The subthalamic nucleus in Parkinson's disease: somatotopic organization and physiological characteristics

Abstract

Single-cell recording of the subthalamic nucleus (STN) was undertaken in 14 patients with Parkinson's disease submitted to surgery. Three hundred and fifty neurones were recorded and assessed for their response to passive and active movements. Thirty-two per cent were activated by passive and active movement of the limbs, oromandibular region and abdominal wall. All neurones with sensorimotor responses were in the dorsolateral region of the STN. Arm-related neurones were lateral (> or =14 mm plane) to leg-related neurones, which were found more medially (< or =12 mm). Representation of the oromandibular musculature was in the middle of the sensorimotor region (approximately 13 mm plane) and ventral to the arm and leg. Two hundred neurones were adequately isolated for 'off-line' analysis. The mean frequency of discharge was 33 +/- 17 Hz (13-117 Hz). Three types of neuronal discharges were distinguished: irregular (60.5%), tonic (24%) and oscillatory (15.5 %). They were statistically differentiated on the basis of their mean firing frequency and the coefficient of variation of the interspike interval. Neurones responding to movement were of the irregular or tonic type, and were found in the dorsolateral region of the STN. Neurones with oscillatory and low frequency activity did not respond to movement and were in the ventral one-third of the nucleus. Thirty-eight tremor-related neurones were recorded. The majority (84%) of these were sensitive to movement and were located in the dorsolateral region of the STN. Cross power analysis (n = 16) between the rhythmic neuronal activity and tremor in the limbs showed a peak frequency of 5 Hz (4-8 Hz). Neuronal activity of the substantia nigra pars reticulata was recorded 0.5-3 mm below the STN. Eighty neurones were recorded 'on-line' and 27 were isolated for 'off-line' analysis. A tonic pattern of discharge characterized by a mean firing rate of 71 +/- 28 Hz (35-122 Hz) with a mean coefficient of variation of the interspike interval of 0.85 +/- 0.29 ms was found. In only three neurones (11%) was there a response to sensorimotor stimulation. The findings of this study indicate that the somatotopic arrangement and electrophysiological features of the STN in Parkinson's disease patients are similar to those found in monkeys.

Deep brain stimulation in Parkinson disease—what went wrong?

“…Recordings of neuronal activity in PD patients and/or in animals have shown that the STN is involved not only in motor [44,45], but also in emotional [26] and motivational [46] processes. A classic paradigm for studying conflict is the Stroop word-colour interference task [47].…”

El núcleo subtalámico en la fisiopatología de la enfermedad de Parkinson y su rol como diana quirúrgica

“…El NST al igual que otras estructuras de los GB presenta una divergencia de la información según los cinco circuitos descritos por Alexander y DeLong 8,9,19,37,38 y se ha demostrado mediante estudios de registro y estimulación eléctrica en animales de experimentación que las neuronas del circuito motor, es decir, aquellas que al ser estimuladas evocan una respuesta motora, se encuentran localizadas en su gran mayoría en la región dorso lateral del núcleo 34,39,40 . Nambu y cols (1996), concluyeron en estudios realizados en monos que este núcleo en su área sensitivo motora presenta una doble representación somatotópica que se presenta en forma de imagen en espejo.…”

“…De los registro oscilatorios 38 tenían la misma frecuencia de descarga que la del temblor y de estos el 84% se encontraban en el área sensitivo motora, por lo que el NST podría tener alguna infl uencia en la aparición del temblor. Finalmente, con este estudio se concluyó que la somatotópia del NST y sus características electrofi siológicas son muy similares en el hombre y en los monos 39 . Estudios de los últimos 5 años proponen la idea de que el NST constituye otra puerta de entrada de los ganglios basales a aferencias corticales 19,[42][43][44] .…”

“…A través de estudios en animales de experimentación como monos y ratas con parkinsonismo inducido y en pacientes con enfermedad de Parkinson se ha encontrado que existen diferentes patrones de descarga de las neuronas del NST 39,[45][46][47][48] . En condiciones normales la mayoría de las neuronas del NST presentan un patrón de descarga de tipo tónica con una frecuencia media entre 5 y 65 HZ y un pequeño grupo presenta descarga de tipo fásica.…”

Correlating Clinical Scores with Anatomical Electrodes Locations for Assessing Deep Brain Stimulation

“…The target for DBS in Parkinson's disease has been moved from the ventro-lateral thalamic nucleus (Vlc) to the medial global pallidus (Gpm) and the Sub-Thalamic Nucleus (STN). Among these three deep brain structures, the STN became the mean target of high-frequency DBS in patients with PD and severe disabled symptoms [2]. Even if STN DBS has proved its efficiency for motor symptoms improvement, several studies have reported adverse-events after DBS surgery affecting cognitive functions, emotion or behavior [3,4,5].…”