Category learning in rodents using touchscreen‐based tasks

Abstract

Categorization is a fundamental cognitive function that organizes our experiences into meaningful “chunks.” This category knowledge can then be generalized to novel stimuli and situations. Multiple clinical populations, including people with Parkinson's disease, amnesia, autism, ADHD and schizophrenia, have impairments in the acquisition and use of categories. Although rodent research is well suited for examining the neural mechanisms underlying cognitive functions, many rodent cognitive tasks have limited translational value. To bridge this gap, we use touchscreens to permit greater flexibility in stimulus presentation and task design, track key dependent measures, and minimize experimenter involvement. Touchscreens offer a valuable tool for creating rodent cognitive tasks that are directly comparable to tasks used with humans. Touchscreen tasks are also readily used with cutting‐edge neuroscientific methods that are difficult to do in humans such as optogenetics, chemogenetics, neurophysiology and calcium imaging (using miniscopes). In this review, we show advantages of touchscreen‐based tasks for studying category learning in rats. We also address multiple factors for consideration when designing category learning tasks, including the limitations of the rodent visual system, experimental design, and analysis strategies.

Prelimbic cortex maintains attention to category-relevant information and flexibly updates category representations

“…This procedure was repeated daily until the rat consumed all pellets within 15 min, which usually took about 7 days. After cart training, rats underwent a daily shaping procedure to learn to interact with the touchscreen ( Broschard, Kim, Love, & Freeman, 2020 ). This procedure included three separate phases; each phase was incrementally similar to the trial sequence used during training and testing sessions.…”

“…Category tasks were created by placing bivariate normal distributions on this transformed stimulus space ( Fig. 1 B; Category A: µ X = 30, σ X = 2.5, µ Y = 50, σ Y = 20; Category B: µ X = 70, σ X = 2.5, µ Y = 50, σ Y = 20; Broschard et al, 2019 , Broschard et al, 2020 , O’Donoghue et al, 2020 ). Each distribution constituted a category, and each point within a distribution represented a category stimulus.…”

“…Rats were randomly assigned to learn one of the four category tasks ( Broschard et al, 2019 , Broschard et al, 2020 ). Rats were given 15 training sessions; each session contained 80 training trials.…”

Concurrent electrophysiological recording and cognitive testing in a rodent touchscreen environment

“…Second, despite its frequent use in human studies of cognitive control, a rodent flanker task with comprehensive similarities to human protocols is not available (however, see 23 , 41 – 44 for innovative rodent flanker task analogs). Third, the use of touchscreen apparatus enables precise control of various dimensions of visual stimuli to facilitate stimulus control 45 , 46 , which is critical for both target and flanker stimuli in rats given their notoriously poor visual acuity. Therefore, the present studies first evaluated the ability of rats to discriminate a variety of touchscreen-based visual stimuli (Experiment 1A) to subsequently serve in test sessions with congruent and incongruent flankers (Experiment 1B).…”

Touchscreen response technology and the power of stimulus‐based approaches in freely behaving animals

“…In a final paper in this Special Issue, 15 Broschard and colleagues review rat models of category learning using touchscreen technology. The flexibility of visual stimulus presentation allows the manipulation and precise quantification of stimulus dimensions and generalization in category learning.…”