In the rodent whisker system, a key model for neural processing and behavioral choices during active sensing, whisker motion is increasingly recognized as only part of a broader motor repertoire employed by rodents during active touch. In particular, recent studies suggest whisker and head motions are tightly coordinated. However, conditions governing the selection and temporal organization of such coordinated sensing strategies remain poorly understood. We videographically reconstructed head and whisker motions of freely moving mice searching for a randomly located rewarded aperture, focusing on trials in which animals appeared to rapidly "correct" their trajectory under tactile guidance. Mice orienting after unilateral contact repositioned their whiskers similarly to previously reported head-turning asymmetry. However, whisker repositioning preceded head turn onsets and was not bilaterally symmetric. Moreover, mice selectively employed a strategy we term contact maintenance, with whisking modulated to counteract head motion and facilitate repeated contacts on subsequent whisks. Significantly, contact maintenance was not observed following initial contact with an aperture boundary, when the mouse needed to make a large corrective head motion to the front of the aperture, but only following contact by the same whisker field with the opposite aperture boundary, when the mouse needed to precisely align its head with the reward spout. Together these results suggest that mice can select from a diverse range of sensing strategies incorporating both knowledge of the task and whisk-by-whisk sensory information and, moreover, suggest the existence of high level control (not solely reflexive) of sensing motions coordinated between multiple body parts.

Objective Behavioral neuroscience studies in freely moving rodents require small, light-weight implants to facilitate neural recording and stimulation. Our goal was to develop an integrated package of 3D printed parts and assembly aids for labs to rapidly fabricate, with minimal training, an implant that combines individually positionable microelectrodes, an optical fiber, zero insertion force (ZIF-clip) headstage connection, and secondary recording electrodes, e.g. for electromyograms (EMG). Approach Starting from previous implant designs that position recording electrodes using a control screw, we developed an implant where the main drive body, protective shell, and non-metal components of the microdrives are 3D printed in parallel. We compared alternative shapes and orientations of circuit boards for electrode connection to the headstage, in terms of their size, weight, and ease of wire insertion. We iteratively refined assembly methods, and integrated additional assembly aids into the 3D printed casing. Main Results We demonstrate the effectiveness of the OptoZIF Drive by performing real time optogenetic feedback in behaving mice. A novel feature of the OptoZIF Drive is its vertical circuit board, which facilities direct ZIF-clip connection. This feature requires angled insertion of an optical fiber that still can exit the drive from the center of a ring of recording electrodes. We designed an innovative 2-part protective shell that can be installed during the implant surgery to facilitate making additional connections to the circuit board. We use this feature to show that facial EMG in mice can be used as a control signal to lock stimulation to the animal's motion, with stable EMG signal over several months. To decrease assembly time, reduce assembly errors, and improve repeatability, we fabricate assembly aids including a drive holder, a drill guide, an implant fixture for microelectode “pinning”, and a gold plating fixture. Significance The expanding capability of optogenetic tools motivates continuing development of small optoelectric devices for stimulation and recording in freely moving mice. The OptoZIF Drive is the first to natively support ZIF-clip connection to recording hardware, which further supports a decrease in implant cross-section. The integrated 3D printed package of drive components and assembly tools facilities implant construction. The easy interfacing and installation of auxiliary electrodes makes the OptoZIF Drive especially attractive for real time feedback stimulation experiments.

The rodent whisker system is a common model for somatosensory neuroscience and sensorimotor integration. In support of ongoing efforts to assess neural stimulation approaches for future sensory prostheses, in which we deliver optogenetic stimulation to the somatosensory cortex of behaving mice, we must coordinate feedback in real time with active sensing whisker motions. Here we describe methods for extracting the times of whisker palpations from bilateral bipolar facial electromyograms (EMG). In particular, we show onset times extracted offline from EMG envelopes lead whisker motion onsets extracted from high speed video (HSV) by ≈ 16 ms. While HSV provides ground truth for sensing motions, it is not a feasible source of real time information suitable for neurofeedback experiments. As an alternative, we find the temporal derivative of the EMG envelope reliably predicts whisker motion onsets with short latency. Thus EMG, although providing noisy and partial information, can serve well as an input to control algorithms for testing neural processing of active sensing information, and providing stimulation for artificial touch experiments.

Active sensing incorporates closed-loop behavioral selection of information during sensory acquisition. The rodent whisker tactile system provides an ideal platform for studying these processes. We developed methods to deliver optogenetic feedback to mouse primary somatosensory cortex (SI), timelocked to active sensing motions (whisking) estimated through facial electromyography (EMG). To explore the impact of SI activity on individual whisker motions, we delivered stimulation locked to EMG threshold crossings at multiple delays. We found that stimulation regularized whisking (increasing overall periodicity), and shifted whisking frequency. These behavioral changes emulate changes observed when rodents actively contact objects, suggesting a role for SI in action selection that could guide design of sensory neuroprostheses sensitive to active sensing context.

Patients who suffer from Parkinson’s Disease are more prone to postural instability, a major risk factor for falls. One of the most common clinical methods of gauging the severity of a patient’s postural instability is with the retropulsion test [1], in which a clinician perturbs the balance of the patient and then rates their response to the perturbation. This test is subjective and largely based on the observations made by the clinician. In order to improve postural instability diagnosis and encourage more meaningful therapies for this cognitive-motor symptom, there is a clinical need to enable more objective, quantifiable approaches to measuring postural instability. In this paper, we describe a novel computational approach to quantifying the number, length, and trajectory of steps taken during a retropulsion test or other type of balance perturbation from a single camera facing the anterior side (front) of the subject. The computational framework involved first analyzing the video data using markerless pose estimation algorithms to track the movement of the subject’s feet. These pixel data were then converted from 2D to 3D using calibrated transformation functions, and then analyzed for consistency when compared to the known step lengths. The testing data showed accurate step length estimation within 1 cm, which suggests this computational approach could have utility in a variety of clinical environments.