Different Forms of Plasticity Interact in Adult Humans

Abstract

Neuroplasticity is maximal during development and declines in adulthood, especially for sensory cortices. On the other hand, the motor and prefrontal cortices retain plasticity throughout the lifespan. This difference has led to a modular view of plasticity in which different brain regions have their own plasticity mechanisms that do not depend or translate on others. Recent evidence shows that visual and motor plasticity share common neural mechanisms (e.g. GABAergic inhibition), indicating a possible link between these different forms of plasticity, however, the interaction between visual and motor plasticity has never been tested directly. Here we show that when visual and motor plasticity are elicited at the same time in adult humans, visual plasticity is impaired, while motor plasticity is spared. Moreover, simultaneous activation of working memory and visual plasticity also leads to impairment in visual plasticity. These unilateral interactions between visual, working memory and motor plasticity demonstrate a clear link between these three forms of plasticity. We conclude that local neuroplasticity in separate systems might be regulated globally, to preserve overall homeostasis in the brain.Significance statementHere we investigated for the first time the interaction between visual plasticity, motor plasticity, and working memory in a group of adult human volunteers. We found a unilateral interaction between these forms of plasticity: when homeostatic visual plasticity is induced at the same time as motor plasticity or working memory, visual plasticity is disrupted. Our results indicate the existence of a global regulation mechanism in the brain linking different forms of plasticity. Understanding the link between different forms of plasticity is crucial for the development of new neuro-rehabilitative interventions on neurological diseases and brain injury.

Phosphene and Motor Transcranial Magnetic Stimulation Thresholds Are Correlated: A Meta-Analytic Investigation

“…It is also possible that motor and visual areas have different excitability thresholds. For example, even though brain plasticity is presumed to be globally controlled through GABAergic processes in the visual (Greifzu et al, 2014; Harauzov et al, 2010) and motor (McLean et al, 1996; Schabrun & Hodges, 2012; Thapa et al, 2021; Ziemann et al, 2001) system, it has been shown that when plasticity is elicited simultaneously for the visual and motor system, motor plasticity may remain intact at the cost of visual plasticity (Sarı & Lunghi, 2023). However, the consistent findings of a correlation between PT and rMT across all our analyses, indicate that, even if qualitatively different, the two cortical excitability measures are indeed described by a linear relationship.…”

Measuring the reliability of binocular rivalry

“…Forty volunteers, mean age 28.6 ± 0.72 years, 25 females (including authors I.S. and C.L) took part in experiment 1 ( Sarı & Lunghi, 2023 ). Thirty-three volunteers, mean age 25.8 ± 0.11 years, 18 females (including authors M.A.…”

Exercise-induced neuroplasticity: a new perspective on rehabilitation for chronic low back pain

“…In fact, neuroplasticity exhibits stage-specific and modular differences. During human development, neuroplasticity is strongest; in adulthood, certain brain regions such as the sensory cortex experience a decrease in plasticity, but areas like the motor cortex, prefrontal cortex, and hippocampus maintain a high level of plasticity ( Karni et al, 1995 ; Sarı and Lunghi, 2023 ).…”

“…Cortical excitation and inhibition (E/I) balance is one of the important mechanisms for maintaining its internal homeostasis and normal function. Studies have shown that patients with CLBP have disrupted E/I balance in the motor and prefrontal cortices ( Sarı and Lunghi, 2023 ), and the resulting excitability changes in the related cortices and related transmission pathways may be one of the important reasons for the persistence of pain ( Parker et al, 2016 ; Schabrun et al, 2017 ). Cortical excitability includes two forms: short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF).…”