Neuromodulation refers to processes that modify the ongoing electrical and chemical signaling among groups of neurons in the brain. It is distinct from neurotransmission, which is the direct transmittal of information from one neuron to another. Neuromodulation modifies neurotransmission: it changes the excitability of neurons, and therefore the how they will communicate in response to chemical or electrical input signals. Neuromodulation is a critical mechanism for adapting to environmental stimuli, allocating cognitive resources, and regulating arousal, appetitive behaviors, movement, and mood.
In both neurotransmission and neuromodulation, a chemical neurotransmitter acts on local postsynaptic receptors, but neurotransmission is a more rapid process (on the order of milliseconds) that occurs at the levels of the individual synapse and involves ion-channel coupled receptors. Neuromodulation is a much slower process (on the order of several hundred milliseconds to seconds) that occurs on a larger scale involving ensembles of neurons in microcircuits or networks, and involves G-protein-coupled receptors. Neurotransmission represents ongoing neuronal spiking that is related to input signals from other neurons or from the environment, while neuromodulation modifies the excitability and therefore the spiking rate and pattern of the neurons.
Neuromodulation also refers to treatments that modify the responsiveness of neural networks. Most commonly, neuromodulation is used to describe an emerging class of technologies that apply electromagnetic energy to the nervous system, rather than by administering medications. Several of these therapies are non-invasive, including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), while others are invasive and require direct stimulation of the brain, such as deep brain stimulation (DBS) and electrocortical stimulation. All these therapies can be used to stimulate specific brain targets and relieve symptoms of depression, epilepsy, tremor, Parkinson’s disease, and pain, among other symptoms. More generally, these techniques may be used in healthy individuals or patients to enhance attention and concentration, memory, cognitive processing, decision-making, and mood. The mechanism of action of these techniques is not fully understood: even when applied to a specific brain target or pathway, neuromodulation signals can spread rapidly through brain networks affecting multiple areas and brain systems. Neuromodulation techniques appear to share the common effect of increasing neuroplasticity, altering brain connectivity, and thereby altering brain network function.
The concept of neuromodulation also can be used to explain the effects of medication treatments that affect serotonin (5-HT), norepinephrine (NE), dopamine (DA), and acetylcholine (Ach), which are termed “neuromodulatory neurotransmitters.” These neurotransmitters are produced by small groups of neurons in specific deep gray structures of the brain (e.g., 5-HT in the raphe nuclei, NE in the locus coeruleus), and diffuse through pathways to affect large areas of the nervous system. These neurotransmitters act in contrast to γ-Aminobutyric acid (GABA) or glutamate, which act primarily through classical synaptic transmission in which a presynaptic neuron directly signals a postsynaptic neuron. Neuromodulatory neurotransmitters diffuse through brain tissue and alter the firing rate and pattern of neurons involved in classical neurotransmission. Medications therefore act as modulators of synaptic neurotransmission by directly affecting serotonin, norepinephrine (i.e., antidepressants) or dopamine (i.e.. antipsychotics) levels.
The Neuromodulation Division of the UCLA Semel Institute utilizes state-of-the-art techniques to treat neuropsychiatric illness, and to understand brain function in health and disease. Our transdisciplinary Division brings together leading faculty from Psychiatry, Neurosurgery, Neurology, and Engineering to utilize and develop individualized treatment approaches for psychiatric and neurological disorders. With cutting edge programs that utilize both invasive and non-invasive technologies, the Division has world-class treatment and research programs in epilepsy, mood disorders, pain, Parkinson’s disease, ADHD, and memory. The Division is uniquely positioned to integrate basic with applied science approaches and lead the field to meet the demand for novel neuromodulation treatments.
The Neuromodulation Division of the UCLA Semel Institute enables:
- Improvement and application of psychiatric treatments guided by neuroimaging
- Research elucidating mechanisms of neuromodulatory effects on neurophysiology and behavior
- Development of novel neuromodulatory methods through collaboration between neuroscientists and engineers
- Design, implementation, and testing of novel neuromodulatory devices in model systems
- Transfer of novel technology and treatments into human clinical trials
- Collaborative forums and interface between internal and external experts in the field of Neuromodulation
- Educational opportunities for members and training fellows to present their ongoing scientific findings
- Sharing of common resources and analysis tools between research programs allowing for the building of richer data sets and novel collaborations