Cerebellar Roles in Frequency Competitive Motor Learning of the Vestibulo-ocular Reflex.

Biological motions commonly contain multiple frequency components in which each fundamental has to be adjusted by motor learning to acquire a new motor skill or maintain acquired skills. At times during this motor performance one frequency component needs to be enhanced (gain-up) while another is suppressed (gain-down). This pattern of simultaneous gain-up and -down adjustments at different frequencies is called frequency competitive motor learning. Currently we investigated cerebellar roles in this behavior utilizing the goldfish vestibulo-ocular reflex (VOR). Previously, VOR motor learning was shown in primates to be frequency selective and exhibit frequency competitive motor learning. Here we demonstrate that the goldfish VOR performs frequency competitive motor learning when high and low frequency components are trained to gain-up and gain-down, respectively. However, when the two frequency components were trained in the opposite directions only gain-up component was observed. We also found that cerebellectomy precluded any frequency competitive VOR motor learning. Complementary single unit recordings from vestibulo-cerebellar Purkinje cells revealed changes in firing modulation along with gain-down learning, but not with gain-up learning irrespective of frequency. These results demonstrate that the cerebellum is required for all frequency competitive VOR motor learning and Purkinje cell activity therein is well correlated with all gain-down behaviors independent of frequency. However, frequency competitive gain-up learning requires intact, recursive brainstem/cerebellar pathways. Collectively these findings support the idea that VOR gain-up and gain-down learning utilize separate brainstem/cerebellar circuitry that, in turn, clearly underlies the unique ability of the oculomotor system to deal with multiple frequency components.

A Case of Diffuse Astrocytoma with 32-year Survival after Boron Neutron Capture Therapy.

A 39-year-old man had received boron neutron capture therapy (BNCT) for a grade II astrocytoma (compatible with diffuse astrocytoma, not otherwise specified in the WHO 2016 criteria). He returned to his previous work after surgery, but, 7 years later, he suddenly developed seizures, and his health condition deteriorated. Therefore, he underwent a second surgery. The mass removed in the second operation was mostly necrotic as a result of previous radiation treatment. He then showed no signs of recurrence and did not require any treatment other than antiepileptic drugs for 25 years. He was able to be employed by a listed company until the age of 65 years for light jobs as a physically handicapped individual. This case suggests the effectiveness of BNCT even for rather low-grade astrocytomas.