Cannabinoids modulate associative cerebellar learning via alterations in behavioral state.

Cannabinoids are notorious and profound modulators of behavioral state. In the brain, endocannabinoids act via Type 1-cannabinoid receptors (CB1) to modulate synaptic transmission and mediate multiple forms of synaptic plasticity. CB1 knockout (CB1KO) mice display a range of behavioral phenotypes, in particular hypoactivity and various deficits in learning and memory, including cerebellum-dependent delay eyeblink conditioning. Here we find that the apparent effects of CB1 deletion on cerebellar learning are not due to direct effects on CB1-dependent plasticity, but rather, arise as a secondary consequence of altered behavioral state. Hypoactivity of CB1KO mice accounts for their impaired eyeblink conditioning across both animals and trials. Moreover, learning in these mutants is rescued by walking on a motorized treadmill during training. Finally, cerebellar granule-cell-specific CB1KOs exhibit normal eyeblink conditioning, and both global and granule-cell-specific CB1KOs display normal cerebellum-dependent locomotor coordination and learning. These findings highlight the modulation of behavioral state as a powerful independent means through which individual genes contribute to complex behaviors.

Shared and specific signatures of locomotor ataxia in mutant mice.

Several spontaneous mouse mutants with deficits in motor coordination and associated cerebellar neuropathology have been described. Intriguingly, both visible gait alterations and neuroanatomical abnormalities throughout the brain differ across mutants. We previously used the LocoMouse system to quantify specific deficits in locomotor coordination in mildly ataxic Purkinje cell degeneration mice (pcd; Machado et al., 2015). Here, we analyze the locomotor behavior of severely ataxic reeler mutants and compare and contrast it with that of pcd. Despite clearly visible gait differences, direct comparison of locomotor kinematics and linear discriminant analysis reveal a surprisingly similar pattern of impairments in multijoint, interlimb, and whole-body coordination in the two mutants. These findings capture both shared and specific signatures of gait ataxia and provide a quantitative foundation for mapping specific locomotor impairments onto distinct neuropathologies in mice.

Spatial and Temporal Locomotor Learning in Mouse Cerebellum.

Stable and efficient locomotion requires the precise coordination of movement across the limbs and body. Learned changes in interlimb coordination can be induced by exposure to a split-belt treadmill that imposes different speeds under each side of the body. Here, we demonstrate locomotor learning on a split-belt treadmill in mice. Mouse locomotor adaptation is specific to measures of interlimb coordination, has spatial and temporal components that adapt at different rates, and is context specific. The many similarities between human and mouse locomotor adaptation suggest that this form of locomotor learning is highly conserved across vertebrates. Using a variety of approaches, we demonstrate that split-belt adaptation in mice specifically depends on the intermediate cerebellum but is insensitive to large lesions of the cerebral cortex. Finally, cell-type-specific chemogenetics combined with quantitative behavioral analysis reveals that spatial and temporal components of locomotor adaptation are dissociable on the circuit level. VIDEO ABSTRACT.

A quantitative framework for whole-body coordination reveals specific deficits in freely walking ataxic mice.

The coordination of movement across the body is a fundamental, yet poorly understood aspect of motor control. Mutant mice with cerebellar circuit defects exhibit characteristic impairments in locomotor coordination; however, the fundamental features of this gait ataxia have not been effectively isolated. Here we describe a novel system (LocoMouse) for analyzing limb, head, and tail kinematics of freely walking mice. Analysis of visibly ataxic Purkinje cell degeneration (pcd) mice reveals that while differences in the forward motion of individual paws are fully accounted for by changes in walking speed and body size, more complex 3D trajectories and, especially, inter-limb and whole-body coordination are specifically impaired. Moreover, the coordination deficits in pcd are consistent with a failure to predict and compensate for the consequences of movement across the body. These results isolate specific impairments in whole-body coordination in mice and provide a quantitative framework for understanding cerebellar contributions to coordinated locomotion.

Interaction of age and opioid dependence on length of hospital stay for spine surgery patients.

Clinical information suggests that opioid dependence is a major contributor to poor outcomes involving health status and to increased length of stay in hospital settings. Before spine surgery, 150 patients who were using an opioid medication for pain relief were interviewed using the six World Health Organization (WHO) guidelines for the diagnosis of opioid dependence. Three groups were defined: opioid-dependent, nonopioid-dependent, and a subclinical group. Results revealed an average of 20% of patients (N = 30) who met the WHO criteria for the diagnosis of opioid dependence. There were significant positive correlations between age and number of positive WHO criteria, length of stay, and time under surgery. Length of stay was significantly higher for the older age group (> 55 yr.). ANCOVA analysis using two opioid dependence groups (+ and -) and age group as independent variables affecting length of stay, after controlling for type of surgery, pain intensity, and number of previous spine surgeries, revealed that effects of opioid dependence status and age were significant but their interaction was not. Age did add length of stay independently of opioid dependence status; older adults remain in the hospital longer for various reasons probably associated with comorbidities.

The fifth vital sign--what does it mean?

Acute pain is reported as a presenting symptom in over 80% of physician visits. Chronic pain affects an estimated 76.2 million Americans--more than diabetes, heart disease, and cancer combined. It has been estimated to be undertreated in up to 80% of patients in some settings. Pain costs the American public more than $100 billion each year in health care, compensation, and litigation. That's why pain was officially declared "The Fifth Vital Sign." Henceforth the evaluation of pain became a requirement of proper patient care as important and basic as the assessment and management of temperature, blood pressure, respiratory rate, and heart rate. The numeric pain scale certainly has a place in care and in pain management; however, it is important to assess the patient's communication and self-management style and to recognize that patients, like pain, are on a continuum with varied styles of communication and adaptation. It is easy to get lost in the process, even when the process is initiated with the best of intentions. In the quest for individualized medicine, it might be best to keep pain assessment in the individualization arena.