Biomedical subjects

Sara N Burke

Publications and source records attributed to Sara N Burke.

7 recordsLinked to original sources

PubMed2026

Individual Differences in Cognitive Aging Rodent Datasets (ID-CARD): A collaborative platform for behavioral analysis across the lifespan.

Understanding cognitive aging requires approaches that capture individual variability while enabling integration across studies. In rodent models, behavioral data are central to this effort, yet cross-laboratory differences in experimental design limit comparability and constrain secondary analysis. To address this gap, we developed the Individual Differences in Cognitive Aging Rodent Datasets (ID-CARD), a first-of-its-kind collaborative repository aggregating trial-level Morris water maze data from multiple laboratories. ID-CARD is designed to support large-scale, integrative analyses and to facilitate secondary use of existing behavioral data in alignment with emerging data-sharing and transparency initiatives. Rather than imposing retrospective harmonization of experimental protocols, we implemented a normalization and modeling framework that enables comparison of learning trajectories while preserving meaningful variation across studies. Behavioral data from > 5000 rats spanning common strains, both sexes, and multiple ages were normalized in training and performance domains and fit with a logarithmic function to derive an error accumulation rate coefficient (EARC) as a measure of spatial learning. Age was strongly associated with increased EARC, indicating attenuated learning, even after adjusting for non-spatial cue performance. Analyses of goodness of fit revealed systematic structure in learning dynamics, where age was associated with reduced learning-curve conformity after accounting for overall performance. Inter-individual variability in spatial learning also increased with age, with strain-specific interactions. These findings demonstrate that integrated analysis of heterogeneous behavioral datasets can yield robust, individual-level insights into cognitive aging. ID-CARD provides a scalable resource and analytic framework to advance discovery in behavioral neuroscience by enabling reuse, integration, and comparative analysis of existing data.

Cognitive aging↗

PubMed2006

Phase precession in hippocampal interneurons showing strong functional coupling to individual pyramidal cells.

Although hippocampal interneurons typically do not show discrete regions of elevated firing in an environment, such as seen in pyramidal cell place fields, they do exhibit significant spatial modulation (McNaughton et al., 1983a). Strong monosynaptic coupling between pyramidal neurons and nearby interneurons in the CA1 stratum pyramidale has been strongly implicated on the basis of significant, short-latency peaks in cross-correlogram plots (Csicsvari et al., 1998). Furthermore, interneurons receiving a putative monosynaptic connection from a simultaneously recorded pyramidal cell appear to inherit the spatial modulation of the latter (Marshall et al., 2002). Buzsaki and colleagues hypothesize that interneurons may also adopt the firing phase dynamics of their afferent place cells, which show a phase shift relative to the hippocampal theta rhythm as a rat passes through the place field ("phase precession"). This study confirms and extends the previous reports by showing that interneurons in the dorsal and middle hippocampus with putative monosynaptic connections with place cells recorded on the same tetrode share other properties with their pyramidal cell afferents, including the spatial scale of the place field of pyramidal cell, a characteristic of the septotemporal level of the hippocampus from which the cells are recorded, and the rate of phase precession, which is slower in middle regions. Furthermore, variations in pyramidal cell place field scale within each septotemporal level attributable to task variations are similarly associated with variations in interneuron place field scale. The available data strongly suggest that spatial selectivity of CA1 stratum pyramidale interneurons is inherited from a small cluster of local pyramidal cells and is not a consequence of spatially selective synaptic input from CA3 or other sources.

Action Potentials↗

PubMed2006

Organization of hippocampal cell assemblies based on theta phase precession.

The factors that control the spatial tuning of hippocampal neurons are incompletely understood, and there is no generally agreed upon definition of what constitutes a "place field". One factor that must be considered is the phenomenon of "phase precession". As a rat passes through the place field of a particular hippocampal neuron, its spikes shift to earlier phases of the theta rhythm. Except for the special cases discussed herein, the phase shift never exceeds 360 degrees. Moreover, under conditions in which place field sizes change dynamically, precession rate is tightly coupled with the place field size, suggesting that a single cycle of theta phase precession could be used to define unitary place field boundaries. Theta phase precession implies that the "cell assembly" of active hippocampal neurons changes systematically over the course of a single theta cycle. A given cell can exhibit more than one place field in a given environment, each field showing the same pattern of 360 degrees of phase precession. The existence of multiple fields implies that one cell can participate in multiple cell assemblies within the same environment. We show here that place fields, defined as a single cycle of phase precession, can overlap spatially, with the result that the cell fires with spikes clustered at two different phases over the theta cycles in which the fields overlap. Thus, the same neuron can participate in different cell assemblies within a single theta cycle.

Action Potentials↗

PubMed2006

Neural plasticity in the ageing brain.

The mechanisms involved in plasticity in the nervous system are thought to support cognition, and some of these processes are affected during normal ageing. Notably, cognitive functions that rely on the medial temporal lobe and prefrontal cortex, such as learning, memory and executive function, show considerable age-related decline. It is therefore not surprising that several neural mechanisms in these brain areas also seem to be particularly vulnerable during the ageing process. In this review, we discuss major advances in our understanding of age-related changes in the medial temporal lobe and prefrontal cortex and how these changes in functional plasticity contribute to behavioural impairments in the absence of significant pathology.

Aging↗

PubMed2005

Differential encoding of behavior and spatial context in deep and superficial layers of the neocortex.

Rodent hippocampal activity is correlated with spatial and behavioral context, but how context affects coding in association neocortex is not well understood. The cellular distribution of the neural activity-regulated immediate-early gene Arc was used to monitor the activity history of cells in CA1, and in deep and superficial layers of posterior parietal and gustatory cortices (which encode movement and taste, respectively), during two behavioral epochs in which spatial and behavioral context were independently manipulated while gustatory input was held constant. Under conditions in which the hippocampus strongly differentiated behavioral and spatial contexts, deep parietal and gustatory layers did not discriminate between spatial contexts, whereas superficial layers in both neocortical regions discriminated well. Deep parietal cells discriminated behavioral context, whereas deep gustatory cortex neurons encoded the two conditions identically. Increased context sensitivity of superficial neocortical layers, which receive more hippocampal outflow, may reflect a general principle of neocortical organization for memory retrieval.

Animals↗

PubMed2004

3D-catFISH: a system for automated quantitative three-dimensional compartmental analysis of temporal gene transcription activity imaged by fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) of neural activity-regulated, immediate-early gene (IEG) expression provides a method of functional brain imaging with cellular resolution. This enables the identification, in one brain, of which specific principal neurons were active during each of two distinct behavioral epochs. The unprecedented potential of this differential method for large-scale analysis of functional neural circuits is limited, however, by the time-intensive nature of manual image analysis. A comprehensive software tool for processing three-dimensional, multi-spectral confocal image stacks is described which supports the automation of this analysis. Nuclei counterstained with conventional DNA dyes and FISH signals indicating the sub-cellular distribution of specific, IEG RNA species are imaged using different spectral channels. The DNA channel data are segmented into individual nuclei by a three-dimensional multi-step algorithm that corrects for depth-dependent attenuation, non-isotropic voxels, and imaging noise. Intra-nuclear and cytoplasmic FISH signals are associated spatially with the nuclear segmentation results to generate a detailed tabular/database and graphic representation. Here we present a comprehensive validation of data generated by the automated software against manual quantification by human experts on hippocampal and parietal cortical regions (96.5% concordance with multi-expert consensus). The high degree of reliability and accuracy suggests that the software will generalize well to multiple brain areas and eventually to large-scale brain analysis.

Algorithms↗

PubMedDate not supplied

Visual sensitivity across the menstrual cycle.

This study was designed to evaluate the hypothesis that hormonal change can affect lower level light-adaptation processes, which are likely to be retinally based. Foveal visual sensitivities were measured across several menstrual cycles of four women not using hormonally acting medication and across several menstrual cycles of three women using a triphasic oral contraceptive. One woman, diagnosed with premenstrual syndrome (PMS), was a subject for both groups. Sensitivities were measured for a series of test wavelengths for 580-nm backgrounds of 2.0 and 4.0 log td. Of the six individuals tested, one had clear evidence of visual-adaptation changes occurring in phase with the menstrual cycle. Prior to using the oral contraceptive, this individual (the PMS subject) experienced changes of short-wavelength-sensitive (SWS)-cone-mediated sensitivities of up to about 1.4 log unit on the 4.0 log td background. Her SWS-cone-mediated sensitivities tended to be highest near ovulation and lowest premenstrually. Threshold-versus-illuminance (TVI) curves confirmed that the rate of sensitivity decrease with increasing background illuminance (i.e. the TVI slope) was greater premenstrually. The degree of background-induced desensitization within her middle-wavelength-sensitive (MWS)/long-wavelength-sensitive (LWS) cone pathways also appeared to vary cyclically, but the magnitude of the variation was smaller and the time course appeared to be different. When this subject began oral contraceptive use, the patterns of sensitivity change were all altered. None of the other five subjects experienced changes of SWS-cone-mediated vision that were cyclic and significantly adaptation-state dependent. However, there was evidence for a limited degree of cyclic adaptation change within the MWS/LWS cone pathways of at least one additional subject. We conclude that hormonal change can--for some unknown proportion of women--be linked to alterations of retinal function. However, the alterations are not the same for all visual pathways, and there are pronounced individual differences. The data also demonstrate that individuals' visual adaptation capabilities can vary substantially over periods of weeks.

Adaptation, Physiological↗