Also based on Justin's link from the Minnesota Historical Society:
"Insanity Record Books. Frequently, probate courts kept separate “insanity” books. These books recorded a summary of the mental competency cases that came before the court and frequently included a detailed medical evaluation of the individual whose competency was being questioned. If declared to be not competent to conduct one’s own affairs, an individual may have been committed to a state hospital. These insanity records may assist the researcher in searching further in other records. Insanity records, frequently dated before 1920, are available for a substantial number of counties. Access to certain information may be restricted."
The record for your ancestor, and the record below his, do not have minute book notations as the records for probate cases do. In the remarks field the phrase "No record" is recorded. This most likely means that if you were to obtain file 354 for your ancestor, the information in the file will lead you to one of the "insanity books".