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Selected AbstractsSocial context affects testosterone-induced singing and the volume of song control nuclei in male canaries (Serinus canaria)DEVELOPMENTAL NEUROBIOLOGY, Issue 10 2006Géraldine Boseret Abstract The contribution of social factors to seasonal plasticity in singing behavior and forebrain nuclei controlling song, and their interplay with gonadal steroid hormones are still poorly understood. In many songbird species, testosterone (T) enhances singing behavior but elevated plasma T concentrations are not absolutely required for singing to occur. Singing is generally produced either to defend a territory or to attract a mate and it is therefore not surprising that singing rate can be influenced by the sex and behavior of the social partner. We investigated, based on two independent experiments, the effect of the presence of a male or female partner on the rate of song produced by male canaries. In the first experiment, song rate was measured in dyads composed of one male and one female (M-F) or two males (M-M). Birds were implanted with T-filled Silastic capsules or with empty capsules as control. The number of complete song bouts produced by all males was recorded during 240 min on week 1, 2, 4, and 8 after implantation. On the day following each recording session, brains from approximately one-fourth of the birds were collected and the volumes of the song control nuclei HVC and RA were measured. T increased the singing rate and volume of HVC and RA but these effects were affected by the social context. Singing rates were higher in the M-M than in the M-F dyads. Also, in the M-M dyads a dominance-subordination relationship soon became established and dominant males sang at higher rates than subordinates in T-treated but not in control pairs. The differences in song production were not reflected in the size of the song control nuclei: HVC was larger in M-F than in M-M males and within the M-M dyads, no difference in HVC or RA size could be detected between dominant and subordinate males. At the individual level, the song rate with was positively correlated with RA and to a lower degree HVC volume, but this relationship was observed only in M-M dyads, specifically in dominant males. A second experiment, carried out with castrated males that were all treated with T and exposed either to another T-treated castrate or to an estradiol-implanted female, confirmed that song rate was higher in the M-M than in the M-F condition and that HVC volume was larger in heterosexual than in same-sex dyads. The effects of T on singing rate and on the volume of the song control nuclei are thus modulated by the social environment, including the presence/absence of a potential mate and dominance status among males. 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Short-term plasticity visualized with flavoprotein autofluorescence in the somatosensory cortex of anaesthetized ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2004Hiroatsu Murakami Abstract In the present study, short-term plasticity of somatosensory neural responses was investigated using flavoprotein autofluorescence imaging in rats anaesthetized with urethane (1.5 g/kg, i.p.) Somatosensory neural activity was elicited by vibratory skin stimulation (50 Hz for 1 s) applied on the surface of the left plantar hindpaw. Changes in green autofluorescence (, = 500,550 nm) in blue light (, = 450,490 nm) were elicited in the right somatosensory cortex. The normalised maximal fluorescence responses (,F/F) was 2.0 ± 0.1% (n = 40). After tetanic cortical stimulation (TS), applied at a depth of 1.5,2.0 mm from the cortical surface, the responses elicited by peripheral stimulation were significantly potentiated in both peak amplitude and size of the responsive area (both P < 0.02; Wilcoxon signed rank test). This potentiation was clearly observed in the recording session started 5 min after the cessation of TS, and returned to the control level within 30 min. However, depression of the responses was observed after TS applied at a depth of 0.5 mm. TS-induced changes in supragranular field potentials in cortical slices showed a similar dependence on the depth of the stimulated sites. When TS was applied on the ipsilateral somatosensory cortex, marked potentiation of the ipsilateral responses and slight potentiation of the contralateral responses to peripheral stimulation were observed after TS, suggesting the involvement of commissural fibers in the changes in the somatosensory brain maps. The present study clearly demonstrates that functional brain imaging using flavoprotein autofluorescence is a useful technique for investigating neural plasticity in vivo. [source] Diurnal variations in the waking EEG: comparisons with sleep latencies and subjective alertnessJOURNAL OF SLEEP RESEARCH, Issue 3 2000Lafrance Daytime measures of sleep latency and subjective alertness do not correlate with one another, suggesting that they assess different aspects of alertness. In addition, their typical diurnal variations show very different time courses. Quantitative analysis of the waking electroencephalogram (EEG) has been proposed as an objective measure of alertness, but it is not clear how it compares with other measures. In this study, the waking EEG was measured in the daytime to determine the presence of diurnal variations in the activity of standard frequency bands and to compare these variations with the temporal patterns typical of sleep propensity and subjective alertness. Alertness was evaluated in four men and 12 women, aged 19,33 y. Assessments were conducted every 2 h, from 10.00 to 24.00, in the following order: a visual analogue scale of alertness, a waking EEG recording and a sleep latency test. The waking EEG was recorded with eyes open. For each recording session, 32,60 s of artefact-free signals were selected from the C3/A2 derivation, then subjected to amplitude spectral analysis. Four EEG frequency bands showed significant diurnal variations: delta, theta, sigma and beta1. None of these variations showed a significant correlation with the temporal patterns of sleep latencies or subjective alertness. At the individual level, however, theta band activity increased when subjective alertness decreased, suggesting that the theta band can be used to monitor variations in alertness in a given individual, even at the moderate levels of sleepiness experienced during the daytime. [source] 22 Comparison of multichannel electrogastrograms obtained with the use of three different electrode typesNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2006K JONDERKO Background/Aims:, Multichannel recording of the gastric myoelectrical activity (GMA) is a promising evolution of electrogastrography. In the study we searched for electrodes the most suitable to obtain high quality multi-channel electrogastrograms. Methods:, Twelve young volunteers (9 F, 3 M, aged 24.3 ± 0.6 years) underwent on separate days three four-channel electrogastrographic recordings of the GMA: 30 min fasted and 90 min after a solid meal stimulation. The electrogastrograms were recorded in randomized order with 3M Red Dot class Ag/AgCl electrodes designed primarily for long-term electrocardiographic monitoring: type2222 (conductive area, CA/total area, TA): 2.00/10.24 cm2, type2271 2.54/29.64 cm2, type2660 11.64/11.64 cm2 (total surface conductive!) and subsequently analysed with Polygram NetÔ EGG 311224 software (Medtronic, USA). Electrical resistance between active electrodes relative to the reference one was measured with a digital ohmmeter before and after the recording session. Results:, Type2660 yielded consistently higher electrical resistance than the other electrode types, moreover in the case of type2271 and type2660 electrical conductivity significantly improved at the end of the recording relative to the basal measurement. Analysis of variance involving the relative time-share of normogastria, meal-induced change in dominant power, as well as a set of parameters unique for the multichannel electrogastrography and intended to characterize the so-called spatial displacement of the gastric slow waves did not reveal any statistically significant effect of the electrode type on the parameters of the multichannel electrogastrogram. Although, when particular numerical data were inspected, type2271 was found to perform slightly worse than the other electrode types. Type2271 was also rated the less handy among the electrodes tested. Conclusion:, Multichannel surface electrogastrography seems to be technically feasible with any type of high quality Ag/AgCl electrodes available on the market, whereas small dimensions enabling easy placement on the abdomen may be a feature favouring the choice of a particular electrode type for this examination. [source] Functional interaction between the associative parietal cortex and hippocampal place cell firing in the ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005Etienne Save Abstract The hippocampus and associative parietal cortex (APC) both contribute to spatial memory but the nature of their functional interaction remains unknown. To address this issue, we investigated the effects of APC lesions on hippocampal place cell firing in freely moving rats. Place cells were recorded from APC-lesioned and control rats as they performed a pellet-chasing task in a circular arena containing three object cues. During successive recording sessions, cue manipulations including object rotation in the absence of the rat and object removal in the presence of the rat were made to examine the control exerted by the objects or by non-visual intramaze cues on place field location, respectively. Object rotations resulted in equivalent field rotation for all cells in control rats. In contrast, a fraction of place fields in APC-lesioned rats did not rotate but remained stable relative to the room. Object removal produced different effects in APC-lesioned and control rats. In control rats, most place fields remained stable relative to the previous object rotation session, indicating that they were anchored to olfactory and/or idiothetic cues. In APC-lesioned rats, a majority of place fields shifted back to their initial, standard location, thus suggesting that they relied on uncontrolled background cues to maintain place field stability. These results provide strong evidence that the hippocampus and the APC cooperate in the formation of spatial memory and suggest that the APC is involved in elaboration of a hippocampal map based on proximal landmarks. [source] The effect of electrical and mechanical stimulation on the regenerating rodent facial nerve,THE LARYNGOSCOPE, Issue 6 2010Tessa Hadlock MD Abstract Objectives/Hypothesis: Investigators have long sought realistic methods to accelerate regeneration following nerve injury. Herein, we investigated the degree to which manual target muscle manipulation and brief electrical stimulation of the facial nerve, alone or in combination, affects recovery following rat facial nerve injury. Study Design: Prospective, randomized animal study. Methods: Sixty rats were randomized to three groups: brief electrical stimulation (BES), mechanical stimulation of the whisker pad (MEC), or both (COMBO). Animals underwent facial nerve transection and immediate microsurgical repair. In BES and COMBO groups, transection was preceded by 1-hour (3 V, 20 Hz square wave) electrical stimulation. Animals were tested weekly, with 5-minute recording sessions of whisker movement. In the MEC and COMBO groups, animals received 5 minutes of daily massage to the left whisker pad throughout the recovery period. Whisking behavior was analyzed for comparisons. Results: The BES and MEC groups demonstrated improved functional recovery in all whisking parameters compared with the COMBO group or historical controls at most time points between postoperative weeks 1 and 7. After 12 weeks, functional recovery remained superior in the BES and MEC groups compared with the COMBO and control groups, although the effect was no longer statistically significant. Conclusions: We observed an accelerative recovery effect of either electrical nerve stimulation or massage of the whisker pad on whisking behavior. The combination of both interventions had a negating effect on the acceleration of recovery. The potential clinical utility of these modalities bears consideration, and their negating interaction warrants further study. Laryngoscope, 2010 [source] | |||||||||||||