The mammalian visual system, from retina to neocortex, has been extensively studied at both anatomical and functional levels. Anatomy indicates the cortico-thalamic system is hierarchical, but characterization of cellular-level functional interactions across multiple levels of this hierarchy is lacking, partially due to the challenge of simultaneously recording activity across numerous regions. Here, we describe a large, open dataset (part of the Allen Brain Observatory) that surveys spiking from units in six cortical and two thalamic regions responding to a battery of visual stimuli. Using spike cross-correlation analysis, we find that inter-area functional connectivity mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas. Classical functional measures of hierarchy, including visual response latency, receptive field size, phase-locking to a drifting grating stimulus, and autocorrelation timescale are all correlated with the anatomical hierarchy. Moreover, recordings during a visual task support the behavioral relevance of hierarchical processing. Overall, this dataset and the hierarchy we describe provide a foundation for understanding coding and dynamics in the mouse cortico-thalamic visual system..
Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections.
Abstract. Over recent decades Antarctic sea-ice extent has increased, alongside
widespread ice shelf thinning and freshening of waters along the Antarctic
margin. In contrast, Earth system models generally simulate a decrease in
sea ice. Circulation of water masses beneath large-cavity ice shelves is not
included in current Earth System models and may be a driver of this
phenomena. We examine a Holocene sediment core off East Antarctica that
records the Neoglacial transition, the last major baseline shift of
Antarctic sea ice, and part of a late-Holocene global cooling trend. We
provide a multi-proxy record of Holocene glacial meltwater input, sediment
transport, and sea-ice variability. Our record, supported by high-resolution
ocean modelling, shows that a rapid Antarctic sea-ice increase during the
mid-Holocene (∼ 4.5 ka) occurred against a backdrop of
increasing glacial meltwater input and gradual climate warming. We suggest
that mid-Holocene ice shelf cavity expansion led to cooling of surface
waters and sea-ice growth that slowed basal ice shelf melting.
Incorporating this feedback mechanism into global climate models will be
important for future projections of Antarctic changes.
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