Quantitative Relations of Fetal and Maternal Pitiutary-Adrenal Systems I. EFFECTS OF MATERNAL HYPOPHYSECTOMY

A B S T R A C T Even though certain aspects of the fetal pituitary-adrenal system have been extensively studied, much remains to be learned of its basic development and function. In the present work, the effect of maternal hypophysectomy upon quantitative pituitary-adrenal relations in mother and fetus was investigated in pregnant beagle dogs. At 57 days gestation in each of seven normal animals and seven animals 3 wk posthypophysectomy, a cannula for collection of adrenal effluent was placed in a single fetus in utero under halothane anesthesia. A timed fetal adrenal sample was obtained; ACTH (10 mU) was injected into the fetus; 3 min thereafter a second fetal adrenal sample was collected and fetal and maternal peripheral arterial samples were drawn. All fetuses and their adrenal glands were weighed. Concentrations of cortisol and corticosterone were determined by a modification of the double-isotope dilution derivative method of Kliman and Peterson. Mean peripheral cortisol concentrations in mother and fetus were 92 and 94 ng/ml, respectively (ratio 1.0), in normal pregnancies and 11 and 54 ng/ml, respectively (ratio 0.2), in maternal hypophysectomy pregnancies. ternal-fetal ratio of peripheral cortisol concentrations from 1.0 to 0.2 occasioned by maternal hypophysectomy neither supports nor rules out the presence of specific placental mechanisms affecting relative concentrations of cortisol in mother and fetus. It does suggest, however, that the relative steroid input into maternal and fetal compartments is one of the factors which influences such concentration ratios. Concentrations of cortisol were significantly higher in fetal adrenal effluent (pre-ACTH) than in fetal peripheral plasma in normal pregnancies, which demonstrates secretion of cortisol by the fetus and shows that corticosteroid of maternal origin does not lead to complete suppression of fetal pituitary-adrenal function. Cortisol secretion rates in response to exogenous ACTH were essentially the same in fetuses in normal and hypophysectomy pregnancies (132 and 128 ng/min, respectively). Thus, fetal adrenal responsiveness to ACTH, i.e., maximum secretory capacity, is not enhanced by increased ACTH stimulation sufficient to induce adrenal hypertrophy in the same fetuses. INTRODUCTION Corticosteroid metabolism involves multiple factors in individuals after birth but is of even greater complexity in the fetus. Specifically involved in the fetus are a developing biochemical capacity for steroid synthesis within the fetal adrenal gland, a maturing fetal central nervous system-hypophyseal-adrenal control mechanism, and functional endocrine relations with the placenta and the mother. The human fetal adrenal cortex, from midpregnancy and even earlier, has been demonstrated to possess enzyme systems capable of forming diverse steroid molecules from acetate but to have, at the sam

Topological Evolution of Dynamical Networks: Global Criticality from Local Dynamics

We evolve network topology of an asymmetrically connected threshold network by a simple local rewiring rule: quiet nodes grow links, active nodes lose links. This leads to convergence of the average connectivity of the network towards the critical value $K_c =2$ in the limit of large system size $N$. How this principle could generate self-organization in natural complex systems is discussed for two examples: neural networks and regulatory networks in the genome.Comment: 4 pages RevTeX, 4 figures PostScript, revised versio

A demonstration of 'broken' visual space

It has long been assumed that there is a distorted mapping between real and ‘perceived’ space, based on demonstrations of systematic errors in judgements of slant, curvature, direction and separation. Here, we have applied a direct test to the notion of a coherent visual space. In an immersive virtual environment, participants judged the relative distance of two squares displayed in separate intervals. On some trials, the virtual scene expanded by a factor of four between intervals although, in line with recent results, participants did not report any noticeable change in the scene. We found that there was no consistent depth ordering of objects that can explain the distance matches participants made in this environment (e.g. A > B > D yet also A < C < D) and hence no single one-to-one mapping between participants’ perceived space and any real 3D environment. Instead, factors that affect pairwise comparisons of distances dictate participants’ performance. These data contradict, more directly than previous experiments, the idea that the visual system builds and uses a coherent 3D internal representation of a scene

Short and Intense Tailor-Made Notched Music Training against Tinnitus: The Tinnitus Frequency Matters

Tinnitus is one of the most common diseases in industrialized countries. Here, we developed and evaluated a short-term (5 subsequent days) and intensive (6 hours/day) tailor-made notched music training (TMNMT) for patients suffering from chronic, tonal tinnitus. We evaluated (i) the TMNMT efficacy in terms of behavioral and magnetoencephalographic outcome measures for two matched patient groups with either low (≤8 kHz, N = 10) or high (>8 kHz, N = 10) tinnitus frequencies, and the (ii) persistency of the TMNMT effects over the course of a four weeks post-training phase. The results indicated that the short-term intensive TMNMT took effect in patients with tinnitus frequencies ≤8 kHz: subjective tinnitus loudness, tinnitus-related distress, and tinnitus-related auditory cortex evoked activity were significantly reduced after TMNMT completion. However, in the patients with tinnitus frequencies >8 kHz, significant changes were not observed. Interpreted in their entirety, the results also indicated that the induced changes in auditory cortex evoked neuronal activity and tinnitus loudness were not persistent, encouraging the application of the TMNMT as a longer-term training. The findings are essential in guiding the intended transfer of this neuro-scientific treatment approach into routine clinical practice

A Postnatal Critical Period for Orientation Plasticity in the Cat Visual Cortex

Orientation selectivity of primary visual cortical neurons is an important requisite for shape perception. Although numerous studies have been previously devoted to a question of how orientation selectivity is established and elaborated in early life, how the susceptibility of orientation plasticity to visual experience changes in time remains unclear. In the present study, we showed a postnatal sensitive period profile for the modifiability of orientation selectivity in the visual cortex of kittens reared with head-mounted goggles for stable single-orientation exposure. When goggle rearing (GR) started at P16-P30, 2 weeks of GR induced a marked over-representation of the exposed orientation, and 2 more weeks of GR consolidated the altered orientation maps. GR that started later than P50, in turn, induced the under-representation of the exposed orientation. Orientation plasticity in the most sensitive period was markedly suppressed by cortical infusion of NMDAR antagonist. The present study reveals that the plasticity and consolidation of orientation selectivity in an early life are dynamically regulated in an experience-dependent manner

Feel it in my bones: Composing multimodal experience through tissue conduction

We outline here the feasibility of coherently utilising tissue conduction for spatial audio and tactile input. Tissue conduction display-specific compositional concerns are discussed; it is hypothesised that the qualia available through this medium substantively differ from those for conventional artificial means of appealing to auditory spatial perception. The implications include that spatial music experienced in this manner constitutes a new kind of experience, and that the ground rules of composition are yet to be established. We refer to results from listening experiences with one hundred listeners in an unstructured attribute elicitation exercise, where prominent themes such as “strange”, “weird”, “positive”, “spatial” and “vibrations” emerged. We speculate on future directions aimed at taking maximal advantage of the principle of multimodal perception to broaden the informational bandwidth of the display system. Some implications for composition for hearing-impaired are elucidated.n/

Perceived intensity of somatosensory cortical electrical stimulation

Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood. Based on prior work in cortical stimulation, we hypothesized that perceived intensity of electrical stimulation may be explained by the population response of the neurons affected by the stimulus train. To explore this hypothesis, we modeled perceived intensity of a stimulation pulse train with a leaky neural integrator. We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex. We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train

Morphological brain differences between adult stutterers and non-stutterers

BACKGROUND: The neurophysiological and neuroanatomical foundations of persistent developmental stuttering (PDS) are still a matter of dispute. A main argument is that stutterers show atypical anatomical asymmetries of speech-relevant brain areas, which possibly affect speech fluency. The major aim of this study was to determine whether adults with PDS have anomalous anatomy in cortical speech-language areas. METHODS: Adults with PDS (n = 10) and controls (n = 10) matched for age, sex, hand preference, and education were studied using high-resolution MRI scans. Using a new variant of the voxel-based morphometry technique (augmented VBM) the brains of stutterers and non-stutterers were compared with respect to white matter (WM) and grey matter (GM) differences. RESULTS: We found increased WM volumes in a right-hemispheric network comprising the superior temporal gyrus (including the planum temporale), the inferior frontal gyrus (including the pars triangularis), the precentral gyrus in the vicinity of the face and mouth representation, and the anterior middle frontal gyrus. In addition, we detected a leftward WM asymmetry in the auditory cortex in non-stutterers, while stutterers showed symmetric WM volumes. CONCLUSIONS: These results provide strong evidence that adults with PDS have anomalous anatomy not only in perisylvian speech and language areas but also in prefrontal and sensorimotor areas. Whether this atypical asymmetry of WM is the cause or the consequence of stuttering is still an unanswered question