Dynamic Network Connectivity (DNC): A New Form of Rapid Neuroplasticity

Recent physiological research has shown that neuromodulators can rapidly alter the strength of dlPFC network firing on a timescale of seconds, through powerful influences on the open states of ion channels residing near network synapses, a process called Dynamic Network Connectivity (DNC) . This work has shown that the highly evolved circuits of dlPFC are often modulated in a fundamentally different manner than sensory/motor or subcortical circuits, providing great flexibility in the pattern and strength of network connections.

These neuromodulatory processes allow moment-by-moment changes in synaptic strength without alterations in underlying architecture, and can bring circuits “on-line” or “off-line” based on arousal state, thus coordinating the neural systems in control of behavior, thought and emotion. However, this extraordinary flexibility also confers great vulnerability, and errors in this process likely contribute to cognitive deficits in disorders such as schizophrenia.

If you are interested: Arnsten AFT, Wang MJ, Paspalas CD (2012) Neuromodulation of thought: Flexibilities and vulnerabilities in prefrontal cortical network synapses. Neuron 76: 223-239.

Working memory differs from long-term memory consolidation in a number of elementary ways. Working memory is a momentary (timescale of seconds), ever-changing pattern of recurrent activation of relatively stable architectural networks, while long-term memory consolidation retains events as structural changes in synapses. In LTP, increased calcium and cAMP lead to architectural changes creating a stable, mushroom-shaped spine. In contrast, in layer III of the dlPFC, there are momentary changes in the strength of connections due to ion channel opening, but the architecture remains the same. In these spines, high levels of calcium and cAMP weaken connectivity via opening of K+ channels near the synapse or in the spine neck.

The long, thin shape of spines in layer III of dlPFC likely facilitates the rapid gating of synaptic strength. The vast majority of spines in layer III of the dlPFC are long and thin, even in very old animals, suggesting that they are not waiting to become mushroom spines, but rather, subserve the recurrent, excitatory connections that generate working memory.