By Elodie Vaz | Published on May 21,
2026 | 4 min read
Depression remains
one of the major challenges of contemporary psychiatry. Despite the proven
effectiveness of certain treatments, the precise biological mechanisms that
allow the brain to recover from a depressive state remain largely unclear. A
team from UCLA Health now claims to have reached a major milestone. In a study
published on May 7 in Cell, researchers describe for the first time how
an accelerated form of transcranial magnetic stimulation (TMS) physically
repairs brain circuits altered by stress, paving the way for a mechanistic
understanding of the antidepressant effects of this therapy.
Repetitive
transcranial magnetic stimulation (rTMS) is a non-invasive technique approved
by the FDA, primarily used in patients suffering from treatment-resistant
depression. It relies on the application of electromagnetic pulses through a
coil placed on the scalp in order to modulate the activity of targeted brain
regions, particularly the prefrontal cortex. However, while the clinical
benefits of the method have been known for several years, its action at the
cellular level has until now remained a “black box.”
Finally understanding
how TMS works
The objective of the
UCLA-led study was precisely to decipher the neuronal mechanisms responsible
for the rapid effects observed with a new generation of protocols: accelerated
intermittent theta burst stimulation (aiTBS). Unlike traditional protocols requiring
six weeks of daily sessions, this approach condenses treatment into just five
days and often provides rapid relief from depressive symptoms.
The study was co-led
by Dr. Scott Wilke and Dr. Laura DeNardo. According to Dr. Wilke, this research
marks a turning point. “This work allows us to bridge our clinical observations
with the cellular-level insights that only cutting-edge neuroscience tools can
provide. For the first time, we can precisely observe which brain cells are
modified by this rapid treatment and how this restoration promotes recovery
from depression-related behaviors.”
To study the
biological effects of aiTBS, the researchers developed, in collaboration with
the National Institutes of Health, an experimental model reproducing the
protocols used in human clinical practice. Mice subjected to chronic stress in
order to mimic certain features of depression were stimulated while awake,
while their brain activity was observed in real time.
The researchers
focused particularly on dendritic spines, tiny structures essential for
synaptic communication between neurons. They observed that chronic stress
caused a significant loss of these structures in the prefrontal cortex, a key
region involved in regulating emotions and adaptive behaviors.
Targeted restoration
of neural circuits
The study’s major
finding lies in the highly selective nature of the stimulation’s effects. Just
one day of aiTBS was enough to restore lost synaptic connections, but only in a
specific subtype of neurons: intratelencephalic (IT) neurons. Neighboring neuronal
populations remained largely unchanged.
Professor Michael
Gongwer emphasized the researchers’ surprise: “We initially thought that
transcranial magnetic stimulation would broadly affect the prefrontal cortex,
but its effects turned out to be remarkably precise. Observing the reappearance
of lost synaptic structures, and then seeing those same neurons regain activity
during behavior, was incredibly exciting.”
The experiments also
showed that when the activity of IT neurons is blocked during stimulation, the
antidepressant effects disappear completely. According to Dr. DeNardo, this
demonstrates that these neurons play a central role in behavioral recovery. “Stress
disrupts the structural scaffolding that neurons rely on to communicate. By
restoring these structures in IT neurons, stimulation reactivates the circuits
that support adaptive behaviors.”
Behavioral benefits
were observed within 24 hours following treatment and persisted for at least
one week after a single day of stimulation. According to Dr. Wilke, this
persistence is essential. “What is striking is that this is not simply a
temporary modification of activity. The treatment restores neuronal structure
in a way that enables the recovery of normal circuit function and normal
behavior.”
Toward precision
neuromodulation
Although the authors
emphasize that animal models cannot reproduce the full complexity of human
depression, this study provides one of the most compelling demonstrations to
date of the link between brain stimulation, synaptic repair, and behavioral
improvement.
Beyond depression,
TMS is already being used in several disorders associated with dysfunctions in
specific neural circuits, including OCD, chronic pain, PTSD, and tinnitus. This
work could therefore accelerate the emergence of personalized neuromodulation.
As Dr. Wilke summarizes: “Every patient is unique. By studying these treatments
in mice, we can systematically test how different stimulation parameters modify
brain circuits, which could ultimately help us tailor neuromodulation therapies
to each patient.”
Read next: Optimism:
an unexpected protective factor against dementia
About the Author – Elodie Vaz
Health journalist, CFPJ graduate (2023).
Élodie explores the marks diseases leave on bodies and, more broadly, on
human life. A registered nurse since 2010, she spent twelve years at patients’
bedsides before exchanging her stethoscope for a notebook. She now investigates
the links between environment and health, convinced that the vitality of life
cannot be reduced to that of humans.
