bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.08.25.744599

The circadian system is affected by Alzheimers disease independently from amyloid beta deposits

Calligaro, H.·Khov, B.·Noel, K.·Glina, A.·van Rosmalen, L.·Ramasamy, R.·Li, Y.·Lam, M. T. Y.·Le, H.·Kim, K.-Y.·Ju, W.-K.·Ellisman, M.·Panda, S.
View original source ↗Export metadata ↓

Abstract

Circadian disruption, notably sleep disturbances, serves as an early indicator of Alzheimers disease (AD), preceding cognitive symptoms like memory loss. The suprachiasmatic nucleus (SCN) governs biological rhythms and receives direct retinal input via melanopsin-expressing retinal ganglion cells (mRGCs) to synchronize with environmental light cycles. The anatomical and functional basis for circadian disruption in AD remains unclear. Here, we explored the multi-level relationships between gene expression, the SCN connectome, and regulations of sleep and circadian rhythms in the APP/PS1 mouse model. The sleep architecture of APP/PS1 mice displayed significantly reduced rapid eye movement sleep (REM), associated with a reduced daily core body temperature amplitude and locomotor hyperactivity. Lastly, APP/PS1 mice showed an impaired response to acute light pulse stimulation and present hyperactivity of mRGCs at a young age and hypoactivity of these cells at older ages. These physiological functions are known to be, at least in part, regulated by the SCN, the main target of mRGCs. We noted several modifications in SCN connectomics using serial blockface electron microscopy (SBEM), including a reduction of the dendro-dendritic chemical synapse (DDCS) network that receives a large part of the retinal input and is thought to be crucial for synchronicity between SCN neurons. In addition, we observed multiple signs of dystrophy, including modifications of the shape of dendrites and cell soma, accumulation of aggregated lysosomes, and swelling of axons. At the same time, we investigated the changes in gene expression using spatial transcriptomics. The SCN presents changes in the expression of genes associated with synapse formation, cell adhesion, and neurite growth. These results suggest that, despite the absence of amyloid plaques in the ventral hypothalamus, the SCN of APP/PS1 mice still undergo profound gene expression changes, impacting connectomics and physiological functions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC="FIGDIR/small/744599v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@ceedb0org.highwire.dtl.DTLVardef@156cfaaorg.highwire.dtl.DTLVardef@5bc262org.highwire.dtl.DTLVardef@36df4d_HPS_FORMAT_FIGEXP M_FIG C_FIG

Explore related subjects

neurosciencePreprint

Keep this discovery

BibTeXRIS

Calligaro, H., Khov, B., Noel, K., Glina, A., van Rosmalen, L., Ramasamy, R., Li, Y., Lam, M. T. Y., Le, H., Kim, K.-Y., Ju, W.-K., Ellisman, M., Panda, S.. 2026-09-01. The circadian system is affected by Alzheimers disease independently from amyloid beta deposits. https://doi.org/10.64898/2026.08.25.744599

Cite the original work for its findings. Save a collection to share your selection of sources.

Discover connections

Preprint resourcePreprint subjectneuroscience subject

Connections use source metadata and explicit phrase matches, not verified experimental comparisons.

KEEP EXPLORING

Related preprints

bioRxiv2026

Evolution and Human Neural Individuality

Individuality is a defining feature of human biology. The functional network architecture of the human brain harbors person-specific qualities and forms individualized connectivity profiles that function as a neural fingerprint, both stable and unique across time. Here, using fMRI data from 431 Human Connectome Project participants, we examined whether neural individuality is more strongly exhibited in brain regions bearing signatures of recent human evolution. We calculated region-wise fingerprinting accuracy and associated it with four properties of evolutionary cortical organization: cortical expansion, myelin content estimate (T1w/T2w), human-specific gene-expression profiles, and functional homology to other primates. Across all four measures, neural individuality was strongest in cortical areas showing greater evolutionary novelty in humans, particularly frontoparietal control and default mode networks, and weaker in more conserved primary regions. Our findings connect evolutionary variation across species with stable functional variation among individuals.

neuroscience↗
bioRxiv2026

Motor planning and execution establish distinct feedforward and feedback motor histories

Movements are systematically affected by the recent motor history. These history effects may be induced either by reused motor plans or from lingering tuning of the previous movements' execution. We dissociated planning and execution using four experimental manipulations across two complementary motor paradigms. We isolated planning by preventing execution with stop signals and mechanical blocks, and execution by moving participants' hand passively using a robot manipulandum. History effects emerged in feedforward movement aspects - reaction time and early movement kinematics - following isolated planning. In contrast, they were absent or markedly reduced for isolated execution. History effects emerged also in late movement aspect that involves sensory feedback during execution - movement accuracy and precision - but only when movements were both planned and executed. Feedforward effects generalized across hands, whereas feedback effects were effector specific. Thus, prior motor planning and execution make distinct and complementary contributions in shaping future motor behavior.

neuroscience↗
bioRxiv2026

A cognitive representation in primary visual cortex modulated by vision

Primary visual cortex (V1) is a critical substrate for mammalian vision. Traditionally, visual inputs are thought to be the main drivers of V1 activity, with internal signals playing a modulatory role. Here we show that this relationship is inverted for a large fraction of V1 neurons. In rats completing a navigation task in darkness, these neurons encoded progress along physically distinct paths with a shared turn structure. Under illumination, visual stimuli gain-modulated this path-invariant activity rather than replacing it with stimulus-driven responses. Path-invariant V1 neurons were also preferentially coordinated with hippocampal ensembles during sharp-wave ripples, linking them to a brain-wide network involved in learning. These findings establish that an internal model of the world can serve as a primary driver of activity in sensory cortex.

neuroscience↗