Biology subjects

de la iglesia, H.

Publications and source records attributed to de la iglesia, H..

3 recordsLinked to original sources

bioRxiv2025

Modern Times: Longitudinal Study of Toba/Qom Communities Reveals Delay and Shortening of Sleep in Real-Time Across Electrification

While artificial light and digital technologies are widely assumed to delay and curtail sleep, direct, longitudinal evidence documenting these changes is remarkably scarce. From 2012 to 2024, we conducted a longitudinal study of native Toba/Qom communities in northern Argentina, including rural groups newly introduced to electricity and semi-urban groups with earlier access to electricity. Using linear mixed-effects models on a dataset of over 12,000 actigraphically recorded sleep events from 156 participants at different times, we observed striking shifts in sleep dynamics. Remarkably, both groups showed delays of up to 1.4 hours in sleep timing, and participants from rural communities lost a full hour of sleep within just a decade. These changes occurred across a period that included, first, the introduction of electricity to rural communities after 2016, and, in more recent years, the spread of the internet and smartphone use among the Toba/Qom. Our models reveal that these events alone cannot fully explain the observed shifts in sleep timing, suggesting that broader processes of modernization and acculturation, beyond electric light and digital devices alone, may be driving sleep changes. The rapid transformations observed in these communities mirror, within a single decade, the likely trajectory of human sleep across the 20th and early 21st centuries, underscoring the complex ways modern environments reshape sleep behavior.

physiology↗

bioRxiv2024

Ultrastructural correlates of circadian structural plasticity

In Drosophila, about 250 clock neurons in the brain form a network that orchestrates circadian rhythmicity. Among them, eight small Lateral ventral Neurons (s-LNvs) play a critical role, synchronizing the circadian ensemble via the neuropeptide Pigment-Dispersing Factor (PDF). Moreover, their neurites show daily variations in morphology, PDF levels, synaptic markers and connectivity. This process, called circadian structural plasticity, is ill-defined at the subcellular level. Here, we present 3D volumes of the s-LNv terminals generated by Serial Block-face Scanning Electron Microscopy (SBEM) at three key time points, two hours before lights-ON, two hours after lights-ON, and two hours after lights-OFF. We report a reduction in the number of neuronal varicosities at night, which reflects (and probably regulates) the cycling of the components we found therein. Indeed, in the morning we observed more presynaptic sites and increased accumulation and release of dense core vesicles. These rhythms were paralleled by periodic changes in mitochondrial structure that suggest daily modulation of their activity. We propose that circadian plasticity of the functionally relevant structures within presynaptic varicosities cyclically modulates the influence of the s-LNvs on the clock network.

neuroscience↗

bioRxiv2024

Lack of circadian entrainment and limited nocturnal plasticity in response to a cyclic aversive stimulus in a diurnal rodent, the antelope ground squirrel (Ammospermophilus leucurus)

Recent studies have shown that cyclic aversive stimuli, such as random footshocks, act as a nonphotic zeitgeber to entrain circadian behaviors in nocturnal rodents, a pattern termed "fear entrainment". However, it remains unknown whether diurnal species exhibit similar plasticity in behavioral timing. This study aimed to determine if antelope ground squirrels (Ammospermophilus leucurus; AGS), a naturally diurnal rodent, can also shift their activity patterns to cyclic aversive stimuli. We conducted two experiments with 20 AGS housed in custom cages featuring a safe nesting area and a separate foraging area (for feeding and drinking), rendered aversive by presentation of unsignaled, time-specific footshocks. In the first experiment, animals were subjected to a 12:12 light-dark (LD) cycle. One group experienced aversion during the light phase, while the control group received the same treatment during the dark phase. In the second experiment, a 16:8 LD cycle was used, and animals were divided into three groups with the foraging area rendered aversive either during the first or second half of the light phase or during the dark phase. Following each of these treatments, animals were released into constant darkness (DD) to assess the phase and period of free-running rhythms. Contrary to previous findings in nocturnal rodents, AGS did not exhibit consistent shifts in activity to avoid footshocks. Most animals maintained their normal diurnal activity, with only minor and inconsistent phase shifts. In experiment two, animals exposed to footshocks during half of the light phase also failed to reliably shift activity to the opposite "safe" portion of the light phase. Together, these findings show AGS lack the ability to entrain to cyclic aversive stimuli or become nocturnal; this result suggests a lack of substantial plasticity in activity timing. These results highlight the importance of considering species-specific differences in nonphotic circadian entrainment and temporal niche plasticity.

animal behavior and cognition↗