Quantifying accuracy and precision from continuous response data in studies of spatial perception and crossmodal recalibration.

The ability to detect the absolute location of sensory stimuli can be quantified with either error-based metrics derived from single-trial localization errors or regression-based metrics derived from a linear regression of localization responses on the true stimulus locations. Here we tested the agreement between these two approaches in estimating accuracy and precision in a large sample of 188 subjects who localized auditory stimuli from different azimuthal locations. A subsample of 57 subjects was subsequently exposed to audiovisual stimuli with a consistent spatial disparity before performing the sound localization test again, allowing us to additionally test which of the different metrics best assessed correlations between the amount of crossmodal spatial recalibration and baseline localization performance. First, our findings support a distinction between accuracy and precision. Localization accuracy was mainly reflected in the overall spatial bias and was moderately correlated with precision metrics. However, in our data, the variability of single-trial localization errors (variable error in error-based metrics) and the amount by which the eccentricity of target locations was overestimated (slope in regression-based metrics) were highly correlated, suggesting that intercorrelations between individual metrics need to be carefully considered in spatial perception studies. Secondly, exposure to spatially discrepant audiovisual stimuli resulted in a shift in bias toward the side of the visual stimuli (ventriloquism aftereffect) but did not affect localization precision. The size of the aftereffect shift in bias was at least partly explainable by unspecific test repetition effects, highlighting the need to account for inter-individual baseline differences in studies of spatial learning.

Deep brain pulse-generator and lead-extensions: subjective sensations related to measured parameters.

This study analyzed subjective sensations caused by DBS pulse-generator and lead-extensions in relation with objectively measured parameters. In 50 patients implant-related sensations were evaluated. The pulse-generator mobility was video-analyzed. Insufficient lead-extension/pulse-generator tolerability (72%/84%) was documented. Furthermore, 54% of the patients described movement impairments and 48% cosmetic deformity. High body mass index (BMI) was associated with low lead-extension related pain (P < 0.001). High generator mobility resulted in high lead-extension related pain (P < 0.001). Compared with lead-extension type 7482, type 7495 showed less lead-extension related pain (P = 0.0138), we suppose secondary to surgical tunneling instruments with a larger tip diameter. The lead-extension path with one tissue tunnel for both lead-extensions had 36% lead-extension related pain versus 11% for the path with one single tunnel for each lead-extension. Smaller pulse-generators for better cosmetic results, surgical procedures using larger tunneling instruments and one single tunnel for each lead-extension would provide better results for patients with BMI <30.