Learning and cognitive flexibility in two-choice visual discrimination tasks are similar in juvenile and adult sheep

The sheep is a valuable species for studying neurodevelopment. The two-choice visual discrimination-reversal task is a widely used set-shifting task assessing function of fronto-striatal brain networks but whether lambs can complete this task has not yet been evaluated. Here we compared cognitive performance in mature adult Texel ewes (n = 12, 1.4-6.4 years old at start of training) and their weaned Texel lambs (n = 5 females, n = 8 non-castrated males, 4.1-5.5 months old) during training and testing in visual attention and two-choice discrimination-reversal tasks within a semi-automated operant system. Adult ewes completed the visual attention task in fewer sessions than lambs ( p = 0.030) and a greater proportion of ewes than lambs completed the visual attention task within 10 training sessions (ewes: 8/12; lambs: 3/13; p = 0.028). Numbers of trials taken to reach the learning criterion in the two-choice visual discrimination-reversal task, however, did not differ between adult ewes and lambs during the first acquisition ( p = 0.494), or the first ( p = 0.955) or second reversal ( p = 0.314) phases. Adult ewes completed the second acquisition phase in fewer trials than lambs ( p = 0.031). This study confirms that learning and cognitive flexibility can be evaluated using a two-choice visual discrimination-reversal task in growing lambs as well as adult ewes, but that visual attention may take longer to achieve in lambs. This allows longitudinal assessment of the impacts of pregnancy exposures and responses to interventions in sheep models. • Cognitive tests to assess brain function in sheep need validation in juveniles (lambs) • Visual attentiveness was acquired more rapidly in adult ewes than lambs • Ewes and their lambs performed similarly in two-choice visual discrimination tests • Our results enable studies of brain function in sheep in juveniles as well as adults