Association of Cannabis Use During Adolescence With Neurodevelopment

IMPORTANCE

Animal studies have shown that the adolescent brain is sensitive to disruptions in endocannabinoid signaling, resulting in altered neurodevelopment and lasting behavioral effects. However, few studies have investigated ties between cannabis use and adolescent brain development in humans.

OBJECTIVE

To examine the degree to which magnetic resonance (MR) imaging-assessed cerebral cortical thickness development is associated with cannabis use in a longitudinal sample of adolescents.

DESIGN, SETTING, AND PARTICIPANTS

Data were obtained from the community-based IMAGEN cohort study, conducted across 8 European sites. Baseline data used in the present study were acquired from March 1, 2008, to December 31, 2011, and follow-up data were acquired from January 1, 2013, to December 31, 2016. A total of 799 IMAGEN participants were identified who reported being cannabis naive at study baseline and had behavioral and neuroimaging data available at baseline and 5-year follow-up. Statistical analysis was performed from October 1, 2019, to August 31, 2020.

MAIN OUTCOMES AND MEASURES

Cannabis use was assessed at baseline and 5-year follow-up with the European School Survey Project on Alcohol and Other Drugs. Anatomical MR images were acquired with a 3-dimensional T1-weighted magnetization prepared gradient echo sequence. Quality-controlled native MR images were processed through the CIVET pipeline, version 2.1.0.

RESULTS

The study evaluated 1598 MR images from 799 participants (450 female participants [56.3%]; mean [SD] age, 14.4 [0.4] years at baseline and 19.0 [0.7] years at follow-up). At 5-year follow-up, cannabis use (from 0 to >40 uses) was negatively associated with thickness in left prefrontal (peak: t785 = -4.87, cluster size = 1558 vertices; P = 1.10 × 10-6, random field theory cluster corrected) and right prefrontal (peak: t785 = -4.27, cluster size = 1551 vertices; P = 2.81 × 10-5, random field theory cluster corrected) cortices. There were no significant associations between lifetime cannabis use at 5-year follow-up and baseline cortical thickness, suggesting that the observed neuroanatomical differences did not precede initiation of cannabis use. Longitudinal analysis revealed that age-related cortical thinning was qualified by cannabis use in a dose-dependent fashion such that greater use, from baseline to follow-up, was associated with increased thinning in left prefrontal (peak: t815.27 = -4.24, cluster size = 3643 vertices; P = 2.28 × 10-8, random field theory cluster corrected) and right prefrontal (peak: t813.30 = -4.71, cluster size = 2675 vertices; P = 3.72 × 10-8, random field theory cluster corrected) cortices. The spatial pattern of cannabis-related thinning was associated with age-related thinning in this sample (r = 0.540; P < .001), and a positron emission tomography-assessed cannabinoid 1 receptor-binding map derived from a separate sample of participants (r = -0.189; P < .001). Analysis revealed that thinning in right prefrontal cortices, from baseline to follow-up, was associated with attentional impulsiveness at follow-up.

CONCLUSIONS AND RELEVANCE

Results suggest that cannabis use during adolescence is associated with altered neurodevelopment, particularly in cortices rich in cannabinoid 1 receptors and undergoing the greatest age-related thickness change in middle to late adolescence.

Localized electro-thermal processing: a new route to the patterning of magnetic recording media

Previous reports have detailed the fabrication of media able to support high density magnetic recording in both longitudinal and perpendicular formats by the global rapid thermal processing of sputtered non-magnetic precursor films. During processing in this manner a magnetic element is released from its nitride and agglomerates to form a random near mono-dispersion of magnetic nano-particles. Here we explore, primarily through modelling and simulation, the feasibility of processing similarly formulated precursor media not globally but locally. We investigate the potential of using conducting nano-probe tips to produce, via electro-thermal (Joule) heating, a nano-patterned recording medium in the form of regular arrays of magnetic islands in a non-magnetic host. In the first instance we concentrate on the simplest cobalt based precursor medium for which both initial simulation and experimental studies indicate the formation of magnetic islands with dimensions of the order of the tip diameter; this is relatively straightforward. The results signify that if practical production scenarios can be devised to produce technologically significant areas of recording media by the rapid multi-probe repetition of this technique, then processing in this manner offers a promising route to areal recording densities of perhaps 5 Terabit/in(2) even with the simplest cobalt media. We also note that the electro-thermal processing method is potentially extendable to the production of a wide variety of magnetic materials (e.g. PtCo, FeCo, NiFe alloys) and, applied via electrical nano-imprinting type techniques, to the production of a wide variety of patterned structures.

Effect of twisting hamstring tendon grafts on strength and joint laxity through the range of knee movement

Twisting or braiding of hamstring tendon grafts for use in anterior cruciate ligament reconstructions has been advocated to increase their strength and stiffness under load. In this study, a two-dimensional model was used to determine the failure strength of twisted and parallel grafts and associated knee laxity under simulated physiological loading conditions. For validation, mechanical tests of tendon grafts were also simulated with these models. The simulated physiological loading of the graft models showed that knees with twisted grafts had greater laxity than knees with parallel grafts, although there was little difference in failure load between the two graft configurations. The tensile loading of the graft models showed little difference in failure load when the tendons were modelled using line segments. When the tendons were considered as three-dimensional helical elements, which more accurately describe the tendon structure, the failure load of the twisted graft decreased significantly. This research provided no evidence to support the belief that a twisted tendon graft is a superior graft configuration relative to a parallel tendon graft.

Auditory enhancement of changes in spectral amplitude

An auditory enhancement effect occurs when one component of a harmonic series is omitted for a few hundred milliseconds and then reintroduced: The reintroduced harmonic stands out perceptually. Three experiments are reported that studied a version of this effect in which several components of a harmonic series are enhanced to define the formants of a vowel. Using the accuracy of vowel identification to measure the prominence of the formant peaks in the effective auditory representation, forms of the effect were identified that are qualitatively similar to the incremental and decremental responses seen in primary auditory-nerve fibers. These results are compatible with an origin for the enhancement effect in peripheral auditory adaptation. However, an additional mechanism is required to account for the demonstration [Viemeister and Bacon, J. Acoust. Soc. Am. 71, 1502-1507 (1982)] that enhancement can involve a true gain in the frequency region of the reintroduced component. These effects demonstrate one way in which the auditory system may attenuate the prominence of background noises while preserving the ability to represent changes in spectral amplitude produced by newly arriving signals.