.8 and 18.7 milliseconds. Bipolar derivation revealed phase reversal with median nerve stimulation contralateral to the DBS electrode in 6 patients. There was no difference in SEP amplitude and latency between on and off medication states. We also studied the high frequency oscillations (HFOs) by filtering the signal between 500 and 2,500 Hz. The HFOs could be identified only from contralateral stimulation and had intraburst frequencies of 1061 ± 121 Hz, onset latencies of 13.8 ± 1.2 milliseconds, and burst durations of 7.3 ± 1.1 milliseconds. Among the 10 recordings with HFOs, only 1 had possible phase reversal in the bipolar derivation. Our results suggest that there are direct somatosensory inputs to the PPNR. The slow components and HFOs of the SEP have different origins.
authors.affiliation: Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: I-Jin
authors.initials: IJ
authors.lastname: Yeh
authors.forename: Eric W
authors.initials: EW
authors.lastname: Tsang
authors.forename: Clement
authors.initials: C
authors.lastname: Hamani
authors.forename: Elena
authors.initials: E
authors.lastname: Moro
authors.forename: Filomena
authors.initials: F
authors.lastname: Mazzella
authors.forename: Yu-Yan
authors.initials: YY
authors.lastname: Poon
authors.forename: Andres M
authors.initials: AM
authors.lastname: Lozano
authors.forename: Robert
authors.initials: R
authors.lastname: Chen
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D055592:Biophysical Phenomena / Q000502:physiology; D046690:Deep Brain Stimulation / Q000379:methods; D004567:Electrodes, Implanted; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D010300:Parkinson Disease / Q000473:pathology; D045042:Pedunculopontine Tegmental Nucleus / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D013494:Supranuclear Palsy, Progressive / Q000473:pathology