Papers for the month of April 2016

Haigh, S. M., Gupta, A., Barb, S. M., Glass, S. A. F., Minshew, N. J., Dinstein, I., Heeger, D. J., Eack, S. M., Behrmann, M.

"Differential sensory fMRI signatures in autism and schizophrenia: Analysis of amplitude and trial-to-trial variability"
Schizophrenia Research, 0:0

Mouse over here for a brief summary or click to open article in a new tab.Comparison of sensory fMRI responses in individuals with autism, individuals with schizophrenia and healthy controls. Both autism and schizophrenia showed reduced signal-to-noise ratios (SNR) in visual, auditory and somatosensory responses. However, while reduced SNR was due to greater trial-to-trial variability in autism, schizophrenia showed normal variability and reduced response amplitudes. This suggests different mechanisms underlying sensory abnormalities in autism and schizophrenia.

Lee, A. C. H., Geskin, J. Z., Graham,K. S., and Barense, M. D.

"Temporal lobe contribution to perceptual function: A tale of three patient groups"
Neuropsychologia, in press; PMID: 27150707:doi: 10.1016/j.neuropsychologia.2016.05.002

Mouse over here for a brief summary or click to open article in a new tab.There has been growing recognition of the contribution of medial temporal lobe structures to non-mnemonic functions, such as perception. To evaluate the nature of this contribution, we contrast the perceptual performance of three patients groups, all of whom have a perturbation of these temporal lobe structures: patients with focal hippocampal (HC) lesions, those with lesions to the medial temporal lobe (MTL) that include HC and perirhinal cortex (PrC) and those with congenital prosopagnosia (CP), whose deficit has been attributed to the disconnection of the anterior temporal lobe from more posterior structures. All participants completed a range of ‘oddity’ tasks in which they determined which of four visual stimuli in a display was the ‘odd-one-out’. There were five stimulus categories including faces, scenes, objects (high and low ambiguity) and squares of different sizes. The group profiles were easily differentiable. Whereas the HC group stood out for its difficulty in discriminating scenes and the CP group stood out for its disproportionate difficulty in discriminating faces with milder effects for faces and high ambiguity objects, the MTL group evinced a more general discrimination deficit for faces, scenes and high ambiguity objects. The group differences highlight distinct profiles for each of the three groups and distinguish the signature perceptual impairments following more extended temporal lobe alterations.

Oby E., Perel S., Sadtler P., Ruff D., Mischel J., Montez D., Cohen M.

"Extracellular voltage threshold settings can be tuned for optimal encoding of movement and stimulus parameters."
Journal of Neural Engineering, 13(3):036009

Mouse over here for a brief summary or click to open article in a new tab.We introduce a procedure to determine the best threshold for extracting information from extracellular recordings. We apply this procedure in two distinct contexts: the encoding of kinematic parameters from neural activity in primary motor cortex (M1), and visual stimulus parameters from neural activity in primary visual cortex (V1).

Hall, N.J.

"Express saccades and superior colliculus responses are sensitive to short-wavelength cone contrast"
Proceedings of the National Academy of Sciences, 00:00

Mouse over here for a brief summary or click to open article in a new tab.It is widely believed that the superior colliculus (SC) is unable to use input from short-wavelength–sensitive cones (S-cones) in the retina. Contrary to this assumption, we show that express saccades, an SC-dependent behavior, are sensitive to S-cone contrast. This finding demonstrates that S-cone stimuli cannot be used to infer SC contributions to behavior.

Hirshorn, E. A., Wrencher, A., Durisko, C., Moore, M. W.,

"Fusiform Gyrus Laterality in Writing Systems with Different Mapping Principles: An Artificial Orthography Training Study."
Journal of cognitive neuroscience., 28(6):882-894.

Mouse over here for a brief summary or click to open article in a new tab.Writing systems vary in many ways, making it difficult to account for cross-linguistic neural differences. For example, orthographic processing of Chinese characters activates the mid-fusiform gyri (mFG) bilaterally, whereas the processing of English words predominantly activates the left mFG. Because Chinese and English vary in visual processing (holistic vs. analytical) and linguistic mapping principle (morphosyllabic vs. alphabetic), either factor could account for mFG laterality differences. We used artificial orthographies representing English to investigate the effect of mapping principle on mFG lateralization. The fMRI data were compared for two groups that acquired foundational proficiency: one for an alphabetic and one for an alphasyllabic artificial orthography. Greater bilateral mFG activation was observed in the alphasyllabic versus alphabetic group. The degree of bilaterality correlated with reading fluency for the learned orthography in the alphasyllabic but not alphabetic group. The results suggest that writing systems with a syllable-based mapping principle recruit bilateral mFG to support orthographic processing. Implications for individuals with left mFG dysfunction will be discussed.

Venkatesh P, Grover P

" Is the direction of greater Granger causal influence the same as the direction of information flow?"
2015 53rd Annual Allerton Conference on Communication, Control, and Computing (Allerton) , 2015:672 - 679

Mouse over here for a brief summary or click to open article in a new tab.We provide information-theoretic counterexamples demonstrating that Granger causality (and its generalization, directed information) can easily yield the incorrect direction of information flows. This holds even when all nodes in the system are measured (i.e., there is no latent variable). We also discuss what techniques could yield the correct direction (a part of our ongoing work).

"Sensorimotor Convergence in Circuitry of the Motor Cortex"
The Neuroscientist, epub ahead of print:epub ahead of print

Mouse over here for a brief summary or click to open article in a new tab.Here, I review the general pathways that convey ascending sensory and descending motor information, using the rodent whisker system as a model to take advantage of the cell type specificity possible in this model. I then detail the circuits in motor cortex in which incoming information from somatosensory cortex and thalamus is integrated. I close with a brief description of changes in these circuits during motor learning.

Mason, R., Just, M.

"Neural Representations of Physics Concepts"
Psychological Science, 10.1177/0956797616641941:1-10

Mouse over here for a brief summary or click to open article in a new tab.The research showed how learning physics concepts is accomplished by repurposing neural structures that were originally used for general everyday purposes. More specifically, the brain is able to learn physics concepts because of its ability to understand the four fundamental concepts of causal motion, periodicity, energy flow and algebraic (sentence-like) representations.

Hanmi Lee, Eva Bach, Jihyun Noh, Eric Delpire

"Hyperpolarization-independent maturation and refinement of GABA/glycinergic connections in the auditory brain stem"
J. Neurophysiology, 115(3):1170-1182

Mouse over here for a brief summary or click to open article in a new tab.During development GABA and glycine synapses are initially excitatory before they gradually become inhibitory. This transition is due to a developmental increase in the activity of neuronal potassium-chloride cotransporter 2 (KCC2), which shifts the chloride equilibrium potential (ECl) to values more negative than the resting membrane potential. While the role of early GABA and glycine depolarizations in neuronal development has become increasingly clear, the role of the transition to hyperpolarization in synapse maturation and circuit refinement has remained an open question. Here we investigated this question by examining the maturation and developmental refinement of GABA/glycinergic and glutamatergic synapses in the lateral superior olive (LSO), a binaural auditory brain stem nucleus, in KCC2-knockdown mice, in which GABA and glycine remain depolarizing. We found that many key events in the development of synaptic inputs to the LSO, such as changes in neurotransmitter phenotype, strengthening and elimination of GABA/glycinergic connection, and maturation of glutamatergic synapses, occur undisturbed in KCC2-knockdown mice compared with wild-type mice. These results indicate that maturation of inhibitory and excitatory synapses in the LSO is independent of the GABA and glycine depolarization-to-hyperpolarization transition.

Park J., Wood J., Bondi C., Del Arco A.

"Anxiety evokes hypofrontality and disrupts rule-relevant encoding by dorsomedial prefrontal cortex neurons."
The Journal of Neuroscience, 36(11):3322-3335

Mouse over here for a brief summary or click to open article in a new tab.Using a clinically valid experimental model, we find that, under anxiety, decision making may be skewed by salient and conflicting environmental stimuli at the expense of flexible top-down guided choices. We also find that anxiety suppresses spontaneous activity of PFC neurons, and weakens encoding of task rules by dorsomedial PFC neurons.

Jason Samonds, Christopher Tyler.

"Evidence of stereoscopic surface disambiguation in the responses of V1 neurons"
Cerebral Cortex, doi: 10.1093/cercor/bhw064. First published online: March 10, 2016:1-16

Mouse over here for a brief summary or click to open article in a new tab.This paper provided evidence for surface filling-in at the level of V1 . It showed very sparse disparity signals in the contextual surround can bias the responses of V1 disparity-tuned neurons to a bistable stimuli over their receptive fields in a way that is consistent with perception. The results provided explicit evidence that cooperative computational circuits implemented by recurrent circuits for solving the stereo correspondence problem can also produce effects of perceptual filling-in and surface interpolation.

Coffman B.A., Haigh S.M., Murphy T.K.

"Event-Related Potentials Demonstrate Deficits in Acoustic Segmentation in Schizophrenia"
Schizophrenia Research, 73:109-115

Mouse over here for a brief summary or click to open article in a new tab.Event-related potentials were examined in response to grouped tones to elucidate schizophrenia-related differences in acoustic segmentation. We report for the first time in healthy subjects a sustained potential that begins with group initiation and ends with the last tone of the group. These potentials were reduced in schizophrenia, with the greatest differences in responses to first and final tones.

"Tonal frequency affects amplitude but not topography of rhesus monkey cranial EEG components"
Hearing Research, 336:29-43

Mouse over here for a brief summary or click to open article in a new tab.Detailed description of auditory evoked EEG potentials using a high-density full-coverage cranial EEG system in rhesus monkeys


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