Abstract
The primary visual cortex (V1) is widely used to study brain plasticity, which is not only crucial for normal brain function, such as learning and memory, but also for recovery after brain injuries such as stroke. In standard cage (SC) raised mice, experience-dependent ocular dominance (OD) plasticity in V1 declines with age and is compromised by a lesion in adjacent and distant cortical regions. In contrast, mice raised in an enriched environment (EE), exhibit lifelong OD plasticity and are protected from losing OD plasticity after a stroke-lesion in the somatosensory cortex. Since SC mice with an access to a running wheel (RW) displayed preserved OD plasticity during aging, we investigated whether physical exercise might also provide a plasticity promoting effect after a cortical stroke. To this end, we tested if adult RW-raised mice preserved OD plasticity after stroke and also if short-term running after stroke restored OD plasticity to SC mice. Indeed, unlike mice without a RW, adult RW mice continued to show OD plasticity even after stroke, and a 2 weeks RW experience after stroke already restored lost OD plasticity. Additionally, the experience-enabled increase of the spatial frequency and contrast threshold of the optomotor reflex of the open eye, normally lost after a stroke, was restored in both groups of RW mice. Our data suggest that physical exercise alone can not only preserve visual plasticity into old age, but also restore it after a cortical stroke.
Highlights
Neuronal plasticity in the adult brain is indispensable to allow adaptive changes during aging and after lesions
We analyzed whether voluntary physical exercise is beneficial for rescuing plasticity after a cortical stroke, in addition to being crucial for preserving visual plasticity into adulthood
Our results provide clear evidence that this was the case: raising mice in standard cage (SC) equipped with a running wheel (RW) prevented impairments of visual plasticity after a stroke in S1-in contrast to SC-mice (Greifzu et al, 2011; Pielecka-Fortuna et al, 2015b)
Summary
Neuronal plasticity in the adult brain is indispensable to allow adaptive changes during aging and after lesions. A well-known model system to study experience-dependent circuit changes is ocular dominance (OD) plasticity in the primary visual cortex (V1): occluding one eye of vision for a couple of days induces an OD shift towards the open eye. This phenomenon was first described in kittens (Wiesel and Hubel, 1963) and later in mice (Dräger, 1978). Running Rescues Visual Plasticity after Stroke housing groups) and cognitive (regularly changed labyrinths or toys) stimulation, can overcome plasticity limitations (Sale et al, 2007; Baroncelli et al, 2010; Scali et al, 2012) and preserve a lifelong OD-plasticity in mice (Greifzu et al, 2014, 2016a). Even short-term running, just during the 7-day MD period restored OD-plasticity to adult SC-raised mice
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