Scanned optogenetic control of mammalian somatosensory input to map input-specific behavioral outputs

Abstract

Somatosensory stimuli guide and shape behavior, from immediate protective reflexes to longer-term learning and higher-order processes related to pain and touch. However, somatosensory inputs are challenging to control in awake mammals due to the diversity and nature of contact stimuli. Application of cutaneous stimuli is currently limited to relatively imprecise methods as well as subjective behavioral measures. The strategy we present here overcomes these difficulties, achieving 'remote touch' with spatiotemporally precise and dynamic optogenetic stimulation by projecting light to a small defined area of skin. We mapped behavioral responses in freely behaving mice with specific nociceptor and low-threshold mechanoreceptor inputs. In nociceptors, sparse recruitment of single action potentials shapes rapid protective pain-related behaviors, including coordinated head orientation and body repositioning that depend on the initial body pose. In contrast, activation of low-threshold mechanoreceptors elicited slow-onset behaviors and more subtle whole-body behaviors. The strategy can be used to define specific behavioral repertoires, examine the timing and nature of reflexes, and dissect sensory, motor, cognitive and motivational processes guiding behavior.

Reproducible and fully automated testing of nocifensive behavior in mice

“…To date, all reports of withdrawal from transcutaneous optogenetic stimulation used a pulse of blue light or pulse trains, 28 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 with one exception, which used sustained light to activate keratinocytes. 50 Yet different photostimulus waveforms may reveal different information about the neural control of behavior (see discussion ), so testing with different waveforms will provide greater information than testing with any one waveform.…”

Reproducible and fully automated testing of nocifensive behavior in mice

“…Past studies have varied the number, rate, or intensity of pulses, but in the suprathreshold regime, with consequences for the amount of licking, jumping, or vocalization. To our knowledge, only one previous study (Iyer et al, 2016) 2021) recently described a device that uses galvanometric mirrors to direct photostimuli and high-speed substage video to measure withdrawal (Schorscher-Petcu et al, 2021). Their device is very elegant but reliance on high-speed video to detect withdrawals likely precludes closed-loop control, and nor is their device fully automated or high-throughput.…”

“…To date, all reports of withdrawal from transcutaneous optogenetic stimulation used a pulse of blue light or a train of pulses (Abdo et al, 2019;Arcourt et al, 2017;Barik et al, 2018;Beaudry et al, 2017;Browne et al, 2017;Chamessian et al, 2019;Daou et al, 2013;Dhandapani et al, 2018;Iyer et al, 2014;Schorscher-Petcu et al, 2021;Sharif et al, 2020;Tashima et al, 2018;Warwick et al, 2021), with one exception, which used sustained light to activate keratinocytes (Baumbauer et al, 2015) (see also Discussion). Pulsed stimuli evoke precisely timed spikes (Browne et al, 2017), leading to spikes that are synchronized across co-activated neurons (Ratté et al, 2013), which may not accurately reflect the spiking patterns evoked by many types of somatosensory stimuli.…”

Open-source tools for behavioral video analysis: Setup, methods, and best practices

“…Pose estimation methods have been crucial for several recent publications on topics as diverse as tracking fluid consumption to understand the neural coding of reward prediction errors ( Ottenheimer et al, 2020 ), accounting for the effects of wind on the behavior of Drosophila ( Okubo et al, 2020 ), understanding the contributions of tactile afferents and nociceptors to the perception of touch in freely moving mice ( Schorscher-Petcu et al, 2021 ), understanding interactions between tactile processing by the rodent whisker system and its ability to guide locomotion ( Warren et al, 2021 ), and measuring the relationship between eye movements and neural activity in freely behaving rodents ( Keshavarzi et al, 2022 ). While a number of studies are emerging that take advantage of methods for pose estimation, there is still not enough widespread adoption of the methods across the research community, perhaps in part due to the technical nature of collecting high-quality video recordings as well as setting up and using methods for pose estimation.…”