Papers for the month of August 2014


"Neural constraints on learning"
Nature, 512:423-426

Mouse over here for a brief summary or click to open article in a new tab.We explored the extent to which new patterns of neural activity can be generated through learning. The work combines closed-loop brain-computer interface learning with a computational framework to examine how networks of neurons reorganize while animals learn. Our results provide a novel network-level explanation for why some behaviors are easier to learn than others.


"Dimensionality reduction for large-scale neural recordings"
Nature Neuroscience, AOP:AOP

Mouse over here for a brief summary or click to open article in a new tab.In the last decade, the field has experienced rapid growth in the quantity and complexity of recorded neural activity. To address this challenge, many groups have adopted dimensionality reduction methods to analyze neural activity. This review article discusses the scientific motivation for applying dimensionality reduction methods to neural population activity, surveys the available methods, and provides examples of scientific discoveries they have enabled.


"Magic Angle-Enhanced MRI of Fibrous Microstructures in Sclera and Cornea with and without Intraocular Pressure Loading"
Investigative Ophthalmology & Visual Science, in press:in press

Mouse over here for a brief summary or click to open article in a new tab.Magic angle-enhanced MRI can detect ocular fibrous microstructures without contrast agents or coatings, and can reveal their MR tissue property changes with intraocular pressure loading. This technique may open up new avenues for assessment of the biomechanical and biochemical properties of ocular tissues in aging and in diseases involving the corneoscleral shell.


"Using artificial orthographies for studying cross-linguistic differences in the cognitive and neural profiles of reading"
Journal of Neurolinguistics, 31:69-85

Mouse over here for a brief summary or click to open article in a new tab.Reading and writing are cultural inventions that have become vital skills to master in modern society. Unfortunately, writing systems are not equally learnable and many individuals struggle to become proficient readers.


"Model Specification and the Reliability of fMRI Results: Implications for Longitudinal Neuroimaging Studies in Psychiatry"
Plos One, 9(8):e105169

Mouse over here for a brief summary or click to open article in a new tab.In this paper we examine the relationship between the reliability of task-based fMRI assessments separated by a long test-retest interval and the adequacy of the statistical models used to analyze the data.


"Developmental plateauin visual object processing from adolescence to adulthood in autism"
Brain and Cognition, 11:124

Mouse over here for a brief summary or click to open article in a new tab.Face recognition deficits in autism become more robust and generalize to other objects by adulthood, reflecting continued atypical brain maturation. Across tasks, the deficit in autism increased between adolescence and adulthood, reflecting a lack of typical improvement.


"Image familiarity sharpens response dynamics of neurons in inferotemporal cortex"
Nature Neuroscience, Epub ahead of print:000

Mouse over here for a brief summary or click to open article in a new tab.Making images familiar through repeated viewing reduces the strength with which the brain responds to them. Here we show that the reduction in response strength comes with a hidden advantage. The brain is much better able to track rapidly changing displays when they consist of familiar than when they consist of novel images.


"Selective Activation of Ipsilateral Motor Pathways in Intact Humans"
The Journal of Neuroscience, in press:2014

Mouse over here for a brief summary or click to open article in a new tab.It has been proposed that ipsilateral motor pathways play a role in the control of ipsilateral movements and recovery of function after injury. However, the extent to which ipsilateral motor pathways are involved in voluntary activity in intact humans remains largely unknown. Using transcranial magnetic stimulation over the arm representation of the motor cortex we examined ipsilateral motor evoked potentials (iMEPs) in a proximal arm muscle during increasing levels of unilateral and bilateral isometric force in a sitting position. We demonstrate that iMEPs area and amplitude decreased during bilateral activation of homonymous elbow flexor muscles and increased during bilateral activation of heteronymous elbow flexor and extensor muscles compared with a unilateral contraction, regardless of the force tested. To further understand the neuronal inputs involved in the bilateral effects we examined the contribution from neck afferents projecting onto ipsilateral motor pathways. Medial (away from the muscle tested) and lateral (toward the muscle tested) rotation of the head enhanced bilateral iMEPs effects from homonymous and heteronymous muscles, respectively. In contrast, head flexion and extension exerted nonspecific bilateral effects on iMEPs. Intracortical inhibition, in the motor cortex where iMEPs originated, was modulated in the same direction as iMEPs. We conclude that ipsilateral projections to proximal arm muscles can be selectively modulated by voluntary contraction of contralateral arm muscles, likely involving circuits mediating asymmetric tonic neck reflexes acting, at least in part, at the cortical level. The pattern of bilateral actions may represent a strategy to engage ipsilateral motor pathways in a motor


"Detection of high-frequency oscillations by hybrid depth electrodes in standard clinical intracranial EEG recordings"
Frontiers in Neurology, 5:149

Mouse over here for a brief summary or click to open article in a new tab.High-frequency oscillations (HFOs) have been proposed as a novel marker for epileptogenic tissue, yet in contrast to data recorded on research-customized recording systems, data from clinical acquisition systems remain an underutilized resource for HFO detection in most centers. HFOs in intracranial EEG detected by an offline, semi-automated method were validated in a clinical EEG viewer, demonstrating that (1) this clinical system allows for the visualization of HFOs and (2) with effective signal processing, clinical recordings can yield valuable information for offline analysis.


"Correlations in V1 Are Reduced by Stimulation Outside the Receptive Field"
The Journal of Neuroscience, 34(34):11222-11227

Mouse over here for a brief summary or click to open article in a new tab.We recorded the activity of dozens of cells using microelectrode arrays implanted in the superficial layers of V1 in anesthetized macaque monkeys. We presented annular stimuli that encircled —but did not impinge upon— the RFs of the recorded cells. We found that these “extra-classical” stimuli reduced correlations in the absence of stimulation of the RF, closely resembling the decorrelating effects of stimulating the RFs directly.


"Multi-faceted aspects of chunking enable robust algorithms"
Journal of Neurophysiology, 2014:00028

Mouse over here for a brief summary or click to open article in a new tab.We describe a new method for studying the development of chunking behaviors during sequential motor behaviors.


"To sort or not to sort: the impact of spike-sorting on neural decoding performance"
Journal of Neural Engineering, 11:056005

Mouse over here for a brief summary or click to open article in a new tab.We evaluate the effect of various spike sorting methods on the efficiency of BCIs. We find that discarding noise waveform degrades decoding, and that basic spike-sorting adds value to the low-threshold waveform-crossing methods often used in BCI decoding.


"“The organization and dynamics of corticostriatal pathways link the medial orbitofrontal cortex to future behavioral responses.” "
Journal of Neurophysiology, 000:000

Mouse over here for a brief summary or click to open article in a new tab.The anatomical organization and functional network properties of frontal corticostriatal systems mediate a link between responses in the medial orbitofrontal cortex and fast adaptive behavior in humans.