Effects of various protocols on network connectivity.

N: No. experiments; FSCS: Fraction of functional connections with Significantly Changed Strength; : mean strength change of significantly affected functional connections.; : mean absolute strength change of significantly affected connections. PI: plasticity index. PI = 1 means that the strength of all functional connections changed by 100%; PI = 0 means no connectivity changes. All values are expressed as mean ± SD. The first three rows show results from ∼5 hour protocols, the last three rows describe ∼1 hour protocols. A ∼1 (or ∼5) hours protocol means that a stimulation period lasted for ∼1 (or ∼5) hours. These were preceded and followed by spontaneous recordings and therefore complete experiments always lasted longer than one (or five) hours.
The plasticity index (PI) of the training protocol was significantly larger than those of random or no stimulation (1,2: t-test, p<0.05). The difference between (5 hour) Random- and no stimulation was not significant (p = 0.08). Using 1 hour protocols the difference between random and no stimulation was significant (3: p<0.05), the difference between single electrode- and no stimulation was not (p = 0.08). All plasticity indices, except after 1 hour without stimulation, were significantly larger than 0 (p<0.05).