Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB299

Poster Communications

Differential selectivity and distributed pattern of S1 neurons for multiple features of touch and pain mechanosensations

Y. Kim3, C. Kim4, H. Yoon2, S. Kim3, S. Kim1,2

1. Department of Physiology, Kyung Hee University College of Korean Medicine, Seoul, Korea (the Republic of). 2. Department of Science in Korean Medicine, Kyung Hee University Graduate School, Seoul, Korea (the Republic of). 3. Department of Physiology, Seoul National University School of Medicine, Seoul, Korea (the Republic of). 4. Department of Physiology, Gacheon University College of Korean Medicine, Kyunggi-do, Korea (the Republic of).

The primary somatosensory (S1) cortex plays an important role in the perception and discrimination of touch and pain mechanosensations. Traditionally, neurons in the somatosensory system including S1 cortex have been classified into low/high threshold (non-nociceptive/nociceptive) and wide dynamic range (convergent) neurons by their electrophysiological responses to innocuous and noxious stimuli, such as brush-stroke and forceps-pinch. Besides this ‘modality' (innocuous/noxious) feature, each stimulus also includes other stimulus features: ‘texture' (brush hairs/forceps steel arms), ‘dynamics' (dynamic stroke/static press) and ‘intensity' (weak/strong). However, it remains unknown how S1 neurons comprehensively encode such diverse features of cutaneous mechanical stimuli at single cell and population levels. Using in vivo two-photon Ca2+ imaging in lightly anesthetized (1% isoflurane) mice expressing GCaMP6s in the layer 2/3 neurons of S1 cortex, we identified clearly separated response patterns of S1 neural population with distinct tuning properties of individual cells to texture, dynamics and modality features of the cutaneous stimuli. Among cells other than broadly tuned neurons, the majority showed highly selective response to the difference in texture, but low selectivity to the difference in dynamics or modality with slightly more specificity to dynamics while they could be decoded using the response patterns of neural populations. In addition, more neurons are recruited and stronger Ca2+ responses are evoked as the intensity of forceps-pinch is gradually increased (<2g, 100g, 200g, 300g pressure), showing a non-linear positive relationship with steep and gentle slopes. Our results suggest that S1 neurons inclusively encode multiple features of cutaneous mechanosensations through differential selectivity and distributed pattern responses, and raise a caution about ignoring other aspects of the sensory stimuli when classifying neurons by a single stimulus feature.

Where applicable, experiments conform with Society ethical requirements