Automatic subthalamic nucleus detection from microelectrode recordings based on noise level and neuronal activity

1. To gain a better understanding of the pathophysiology of hemiballismus in primates, and to test directly the hypothesis that the subthalamopallidal projection is excitatory, we studied the effects of lesions of the subthalamic nucleus (STN) on neuronal activity in the globus pallidus (GP) of monkeys during performance of a motor behavioral task. 2. Animals were trained to position and hold a manipulandum to which torque pulses were applied, producing elbow flexion and extension. The activity of neurons in the external (GPe) and internal (GPi) segments of GP was recorded in two monkeys during task performance before and after STN lesions. The STN was lesioned by the fiber-sparing neurotoxins ibotenic acid and/or kainic acid. 3. After lesioning, the firing rate of neurons in both segments of GP, which was measured during the period of holding before torque application, was significantly decreased in both animals. The mean of discharge rates of GPi neurons decreased (P < 0.001) from 69.8 (n = 169, SD = 21.6) to 47.4 spikes/s (n = 180, SD = 22.6) after lesioning. The mean of discharge rates of GPe neurons decreased from 63.6 spikes/s (n = 218, SD = 25.1) before lesions to 41.0 spikes/s (n = 208, SD = 18.1) after lesioning. 4. These results provide further evidence that STN gives rise to a major excitatory input to both segments of the GP and support the hypothesis that dyskinesias result from decreased GPi output.

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Neuronal Activity of the Human Subthalamic Nucleus in the Parkinsonian and Nonparkinsonian State

Journal of Neurophysiology ◽

10.1152/jn.90574.2008 ◽

2008 ◽

Vol 100 (5) ◽

pp. 2515-2524 ◽

Cited By ~ 110

Author(s):

F. Steigerwald ◽

M. Pötter ◽

J. Herzog ◽

M. Pinsker ◽

F. Kopper ◽

...

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Basal Ganglia ◽

Essential Tremor ◽

Subthalamic Nucleus ◽

Neuronal Activity ◽

Single Units ◽

Exact Test ◽

Spectral Peaks ◽

Time Changes

We recorded resting-state neuronal activity from the human subthalamic nucleus (STN) during functional stereotactic surgeries. By inserting up to five parallel microelectrodes for single- or multiunit recordings and applying statistical spike-sorting methods, we were able to isolate a total of 351 single units in 65 patients with Parkinson's disease (PD) and 33 single units in 9 patients suffering from essential tremor (ET). Among these were 93 pairs of simultaneously recorded neurons in PD and 17 in ET, which were detected either by the same ( n = 30) or neighboring microelectrodes ( n = 80). Essential tremor is a movement disorder without any known basal ganglia pathology and with normal dopaminergic brain function. By comparing the neuronal activity of the STN in patients suffering from PD and ET we intended to characterize, for the first time, changes of basal ganglia activity in the human disease state that had previously been described in animal models of Parkinson's disease. We found a significant increase in the mean firing rate of STN neurons in PD and a relatively larger fraction of neurons exhibiting burstlike activity compared with ET. The overall proportion of neurons exhibiting intrinsic oscillations or interneuronal synchronization as defined by significant spectral peaks in the auto- or cross-correlations functions did not differ between PD and ET when considering the entire frequency range of 1–100 Hz. The distribution of significant oscillations across the theta (1–8 Hz), alpha (8–12 Hz), beta (12–35 Hz), and gamma band (>35 Hz), however, was uneven in ET and PD, as indicated by a trend in Fisher's exact test ( P = 0.05). Oscillations and pairwise synchronizations within the 12- to 35-Hz band were a unique feature of PD. Our results confirm the predictions of the rate model of Parkinson's disease. In addition, they emphasize abnormalities in the patterning and dynamics of neuronal discharges in the parkinsonian STN, which support current concepts of abnormal motor loop oscillations in Parkinson's disease.

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