Extraocular muscle activity, rapid eye movements and the development of active and quiet sleep

Rapid eye movements (REMs), traditionally measured using the electrooculogram (EOG), help to characterize active sleep in adults. In early infancy, however, they are not clearly expressed. Here we measured extraocular muscle activity in infant rats at 3 days of age (P3), P8 and P14-15 in order to assess the ontogeny of REMs and their relationship with other forms of sleep-related phasic activity. We found that the causal relationship between extraocular muscle twitches and REMs strengthened during the first two postnatal weeks, reflecting increased control of the extraocular muscles over eye movements. As early as P3, however, phasic bursts of extraocular muscle twitching occurred in synchrony with twitching in other muscle groups, producing waves of phasic activity interspersed with brief periods of quiescence. Surprisingly, the tone of the extraocular muscles, invisible to standard EOG measures, fluctuated in synchrony with the tone of other muscle groups; focal electrical stimulation within the dorsolateral pontine tegmentum, an area that has been shown to contain wake-on neurons in P8 rats, resulted in the simultaneous activation of high tone in both nuchal and extraocular muscles. Finally, when state-dependent neocortical electroencephalographic activity was observed at P14, it had already integrated fully with sleep and wakefulness as defined using electromyographic criteria alone; this finding is not consistent with the notion that active sleep in infants at this age is 'half-activated.' All together, these results indicate exquisite temporal organization of sleep soon after birth and highlight the possible functional implications of homologous activational states in striated muscle and neocortex.     

Mice deficient in the chemokine receptor CXCR4 exhibit impaired limb innervation and myogenesis

The chemokine CXCL12/SDF-1 and its receptor CXCR4 regulate the development and the function of the hematopoietic system and control morphogenesis of distinct brain areas. Here, we demonstrate that inactivation of CXCR4 results in a massive loss of spinal cord motoneurons and dorsal root ganglion neurons and, subsequently, in a reduced innervation of the developing mouse fore- and hindlimbs. However, only the death of sensory neurons seems to be a direct consequence of receptor inactivation as suggested by the observations that DRG neurons, but not motoneurons, of wild-type animals express CXCR4 and respond to CXCL12 with an increase in cell survival. In contrast, the increased death of motoneurons in CXCR4-deficient animals seems to result from impaired limb myogenesis and a subsequent loss of muscle-derived neurotrophic support. In summary, our findings unravel a previously unrecognized complex role of CXCL12/CXCR4 in the control of limb neuromuscular development.     

Towards an explicit account of implicit learning

PURPOSE OF REVIEW: The human brain supports acquisition mechanisms that can extract structural regularities implicitly from experience without the induction of an explicit model. Reber defined the process by which an individual comes to respond appropriately to the statistical structure of the input ensemble as implicit learning. He argued that the capacity to generalize to new input is based on the acquisition of abstract representations that reflect underlying structural regularities in the acquisition input. We focus this review of the implicit learning literature on studies published during 2004 and 2005. We will not review studies of repetition priming ('implicit memory'). Instead we focus on two commonly used experimental paradigms: the serial reaction time task and artificial grammar learning. Previous comprehensive reviews can be found in Seger's 1994 article and the Handbook of Implicit Learning. RECENT FINDINGS: Emerging themes include the interaction between implicit and explicit processes, the role of the medial temporal lobe, developmental aspects of implicit learning, age-dependence, the role of sleep and consolidation. SUMMARY: The attempts to characterize the interaction between implicit and explicit learning are promising although not well understood. The same can be said about the role of sleep and consolidation. Despite the fact that lesion studies have relatively consistently suggested that the medial temporal lobe memory system is not necessary for implicit learning, a number of functional magnetic resonance studies have reported medial temporal lobe activation in implicit learning. This issue merits further research. Finally, the clinical relevance of implicit learning remains to be determined.     

Improved naming after TMS treatments in a chronic, global aphasia patient--case report

We report improved ability to name pictures at 2 and 8 months after repetitive transcranial magnetic stimulation (rTMS) treatments to the pars triangularis portion of right Broca's homologue in a 57 year-old woman with severe nonfluent/global aphasia (6.5 years post left basal ganglia bleed, subcortical lesion). TMS was applied at 1 Hz, 20 minutes a day, 10 days, over a two-week period. She received no speech therapy during the study. One year after her TMS treatments, she entered speech therapy with continued improvement. TMS may have modulated activity in the remaining left and right hemisphere neural network for naming.     

Could flies explain the elusive epidemiology of campylobacteriosis?

Background  

Unlike salmonellosis with well-known routes of transmission, the epidemiology of campylobacteriosis is still largely unclear. Known risk factors such as ingestion of contaminated food and water, direct contact with infected animals and outdoor swimming could at most only explain half the recorded cases.     

Death in two female Prader-Willi syndrome patients during the early phase of growth hormone treatment

Reports on sudden death in Prader-Willi syndrome (PWS) patients after the start of growth hormone (GH) treatment have been published recently. We observed a 4.7-y-old girl who showed a continuous increase in pulmonary artery pressure and died of cardiorespiratory failure 7 wk after GH therapy had been initiated, and a 9.3-y-old girl with additional trisomy 21 who died during a minor respiratory infection 6 mo after GH had been started. Both patients were overweight (weight for height 127% and 224%, respectively). GH-induced fluid retention may have occurred in the younger girl. In contrast to the reported cases, our PWS patients were female. CONCLUSION: Our cases illustrate the difficulty of differentiation between possible GH side effects and the natural course of disease, in particular with respect to obesity-related comorbidity and mortality.     

Can reduced smoking be a way for smokers not interested in quitting to actually quit?

The predominating way to stop smoking is to do it abruptly. At every given time, the large majority of smokers are not motivated or willing to try and give up. Some smokers are entirely happy with their smoking, a larger group would like to smoke less and a third group wants to quit. With the abrupt quitting message we are only addressing those wanting to quit. Maybe not even all, since some of them may have tried many times already and learned that they cannot quit abruptly. They may have given up on giving up. Some interesting results are given in recent studies that have recruited smokers not motivated to quit but interested in reducing their smoking. From nine randomized placebo-controlled trials where smokers were given behavioural support and pharmacological assistance, motivation to quit seemed to have increased, and in each trial, a proportion of these unmotivated smokers gave up smoking. It is suggested that for smokers unable or not interested in giving up abruptly, a softer and more gradual approach should be considered. Such an approach may bring new smokers into treatment, produce more people wanting to quit and improve public health.     

Partition congruences and the Andrews-Garvan-Dyson crank

In 1944, Freeman Dyson conjectured the existence of a "crank" function for partitions that would provide a combinatorial proof of Ramanujan's congruence modulo 11. Forty years later, Andrews and Garvan successfully found such a function and proved the celebrated result that the crank simultaneously "explains" the three Ramanujan congruences modulo 5, 7, and 11. This note announces the proof of a conjecture of Ono, which essentially asserts that the elusive crank satisfies exactly the same types of general congruences as the partition function.