?Professor Poo Mu-ming, Paul Licht Distinguished Professor in Biology at the University of California, Berkeley, and Director of Institute of Neuroscience of Chinese Academy of Sciences, gave a talk titled “Neural Plasticity: From Synapse to Cognition” at a City University Distinguished Lecture on 13 April.

In his talk, Professor Poo pointed out that the cognitive functions of the brain, such as learning and memory, depended on the ability of neural circuits to change their properties of signal processing in response to prior use. Many of these use-dependent changes (“plasticity”) occur at synapses where signals are transmitted between neurons.

Professor Poo’s studies found that the timing of neuronal activities (spikes) in the pre- and post-synaptic neurons determines whether a synapse undergoes long-term potentiation (LTP) or long-term depression (LTD), a phenomenon known as “Spike Timing-Dependent Plasticity” (STDP), which may provide the mechanism for coding and storing the information on the temporal sequence and interval of sensory signals, two key elements of episodic memories.

There are billions of synapses in human brains. In an experiment exploring how memory was stored in a specific synapse, Professor Poo found that fear memory was stored in part of the auditory cortex. Memory storage involves structural rewiring of synaptic connections that add new synaptic partners to existing synaptic elements. This is a new finding as scientists tend to believe that rewiring involves formation of completely new connections.

Professor Poo also argued that higher cognitive functions in humans such as self-awareness might originate from experience-dependent neural plasticity. His research team found that mirror self-recognition, a cognitive function known to be limited only to humans and great apes, could be acquired by rhesus monkeys following training of visual-somatosensory association.

The new findings provide insight on the potential for functional recovery from injuries and diseases of the adult brain.