Seminars are open to all visitors and start Monday at 16:00 sharp. Coffee and tea will be served from 15:45. The seminar series lectures are in a colloquiumzaal at the third floor (entrance level) of the Faculty building of Erasmus MC.
Randy Bruno
Synapse Hunting In Vivo
| 2008-09-01 | Room: Colloq. K |
The various regions of the mamalian brain are now understood in terms of their major functions and the gross anatomical pathways interconnecting them. Nevertheless, their precise architecture is largely unknown at the level of synaptic connections between individual processing units (neurons). I have been examining in vivo neural networks in the context of the connectivity between two main brain regions: thalamus and cortex. Sensory stimuli from our environment reach the cortex via the thalamocortical projection, a group of axons thought to be among the most powerful in the brain. Surprisingly, these axons account for only ~15% of synapses onto cortical neurons. The thalamocortical pathway might thus achieve its effectiveness via high-efficacy thalamocortical synapses or via amplification within the main cortical input layer. I recently measured in vivo the excitatory postsynaptic potential evoked by a single synaptic connection and found that thalamocortical synapses have low efficacy. Convergent inputs, however, are both numerous and synchronous, and intracortical amplification is not required. These results suggest a mechanism of cortical activation by which thalamic input alone can drive cortex. I will also discuss ongoing anatomical studies to examine the plasticity of this projection.