Revisiting the adaptive and maladaptive effects of crossmodal plasticity.

One of the most striking demonstrations of experience-dependent plasticity comes from studies of sensory-deprived individuals (e.g., blind or deaf), showing that brain regions deprived of their natural inputs change their sensory tuning to support the processing of inputs coming from the spared senses. These mechanisms of crossmodal plasticity have been traditionally conceptualized as having a double-edged sword effect on behavior. On one side, crossmodal plasticity is conceived as adaptive for the development of enhanced behavioral skills in the remaining senses of early-deaf or blind individuals. On the other side, crossmodal plasticity raises crucial challenges for sensory restoration and is typically conceived as maladaptive since its presence may prevent optimal recovery in sensory-re-afferented individuals. In the present review we stress that this dichotomic vision is oversimplified and we emphasize that the notions of the unavoidable adaptive/maladaptive effects of crossmodal reorganization for sensory compensation/restoration may actually be misleading. For this purpose we critically review the findings from the blind and deaf literatures, highlighting the complementary nature of these two fields of research. The integrated framework we propose here has the potential to impact on the way rehabilitation programs for sensory recovery are carried out, with the promising prospect of eventually improving their final outcomes.

[Cortical plasticity and changes in tinnitus: treatment options]. / Kortikale Plastizität und Veränderungen bei Tinnitus: Therapeutische Optionen.

A growing consensus in current tinnitus research suggests central nervous changes as the cause of tinnitus. Several animal and human experimental studies were able to show altered tonotopic representations as well as spontaneous activity in the auditory cortex. However, a causal relationship between altered neurophysiological processes and aspects of tinnitus are still missing. Furthermore, it is likely that the importance of diverse processes changes with continuing duration of tinnitus. These open questions complicate the development of effective treatments. Nevertheless, today several neuroscientifically motivated treatments are available, or treatments that can be integrated into a neuroscientific framework. This article gives an overview of current neuroscientific developments in tinnitus research and discusses their implications for the treatment of tinnitus.

Relationship between age and semen parameters in men with normal sperm concentration: analysis of 6022 semen samples.

This study evaluates retrospectively the relationship between age and semen parameters among men with normal sperm concentration. It was based on computerized data and performed in an Academic Fertility and IVF Unit. Six thousand and twenty-two semen samples with sperm concentrations of >or=20 x 10(6) ml(-1) were examined according to WHO criteria and analysed in relation to patients' age. For each age group, mean values +/- SD of semen volume, sperm concentration, percentage of motile spermatozoa, normal morphology, acrosome index, total sperm count/ejaculate, total motile sperm count/ejaculate and sexual abstinence duration were examined. A peak semen volume of 3.51 +/- 1.76 ml(-1) was observed at age >or=30 to <35 years and a lowest volume of 2.21 +/- 1.23 ml(-1) was observed at age >or=55 years (P<0.05). Sperm motility was found to be inversely related to age with peak motility of 44.39 +/- 20.69% at age <25 years and lowest motility of 24.76 +/- 18.27% at age >or=55 years (P<0.05). A reduction of 54% was observed for total motile sperm, between values of 103.34 +/- 107 x 10(6) at age >or=30 to <35 years and 46.68 +/- 53.73 x 10(6) (P<0.05) at age >55 years. A statistically significant and inverse relationship was observed between semen volume, sperm quality and patient age, in spite of prolonged sexual abstinence duration. Top sperm parameters were observed at age >or=30 to <35 years, while the most significant reduction in sperm parameters occurred after the age of 55 years.

Relationship between sexual abstinence duration and the acrosome index in teratozoospermic semen: analysis of 1800 semen samples.

A high acrosome index (percentage of sperm with normal acrosome morphology--cutoff value > or =10%) is known to be associated with an improved fertilization rate in conventional IVF. A retrospective evaluation of the relationship between duration of sexual abstinence and acrosome index among oligozoospermic and normozoospermic semen samples with teratozoospermia was undertaken. A significant (P = 0.001) decrease in the acrosome index was observed among the normozoospermic samples (n = 1264) between the peak value of 10.2 +/- 3.6% on day 2 and 8.5 +/- 4.0% on day 5 of abstinence, while for the oligozoospermic samples (n = 536) the peak value of 8.7 +/- 3.5% was observed on day 1 and the lowest values of 6.8 +/- 3.7% (P = 0.04) on day 5 of abstinence. The results suggest that an optimal acrosome index will be obtained following a short sexual abstinence.

One set of sounds, two tonotopic maps: exploring auditory cortex with amplitude-modulated tones.

OBJECTIVE: The possibility of simultaneously observing activation of primary and secondary auditory cortices has been demonstrated by Engelien et al. [Hear Res 2000;148:153-60]. METHODS: Such a dual monitoring by means of neuromagnetic recordings can be achieved when a subject is stimulated by brief pulses of 40Hz-modulated tones. Depending on the frequency filter applied, either the steady-state field (SSF) or the N1m can be extracted from the evoked magnetic field complex. RESULTS: Using this "combined" (two-maps) paradigm with 4 carrier frequencies, we show that it is possible to synchronously screen two tonotopic maps--one map each reflected either by the SSF or the N1m. Indicators are the systematic variation in the location (higher frequencies are more posterior) and orientation (higher frequencies oriented differently in the sagittal plane) of the equivalent current dipole (ECD). These parameters were compared with those obtained from "classic" (one map) paradigms in which either a pure tone elicits an N1m or a 40 Hz continuous (3 s) stimulation produces an SSF. Overall the results were similar, however, systematic differences between the paradigms were found for ECD localization, dipole strength, amplitude, and phase. CONCLUSIONS AND SIGNIFICANCE: One possible interpretation of these results is that different tonotopically arranged cortical fields were involved in the generation of the components.