Geneeskundige Stichting Koningin Elisabeth verslag - GSKE - FMRE

Discussion
As reported previously (Sato et al. 1992) the SS firing after a CS in PCs showed three different
patterns such as pure pause, pause followed by facilitation and pause followed by reduction.
The analysis by Sato et al., however, was based on average firing behavior only. When analyzing
individual CSs we found that for each type of PC an simple spiking after the pause can show
any of the three patterns. In other words, the classification by Sato et al. describes a trend but
does not predict SS patterns in single trials.
An unexpected finding of this study is that SS firing before a CS is slower, independent of the
pattern after the CS. This could cause misclassification of PCs into PC type 2. In fact, 5 out of
34 PCs were classified as PC type 2 because of the slower firing before a CS even though SSs
were not facilitated after a CS. This result is different from that of Miall et al (1998) who found
an increased SS firing rate before a CS, but they looked at a different time window (150 ms
before CS) compared to our data (on average 100 to 0 ms before CS). The mechanism causing
slower SS firing shortly before a CS is unknown at present and requires further study.
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