Cortically evoked responses of human pallidal neurons recorded during stereotactic neurosurgery

Abstract

Responses of neurons in the globus pallidus (GP) to cortical stimulation were recorded for the first time in humans. We performed microelectrode recordings of GP neurons in 10 Parkinson's disease (PD) patients and 1 cervical dystonia (CD) patient during surgeries to implant bilateral deep brain stimulation electrodes in the GP. To identify the motor territories in the external (GPe) and internal (GPi) segments of the GP, unitary responses evoked by stimulation of the primary motor cortex were observed by constructing peristimulus time histograms. Neurons in the motor territories of the GPe and GPi responded to cortical stimulation. Response patterns observed in the PD patients were combinations of an early excitation, an inhibition, and a late excitation. In addition, in the CD patient, a long-lasting inhibition was prominent, suggesting increased activity along the cortico-striato-GPe/GPi pathways. The firing rates of GPe and GPi neurons in the CD patient were lower than those in the PD patients. Many GPe and GPi neurons of the PD and CD patients showed burst or oscillatory burst activity. Effective cathodal contacts tended to be located close to the responding neurons. Such unitary responses induced by cortical stimulation may be of use to target motor territories of the GP for stereotactic functional neurosurgery. Future findings utilizing this method may give us new insights into understanding the pathophysiology of movement disorders.

Selective stimulation of the subthalamic nucleus

“…Seizures also occur in other intraoperative procedures during which the cortex is stimulated repetitively (incidence of 1.2 %) (Szelenyi et al 2007). Interestingly, subdural MCS has been applied with a similar stimulation protocol without inducing epileptic seizures (Nishibayashi et al 2011). The main difference between the stimulation protocols is that Nishibayashi et al applied a lower number of stimuli and the electrode contact size was larger.…”

“…Unfortunately, the existence of the early response could not be studied, because of a large stimulation artifact. Electrical stimulation of the motor cortex to locate the motor areas of the GPi and GPe has also been performed (successfully) by Nishibayashi et al (Nishibayashi et al 2011). MCS and subsequent STN recording has not yet been applied in human.…”

“…Synapse 40: 145-153. Nishibayashi, H., M. Ogura, K. Kakishita, S. Tanaka, Y. Tachibana, A. Nambu, H. Kita and T. Itakura (2011 …”

“…Optimization, to identify the motor part, is currently done by intra-operative neurophysiological measurements, such as spontaneous neuronal firing, neuronal kinesthetic responses and beta-power in the local field potential (Chen et al 2006;Gross et al 2006;de Solages et al 2011). Earlier, Nishibayashi et al (Nishibayashi et al 2011) applied subdural motor cortex stimulation (MCS) in humans in order to identify the motor area of the globus pallidus internus and externus. This report will provide insight in the cortically evoked responses of the human STN neurons.…”

“…Secondly, we will employ the model to determine protocols that selectively target these populations. Although this paper is aimed at chronic MCS for PD, the outcome can also be useful for other applications, such as MCS for pain and stroke treatment and acute MCS to target the STN or GPi motor regions during DBS surgery (Nishibayashi et al 2011; …”