Survey of spiking in the mouse visual system reveals functional hierarchy.

The anatomy of the mammalian visual system, from the retina to the neocortex, is organized hierarchically1. However, direct observation of cellular-level functional interactions across this hierarchy is lacking due to the challenge of simultaneously recording activity across numerous regions. Here we describe a large, open dataset-part of the Allen Brain Observatory2-that surveys spiking from tens of thousands of units in six cortical and two thalamic regions in the brains of mice responding to a battery of visual stimuli. Using cross-correlation analysis, we reveal that the organization of inter-area functional connectivity during visual stimulation mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas3. We find that four classical hierarchical measures-response latency, receptive-field size, phase-locking to drifting gratings and response decay timescale-are all correlated with the hierarchy. Moreover, recordings obtained during a visual task reveal that the correlation between neural activity and behavioural choice also increases along the hierarchy. Our study provides a foundation for understanding coding and signal propagation across hierarchically organized cortical and thalamic visual areas.

A cohort study comparing pharmacist activities during participation in general medical ward rounds: telehealth versus in-person during the COVID-19 pandemic.

BACKGROUND: The COVID-19 pandemic created systemic challenges in patient care delivery. AIM: To evaluate the impact on pharmacist activities during pharmacist participation in ward rounds via telehealth, compared to physical attendance. METHOD: A single-centre, retrospective cohort study conducted from 18th Aug through 26th Oct 2020. Patients admitted to COVID and non-COVID general medical teams were included. Pharmacists attended ward rounds via telehealth for COVID teams; physical attendance continued for non-COVID teams. Telehealth involved pharmacists interacting with clinicians and patients virtually via videoconferencing whilst stationed remotely on the ward. Routine clinical pharmacy activities during telehealth ward rounds were compared to those during face-to-face ward rounds using comparative statistics. RESULTS: Among the 1230 patients included (762 COVID, 468 non-COVID), pharmacist participation in telehealth ward rounds demonstrated significantly more documented activities compared with face-to-face rounds (mean 6.7 vs 4.9 per patient per day, p < 0.001). The telehealth cohort exhibited a higher number of orders placed via pharmacy-partnered medication charting (3.0 vs 2.4 per patient per day, p < 0.001), medication orders verified (2.3 vs 1.1, p < 0.001), and documented pharmacy notes (0.6 vs 0.2, p < 0.001). No significant difference was observed in medication requests processed (0.4 vs 0.4, p = 738), whilst non-COVID patients had more discharge prescription items generated (0.3 vs 0.7, p < 0.001). CONCLUSION: Pharmacist involvement in medical ward rounds via telehealth enabled the ongoing provision of advanced clinical pharmacy services to inpatients in isolation rooms during the COVID-19 pandemic. This approach resulted in a greater number of pharmacy activities during telehealth ward rounds compared to standard in-person attendance.

A whole-brain monosynaptic input connectome to neuron classes in mouse visual cortex.

Identification of structural connections between neurons is a prerequisite to understanding brain function. Here we developed a pipeline to systematically map brain-wide monosynaptic input connections to genetically defined neuronal populations using an optimized rabies tracing system. We used mouse visual cortex as the exemplar system and revealed quantitative target-specific, layer-specific and cell-class-specific differences in its presynaptic connectomes. The retrograde connectivity indicates the presence of ventral and dorsal visual streams and further reveals topographically organized and continuously varying subnetworks mediated by different higher visual areas. The visual cortex hierarchy can be derived from intracortical feedforward and feedback pathways mediated by upper-layer and lower-layer input neurons. We also identify a new role for layer 6 neurons in mediating reciprocal interhemispheric connections. This study expands our knowledge of the visual system connectomes and demonstrates that the pipeline can be scaled up to dissect connectivity of different cell populations across the mouse brain.

Measuring Stimulus-Evoked Neurophysiological Differentiation in Distinct Populations of Neurons in Mouse Visual Cortex.

Despite significant progress in understanding neural coding, it remains unclear how the coordinated activity of large populations of neurons relates to what an observer actually perceives. Since neurophysiological differences must underlie differences among percepts, differentiation analysis-quantifying distinct patterns of neurophysiological activity-has been proposed as an "inside-out" approach that addresses this question. This methodology contrasts with "outside-in" approaches such as feature tuning and decoding analyses, which are defined in terms of extrinsic experimental variables. Here, we used two-photon calcium imaging in mice of both sexes to systematically survey stimulus-evoked neurophysiological differentiation (ND) in excitatory neuronal populations in layers (L)2/3, L4, and L5 across five visual cortical areas (primary, lateromedial, anterolateral, posteromedial, and anteromedial) in response to naturalistic and phase-scrambled movie stimuli. We find that unscrambled stimuli evoke greater ND than scrambled stimuli specifically in L2/3 of the anterolateral and anteromedial areas, and that this effect is modulated by arousal state and locomotion. By contrast, decoding performance was far above chance and did not vary substantially across areas and layers. Differentiation also differed within the unscrambled stimulus set, suggesting that differentiation analysis may be used to probe the ethological relevance of individual stimuli.

Mangrove growth in New Zealand estuaries: the role of nutrient enrichment at sites with contrasting rates of sedimentation.

Mangrove forest coverage is increasing in the estuaries of the North Island of New Zealand, causing changes in estuarine ecosystem structure and function. Sedimentation and associated nutrient enrichment have been proposed to be factors leading to increases in mangrove cover, but the relative importance of each of these factors is unknown. We conducted a fertilization study in estuaries with different sedimentation histories in order to determine the role of nutrient enrichment in stimulating mangrove growth and forest development. We expected that if mangroves were nutrient-limited, nutrient enrichment would lead to increases in mangrove growth and forest structure and that nutrient enrichment of trees in our site with low sedimentation would give rise to trees and sediments that converged in terms of functional characteristics on control sites in our high sedimentation site. The effects of fertilizing with nitrogen (N) varied among sites and across the intertidal zone, with enhancements in growth, photosynthetic carbon gain, N resorption prior to leaf senescence and the leaf area index of canopies being significantly greater at the high sedimentation sites than at the low sedimentation sites, and in landward dwarf trees compared to seaward fringing trees. Sediment respiration (CO(2) efflux) was higher at the high sedimentation site than at the low one sedimentation site, but it was not significantly affected by fertilization, suggesting that the high sedimentation site supported greater bacterial mineralization of sediment carbon. Nutrient enrichment of the coastal zone has a role in facilitating the expansion of mangroves in estuaries of the North Island of New Zealand, but this effect is secondary to that of sedimentation, which increases habitat area and stimulates growth. In estuaries with high sediment loads, enrichment with N will cause greater mangrove growth and further changes in ecosystem function.