This paper is a commentary to introduce how rehabilitation professionals can use a new, body-worn sensor system to obtain objective measures of balance and gait. Current assessments of balance and gait in clinical rehabilitation are largely limited to subjective scales, simple stop-watch measures, or complex, expensive machines not practical or largely available. Although accelerometers and gyroscopes have been shown to accurately quantify many aspects of gait and balance kinematics, only recently a comprehensive, portable system has become available for clinicians. By measuring body motion during tests that clinicians are already performing, such as the Timed Up and Go test (TUG) and the Clinical Test of Sensory Integration for Balance (CITSIB), the additional time for assessment is minimal. By providing instant analysis of balance and gait and comparing a patient’s performance to age-matched control values, therapists receive an objective, sensitive screening profile of balance and gait strategies. This motion screening profile can be used to identify mild abnormalities not obvious with traditional clinical testing, measure small changes due to rehabilitation, and design customized rehabilitation programs for each individual’s specific balance and gait deficits.

Anticipatory postural adjustments (APAs) prior to gait initiation have been largely studied in in traditional, laboratory settings using force plates under the feet to characterize the displacement of the center of pressure. However clinical trials and clinical practice would benefit from a portable, inexpensive method for characterizing APAs. Therefore, the main objectives of this study were: 1) to develop a novel, automatic IMU-based method to detect and characterize APAs during gait initiation and 2) to measure its test-retest reliability. Experiment I was carried out in the laboratory to determine the validity of the IMU-based method in ten subjects with PD (OFF medication) and 12 control subjects. Experiment II was carried out in the clinic, to determine test-retest reliability of the IMU-based method in a different set of 17 early-to-moderate, treated subjects with PD (tested ON medication) and 17 age-matched control subjects. Results showed that gait initiation characteristics (both APAs and 1st step) detected with our novel method were significantly correlated to the characteristics calculated with a force plate and motion analysis system. The size of APAs measured with either inertial sensors or force plate were significantly smaller in subjects with PD than in control subjects (p<0.05). Test-retest reliability for the gait initiation characteristics measured with inertial sensors was moderate-to-excellent (.56

An important question in sensory neuroscience is what coding strategies and mechanisms are used by the brain to detect and discriminate among behaviorally relevant stimuli. There is evidence that sensory systems migrate from a distributed and redundant encoding strategy at the periphery to a more heterogeneous encoding in cortical structures. It has been hypothesized that heterogeneity is an efficient encoding strategy that minimizes the redundancy of the neural code and maximizes information throughput. Evidence of this mechanism has been documented in cortical structures. In this study, we examined whether heterogeneous encoding of complex sounds contributes to efficient encoding in the auditory midbrain by characterizing neural responses to behaviorally relevant vocalizations in the mouse inferior colliculus (IC). We independently manipulated the frequency, amplitude, duration, and harmonic structure of the vocalizations to create a suite of modified vocalizations. Based on measures of both spike rate and timing, we characterized the heterogeneity of neural responses to the natural vocalizations and their perturbed variants. Using information theoretic measures, we found that heterogeneous response properties of IC neurons contribute to efficient encoding of behaviorally relevant vocalizations.

In this feasibility study, we present a novel, wearable prototype of tactile biofeedback to alleviate gait disturbances, such as freezing of gait in Parkinson’s disease. We designed and tested a phase-dependent tactile biofeedback system that can be easily worn on the feet, with a simple switch to turn it on or off. Preliminary validation was performed in 8 subjects with Parkinson’s disease who show freezing during a turning in place test. A metronome, control condition was used to compare effectiveness in alleviating freezing. Promising results were obtained, both in term of acceptability of the device, and improving motor performance.

Holmstrom L, Roberts PD, Portfors CV. Responses to social vocalizations in the inferior colliculus of the mustached bat are influenced by secondary tuning curves. J Neurophysiol 98: [3461][3462][3463][3464][3465][3466][3467][3468][3469][3470][3471][3472] 2007. First published October 10, 2007; doi:10.1152/jn.00638.2007. Neurons in the inferior colliculus (IC) of the mustached bat integrate input from multiple frequency bands in a complex fashion. These neurons are important for encoding the bat's echolocation and social vocalizations. The purpose of this study was to quantify the contribution of complex frequency interactions on the responses of IC neurons to social vocalizations. Neural responses to single tones, two-tone pairs, and social vocalizations were recorded in the IC of the mustached bat. Three types of data driven stimulus-response models were designed for each neuron from single tone and tone pair stimuli to predict the responses of individual neurons to social vocalizations. The first model was generated only using the neuron's primary frequency tuning curve, whereas the second model incorporated the entire hearing range of the animal. The extended model often predicted responses to many social vocalizations more accurately for multiply tuned neurons. One class of multiply tuned neuron that likely encodes echolocation information also responded to many of the social vocalizations, suggesting that some neurons in the mustached bat IC have dual functions. The third model included two-tone frequency tunings of the neurons. The responses to vocalizations were better predicted by the two-tone models when the neuron had inhibitory frequency tuning curves that were not near the neuron's primary tuning curve. Our results suggest that complex frequency interactions in the IC determine neural responses to social vocalizations and some neurons in IC have dual functions that encode both echolocation and social vocalization signals. I N T R O D U C T I O NMany animal species have complex social structures that remain stable through the use of social communication signals. In many species, these signals are acoustic. To correctly interpret an acoustic signal to output an appropriate motor response, the receiver must detect, discriminate, and categorize each particular social vocalization. Presumably these tasks are performed by auditory neurons in the central auditory system, but how social vocalizations are encoded at different levels of the ascending auditory system is not well understood.Few studies have examined encoding of social vocalizations in the auditory midbrain, particularly in mammalian species. The inferior colliculus (IC) is a midbrain structure that is a major relay station for both ascending and descending auditory pathways (Adams 1979). The IC has been well studied in several mammalian species and contains a tonotopic map where low frequencies are represented dorsolaterally and high frequencies represented ventromedially (Lippe and Rubel 1983;Zook et al. 1985). In addition, many neurons in the ...