Decreased, neuroplasticity

• Neuroplasticity, also known as synaptic or brain plasticity, is a mechanism by which the brain undergoes structural and functional changes. It is defined as the brain’s ability to modify its activity in response to extrinsic and intrinsic stimuli, enabling the reorganization of its structure and function — for example, following brain injury. (Puderbaugh et al; 2023)
• The biochemical processes that occur and are associated with synapses and other components of the brain form the foundation of neuroplasticity. These processes involve both functional and structural changes in the brain, enabling adaptation to the environment, learning, memory formation, and rehabilitation following brain injury. (Gulyaeva 2017)

• Basically, neuroplasticity can be defined primarily as the modification of the structure or function of the nervous system in response to environmental changes. (Stee & Peigneux, 2021)

• Synaptic plasticity is time-dependent. (Johson et al; 2023) 

• It is suggested that neuroplasticity is also associated with neurogenesis. (Stee et al., 2021)

• Recently, neuroplastic changes have also been found in the thickness of the myelin sheath and in the diameter of the axon. (Fields, 2015; Xin e Chan, 2020; Tramblay et al., 2021) 

• Although the initial description of neuroplasticity focused solely on the brain, it actually occurs throughout the entire central nervous system. (Liu & Chambers, 1958)

• In basic research, it has been observed that chronic stress leads to impaired neuroplasticity, resulting in neuronal atrophy and synaptic loss in the medial prefrontal cortex (mPFC) and the hippocampus. Structural alterations and changes in specific neural circuits are associated with performance deficits observed in depressed patients during cognitive and neuropsychological tasks. Such deficits are consistent with a reduced ability to interact flexibly with stimuli and to engage in goal-directed cognition efficiently. (Price & Duman, 2020)

The main approaches to detect and measure the reduction of neural plasticity include:

Biochemical and protein markers: altered levels of brain-derived neurotrophic factor (BDNF) are associated with impaired synaptic plasticity, as well as imbalances between excitatory and inhibitory neuronal signaling. (Sarriés-Serrano et al., 2025) 

Neuroimaging or electrophysiological techniques: studies using EEG or fMRI can identify structural and functional changes that may reflect reduced synaptic plasticity. (Herzberg et al., 2024)

Animal models demonstrating reduced synaptic activity: for instance, studies have shown that dopamine depletion induces alterations in hippocampal synaptic plasticity in mice. (Kim et al., 2023)

Behavioral and cognitive/neuropsychological performance assays: deficits in tasks requiring cognitive effort, learning, or memory may indicate altered neuroplasticity and serve as an indirect measurement method. 

Use of indirect biomarkers: peripheral biomarkers, such as those found in blood or saliva, can also serve as indicators of changes related to brain plasticity. (Mougeot et al., 2016)

Neuroplasticity is well characterized in vertebrates. Animal models such as rats and mice are well established as tools for studying neural plasticity. More recently, zebrafish (Danio rerio) have also been used as an experimental model to investigate neuroplasticity. (De Jager et al., 2024; Hall & Tropepe, 2018., Calvo‑Ochoa & Byrd‑Jacobs, 2019) 

Puderbaugh, M. and P. D. Emmady (2023), Neuroplasticity, Hennepin Healthcare and UNC School of Medicine, Atrium Health, last updated 1 May 2023. 

Gulyaeva, N. V. (2017). Molecular mechanisms of neuroplasticity: An expanding universe. Biochemistry (Moscow), 82(3), 237–245. https://doi.org/10.1134/S0006297917030014 

Stee, W., & Peigneux. (2021). Post-learning micro- and macro-structural neuroplasticity changes with time and sleep. Biochemical Pharmacology, 191, 114369. https://doi.org/10.1016/j.bcp.2020.114369 

Fields, R.D. (2015). A new mechanism of nervous system plasticity: activity-dependent myelination. Nature Reviews Neuroscience, 16(12), 756–767. https://doi.org/10.1038/nrn4023 

Xin, W., & Chan, J.R. (2020). Myelin plasticity: sculpting circuits in learning and memory. Nature Reviews Neuroscience, 21, 682–694. https://doi.org/10.1038/s41583-020-00379-8 

Tremblay, S.A., Jäger, A.-T., Huck, J., Giacosa, C., Beram, S., Schneider, U., Grahl, S., Villringer, A., Tardif, C.L., Bazin, P.-L., Steele, C.J., & Gauthier, C.J. (2021). White matter microstructural changes in short-term learning of a continuous visuomotor sequence. Brain Structure and Function, 226, 2061–2077. https://doi.org/10.1007/s00429-021-02267-y 

Liu, C.N., & Chambers, W.W. (1958). Intraspinal sprouting of dorsal root axons: development of new collaterals and preterminals following partial denervation of the spinal cord in the cat. AMA Archives of Neurology and Psychiatry, 79(1), 46–61. https://doi.org/10.1001/archneurpsyc.1958.02340010050005 

Price, R.B., & Duman, R. (2020). Neuroplasticity in cognitive and psychological mechanisms of depression: an integrative model. Molecular Psychiatry, 25, 530–543. https://doi.org/10.1038/s41380-019-0615-x

Sarriés-Serrano, U., Miquel-Rio, L., Santana, N., Paz, V., Sancho-Alonso, M., Callado, L.F., Meana, J.J., & Bortolozzi, A. (2025). Impaired unfolded protein response, BDNF and synuclein markers in the dorsolateral prefrontal cortex and caudate nucleus postmortem of patients with depression and Parkinson’s disease. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 128, 111299. https://doi.org/10.1016/j.pnpbp.2025.111299 

Herzberg, M.P., Nielsen, A.N., Luby, J., & Sylvester, C.M. (2024). Measuring neuroplasticity in human development: the potential to guide the type and timing of mental health interventions. Neuropsychopharmacology. Published online August 5, 2024. https://doi.org/10.1038/s41386-024-01947-7 

Kim, B., Kim, J.-S., Youn, B., & Changjong, L. (2023). Dopamine depletion alters neuroplasticity-related signaling in the rat hippocampus. Experimental Neurobiology, 32(6), 557–567. https://doi.org/10.1080/19768354.2023.2294308 

Mougeot, J.-L.C., Hirsch, M.A., Stevens, C.B., & Mougeot, F.K.B. (2016). Oral biomarkers in exercise-induced neuroplasticity in Parkinson’s disease. Oral Diseases, 22(8), 745–753. https://doi.org/10.1111/odi.12463 

De Jager, J.E., Boesjes, R., Roelandt, G.H.J., Koliaki, I., Sommer, Í.E.C., Schoevers, R.A., & Nuninga, J.O. (2024). Shared effects of electroconvulsive shocks and ketamine on neuroplasticity: a systematic review of animal models of depression. Neuroscience & Biobehavioral Reviews, (105796). https://doi.org/10.1016/j.neubiorev.2024.105796 

Hall, Z.J., & Tropepe, V. (2018). Movement maintains forebrain neurogenesis via peripheral neural feedback in larval zebrafish. eLife, 7, e31045. https://doi.org/10.7554/eLife.31045 

Calvo‑Ochoa, E., & Byrd‑Jacobs, C.A. (2019). The olfactory system of zebrafish as a model for the study of neurotoxicity and injury: implications for neuroplasticity and disease. International Journal of Molecular Sciences, 20(7), 1639. https://doi.org/10.3390/ijms20071639