Decreased motor unit firing rate in the potentiated tibialis anterior in humans

With repeated activity, force production, rate of force production, and relaxation time are impaired. These are characteristics ofa fatigued muscle (Vandenboom, 2004). However, brief bouts of near maximal to maximal activity results in the increased ability of the muscle to generate force, termed post activation potentiation (P AP)(V andervoort et aI., 1983). The purpose of the present study was to characterize motor unit firing rate (MUFR) in the unfatigued, potentiated tibialis anterior (TA). Using a quadrifilar needle electrode, MUFR was measured during a 5s 50% MVC in which the TA was either potentiated or unpotentiated; monopolar electrodes measured surface parameters. A lOs MVC was used to potentiate the muscle. Firing rate decreased significantly from 20.15±2.9Opps to 18.27±2.99pps, while mean power frequency decreased significantly from 60. 13±7.75 Hz to 53.62±8.56 Hz. No change in root mean square (RMS) was observed. Therefore, in the present study, MUFR decreases in response to a potentiated TA.

Charting developmental EEG gamma changes in the auditory modality /

The oscillation of neuronal circuits reflected in the EEG gamma frequency may be fundamental to the perceptual process referred to as binding (the integration of various thoughts and perceptions into a coherent picture). The aim of our study was to expand our knowledge of the developmental course ofEEG gamma in the auditory modality. 2 We investigated EEG 40 Hz gamma band responses (35.2 to 43.0 Hz) using an auditory novelty oddball paradigm alone and with a visual-number-series distracter task in 208 participants as a function of age (7 years to adult) at 9 sites across the sagital and lateral axes (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4). Gamma responses were operationally defined as change in power or a change in phase synchrony level from baseline within two time windows. The evoked gamma response was defined as a significant change from baseline occurring between 0 to 150 ms after stimulus onset; the induced gamma response was measured from 250 to 750 ms after stimulus onset. A significant evoked gamma band response was found when measuring changes in both power and phase synchrony. The increase in both measures was maximal at frontal regions. Decreases in both measures were found when participants were distracted by a secondary task. For neither measure were developmental effects noted. However, evoked gamma power was significantly enhanced with the presentation of a novel stimulus, especially at the right frontal site (F4); frontal evoked gamma phase synchrony also showed enhancement for novel stimuli but only for our two oldest age groups (16-18 year olds and adults). Induced gamma band responses also varied with task-dependent cognitive stimulus properties. In the induced gamma power response in all age groups, target stimuli generated the highest power values at the parietal region, while the novel stimuli were always below baseline. Target stimuli increased induced synchrony in all regions for all participants, but the novel stimulus selectively affected participants dependent on their age and gender. Adult participants, for example, exhibited a reduction in gamma power, but an increase in synchrony to the novel stimulus within the same region. Induced gamma synchrony was more sensitive to the gender of the participant than was induced gamma power. While induced gamma power produced little effects of age, gamma synchrony did have age effects. These results confirm that the perceptual process which regulates gamma power is distinct from that which governs the synchronization for neuronal firing, and both gamma power and synchrony are important factors to be considered for the "binding" hypothesis. However, there is surprisingly little effect of age on the absolute levels of or distribution of EEG gamma in the age range investigated.

The role of the GABAergic system in the production of ultrasonic vocalization in rats /

Ultrasonic vocalization plays an important role in intraspecies communication for rats. It has been well demonstrated that rats will emit 22kHz vocalization in stressfiil or threatening situations. Although the neural mechanism underlying vocahzation is not well understood, it is known that chohnergic input to the basal forebrain induces such alarm calls. A number of experiments have found that intracerebral injection of carbachol, a predominantly muscarinic agonist, into die anterior hypothalamic/preoptic area (AH/POA) rehably induces vocalization similar to naturally emitted ultrasonic calls. It has also been shown that carbachol has extensive inhibitory effects on neuronal firing in the same area. This result impUes that the inhibitory effects of carbachol in the AH/POA could trigger vocahzation, and that the GABAergic system could be involved. The purpose of this study is to investigate the effects ofGABA agonists and antagonists on flie production of carbachol induced 22kHz vocalization. The following hypotheses were examined: 1) apphcation ofGABA (a naturally occurring inhibitory neurotransmitter) will have a synergistic effect with carbachol, increasing vocalization; and 2) tiie apphcation ofGABA antagonists (picrotoxin or bicuculline) will reduce caibachol-induced vocalization. A total of sixty rats were implanted with stainless steel guide cannulae in the AH/POA area. After recovery, animals were locally pretreated with 1) GABA (l-40ng), 2) picrotoxin (1 .5^g) or bicuculhne (0.03ng), or 3) sahne; before injection with carbachol (1 .5^g). The resulting vocalization was measured and quantitated. The results indicate that pretreatment with GABA or GABA antagonists had no significant effect on vocalization. Local pretreatment with GABA did not potentiate the vocal response as measured by its duration, latraicy, and total number of calls. Similarly, pretreatment with picrotoxin or bicuculline had no effects on the same measures of vocalization. The results suggest tfiat chohnoceptive neurons involved in the production of alarm calls are not under direct GABAergic control.

Letter from J.E.A. Masters to Josiah Masters, November 11, 1812

Transcription: Encampment Plattsburgh My Dear Uncle Nov. 11th 1812 We are making every possible preparation to invade Canada. I have no doubt but we march in six days. From the best information I can get it is not contemplated to attack the Isle aux Noix – We shall take into the field 2500 infantry between 3 & 4 hundred cavalry 25 light artillery & 150 artillerists; of the malitia I have no accurate knowledge there is more than 1000 of them, the number of regular troops is mentioned you may rely on as being nearly correct I cannot state to a man as I have not had an opportunity of being the consolidated returns of the different corps. It is said that a [corps formed?] of volunteers are to join us from Vermont. I think it doubtful I believe that we shall have no great difficulty in going to Montreal as to the ultimate policy of the [act it is?] not my duty to judge. Confidential our troops are raw particularly in loading and firing they are much deficient. The 6th and 15th will be able to act with some considerable ... of precision and accuracy the remaining infantry—badly disciplined. Should any thing [occur?] with me my fate be unfortunate the [little?] property willed me by my grandfather will secure you the amount I owe you. General Dearborn I understand is at Burlington on his way here. Some of the prisoners that were taken at Queenstown have [arrived?] at Montreal probably. [Ensign Rich?] is among them. Several officers here became acquainted with him soon after he received his [two illegible words] & speak highly of him. [Always?] affectionately yours J. E. A. Masters P.S. I shall write you again before we march excuse this [scrawl?] my hand are too cold to write a fair hand we shall have here near [400?] sick that are not able to march J. E. A. Masters The [Hon.?] Josiah Masters [Schaghticoke?] N.Y. N. B. Nov. 13th We have orders to be prepared to march on the 15th at 12 oclock. Our baggage will be contained as much as possible. The officers carry no baggage except what they carry in their knapsacks. I am in fine health and am able [Hand?] most any [illegible word] My love to all affectionately Your nephew J. E. A. Masters

Identification and characterization of retinoic acid-induced morphological and electrophysiological changes in an invertebrate nervous system

The vitamin A metabolite, retinoic acid (RA) is known to play an important role in the development, patterning and regeneration of nervous tissue, both in the embryo and in the adult. Classically, RA is known to mediate the transcription of target genes through the binding and activation ofits nuclear receptors: the retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Recently, mounting evidence from many animal models has implicated a number of RA-mediated effects operating independently of gene transcription, and thus highlights nove~ nongenornic actions of RA. For example, recent work utilizing cultured neurons from the pond snaa Lymnaea stagnalis, has shown that RA can elicit a regenerative response, growth cone turning, independently of "classical" transcriptional activation While this work illustrates a novel regeneration-inducing effect in culture, it is currently -unknown whether RA also induces regeneration in situ. This study has sought to determine RA's regenerative effucts at the morphological and molecular levels by utilizing an in situ approach focusing on a single identified dopaminergic neuron which possesses a known "mapped" morphology within the CNS. These studies show, for the first time in an invertebrate, that RA can increase neurite outgrowth of dopaminergic cells that have undergone a nerve-crush injury. Utilizing Western blot analysis, it was shown that this effect appears to be independent of any changes in whole CNS expression levels of either the RAR or RXR. Additionally, utilizing immunohistochemistry, to examine protein localization, there does not appear to be any obvious changes in the RXR expression level at the crush site. Changes in cell morphology such as neurity extension are known to be modulated by changes in neuronal firing activity. It has been previously shown that exposure to RA over many days can lead to changes in the electrophysiological properties of cultured Lymnaea neurons; however, no studies have investigated whether short-term exposure to RA can elicit electrophysiological changes and/or changes in firing pattern of neurons in Lymnaea or any other species. The studies performed here show, for the first time in any species, that short-tenn treatment with RA can elicit significant changes in the firing properties of both identified dopaminergic neurons and peptidergic neurons. This effect appears to be independent of protein synthesis, activation of protein kinase A or phospholipase C, and calcium influx but is both dose-dependent and isomer-dependent. These studies provide evidence that the RXR, but not RAR, may be involved, and that intracellular calcium concentrations decrease upon RAexposure with a time course, dose-dependency and isomer-dependency that coincide with the RA-induced electrophysiological changes. Taken together, these studies provide important evidence highlighting RA as a multifunctional molecule, inducing morphological, molecular and electrophysiological changes within the CNS, and highlight the many pathways through which RA may operate to elicit its effects.

Map - Plan of Attack of a Iagdkommaudo west of Cantigny, 27 May 1918

A map titled "Plan of Attack of a Iagdkommaudo west of Cantigny on 27 May 1918. There are two sketches and the legend indicates that sketch no. 1 is "Firing until 7A.M." and sketch no. 2 is "Firing after 7A.M."

Illustration from the First Field Artillery Brigade Observer

A cartoon by Alban B. Butler (signed), titled "National Salute" and dated 4 July 1918. The illustration shows officers loading a canon and firing.