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title: "The Brain Can Change: What Neuroplasticity Research Actually Tells Us" abstract: "The idea that the adult brain can reorganize itself — forming new synaptic connections, altering neural pathways, and even generating new neurons — overturned a long-held assumption in neuroscience that the brain was fixed after early childhood. The evidence for neuroplasticity is strong, but popular accounts have substantially overstated what it means in practice. Understanding what the brain can and cannot change, and under what conditions, is essential for realistic expectations about learning, recovery, and cognitive aging." topic: health author: nonacademicresearch.org Editorial date: 2026-05-09

The Brain Can Change: What Neuroplasticity Research Actually Tells Us

Abstract

The idea that the adult brain can reorganize itself — forming new synaptic connections, altering neural pathways, and even generating new neurons — overturned a long-held assumption in neuroscience that the brain was fixed after early childhood. The evidence for neuroplasticity is strong, but popular accounts have substantially overstated what it means in practice. Understanding what the brain can and cannot change, and under what conditions, is essential for realistic expectations about learning, recovery, and cognitive aging.

Background

For most of the twentieth century, the dominant view in neuroscience was that the adult brain was essentially fixed. Development occurred during childhood and adolescence, after which the neural architecture was set — a view captured in the dictum attributed to William James (1890) that after a certain age, the nervous system becomes "set like plaster." This view shaped clinical expectations: stroke damage, for example, was considered permanent beyond early recovery windows.

The picture changed dramatically in the second half of the century. A series of convergent discoveries — from studies of sensory cortex reorganization in animals to observations of recovery in stroke patients to brain imaging studies of skilled practitioners — established that the adult brain continues to modify its structure and function in response to experience. The term neuroplasticity became a popular framework for understanding these findings.

The challenge is that neuroplasticity as a concept covers a range of different phenomena — from molecular changes at synapses lasting minutes, to structural reorganization of cortical maps lasting decades — and popular accounts often conflate them, creating unrealistic expectations about what "brain training," skill acquisition, or recovery programs can achieve.

The Evidence

Cortical Map Reorganization

Some of the most compelling early evidence for adult plasticity came from studies of sensory cortex reorganization after injury. Merzenich et al. (1984, Journal of Neuroscience) showed in primates that amputating a finger caused the cortical area previously devoted to that finger to be taken over by adjacent fingers within weeks. The same group later demonstrated that extensive practice of a motor task could expand the cortical representation of the involved fingers in both animals and humans.

These findings were extended to humans by Pascual-Leone et al. (1995, Journal of Neurophysiology), who showed that sighted individuals learning to read Braille showed rapid expansion of the brain region representing the reading finger — changes detectable within days of training.

The London Taxi Driver Study

One of the most widely cited human plasticity studies is Maguire et al. (2000, PNAS), which examined London taxi drivers — who undergo years of intensive navigation training to memorize the city's approximately 25,000 streets. Structural MRI revealed that taxi drivers had significantly larger posterior hippocampi than matched controls, and the size increase correlated with years of experience. A follow-up longitudinal study (Woollett & Maguire, 2011, Current Biology) randomly tracked aspiring taxi drivers through their training period: those who passed the licensing exam showed hippocampal growth; those who failed or dropped out did not. This is among the strongest human evidence that experience can structurally change the adult brain.

Stroke Recovery and Rehabilitation

Neuroplasticity has important implications for stroke rehabilitation. Taub et al. (1993, Science) demonstrated in primates that restraining the unaffected limb after a stroke — forcing use of the impaired limb — produced functional recovery that did not occur without such constraint. This finding was translated into Constraint-Induced Movement Therapy (CI therapy) for humans, which has since been validated in multiple randomized controlled trials. A meta-analysis by Corbetta et al. (2015, European Journal of Physical and Rehabilitation Medicine) found that CI therapy produced significantly better upper limb motor recovery than conventional therapy.

Adult Neurogenesis

A particularly striking claim — that the adult brain generates new neurons — emerged from studies of the hippocampus. Eriksson et al. (1998, Nature Medicine) provided direct evidence of adult neurogenesis in the human hippocampus by examining postmortem brain tissue from cancer patients who had received bromodeoxyuridine (BrdU), a marker of cell division, during their treatment. New neurons were found in the dentate gyrus of the hippocampus.

The functional role of this adult neurogenesis remains debated. Animal models strongly link hippocampal neurogenesis to memory formation and stress resilience, and aerobic exercise reliably increases neurogenesis in rodents. Whether and how this scales to meaningful cognitive benefits in humans remains an active research area.

What "Brain Training" Cannot Do

The popular brain-training industry — programs claiming to improve general intelligence or prevent cognitive decline through targeted computer games — has been substantially deflated by the evidence. Simons et al. (2016, Psychological Science in the Public Interest) conducted a comprehensive review and concluded that there is little evidence that commercial brain-training games transfer to meaningful improvements in everyday cognitive functioning or reduce dementia risk. Near-transfer (improvement on tasks similar to those practiced) is real; far-transfer (improvement on general cognition or unrelated tasks) is not reliably established.

Counterarguments

Some researchers dispute the magnitude of adult neurogenesis in humans, with a high-profile 2018 study in Nature by Sorrells et al. failing to find new neurons in adult hippocampal tissue and arguing the earlier findings were methodological artifacts. This controversy remains unresolved.

There is also ongoing debate about the practical ceiling of plasticity in the adult brain compared to the developing brain. Critical periods — windows of enhanced plasticity during early life for language, vision, and other systems — appear to be real, and while the adult brain retains plasticity, it is generally less extensive than during development.

What We Can Conclude

The evidence that the adult brain can change in response to experience is robust and comes from multiple methodologies including structural imaging, electrophysiology, and natural experiments. These changes have practical implications for rehabilitation, skill learning, and potentially cognitive aging.

The popular extrapolation — that any mental activity will improve cognition, or that targeted training can substantially boost general intelligence — is not supported. Neuroplasticity describes real phenomena at the cellular and circuit level; it does not mean the brain is infinitely malleable or that commercial brain-training programs deliver on their claims.

The actionable evidence points toward specific, demanding practice in a skill domain (structural change follows); aerobic exercise (the strongest behavioral driver of hippocampal neurogenesis in animals); and intensive, constraint-based rehabilitation after injury (for maximizing recovery).

References

• Corbetta, D., et al. (2015). Constraint-induced movement therapy in stroke patients: Systematic review and meta-analysis. European Journal of Physical and Rehabilitation Medicine, 51(4), 473–494.
• Eriksson, P.S., et al. (1998). Neurogenesis in the adult human hippocampus. Nature Medicine, 4(11), 1313–1317. https://doi.org/10.1038/3305
• Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers. PNAS, 97(8), 4398–4403. https://doi.org/10.1073/pnas.070039597
• Merzenich, M.M., et al. (1984). Somatosensory cortical map changes following digit amputation in adult monkeys. Journal of Comparative Neurology, 224(4), 591–605. https://doi.org/10.1002/cne.902240408
• Pascual-Leone, A., et al. (1995). Modulation of muscle responses evoked by transcranial magnetic stimulation during the acquisition of new fine motor skills. Journal of Neurophysiology, 74(3), 1037–1045. https://doi.org/10.1152/jn.1995.74.3.1037
• Simons, D.J., et al. (2016). Do "brain-training" programs work? Psychological Science in the Public Interest, 17(3), 103–186. https://doi.org/10.1177/1529100616661983
• Sorrells, S.F., et al. (2018). Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults. Nature, 555(7696), 377–381. https://doi.org/10.1038/nature25975
• Taub, E., et al. (1993). Technique to improve chronic motor deficit after stroke. Archives of Physical Medicine and Rehabilitation, 74(4), 347–354.
• Woollett, K., & Maguire, E.A. (2011). Acquiring "the Knowledge" of London's layout drives structural brain changes. Current Biology, 21(24), 2109–2114. https://doi.org/10.1016/j.cub.2011.11.018