A miniature kinematic coupling device for mouse head fixation

Head-fixation is a common technique in the preparation of subjects for neuroscience experiments. Accurate alignment, stability, and repeatability during fixation provide experimental consistency, thus enabling the subject to return to the same position over time to provide meaningful data. Head restraint systems inspired by kinematic clamps have been developed to allow micron scale repositioning across imaging epochs in rats. Here we report the development of a light-weight, implantable kinematic coupling (clamp) system that is wearable by mice, and enables repeated positioning to submicron accuracy across imaging epochs. This system uses a stainless steel headplate and a Maxwell-style three-groove kinematic mounting system with magnetic force clamping load. Spheres on the dorsal surface of the headplate provide contact points for vee-groove kinematic features machined into a tabletop mount. Evaluation of the clamp using multiphoton microscopy revealed submicron precision in registration accuracy and stability, allowing cellular resolution calcium imaging in awake, behaving mice. These results indicate that miniaturized implantable kinematic clamps for mice could be valuable for future experiments which require repositioning of subjects across time and different instruments.

Distance estimation from monocular cues in an ethological visuomotor task

In natural contexts, sensory processing and motor output are closely coupled, which is reflected in the fact that many brain areas contain both sensory and movement signals. However, standard reductionist paradigms decouple sensory decisions from their natural motor consequences, and head-fixation prevents the natural sensory consequences of self-motion. In particular, movement through the environment provides a number of depth cues beyond stereo vision that are poorly understood. To study the integration of visual processing and motor output in a naturalistic task, we investigated distance estimation in freely moving mice. We found that mice use vision to accurately jump across a variable gap, thus directly coupling a visual computation to its corresponding ethological motor output. Monocular eyelid suture did not affect performance, thus mice can use cues that do not depend on binocular disparity and stereo vision. Under monocular conditions, mice performed more vertical head movements, consistent with the use of motion parallax cues, and optogenetic suppression of primary visual cortex impaired task performance. Together, these results show that mice can use monocular cues, relying on visual cortex, to accurately judge distance. Furthermore, this behavioral paradigm provides a foundation for studying how neural circuits convert sensory information into ethological motor output.

Intraoperative Simulation: Team Training for Resuscitation While Using Intraoperative Computed Tomography: 2-Dimensional Operative Video

Spine surgeons increasingly use intraoperative computed tomography (iCT) to facilitate surgery. iCT has several advantages, including the ability to decrease radiation exposure, improve surgical accuracy, and decrease operative time.1-3 However, the large footprint of the equipment can impede fast patient access in the event of an emergency resuscitation. This challenge is compounded when the patient is prone with rigid head fixation. To achieve fast, high-quality resuscitation, a large team must overcome numerous challenges. Cohesive team functioning under these circumstances requires planning, practice, and refinement.4 As a result of our simulation sessions, we have made several changes to the setup of our iCT cases. The following equipment is now routinely used: extralong tubing between the anesthesia circuit and patient, portable vital monitor, additional intravenous access is obtained, and extension tubing is used with all lines. We have created educational diagrams to streamline 2 challenging processes: optimal bed placement (for supination) and removal of equipment from the operating room (OR) to accommodate an influx of emergency personnel and equipment. Since the implementation of this protocol, 1 prone posterior cervical patient had intraoperative cardiac arrest. The protocol was followed. Return of spontaneous circulation was achieved within 5 min. The patient was discharged from the hospital with no neurological sequelae. During debriefing, stakeholders uniformly credited the simulated practice with this positive outcome. Emergency planning is a multifaceted process that continually evolves. With a steady flux of personnel and equipment, ongoing practice is essential to ensure readiness. Here, we share the key elements of our twice-yearly simulation. This simulation was performed on a training mannequin. This study did not involve human subjects. Any depictions of care rendered to nonidentifiable patients were standard (nonexperimental).

Mobile intraoperative CT-assisted frameless stereotactic biopsies achieved single-millimeter trajectory accuracy for deep-seated brain lesions in a sample of 7 patients

Background Brain biopsies are crucial diagnostic interventions, providing valuable information for treatment and prognosis, but largely depend on a high accuracy and precision. We hypothesized that through the combination of neuronavigation-based frameless stereotaxy and MRI-guided trajectory planning with intraoperative CT examination using a mobile unit, one can achieve a seamlessly integrated approach yielding optimal target accuracy. Methods We analyzed a total of 7 stereotactic biopsy trajectories for a variety of deep-seated locations and different patient positions. After rigid head fixation, an intraoperative pre-procedural scan using a mobile CT unit was performed for automatic image fusion with the planning MRI images and a peri-procedural scan with the biopsy cannula in situ for verification of the definite target position. We then evaluated the radial trajectory error. Results Intraoperative scanning, surgery, computerized merging of MRI and CT images as well as trajectory planning were feasible without difficulties and safe in all cases. We achieved a radial trajectory deviation of 0.97 ± 0.39 mm at a trajectory length of 60 ± 12.3 mm (mean ± standard deviation). Repositioning of the biopsy cannula due to inaccurate targeting was not required. Conclusion Intraoperative verification using a mobile CT unit in combination with frameless neuronavigation-guided stereotaxy and pre-operative MRI-based trajectory planning was feasible, safe and highly accurate. The setting enabled single-millimeter accuracy for deep-seated brain lesions and direct detection of intraoperative complications, did not depend on a dedicated operating room and was seamlessly integrated into common stereotactic procedures.

Fully autonomous mouse behavioral and optogenetic experiments in home-cage

Goal-directed behaviors involve distributed brain networks. The small size of the mouse brain makes it amenable to manipulations of neural activity dispersed across brain areas, but existing optogenetic methods serially test a few brain regions at a time, which slows comprehensive mapping of distributed networks. Laborious operant conditioning training required for most experimental paradigms exacerbates this bottleneck. We present an autonomous workflow to survey the involvement of brain regions at scale during operant behaviors in mice. Naïve mice living in a home-cage system learned voluntary head-fixation (>1 hour/day) and performed difficult decision-making tasks, including contingency reversals, for 2 months without human supervision. We incorporated an optogenetic approach to manipulate activity in deep brain regions through intact skull during home-cage behavior. To demonstrate the utility of this approach, we tested dozens of mice in parallel unsupervised optogenetic experiments, revealing multiple regions in cortex, striatum, and superior colliculus involved in tactile decision-making.

Respond of the different human cranial bones to pin-type head fixation device

Background At this juncture, there is no consensus in the literature for the use and the safety of pin-type head holders in cranial procedures. Methods The present analysis of the bone response to the fixation of the instrument provides data to understand its impact on the entire skull as well as associated complications. An experimental study was conducted on fresh-frozen human specimens to analyze the puncture hole due to the fixation of each single pin of the pin-type head holder. Cone-beam CT images were acquired to measure the diameter of the puncture hole caused by the instrument according to several parameters: the pin angle, the clamping force, and different neurosurgical approaches most clinically used. Results The deepest hole, 2.67 ± 0.27 mm, was recorded for a 35° angle and a clamping force of 270 N at the middle fossa approach. The shallowest hole was 0.62 ± 0.22 mm for the 43° angle with a pinning force of 180 N in the pterional approach. The pterional approach had a significantly different effect on the depth of the puncture hole compared with the middle fossa craniotomy for 270 N pinning at 35° angle. The puncture hole measured with the 43° angle and 180 N force in prone position is significantly different from the other approaches with the same force. Conclusions These results could lead to recommendations about the use of the head holder depending on the patient’s history and cranial thickness to reduce complications associated with the pin-type head holder during clinical applications.