Neighboring dendrites preferentially generate contacts among their branches.

<p>Pictures are inverted images of hippocampal neurons grown in culture for 5 days and labeled with anti-MAP2 antibody. (A) An isolated neuron with no physical contacts with other neurons made a single contact between its own branches (arrow). (B) Within a neuronal assembly, dendritic branches turn (arrows) to contact branches of neighboring dendrites (red spots). (C, D) A dense culture in which all neurons orient dendritic branches toward a major overlapping area (circled) where heavy crossing takes place (D, red spots). (E) Dendrite-dendrite contact density is significantly higher among grouped rather than isolated neurons. Shown is the mean ± SEM. Scale: 20 µm.