In this study, electroencephalography (EEG) was used to examine the relationship between two leading hypotheses of cognitive aging, the inhibitory deficit and the processing speed hypothesis. We show that older adults exhibit a selective deficit in suppressing task-irrelevant information during visual working memory encoding, but only in the early stages of visual processing. Thus, the employment of suppressive mechanisms are not abolished with aging but rather delayed in time, revealing a decline in processing speed that is selective for the inhibition of irrelevant information. EEG spectral analysis of signals from frontal regions suggests that this results from excessive attention to distracting information early in the time course of viewing irrelevant stimuli. Subdividing the older population based on working memory performance revealed that impaired suppression of distracting information early in the visual processing stream is associated with poorer memory of task-relevant information. Thus, these data reconcile two cognitive aging hypotheses by revealing that an interaction of deficits in inhibition and processing speed contributes to agerelated cognitive impairment.aging ͉ working memory ͉ inhibitory deficit ͉ distraction ͉ attention C ognitive impairment associated with normal aging impacts multiple domains [e.g., attention, working memory (WM) and episodic memory (1)], prompting a search for underlying neural mechanisms that might account for such widespread deficits. Two of the leading cognitive aging hypotheses are the ''processing speed hypothesis,'' in which performance deficits are attributed to a decline in processing speed (2), and the ''inhibitory deficit hypothesis,'' which proposes that impairment in diverse cognitive abilities are the result of an inability to reduce interference from task-irrelevant information (3). Despite widespread behavioral evidence, physiological data characterizing the neural underpinnings of these age-related deficits, and notably the interactions between them, are limited.A recent functional magnetic resonance imaging (fMRI) study supports the presence of an age-related top-down modulation deficit in inhibitory control (4). Top-down modulation is the neural process that underlies our ability to focus on relevant information and ignore irrelevant distractions via both the enhancement and suppression of sensory cortical activity (5, 6). The fMRI data revealed that, although older adults were able to enhance visual cortical activity for relevant information to the same extent as younger individuals, they were unable to adequately suppress activity associated with irrelevant information, and this suppression deficit correlated with their impaired WM performance (4).The current study is directed at exploring the relationship between the inhibitory deficit and processing speed hypothesis, a goal that necessitates obtaining high temporal resolution neural data to dissect the time-course of age-related processing changes. Because of the vascular nature of the fMRI blood o...

BackgroundWe have previously reported that the expression of the messenger ribonucleic acid (mRNA) for the NR2A subunit of the N-methyl-D-aspartate (NMDA) class of glutamate receptor was decreased in a subset of inhibitory interneurons in the cerebral cortex in schizophrenia. In this study, we sought to determine whether a deficit in the expression of NR2A mRNA was present in the subset of interneurons that contain the calcium buffer parvalbumin (PV) and whether this deficit was associated with a reduction in glutamatergic inputs in the prefrontal cortex (PFC) in schizophrenia.MethodsWe examined the expression of NR2A mRNA, labeled with a 35S-tagged riboprobe, in neurons that expressed PV mRNA, visualized with a digoxigenin-labeled riboprobe via an immunoperoxidase reaction, in twenty schizophrenia and twenty matched normal control subjects. We also immunohistochemically labeled the glutamatergic axon terminals with an antibody against vGluT1.ResultsThe density of the PV neurons that expressed NR2A mRNA was significantly decreased by 48-50% in layers 3 and 4 in the subjects with schizophrenia, but the cellular expression of NR2A mRNA in the PV neurons that exhibited a detectable level of this transcript was unchanged. In addition, the density of vGluT1-immunoreactive boutons was significantly decreased by 79% in layer 3, but was unchanged in layer 5 of the PFC in schizophrenia.ConclusionThese findings suggest that glutamatergic neurotransmission via NR2A-containing NMDA receptors on PV neurons in the PFC may be deficient in schizophrenia. This may disinhibit the postsynaptic excitatory circuits, contributing to neuronal injury, aberrant information flow and PFC functional deficits in schizophrenia.

Between 2015 and 2018, Lowell Massachusetts experienced outbreaks in opioid overdoses, HIV, and hepatitis C virus infections (HCV) among people who inject drugs. Through an innovative collaboration between emergency medical services (EMS), public health, and academic partners, we assessed the geographic distribution of opioid-related risks to inform intervention efforts. We analyzed data from three unique data sources for publicly discarded syringes, opioid-related incidents (ORIs), and fatal opioid overdoses in Lowell between 2008 and 2018. We assessed the risk environment over time using a geographic information system to identify and characterize hotspots and noted parallel trends within the syringe discard and ORI data. We identified two notable increases in ORIs per day: the first occurring between 2008 and 2010 (from 0.3 to 0.5), and the second between 2011 and 2014 (from 0.9 to 1.3), following the introduction of fentanyl within local drug markets. We also identified seasonal patterns in the syringe discard, ORI, and overdose data. Through our spatial analyses, we identified significant clusters of discarded syringes, ORIs, and fatal overdoses (p < 0.05), and neighborhoods where high densities of these outcomes overlapped. We found that areas with the highest densities shifted over time, expanding beyond the epicenter of the Downtown neighborhood. Data sharing and analyses among EMS, public health, and academic partners can foster better assessments of local risk environments. Our work, along with new public health efforts in Lowell, led to a city-funded position to improve pick-up and proper disposal of publicly discarded syringes, and better targeted harm reduction services.

A full-size airplane model (the EXPEDITE-RCS model) was developed as part of a benchmark suite for evaluating radar-cross-section (RCS) prediction methods. To generate accurate reference data for the benchmark problems formulated using the model, scale-model targets were additively manufactured, their material properties and RCS were measured, and the measurements were validated with a surface-integral-equation solver. To enable benchmarking of as many computational methods as possible, the following data are made available in a version-controlled online repository: (1) Exterior surface (outer mold line) of the CAD model in two standard file formats. (2) Triangular surface meshes. (3) Measured and predicted monostatic RCS data.