Abstract
Amblyopia is a developmental disorder that results in a wide range of visual deficits. Although brain plasticity is limited in adults, one approach to recovering vision in adults with amblyopia is perceptual learning (PL). Recent evidence suggests that neuromodulators may enhance adult plasticity. Here we asked whether donepezil, a cholinesterase inhibitor, can enhance PL in adults with amblyopia. Nine adults with amblyopia were first trained on a single-letter identification task (letters were presented at low contrast) while taking a daily dose (5 mg) of donepezil throughout training. Following 10,000 trials of training, participants showed improved contrast sensitivity in identifying single letters. However, the magnitude of improvement was no greater than, and the rate of improvement was slower than that obtained in a previous study in which adults with amblyopia were trained using identical experimental protocols but without donepezil (Chung, Li & Levi, 2012). In addition, the transfer of learning to a size-limited (acuity) or to a spacing-limited (crowding) task was less than that found in the previous study with no donepezil administration. After an interval of several weeks, six of these participants returned for a second training task — flanked letter identification (identifying crowded letters) — also with concurrent donepezil administration. Following another 10,000 trials of training, only one observer showed learning for this subsequent training task, which has been previously shown to be highly amenable to PL in adults with amblyopia. Control studies showed that the lack of a learning effect on the flanked letter identification task was not due to either the order of the two training tasks or the use of a sequential training paradigm. Our results reveal that donepezil does not enhance or speed up PL of single-letter identification in adults with amblyopia, and importantly, may even block participants' PL of a task related to crowding.
Meeting abstract presented at VSS 2017