Biology subjects

Foster, B. L.

Publications and source records attributed to Foster, B. L..

4 recordsLinked to original sources

bioRxiv2021

A new tripartite landmark in posterior cingulate cortex

Understanding brain structure-function relationships, and their development and evolution, is central to neuroscience research. Here, we show that morphological differences in posterior cingulate cortex (PCC), a hub of functional brain networks, predict individual differences in macroanatomical, microstructural, and functional features of PCC. Manually labeling 4,319 sulci in 552 hemispheres, we discovered a consistently localized shallow cortical indentation (termed the inframarginal sulcus; ifrms) within PCC that is absent from neuroanatomical atlases, yet co-localized with a region within the cognitive control, but not default mode, network. Morphological analyses in humans and chimpanzees showed that unique properties of the ifrms differ across the lifespan and between hominoid species. Intriguingly, the consistency of the ifrms also debunks the uniqueness of the morphology of Einsteins PCC. These findings support a classic theory that shallow, tertiary sulci serve as landmarks in association cortices. They also beg the question: how many other cortical indentations have we missed?

neuroscience↗

bioRxiv2021

Orientation and color tuning of the human visual gamma rhythm

Narrowband gamma oscillations (NBG: [~]20-60Hz) in visual cortex reflect rhythmic fluctuations in population activity generated by underlying circuits tuned for stimulus location, orientation, and color. Consequently, the amplitude and frequency of induced NBG activity is highly sensitive to these stimulus features. For example, in the non-human primate, NBG displays biases in orientation and color tuning at the population level. Such biases may relate to recent reports describing the large-scale organization of single-cell orientation and color tuning in visual cortex, thus providing a potential bridge between measurements made at different scales. Similar biases in NBG population tuning have been predicted to exist in the human visual cortex, but this has yet to be fully examined. Using intracranial recordings from human visual cortex, we investigated the tuning of NBG to orientation and color, both independently and in conjunction. NBG was shown to display a cardinal orientation bias (horizontal) and also an end- and mid-spectral color bias (red/blue and green). When jointly probed, the cardinal bias for orientation was attenuated and an end-spectral preference for red and blue predominated. These data both elaborate on the close, yet complex, link between the population dynamics driving NBG oscillations and known feature selectivity biases in visual cortex, adding to a growing set of stimulus dependencies associated with the genesis of NBG. Together, these two factors may provide a fruitful testing ground for examining multi-scale models of brain activity, and impose new constraints on the functional significance of the visual gamma rhythm. Significance StatementOscillations in electrophysiological activity occur in visual cortex in response to stimuli that strongly drive the orientation or color selectivity of visual neurons. The significance of this induced gamma rhythm to brain function remains unclear. Answering this question requires understanding how and why some stimuli can reliably generate gamma activity while others do not. We examined how different orientations and colors independently and jointly modulate gamma oscillations in the human brain. Our data show gamma oscillations are greatest for certain orientations and colors that reflect known biases in visual cortex. Such findings complicate the functional significance of gamma activity, but open new avenues for linking circuits to population dynamics in visual cortex. ClassificationNeuroscience

neuroscience↗

bioRxiv2020

Stability of ripple events during task engagement in human hippocampus

Periods of cognitive disengagement, such as rest or sleep, are thought to support the progressive consolidation of episodic memories. During these states, the hippocampus displays transient high-frequency oscillatory bursts, known as ripples, which are thought to promote interactions with the neocortex, consolidating memory traces. More recent findings have suggested ripples in the human hippocampus may also occur during task engagement, particularly for tasks requiring episodic memory processes. However, it is unclear if hippocampal ripples occur during other cognitive states or whether ripple properties are modulated by specific types of task demands. In addition, identifying genuine hippocampal ripple events in the human brain can be methodological challenging. To address these questions, we used intracranial recordings from the human hippocampus to quantify ripple events across perceptual, memory and resting task states. Using spectro-temporal identification of hippocampal ripples, we observed highly similar ripple event properties across tasks, with a modest yet significant increase in ripple properties (rate, duration & amplitude) during resting task states. These ripple event attributes did not differ between hemisphere, nor across or within the time of day examined. Supporting data further highlighted that while hippocampal ripples occurred during all task states, these rates were typically lower than that observed during sleep. Together, these findings highlight that hippocampal ripples occur consistently, but sparsely, during a broad range of cognitive task states. Such findings may be incorporated into existing models of systems consolidation, whereby hippocampal ripples help to initially establish latent memory traces.

neuroscience↗

bioRxiv2020

Monocyte Subsets with High Osteoclastogenic Potential and Their Epigenetic Regulation Orchestrated by IRF8

Osteoclasts (OCs) are bone resorbing cells formed by the serial fusion of monocytes. In mice and humans, three distinct subsets of monocytes exist; however, it is unclear if all of them exhibit osteoclastogenic potential. Here we show that in wild-type mice, Ly6Chi and Ly6Cint monocytes are the primary source of OC formation when compared to Ly6C- monocytes. Their osteoclastogenic potential is dictated by increased expression of signaling receptors and activation of pre-established transcripts, as well as de novo gain in enhancer activity and promoter changes. In the absence of IRF8, a transcription factor important for myelopoiesis and osteoclastogenesis, all three monocyte subsets are programmed to display higher osteoclastogenic potential. Enhanced NFATc1 nuclear translocation and amplified transcriptomic and epigenetic changes initiated at early developmental stages direct the increased osteoclastogenesis in Irf8 deficient mice. Collectively, our study provides novel insights into the transcription factors and active cis-regulatory elements that regulate OC differentiation.

immunology↗