Nicotinic regulation of local and long-range input balance drives top-down attentional circuit maturation

Cognitive function depends on frontal cortex development; however, the mechanisms driving this process are poorly understood. Here, we identify that dynamic regulation of the nicotinic cholinergic system is a key driver of attentional circuit maturation associated with top-down frontal neurons projecting to visual cortex. The top-down neurons receive robust cholinergic inputs, but their nicotinic tone decreases following adolescence by increasing expression of a nicotinic brake, Lynx1. Lynx1 shifts a balance between local and long-range inputs onto top-down frontal neurons following adolescence and promotes the establishment of attentional behavior in adulthood. This key maturational process is disrupted in a mouse model of fragile X syndrome but was rescued by a suppression of nicotinic tone through the introduction of Lynx1 in top-down projections. Nicotinic signaling may serve as a target to rebalance local/long-range balance and treat cognitive deficits in neurodevelopmental disorders.

Sleep Impairment

Sleep is a vital physiological state, and it is essential for optimal daytime function. Sleep patterns undergo tremendous quantitative and structural changes throughout the maturational process from infancy to late adolescence. These universal alterations in sleep and sleep patterns reflect the essential need for optimal sleep during normal healthy development. Unfortunately, sleep loss has become omnipresent in modern adult culture and has also become a widespread phenomenon among children, particularly with respect to adolescents. Specifically, sleep loss in adolescence is a function of multiple normative endogenous changes often amplified by exogenous influences. Substance abuse has also achieved epidemic proportions among today’s adolescents, with well-documented negative functional outcomes. This chapter summarizes objective and subjective studies examining the bidirectional links between alcohol and substance use and inadequate sleep and/or sleep patterns in adolescents.

Use of the Tooth Coronal Pulp Index for Recognition of the Pubertal Growth Period

ABSTRACT Aim The present study aimed to investigate the association between the tooth coronal index (TCI) and the pubertal growth stages (PGS) for children and adolescents. Materials and methods A cross-sectional study was performed using retrospectively collected panoramic and hand-wrist radiographs of 262 individuals (125 males, 137 females). The coronal height (CH) and the coronal pulp cavity height (CPCH) of the left mandibular teeth were measured. Then the TCI for which was calculated according to Ikeda et al (1985). The estimated TCI for individuals with the following PGS after Fishman (1987) are: SMI 4 (S), SMI 5 (DP3 cap), SMI 6 (MP3 cap) and SMI 7 (Mp5 cap). The associations between the TCI and the PGS were investigated by correlation coefficient of Spearman's rho, and the validity values for the PGS were computed. Results Significant correlations were noted between the simple TCI values for premolars and molars and the PGS, and the highest correlation was for the summed TCI for both first and second molars. Utilizing the validity values of the summed TCI for both first and second mandibular molars, the PGS can be predicted as follows: S stage when TCI is 49.17 or lesser, DP3cap stage when TCI is 43.52 or lesser, MP3cap stage when TCI is 36.73 or lesser, and Mp5cap stage when TCI is 26.84 or lesser. Conclusion The TCI values declined along with the maturational process in children and adolescents. The TCI for both first and second molars was the best predictor of the PGS. Clinical significance Panoramic photographs can be beneficial for prediction of the skeletal maturity and treatment planning without resorting to hand-wrist radiographs. How to cite this article Nawaya FR, Burhan AS. Use of the Tooth Coronal Pulp Index for Recognition of the Pubertal Growth Period. J Contemp Dent Pract 2016;17(11):884-889.

What does a neuron learn from multisensory experience?

The brain's ability to integrate information from different senses is acquired only after extensive sensory experience. However, whether early life experience instantiates a general integrative capacity in multisensory neurons or one limited to the particular cross-modal stimulus combinations to which one has been exposed is not known. By selectively restricting either visual-nonvisual or auditory-nonauditory experience during the first few months of life, the present study found that trisensory neurons in cat superior colliculus (as well as their bisensory counterparts) became adapted to the cross-modal stimulus combinations specific to each rearing environment. Thus, even at maturity, trisensory neurons did not integrate all cross-modal stimulus combinations to which they were capable of responding, but only those that had been linked via experience to constitute a coherent spatiotemporal event. This selective maturational process determines which environmental events will become the most effective targets for superior colliculus-mediated shifts of attention and orientation.

Plasticity in the acquisition of multisensory integration capabilities in superior colliculus

The multisensory integration capabilities of superior colliculus (SC) neurons are normally acquired during early postnatal life and adapted to the environment in which they will be used. Recent evidence shows that they can even be acquired in adulthood, and require neither consciousness nor any of the reinforcement contingencies generally associated with learning. This process is believed to be based on Hebbian mechanisms, whereby the temporal coupling of multiple sensory inputs initiates development of a means of integrating their information. This predicts that co-activation of those input channels is sufficient to induce multisensory integration capabilities regardless of the specific spatiotemporal properties of the initiating stimuli. However, one might expect that the stimuli to be integrated should be consonant with the functional role of the neurons involved. For the SC, this would involve stimuli that can be localized. Experience with a non-localizable cue in one modality (e.g., ambient sound) and a discrete stimulus in another (e.g., a light flash) should not be sufficient for this purpose. Indeed, experiments with cats reared in omnidirectional sound (effectively masking discrete auditory events) reveal that the simple co-activation of two sensory input channels is not sufficient for this purpose. The data suggest that experience with the kinds of cross-modal events that facilitate the role of the SC in detecting, locating, and orienting to localized external events is a guiding factor in this maturational process. Supported by NIH grants NS 036916 and EY016716.