Automatic imitation in youngsters with Gilles de la Tourette syndrome: A behavioral study

It is widely known that humans have a tendency to imitate each other and that appropriate modulation of automatic imitative behaviors has a crucial function in social interactions. Gilles de la Tourette syndrome (GTS) is a childhood-onset neuropsychiatric disorder characterized by motor and phonic tics. Apart from tics, patients with GTS are often reported to show an abnormal tendency to automatically imitate others' behaviors (i.e., echophenomena), which may be related to a failure in top-down inhibition of imitative response tendencies. The aim of the current study is to explore the top-down inhibitory mechanisms on automatic imitative behaviors in youngsters with GTS. Error rates and reaction times from 32 participants with GTS and 32 controls were collected in response to an automatic imitation task assessing the influence of observed movements displayed in the first-person perspective on congruent and incongruent motor responses. Results showed that participants with GTS had higher error rates than controls, and their responses were faster than those of controls in incompatible stimuli. Our findings provide novel evidence of a key difference between youngsters with GTS and typically developing participants in the ability to effectively control the production of own motor responses to sensory inputs deriving from observed actions.

A new method to assess foveal morphology with optical coherence tomography

PURPOSE

To measure foveal morphology using optical coherence tomography (OCT).

METHODS

Three examiners classified normal subjects and patients with macular edema and epiretinal membranes from a normative database (299 OCT scans) and a study sample (80 OCT scans) on the basis of the foveal depression appearance (reference classification). The following parameters were measured for each OCT scan: Central Foveal Thickness (CFT), Central Subfield Thickness (CST), Central Subfield Volume (CSV), Centrofoveal Index (CI), Parafoveal Index (PI), and Foveal Indices (FI1, FI2, FI3). Foveal depression of OCT scans in the study sample were classified based on the values of OCT parameters using Bayesian statistics (test classifications).

RESULTS

Agreement between reference and test classifications was of 70% for CFT, 58.7% for CST, 60% for CSV, 80% for CI, 72.5% for PI, 88.7% for FI1, 96.2% for FI2 and 97.5% for FI3.

CONCLUSIONS

IF3 seems to provide a reliable measure of the foveal morphology.

Analysis of the receiver response in lidar measurements

We report on the calculation of the effective telescope area in lidar applications by a ray-tracing approach. This method allows one to consider the true experimental working conditions and hence to obtain accurate values of the effective telescope area as a function of the height. This in turn allows the retrieval of the signal from the ranges where the overlap function is not constant (e.g., lower ranges), thus increasing the useful range interval. Moreover, we show that the spherical mirrors are more appropriate than the parabolic ones for most of the lidar measurements, although a particular alignment procedure, such as the one we describe, must be used.