18. Beyond skeletomotor function of human basal ganglia: Oculomotor, visual and affective neurons

Abstract

Deep brain stimulation (DBS) of targets in basal ganglia is an effective treatment of motor dysfunction in Parkinson’s disease and primary dystonia. However this treatment may be accompanied by unwanted non-motor side effects. To confirm their neurophysiological nature we searched for any neurons in the subthalamic nucleus (STN), substantia nigra pars reticulata (SNr) and globus pallidus (GP) involved in processing of visually presented emotional scenes. Nineteen Parkinson’s disease patients, which underwent implantation of DBS electrodes to STN or GP, were investigated with simultaneous intraoperative microelectrode recordings and single channel electrooculography during a visual emotional task containing a series of photographs varying in emotional valence and arousal. Recordings were analyzed by the WaveClus program which allowed for detection and sorting of individual neurons. Out of 183 neurons that were detected, 130 were found in the STN, 30 in the SNr and 23 in the GP. Twenty percent of the neurons in each of these structures showed eye movement-related activity. In the STN, we observed 35 neurons whose firing rate changed significantly within first 500 ms after presentation of a photograph suggesting their participation in visual or attentional mechanisms. Activity of 14 STN neurons showed significant changes during 500–1500 ms interval in alpha band of the instantaneous firing rate related to the emotional content of presented photographs. Activity of 8 of neurons was related to the arousal while activity of another 6 neurons was changing in relation to the emotional valence. Our results showed that basal ganglia contain relatively high share of oculomotor neurons suggesting their critical role in eye-movement control. In addition, the STN neurons involved in visual processing and in transmission of emotional information provide evidence of separate management of the affective dimensions of valence and arousal. Therefore, it is not surprising that DBS may have various non-motor consequences. Supported by grants: IGA MZ ČR NT12282–5/2011; research projects: MŠM 0021620849, MŠM 6840770012 and PRVOUK-P26/LF1/4.