ICAR: endoscopic skull‐base surgery

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High resolution fMRI reveals distinct forms of associative novelty in the medial temporal lobe

Both Alzheimer’s Disease and Parkinson’s Disease involve alterations to the structure of the medial temporal lobe (MTL). Varying patterns of neuronal connectivity, however, suggest that not only does the MTL support learning and memory, but that its subregions play distinct roles in these processes as well. The exact nature of these contributions remains an area of active investigation. Examinations of associative novelty may offer an important tool for characterizing the processes carried out by different subregions. Associative novelty can be further broken down into associative novelty per se, which are simply novel stimulus configurations, and associative mismatch novelty, which are novel stimulus configurations that violate existing expectations. In this study, we used high resolution fMRI to characterize different associative novelty signals across the MTL; specifically, we were interested in whether there was a dissociation of associative novelty signal types between MTL subregions, or instead, a functional specialization for associative novelty signal types distributed across these subregions. Establishing subregional function could help elucidate the spectrum of cognitive deficits manifest in both Parkinson’s and Alzheimer’s patients.Biological Sciences, School o

Electron and Hole Conductivity in CuInS\u3csub\u3e2\u3c/sub\u3e

Single crystals of CuInS2 have been grown from the melt and annealed in In or S to produce good n- or p-type conductivity, respectively. Two donor levels, one shallow and one deep (0.35 eV), and one acceptor level at 0.15 eV are identified. The hole-mobility data are best fitted with an effective mass , which can be explained by simple, two band . theory if the valence band has appreciable d character. Above 300°K, the hole mobility falls rapidly, evidently due to multiband conduction and/or interband scattering between the nondegenerate and degenerate valence bands. The conduction band mobility appears to be dominated, in many samples, by large concentrations ( \u3e1018cm−3) of native donors and acceptors, which are closely compensated

Repetition suppression in the medial temporal lobe and midbrain is altered by event overlap

Repeated encounters with the same event typically lead to decreased activation in the medial temporal lobe (MTL) and dopaminergic midbrain, a phenomenon known as repetition suppression. In contrast, encountering an event that overlaps with prior experience leads to increased response in the same regions. Such increased responding is thought to reflect an associative novelty signal that promotes memory updating to resolve differences between current events and stored memories. Here, we married these ideas to test whether event overlap significantly modulates MTL and midbrain responses—even when events are repeated and expected—to promote memory updating through integration. While undergoing high-resolution functional MRI, participants were repeatedly presented with objects pairs, some of which overlapped with other, intervening pairs and some of which contained elements unique from other pairs. MTL and midbrain regions showed widespread repetition suppression for non-overlapping pairs containing unique elements; however, the degree of repetition suppression was altered for overlapping pairs. Entorhinal cortex, perirhinal cortex (PRc), midbrain, and PRc—midbrain connectivity showed repetition-related increases across overlapping pairs. Notably, increased PRc activation for overlapping pairs tracked individual differences in the ability to reason about the relationships among pairs—our behavioral measure of memory integration. Within hippocampus, activation increases across overlapping pairs were unique to CA(1), consistent with its hypothesized comparator function. These findings demonstrate that event overlap engages MTL and midbrain functions traditionally implicated in novelty processing, even when overlapping events themselves are repeated. Our findings further suggest that the MTL—midbrain response to event overlap may promote integration of new content into existing memories, leading to the formation of relational memory networks that span experiences. Moreover, the results inform theories about the division of labor within MTL, demonstrating that the role of PRc in episodic encoding extends beyond familiarity processing and item-level recognition