Behavioral and Neural Bases of Tactile Shape Discrimination Learning in Head-Fixed Mice

Sensorimotor strategies and neuronal representations for shape discrimination

“…In freely moving animals, it is difficult to track the whiskers (Petersen et al, 2020;Voigts et al, 2008) and ensure that whiskers alone are used, instead of vision, olfaction, or touch with skin (Mehta et al, 2007). Head fixation enables better whisker tracking and stimulus control, but most tasks for head-fixed mice focus on spatially simple features, like the location or orientation of a pole or the texture of sandpaper (Chen et al, 2013;Kim et al, 2020;O'Connor et al, 2010a). Indeed, the head-fixed mouse is often trimmed to a single whisker, though a few studies have considered multi-whisker behaviors (Brown et al, 2021;Celikel and Sakmann, 2007;Knutsen et al, 2006;Pluta et al, 2017).…”

Learning enhances encoding of time and temporal surprise in primary sensory cortex

“…However, there remains disagreement in the field on this issue: some studies have indeed found learning-related functional changes 21 , while other studies observed more stability across learning. Kim et al (2020) observed a high variability and turnover in the responsiveness and selectivity of barrel cortical cells while mice learned an object-angle discrimination task, but those authors and others 24,25 reported that the proportion of responsive cells remained unchanged across learning. Interestingly, Makino & Komiyama (2015) find that the number of layer 2/3 responsive cells decreases with learning 19 , though that study is in a different modality, and in an aversive conditioning task, which may explain the discrepancy.…”

“…Yet, the degree to which learning-related plasticity occurs in primary somatosensory cortex (S1), and how it manifests, remains unclear: in some cases, stimulus representations have been found to remain stable 24 , with little plasticity 25 .…”

Emerging experience-dependent dynamics in primary somatosensory cortex reflect behavioral adaptation

“…This discrepancy could be a result of the complexity of the chosen behavioral paradigm or it could be because cortical signals are highly dynamic and context driven. More recent findings have shown that signals in primary somatosensory cortex can enhance stimulus selectivity with behavioral training 13 , fluctuate according to the behavioral state 14 , or even remap depending on downstream signals 15 . Together, these findings have opened up many questions and they motivate us to believe that neuronal signals in primary sensory areas may be highly dynamic, context or experience dependent, and part of an adaptive framework.…”

“…It is likely that primary cortical signals are highly dynamic and context driven, depending on the implemented behavioral paradigm. Signals in primary somatosensory cortex can: enhance stimulus selectivity with behavioral training 13 , fluctuate according to the behavioral state 14 , or even remap depending on downstream signals 15 . Neuronal signals in primary sensory areas may be highly dynamic, context or experience dependent, and part of an adaptive framework.…”