Papers for the month of January 2016

Solomon, S.H., Thompson-Schill, S.L.

"A meta-analysis of fMRI decoding: Quantifying influences on human visual population codes."
Neuropsychologia, 82:134-141

Mouse over here for a brief summary or click to open article in a new tab.Information in the human visual system is encoded in the activity of distributed populations of neurons, which in turn is reflected in functional magnetic resonance imaging (fMRI) data. Through a novel multi-study meta-analysis, we have analyzed and modeled relations between decoding strength in the visual ventral stream, and stimulus and methodological variables that differ across studies. As well as revealing principles of regional processing, our results and approach can help investigators select from the thousands of design and analysis options in an empirical manner, to optimize future studies of fMRI decoding.

Weisz, Cat, Rubio, ME

"Excitation by Axon Terminal GABA Spillover in a Sound Localization Circuit"
The Journal of Neuroscience, 36:911-025

Mouse over here for a brief summary or click to open article in a new tab.In this study, a new mechanism of neuronal communication between auditory synapses in the mammalian sound localization pathway is described. Evidence is provided that the inhibitory neurotransmitter GABA can spill over between axon terminals to cause excitation of nearby synapses to further stimulate neurotransmitter release. Excitatory GABA spillover between inhibitory axon terminals may have important implications for the development and refinement of this auditory circuit and may play a role in the ability to precisely localize sound sources

Rosso AL, Aizenstein HJ, Harris T, Newman AB, Satterfield S, Studenski SA, Yaffe K, Health ABC Study

"Cerebral White Matter and Slow Gait: Contribution of Hyperintensities and Normal-appearing Parenchyma"
J Gerontol A Biol Sci Med Sci, 2016 Jan 11:1-5

Mouse over here for a brief summary or click to open article in a new tab.BACKGROUND: White matter hyperintensities (WMH), a common marker of cerebral small vessel disease, and lower microstructural integrity of normal-appearing white matter are associated with slower gait. How these cerebral measures interact in relation to slower gait is unknown. We assessed whether microstructural integrity of normal-appearing white matter, measured by fractional anisotropy (FA), moderates the association of higher WMH with slower gait. METHODS: WMH, FA, and gait speed were acquired for 265 community-dwelling older adults (average age = 82.9 years). RESULTS: The inverse association between WMH and gait was robust to adjustment for age, gender, muscle strength, obesity, stroke, and hypertension (fully adjusted model: βs = -0.19, p = .001). The interaction between WMH and FA was significant; analyses stratified by FA showed that the inverse association between WMH and gait speed was significant only for those with low FA (FA < median, fully adjusted model: βs = -0.28, p = .001). Voxel-based results were similar for participants with FA less than median, there was an inverse association between gait speed and WMH which extended throughout the white matter (genu and body of corpus callosum, anterior limb of internal capsule, corona radiata, and superior longitudinal and fronto-occipital fasciculus). In contrast, for participants with FA ≥ median, the association was limited to the genu of corpus callosum, the cingulum, and the inferior longitudinal fasciculus. CONCLUSIONS: Microstructural integrity is a moderating factor in the association between WMH and gait. Future studies should examine whether higher microstructural integrity represents a source of compensation in those with greater WMH burden to maintain function in late life.

Perera S, Patel KV, Rubin SM, Satterfield S, Harris T, Ensrud K, Orwoll E, Lee CG, Chandler JM, Newman AB, Cauley JA, Guralnik JM, Ferrucci L, Studenski SA

"Gait Speed Predicts Incident Disability: A Pooled Analysis"
Journals of Gerontology: Medical Sciences, 71(1):63-71

Mouse over here for a brief summary or click to open article in a new tab. Background. Functional independence with aging is an important goal for individuals and society. Simple prognostic indicators can inform health promotion and care planning, but evidence is limited by heterogeneity in measures of function. Methods. We performed a pooled analysis of data from seven studies of 27,220 community-dwelling older adults aged 65 or older with baseline gait speed, followed for disability and mortality. Outcomes were incident inability or dependence on another person in bathing or dressing; and difficulty walking ¼ – ½ mile or climbing 10 steps within 3 years. Results. Participants with faster baseline gait had lower rates of incident disability. In subgroups (defined by 0.2 m/s-wide intervals from <0.4 to ≥1.4 m/s) with increasingly greater gait speed, 3-year rates of bathing or dressing dependence trended from 10% to 1% in men, and from 15% to 1% in women, while mobility difficulty trended from 47% to 4% in men and 40% to 6% in women. The age-adjusted relative risk ratio per 0.1 m/s greater speed for bathing or dressing dependence in men was 0.68 (0.57–0.81) and in women: 0.74 (0.66–0.82); for mobility difficulty, men: 0.75 (0.68–0.82), women: 0.73 (0.67–0.80). Results were similar for combined disability and mortality. Effects were largely consistent across subgroups based on age, gender, race, body mass index, prior hospitalization, and selected chronic conditions. In the presence of multiple other risk factors for disability, gait speed significantly increased the area under the receiver operator characteristic curve. Conclusion. In older adults, gait speed predicts 3 year incidence of bathing or dressing dependence, mobility difficulty, and a composite outcome of disability and mortality.

Nunley KA, Ryan CM, Saxton JA, Costacou T, Orchard TJ

"Response to Comment on Nunley et al. Clinically Relevant Cognitive Impairment in Middle-Aged Adults With Childhood-Onset Type 1 Diabetes"
Diabetes Care, 38:1768-1776

Mouse over here for a brief summary or click to open article in a new tab.We would like to thank van Broekhoven and Nefs (1) for their thoughtful comment that depression may explain the high rate of cognitive impairment (28%) we reported among adults with type 1 diabetes (T1D) (2). As our objective was to investigate the biological correlates of cognitive impairment in this patient population, the original article did not address depression. We do, of course, agree that this is an important topic, with studies showing lingering deleterious effects of depression on cognition even after depressive symptoms subside (3). Even so, our knowledge regarding depressive symptoms in adults with childhood-onset T1D remains limited. We therefore appreciate this opportunity to discuss our data on the cross-sectional relationship between cognitive impairment, assessed in 2010–2013 (2), and depressive symptoms, assessed via the Beck Depression Inventory (BDI) in 2004–2006, controlling for education and antidepressant use.

Golub, Matthew

"Brain-computer interfaces for dissecting cognitive processes underlying sensorimotor control"
Curr Opin Neurobiol, 37:53-58

Mouse over here for a brief summary or click to open article in a new tab.Brain-computer interfaces (BCI) are most commonly known for their use in assisting paralyzed or disabled patients. In this review article, we discuss how BCI can be exploited as an experimental paradigm for addressing basic scientific questions about sensorimotor control.


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