Figure 8.

Relationship between synaptic properties and groups of postsynaptic interneurons. Relationship of PP ratio and EPSP amplitude to groups of interneurons as defined by a cluster analysis of axonal, dendritic, and electrical excitability parameters (Helmstaedter et al., 2008c) (color coded). Interneurons belonging to the same group were close in this parameter space (groups translaminar 2, lateral 1, local 1, local 2, local 3, chandelier neurons). Only three groups with two samples each were less similar (groups translaminar 1, lateral 3). Group lateral 2 neurons and L1 inhibitors did not receive input from layer 4 (0 of 1, 0 of 4, respectively). The difference of interneuron groups with respect to synaptic properties was significant (MANOVA, p < 0.01; bootstrapping, p < 0.05) (see Materials and Methods). The three group local 3 interneurons showed significant PP facilitation each (t test, p < 0.05). Note that the synaptic properties of types of interneurons just separated by their axonal projection were not different (p > 0.5) (data not shown). The gray inset shows the classification of interneurons into types and groups as suggested by unsupervised cluster analysis (Helmstaedter et al., 2008c). For a comparison to other interneuron classifications, see Discussion.