Monocular deprivation in adult mice alters visual acuity and single-unit activity

Abstract

It has been discovered recently that monocular deprivation in young adult mice induces ocular dominance plasticity (ODP). This contradicts the traditional belief that ODP is restricted to a juvenile critical period. However, questions remain. ODP of young adults has been observed only using methods that are indirectly related to vision, and the plasticity of young adults appears diminished in comparison with juveniles. Therefore, we asked whether the newly discovered adult ODP broadly reflects plasticity of visual cortical function and whether it persists into full maturity. Single-unit activity is the standard physiological marker of visual cortical function. Using a more optimized protocol for recording single-units, we find evidence of adult ODP of single-units and show that it is most pronounced in deep cortical layers. Furthermore, using visual evoked potentials (VEP), we find that ODP is equally robust in young adults and mature adults and is observable after just one day of monocular deprivation. Finally, we find that monocular deprivation in adults changes spatial frequency thresholds of the VEP, decreasing the acuity of the deprived pathway and improving the acuity of the non-deprived pathway. Thus, in mice, the primary visual cortex is capable of remarkable adaptation throughout life.

Neural mechanisms of recovery following early visual deprivation

“…First, the potential for experience-dependent modification of the visual cortex in adulthood seems generally greater in rodents than in carnivores or primates (Sawtell et al 2003;Pham et al 2004;Fischer et al 2007). Second, as an animal model of human amblyopia, rodents cannot be employed without reservations, since even longterm form deprivation causes only moderate reductions in acuity of only an octave (logMAR 0.3) or less (Pizzorusso et al 2006).…”

Adult visual experience promotes recovery of primary visual cortex from long-term monocular deprivation

“…MD was performed under isoflurane anesthesia (Attane 1%-2%, Minrad), as described previously Pham et al 2004;Fischer et al 2007). Following opening of the deprived eye, a sterile ophthalmic lubricating ointment was applied daily to keep the eye from drying out.…”

“…using standard methods Pham et al 2004;Fischer et al 2007). Briefly, PowerDiva software from Anthony Norcia (Smith Kettlewell Institute of Visual Sciences) was used for data acquisition and analysis.…”

“…Analyses of the raw data were performed using PowerDiva software, as described previously Pham et al 2004;Fischer et al 2007). Spatial frequency thresholds were derived using the algorithm basically as described by Fischer et al (2007).…”

“…A growing number of studies have found morphological and functional changes in motor and sensory neocortex as a result of altered experience or injury in adulthood (Merzenich et al 1984;Jenkins et al 1990;Allard et al 1991;Fox 1992Fox , 1994Skibinska et al 2000;Qi et al 2000;Kaas and Qi 2004). Even in V1, our laboratory and others have found that ocular dominance (OD) plasticity exists in adult mice and rats (Guire et al 1999;Sawtell et al 2003;Pham et al 2004;Lickey et al 2004;Tagawa et al 2005;Hofer et al 2006;Fischer et al 2007). These findings suggest the possibility that the effects of prolonged deprivation imposed early in life can be ameliorated by experience in adulthood.…”