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Objectives The study aimed to investigate the site of the movement related inhibition of the human dorsal column nuclei. Methods Median nerve somatosensory evoked potentials (SEPs) were recorded from 18 patients suffering from Parkinson’s disease, who underwent electrode implantation in the pedunculopontine (PPTg) nucleus. SEPs were recorded at rest and during active or passive movement of the thumb of the stimulated wrist. Results The PPTg electrode recorded a triphasic potential generated in the cuneate nucleus. The PPTg potential was subtended by 2 high frequency oscillation (HFO) components: (1) an earlier one with 1000 Hz frequency and (2) a later one with 1700 Hz frequency. Both HFO components were reduced by movement. No major difference between the effects of either active or passive movement was found. Discussion PPTg electrode can record SEPs generated in the dorsal column nuclei (DCN). We suggest that the 1000 Hz and 1700 Hz HFO bursts are generated at pre- and post-synaptical level, respectively. Conclusion Movement exerts both pre- and post-synaptic inhibition on dorsal column nuclei. Significance Investigating the effect of movement on the DCN activity by an intracerebral electrode located at the human PPTg level confirms what early studies in animals suggested. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To investigate the effect of the voluntary movement on the amplitude of the somatosensory evoked potentials (SEPs) recorded by an epidural electrode at level of the cervical spinal cord (CSC). Methods: Fourteen patients underwent an epidural electrode implant at CSC level for pain relief. After the median nerve stimulation, SEPs were recorded from the epidural electrode and from 4 surface electrodes (in frontal and parietal regions contralateral to the stimulated side, over the 6th cervical vertebra, and on the Erb’s point). SEPs were recorded at rest and during a voluntary flexo-extension movement of the stimulated wrist. Beyond the low-frequency SEPs, also the high-frequency oscillations (HFOs) were analysed. Results: The epidural electrode contacts recorded a triphasic potential (P1–N1–P2), whose negative peak showed the same latency as the cervical N13 response. The epidural potential amplitude was significantly decreased during the voluntary movement, as compared to the rest. Two main HFOs were identifiable: (1) the 1200Hz HFO which was significantly lower in amplitude during movement than at rest, and (2) the 500Hz HFO which was not modified by the voluntary movement. Conclusions: The low-frequency cervical SEP component is subtended by HFOs probably generated by: (1) postsynaptic potentials in the dorsal horn neurones (1200Hz), and (2) presynaptic ascending somatosensory inputs (500Hz). Significance: Our findings show that the voluntary movement may affect the somatosensory input processing also at CSC level. [Copyright &y& Elsevier]

Abstract: Objective: To investigate whether recording from deep intracerebral (IC) electrodes can disclose laser evoked potential (LEP) components generated under the cerebral cortex. Methods: LEPs were recorded to hand and/or perioral region stimulation from 7 patients suffering from Parkinson’s disease, who underwent implant of IC electrodes in the globus pallidum pars interna (GPi), in the subthalamic nucleus (STN) and in the pedunculopontine nucleus (PPN). LEPs were obtained from the IC electrode contacts and from the Cz vertex, referred to the nose. Results: The scalp traces showed a triphasic response (P1-N2-P2). The IC electrodes recorded two main components (ICP2 and ICN2), showing the same latencies as the scalp N2 and P2 potentials, respectively. The ICP2-ICN2 complex was sometimes preceded by a ICP1 wave at the same latency of the scalp P1 response. Conclusions: The LEP components recorded from the IC electrodes mirrored the ones picked up from the Cz lead, thus suggesting that they are probably generated by the opposite pole of the same cortical sources producing the scalp responses. Significance: In the IC traces, there was no evidence of earlier potentials possibly generated within the thalamus or of subcortical far-field responses. This means that the nociceptive signal amplification occurring within the cerebral cortex is necessary to produce identifiable LEP components. [Copyright &y& Elsevier]