In a recent study using advanced electrophysiological and imaging methods, the group succeeded in recording in unprecedented resolution from tuft dendrites of cortical principal pyramidal neurons. Tuft dendrites are the main recipients of feedback and neuromodulatory information of the brain. Despite their importance due to their small size they were never been studied directly. In this study, we and our collaborators (Larkum’s group from Bern) present a generalized new conceptual framework of how information is integrated in the principle neocortical pyramidal neurons. This framework unifies the properties of all fine dendrites in the tree. The thin basal dendrites receiving bottom-up information and the distal tuft dendrites receiving top-down information serve as parallel information integrators where information is locally amplified. This pre-integrated information is passed on to the two main integration zones, the apical Ca2+ initiation zone which serves as the site of integration for feedback connections via NMDA spikes and the axo-somatic integration zone which serve as the main decision zone of the neuron.
Synaptic Integration in Tuft Dendrites, Larkum et al. (2009) Science