Neuromodulation of hippocampal long-term synaptic plasticity

Abstract

Multiple neuromodulators including acetylcholine, noradrenaline, dopamine and serotonin are released in response to uncertainty to focus attention on events where the predicted outcome does not match observed reality. In these situations, internal representations need to be updated, a process that requires long-term synaptic plasticity. Through a variety of common and divergent mechanisms, it is recently shown that all these neuromodulators facilitate the induction and/or expression of long-term synaptic plasticity within the hippocampus. Under physiological conditions, this may be critical for suprathreshold induction of plasticity endowing neuromodulators with a gating function and providing a mechanism by which neuromodulators enable the targeted updating of memory with relevant information to improve the accuracy of future predictions.

Bridging Biological and Artificial Neural Networks with Emerging Neuromorphic Devices: Fundamentals, Progress, and Challenges

“…However, synaptic strength between two individual neurons in a neuronal system could be affected and controlled by other parameters in the system. [268] Izhikevich has built a model based on STDP, bridging the temporal assignment gap of STDP for reinforcement learning (Section 5.3.3) by introducing dopamine, a type of neuromodulator associated with reward. Neuromodulator could be released diffusely and affect and control many synapses within a volume.…”

“…Besides, the brain activities rely greatly on historical events while ANNs emphasize more on the current input. [268,308] Figure 14.…”

“…[267] In adult animals, neuromodulators are usually necessary for the induction of plasticity and provide a temporal gating mechanism for the brain to update the targeted part of the internal representation with relevant information. [268] Izhikevich has built a model based on STDP, bridging the temporal assignment gap of STDP for reinforcement learning (Section 5.3.3) by introducing dopamine, a type of neuromodulator associated with reward. [269] Second, plasticity in a local circuit can be controlled by inhibitory interneurons.…”

Paradoxical effects of exercise on hippocampal plasticity and cognition in mice with a heterozygous null mutation in the serotonin transporter gene

“…It has been established that mice lacking brain 5-HT have impaired exercise-induced cell proliferation, indicating that the pro-proliferative effect of exercise requires the release of 5-HT (Klempin et al, 2013). Neurons containing 5-HT project throughout the neuraxis of the brain from the raphe nuclei, and 5-HT signals through 14 metabotropic receptors and a sole ionotropic receptor, all present in the hippocampus (Jacobs & Azmitia, 1992;Palacios-Filardo & Mellor, 2019). Supporting the idea that the [5-HT]ext is a critical factor, 5-HT signalling through the sole ionotropic 5-HT receptor, the 5-HT 3 receptor, but not the metabotropic 5-HT 1A receptor, was reported to be critical for exercise-induced adult neurogenesis in the hippocampus (Kondo, Nakamura, Ishida, & Shimada, 2014;Rogers et al, 2016).…”

“…Supporting the idea that the [5-HT]ext is a critical factor, 5-HT signalling through the sole ionotropic 5-HT receptor, the 5-HT 3 receptor, but not the metabotropic 5-HT 1A receptor, was reported to be critical for exercise-induced adult neurogenesis in the hippocampus (Kondo, Nakamura, Ishida, & Shimada, 2014;Rogers et al, 2016). The evidence for 5-HT regulating functional plasticity in the hippocampus is not as clear (Araragi & Lesch, 2013;Palacios-Filardo & Mellor, 2019). However, recent in vivo evidence suggests that mechanisms exist where 5-HT facilitates LTP between neurons in the CA1 region of the hippocampus (Cai et al, 2013;Teixeira et al, 2018).…”