Vibrissa-Based Object Localization in Head-Fixed Mice

Abstract

Linking activity in specific cell types with perception, cognition, and action, requires quantitative behavioral experiments in genetic model systems such as the mouse. In head-fixed primates, the combination of precise stimulus control, monitoring of motor output, and physiological recordings over large numbers of trials are the foundation on which many conceptually rich and quantitative studies have been built. Choice-based, quantitative behavioral paradigms for head-fixed mice have not been described previously. Here, we report a somatosensory absolute object localization task for head-fixed mice. Mice actively used their mystacial vibrissae (whiskers) to sense the location of a vertical pole presented to one side of the head and reported with licking whether the pole was in a target (go) or a distracter (no-go) location. Mice performed hundreds of trials with high performance (Ͼ90% correct) and localized to Ͻ0.95 mm (Ͻ6°of azimuthal angle). Learning occurred over 1-2 weeks and was observed both within and across sessions. Mice could perform object localization with single whiskers. Silencing barrel cortex abolished performance to chance levels. We measured whisker movement and shape for thousands of trials. Mice moved their whiskers in a highly directed, asymmetric manner, focusing on the target location. Translation of the base of the whiskers along the face contributed substantially to whisker movements. Mice tended to maximize contact with the go (rewarded) stimulus while minimizing contact with the no-go stimulus. We conjecture that this may amplify differences in evoked neural activity between trial types.

Behaviour-dependent recruitment of long-range projection neurons in somatosensory cortex

“…We used an identical trial structure to the texturediscrimination task to control for non-sensory differences across tasks. Mice could reach similar performance levels 22 compared to texture S1 during texture discrimination. a, Retrograde labelling of S2P and M1P neurons in S1 by AAV6-Cre and CTB-Alexa647 injection, respectively.…”

“…Indeed, fine-scale analysis of principal whisker kinematics showed that sandpaper and pole contacts showed distinct kinematic features. Changes in whisker curvature that relate to contact forces 22 as well as the frequency of high acceleration-velocity 'slip' events associated with texture coding 11,12 were greater during texture discrimination compared to object localization (P , 0.001, Kolmogorov-Smirnov test; Fig. 4a and Supplementary Fig.…”

“…We reasoned that a contrasting task with different requirements could result in a different set of activation patterns between M1P and S2P neurons. To address this, we trained a second set of mice (n 5 4) to a variation of a head-fixed, go/no-go object-localization task (also known as 'object detection with distractors' 22 ) previously reported to activate cortical circuits between S1 and M1 (refs 16, 18, 19, 23, 24) (Fig. 3a, b).…”

Active vibrissal sensing in rodents and marsupials

“…In situations where there are unilateral contacts or where bilateral contacts are not simultaneous, RCP also appears to induce asynchronies in the relative timing of whisker movements on the two sides of the snout. Interestingly, when trained to make a specific discrimination, animals may modify this aspect of control and allow the whiskers to bend more strongly [28]. Further, when the whiskers touch a non-attended surface they may also show more pronounced bending [16], suggesting that RCP is not simply the consequence of some low-level reflex, but is related in some way to the current goals and focus of the animal.…”

Design and performance of an ultra-flexible two-photon microscope for in vivo research

“…The head fixed preparation, known for its wellcontrolled psychophysical conditions (stimulus delivery and response monitoring) in nonhuman primate studies, has been adapted to rodents by numerous groups [14][15][16][17][18][19]. Twophoton imaging of lateral cortical regions in awake, head-fixed animals poses a problem, since tilting the animal to adjust the imaging plane to be tangential to the cortical surface should be avoided.…”