Heidelberg Phoneme Discrimination Test (HLAD): normative data for children of the third grade and correlation with spelling ability.

OBJECTIVE: The Heidelberg Phoneme Discrimination Test (HLAD), developed and standardized in 1998, is widely used in the differential diagnosis of dyslexia. Normative data have only been available for children of the 2nd and 4th grades, while norms for the 3rd grade are still missing. PATIENTS AND METHODS: We assessed three HLAD subtests [auditory phoneme discrimination, kinesthetic phoneme discrimination (repeating minimal pairs) and phoneme analysis] in 140 children of the 3rd grade from eight elementary schools. Writing capacity was tested via DRT3. RESULTS: Comparing children of the 2nd, 3rd and 4th grades, we found a continuing increase in phoneme discrimination capacity with age. This increase was especially evident for the task of auditory comparison. For the 3rd grade, the correlation between HLAD and writing test (qualitative analysis) was 0.55, and 0.36 between HLAD and writing (quantitative analysis). The correlation with writing tasks was highest in the 2nd grade. CONCLUSION: The steady increase in phoneme discrimination capacity from the 2nd to 4th grade may indicate maturation and learning effects at least until the age of 10 years.

Verification of redox-processes as switching and retention failure mechanisms in Nb:SrTiO3/metal devices.

Nanoscale redox reactions in transition metal oxides are believed to be the physical foundation of memristive devices, which present a highly scalable, low-power alternative for future non-volatile memory devices. The interface between noble metal top electrodes and Nb-doped SrTiO3 single crystals may serve as a prominent but not yet well-understood example of such memristive devices. In this report, we will present experimental evidence that nanoscale redox reactions and the associated valence change mechanism are indeed responsible for the resistance change in noble metal/Nb-doped SrTiO3 junctions with dimensions ranging from the micrometer scale down to the nanometer regime. Direct verification of the valence change mechanism is given by spectromicroscopic characterization of switching filaments. Furthermore, it is found that the resistance change over time is driven by the reoxidation of a previously oxygen-deficient region. The retention times of the low resistance states, accordingly, can be dramatically improved under vacuum conditions as well as through the insertion of a thin Al2O3 layer which prevents this reoxidation. These insights finally confirm the resistive switching mechanism at these interfaces and are therefore of significant importance for the study and application of memristive devices based on Nb-doped SrTiO3 as well as systems with similar switching mechanisms.