Papers for the month of April 2017

Rasmussen R., Schwartz A.

"Dynamic range adaptation in primary motor cortical populations"
eLife, 6:1

Mouse over here for a brief summary or click to open article in a new tab.Neural populations from various sensory regions demonstrate dynamic range adaptation in response to changes in the statistical distribution of their input stimuli. These adaptations help optimize the transmission of information about sensory inputs. Here, we show a similar effect in the firing rates of primary motor cortical cells. Our results demonstrate that dynamic range adaptation is neither limited to sensory regions nor to rescaling of monotonic stimulus intensity tuning curves, but may rather represent a canonical feature of neural encoding.

Ly, Cheng

"Noise-enhanced coding in phasic neuron spike trains"
PloS One, 10:1371

Mouse over here for a brief summary or click to open article in a new tab.Phasic neurons respond only to transient inputs and do not show sustained firing to constant input. We investigate the coding properties of phasic neurons in the presence of background noise.

Lemaitre, G., Pyles, J.A., Halpern, A.R., Naviolio, N., Lehet, M.

"Who is that Knocking at My Door? Neural Bases of Sound Source Identification"
Cerebral Cortex, 04 January 2017:1-14

Mouse over here for a brief summary or click to open article in a new tab.When hearing a sound such as knocking on a door, a listener typically identifies both the action (forceful repeated impacts) and the object (a thick wooden board) causing the sound. We investigated the neural bases of this type of sound source identification by having listeners attend to these different aspects of sounds during functional magnetic resonance imaging scans. Our results are consistent with previous studies suggesting that auditory perception is better suited to comprehend the actions rather than the objects producing the sounds in the listeners environment.

Simmonds, DJ., Hallquist MN., Luna B.

"Protracted development of executive and mnemonic brain systems underlying working memory in adolescence: a longitudinal fMRI study"
Neuroimage, 17:1053-8119

Mouse over here for a brief summary or click to open article in a new tab.Abstract Working memory (WM), the ability to hold information on-line to guide planned behavior, improves through adolescence in parallel with continued maturation of critical brain systems supporting cognitive control. Initial developmental neuroimaging studies with one or two timepoints have provided important though varied results limiting our understanding of which and how neural systems change during this transition into mature WM. In this study, we leverage functional magnetic resonance imaging (fMRI) longitudinal data spanning up to 9 years in 129 normally developing individuals to identify which systems demonstrate growth changes that accompany improvements in WM performance. We used a memory guided saccade task that allowed us to probe encoding, pure maintenance, and retrieval neural processes of WM. Consistent with prior research, we found that WM performance continued to improve into the early 20s. fMRI region of interest (ROI) analyses revealed developmental (1) increases in sensorimotor-related (encoding/retrieval) activity in visual cortex from childhood through early adulthood that were associated with WM accuracy and (2) decreases in sustained (maintenance) activity in executive regions from childhood through mid-adolescence that were associated with response latency in childhood and early adolescence. Together these results provide compelling evidence that underlying the maturation of WM is a transition from reliance on executive systems to specialized regions related to the domain of mnemonic requirements of the task leading to optimal performance.

Nicholls FJ, Liu JR

"A Comparison of Exogenous Labels for the Histological Identification of Transplanted Neural Stem Cells."
Cell Transplantation, 26:625-645

Mouse over here for a brief summary or click to open article in a new tab.The interpretation of cell transplantation experiments is often dependent on the presence of an exogenous label for the identification of implanted cells. The exogenous labels Hoechst 33342, 5-bromo-2′-deoxyuridine (BrdU), PKH26, and Qtracker were compared for their labeling efficiency, cellular effects, and reliability to identify a human neural stem cell (hNSC) line implanted intracerebrally into the rat brain. Hoechst 33342 (2 mg/ml) exhibited a delayed cytotoxicity that killed all cells within 7 days. This label was hence not progressed to in vivo studies. PKH26 (5 μM), Qtracker (15 nM), and BrdU (0.2 μM) labeled 100% of the cell population at day 1, although BrdU labeling declined by day 7. BrdU and Qtracker exerted effects on proliferation and differentiation. PKH26 reduced viability and proliferation at day 1, but this normalized by day 7. In an in vitro coculture assay, all labels transferred to unlabeled cells. After transplantation, the reliability of exogenous labels was assessed against the gold standard of a human-specific nuclear antigen (HNA) antibody. BrdU, PKH26, and Qtracker resulted in a very small proportion (<2%) of false positives, but a significant amount of false negatives (∼30%), with little change between 1 and 7 days. Exogenous labels can therefore be reliable to identify transplanted cells without exerting major cellular effects, but validation is required. The interpretation of cell transplantation experiments should be presented in the context of the label’s limitations.

Fang, X., Stafura, J.

"Learning new meanings for known words: Biphasic effects of prior knowledge"
Learning Cognition and Neuroscience, 32:637-649

Mouse over here for a brief summary or click to open article in a new tab.Overall, the results suggest that form-based familiarity facilitates learning earlier, while meaning-based interference becomes more influential later. The co-activation of new and old meanings during learning may play a role in lexicalisation of new meanings.

Matsui K., Fukazawa Y., Kamasawa N.n Harada H., Itakura K., Molnáe E., Abe M., Sakimura K., Shigemoto R.

"The number and distribution of AMPA receptor channels containing fast kinetic GluA3 and GluA4 subunits at auditory nerve synapses depend on the target cells "
Brain Structure and Function, 0:1

Mouse over here for a brief summary or click to open article in a new tab.This study investigated whether AMPA receptors containing fast kinetic GluA3 and GluA4 subunits were differentially expressed at auditory nerve synapses with distinct electrophysiological properties.

Zarco, W., Freiwald, W.*

"A causal relationship between face-patch activity and face-detection behavior."
ELife, 6:18558

Mouse over here for a brief summary or click to open article in a new tab.Disrupting the activity of the medial lateral face patch (ML) using fMRI-targeted microinjections of muscimol leads to anatomically and categorically specific impairments in a naturalistic face detection task.


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