Use of cell phone type cameras to enhance focusing and magnification in optical microscopes.

Cameras with auto-focusing and zoom capability, such as those in cell phones, can simplify focusing a microscope and at the same time provide a wide range of magnification.

Auditory thalamus responses to guinea-pig vocalizations: a comparison between rat and guinea-pig.

Although neuronal responses to species-specific vocalizations have long been described, very few between-species comparisons have been made. In a previous study, a differential representation of species-specific vocalizations was found in the auditory cortex (ACx): marmoset ACx neurons responded more, and more selectively, to marmoset calls than did cat ACx neurons [Wang, X., Kadia, S.C., 2001. Differential representation of species-specific primate vocalizations in the auditory cortices of marmoset and cat. J. Neurophysiol. 86, 2616-2620]. The present study analyzed responses of guinea-pig and rat auditory thalamus neurons to four well-defined guinea-pig vocalizations. Neurons of guinea-pigs (n = 96) and rats (n = 87) displayed similar response strength to guinea-pig vocalizations, and did not exhibit a preference for the natural over the time-reversed version of the calls in both species. This difference with the study by Wang and Kadia might suggest that, in mammals, the selectivity for the natural version of species-specific vocalizations is prominent only at the cortical level.

The auditory acclimatization effect in sensorineural hearing-impaired listeners: evidence for functional plasticity.

The present study provides new data on perceptual and physiological modifications associated with hearing aid (HA) fitting. Eight sensorineural hearing-impaired (SNHI) listeners participated. They had symmetrical hearing loss and were being fitted with binaural HAs for the first time. Perceptual performances were measured four times during auditory rehabilitation, using an intensity discrimination task and a loudness-scaling task. Pure tones of two different frequencies were used, one well amplified by HAs and the other weakly amplified. Two intensity levels were also tested, one rated 'soft' by SNHI listeners and the other 'loud'. Auditory brainstem responses (ABRs) to click stimulation were recorded. All measures were performed without HA. Results were consistent with the auditory acclimatization effect: most modifications induced by HA fitting were found at loud intensity levels and at high frequency, i.e., for acoustic information that was newly available to the listener. While both ears had similar hearing loss and aided gains, some differences between ears appeared in both perceptual tasks and in ABRs. In the right ear, a shortening of wave V latency paralleled perceptual modifications. The present results suggest that HA-fitting induces functional plasticity at the peripheral level of the auditory system.

Functional asymmetries of crossed and uncrossed medial olivocochlear efferent pathways in humans.

In a previous study, a peripheral auditory asymmetry in right-handers was found. The activity of the uncrossed medial olivocochlear efferent pathway has been shown to be more effective in the right than in the left ear. Our aim was to compare right and left medial olivocochlear inhibition during contralateral, ipsilateral and binaural ear stimulation with a broad band noise, in order to better localize this asymmetry. Uncrossed pathway asymmetry was confirmed and the crossed pathway showed a reverse asymmetry: a left ear advantage. These results are in accordance with the assumption that the medial superior olivary complex is the locus of the asymmetry observed. As this nuclear complex receives central efferents, the peripheral auditory asymmetry may be related to the well-known cortical asymmetry.

Intensity-related performances are modified by long-term hearing aid use: a functional plasticity?

It is now well established that the adult central nervous system can reorganize following various environmental changes. In particular, it has been hypothesized that auditory rehabilitation of sensorineural hearing-impaired adults may involve functional plasticity. The present study sought to compare intensity-related performance between two groups of subjects paired for age, gender and absolute thresholds in both ears. One group comprised long-term binaural hearing aid (HA) users and the other non-HA users. The effect of HA use was measured in two intensity tasks, a discrimination-limen-for-intensity task (DLI) and a loudness-scaling task. Results indicated that significant differences exist in loudness perception between long-term HA users and non-HA users, the latter rating intensity as louder than the former. Concerning intensity discrimination performance, a statistical tendency to lower, i.e. better, DLIs in long-term than in non-HA users was revealed. Moreover, significant differences between ears were observed in the loudness-scaling task, with the right ear showing greater inter-group difference than the left ear. This additional result points to a lateralization of the acclimatization effect. Finally, this study suggests significant perceptual modification and thus a possible functional plasticity entailed by HA use.

Auditory rehabilitation effects on speech lateralization in hearing-impaired listeners.

OBJECTIVE: Previous studies reported that the consequences of auditory rehabilitation were lateralized, with the right ear (RE) showing more improvement than the left ear (LE) over the time course of hearing aid (HA) use in elderly patients with symmetrical presbyacusis. It has been suggested that this asymmetry is linked to a change in speech lateralization. The aim of this study was to explore the consequences of HA use on interaural asymmetry in symmetrical sensorineural hearing impairment patients before and 4 months after binaural HA fitting. MATERIAL AND METHODS: Two types of perceptual task were chosen in order to measure speech lateralization: two dichotic listening tasks; and an identification task for a voice onset time continuum. Seven elderly, right-handed patients suffering from symmetrical presbyacusis were selected and tested before HA fitting and 4 months after. All measurements were made without the use of the HA, and the listeners were all first-time HA wearers. RESULTS: Dichotic listening scores for words improved significantly over the course of HA use. Moreover, the dichotic listening task for syllables revealed an increase in auditory asymmetry after 4 months of HA use. Concerning the identification task, a significant difference between ears was found, with only the R E showing significant improvement with HA use. CONCLUSION: These results suggest that auditory rehabilitation is lateralized, with greater change as a result of HA use occurring in the RE than the LE in right-handed patients.

Abnormal peripheral auditory asymmetry in schizophrenia.

OBJECTIVE: Auditory processing difficulties have been reported in schizophrenia. This study explores peripheral auditory function in patients with schizophrenia in whom certain early disturbances of auditory message filtering have been found and may be associated with certain abnormalities which are particularly localised in the left temporal lobe. METHODS: Otoacoustic emissions, including click evoked and spontaneous emissions and measurements of functioning of the medial olivocochlear efferent system were obtained from 12 chronic schizophrenic patients and compared with normative data recorded from 12 normal controls. RESULTS: Otoacoustic emission amplitudes and medial olivocochlear functioning were similar between the normal controls and schizophrenic patients; the schizophrenic patients did, however, differ from the normal controls in otoacoustic emission intensity and in medial olivocochlear asymmetry. A tendency to a higher number of spontaneous peaks, and a significantly higher click evoked otoacoustic emission response amplitude were found in the right ear compared with the left ear of schizophrenic patients. For the medial olivocochlear system, whereas normal controls showed greater attenuation in the right than in the left ear, schizophrenic patients lacked such an asymmetry. CONCLUSION: In the absence of any attention task, the findings show disturbed peripheral lateralisation in schizophrenia of mechanisms involved in auditory information filtering. Such a lack of right ear advantage in medial olivocochlear functioning may thus be a peripheral reflection of central lateralisation anomalies.