100 research outputs found
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Studies of photoreceptor throughput to visual cortex
No full textThe work in this dissertation aims to (1) examine the presence of a functional map in the mouse visual cortex by measuring its variable cone M-opsin and S-opsin inputs, as predicted by the graded dorsoventral cone opsin expression in the retina (Rhim et al., 2017), (2) devise a method for measuring rod saturation and utilize it to characterize differential spatio-temporal tuning between rod-mediated and cone-mediated vision in V1 (Rhim et al., 2021), and (3) study the representation of color and form. We report that the dorsoventral cone opsin expression gradient in the retina is recapitulated in the mouse visual cortex, including primary visual cortex (V1) and higher visual areas (HVAs). This provides a first finding of a functional map in the mouse cortex, next to retinotopy map. Next, we exploit this feature in the mouse cortex to measure variable opsin inputs to the cortex to provide a model to estimate rod saturation. This is a much-needed foundation in mouse vision research, which will help future studies to differentially quantify inputs from the three photoreceptor opsins found in mice: rhodopsin, S-opsin, and M-opsin. We exemplify this by studying the spatio-temporal tuning of rod-mediated vs. cone-mediated vision in V1. Cone-mediated V1 responds to 2.5-fold higher temporal frequencies than rod-mediated V1, highlighting differences in rod vs. cone information throughput. Lastly, we study the mechanisms underlying spatio-chromatic processing in the cortex. We find that V1's spatial frequency (SF) tuning is more low-pass to color contrast than brightness (i.e., luminance) contrast. Furthermore, our data can be accounted by a random wiring model with rhodopsin and cone S-opsin inputs to single-opponent V1 neurons. While classic models of single-opponency require selective wiring for ON and OFF subfields from each photoreceptor class, we find this to be inconsistent with our data. This provides a new insight to mechanism underlying color vision.Psycholog
Enhanced neuronal activity in the medial prefrontal cortex during social approach behavior
No full textAlthough the medial prefrontal cortex (mPFC) is known to play a crucial role in rodent social behavior, little is known aboutmPFCneural correlates of social behavior. In the present study,weexamined single-neuron activity in themPFCof mice performing a modified version of the three-chamber test. We found that a subset of mPFC neurons elevate discharge rates when approaching a stranger mouse but not when approaching an inanimate object or an empty chamber. Our results reveal mPFC neural activity that is correlated with social approach behavior in a widely used social-interaction paradigm. These findings might be helpful for future investigations ofmPFCneural processes underlying social interaction in health and disease. © 2016 The Authors7711Nsciescopu
Representations of color and form in mouse visual cortex
No full textSpatial transitions in color can aid any visual perception task, and its neural representation – an "integration of color and form" – is thought to begin at primary visual cortex (V1). Color and form integration is untested in mouse V1, yet studies show that the ventral retina provides the necessary substrate from green-sensitive rods and UV-sensitive cones. Here, we used two-photon imaging in V1 to measure spatial frequency (SF) tuning along four axes of rod and cone contrast space, including luminance and color. We first reveal that V1 has similar responsiveness to luminance and color, yet average SF tuning is significantly shifted lowpass for color. Next, guided by linear models, we used SF tuning along all four color axes to estimate the proportion of neurons that fall into classic models of color opponency – "single-", "double-", and "non-opponent". Few neurons (~6%) fit the criteria for double-opponency, which are uniquely tuned for chromatic borders. Most of the population can be described as a unimodal distribution ranging from strongly single-opponent to non-opponent. Consistent with recent studies of the rodent and primate retina, our V1 data is well-described by a simple model in which ON and OFF channels to V1 sample the photoreceptor mosaic randomly.See uploaded README files for details.
Below is the top of README_for_dataset.doc.
This describes the uploaded data set used in Rhim and Nauhaus: "Joint representations of color and form in mouse visual cortex described by random pooling from rods and cones". It is a MATLAB .mat file, where each structure pertains to a given figure. In addition to the source data for the figures, it also has the following additions:
The same data set, but prior to culling the population according to the dashed box in the Figure 2 scatter plot. See variables appended with "…_all"
Region-of-interest ID associated with each neuron.
Below is all the information in README_for_simulations.doc.
To run the simulations for Figures 1,6,7, and 8, execute the cells in the high-level scripts of the following: Figure_1.m, Figure_6_7.m, Figure_8.m. Make sure all the other .m files are in your path.Funding provided by: National Institutes of HealthCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000002Award Number: R01EY028657Funding provided by: Whitehall FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100001391Award Number:This data comes from two-photon imaging in mouse primary visual cortex.
There is also Matlab code to run the simulations in figures 1, 6, 7, and 8
Dr. Issac Clark, 1979
No full textDr. Issac Clark and a man exchange a handshake and a plaque award over a podium as others look on.The Atlanta University Center Robert W. Woodruff Library acknowledges the generous support of the National Endowment for Humanities - Humanities Collections and Reference Resources Implementation Project Grant in supporting the processing and digitization of a number of its major archival collections as part of the project: Spreading the Word: Expanding Access to African American Religious Archival Collections at the Atlanta University Center Robert W. Woodruff Library.</em
Sexually dimorphic behavior, neuronal activity, and gene expression in Chd8-mutant mice
No full textAutism spectrum disorders (ASDs) are four times more common in males than in females, but the underlying mechanisms are poorly understood. We characterized sexually dimorphic changes in mice carrying a heterozygous mutation in Chd8 (Chd8+/N2373K) that was first identified in human CHD8 (Asn2373LysfsX2), a strong ASD-risk gene that encodes a chromatin remodeler. Notably, although male mutant mice displayed a range of abnormal behaviors during pup, juvenile, and adult stages, including enhanced mother-seeking ultrasonic vocalization, enhanced attachment to reunited mothers, and isolation-induced self-grooming, their female counterparts do not. This behavioral divergence was associated with sexually dimorphic changes in neuronal activity, synaptic transmission, and transcriptomic profiles. Specifically, female mice displayed suppressed baseline neuronal excitation, enhanced inhibitory synaptic transmission and neuronal firing, and increased expression of genes associated with extracellular vesicles and the extracellular matrix. Our results suggest that a human CHD8 mutation leads to sexually dimorphic changes ranging from transcription to behavior in mice. © 2018, The Author(s
Social deficits in IRSp53 mutant mice improved by NMDAR and mGluR5 suppression
No full textSocial deficits are observed in diverse psychiatric disorders, including autism spectrum disorders and schizophrenia. We found that mice lacking the excitatory synaptic signaling scaffold IRSp53 (also known as BAIAP2) showed impaired social interaction and communication. Treatment of IRSp53 -/- mice, which display enhanced NMDA receptor (NMDAR) function in the hippocampus, with memantine, an NMDAR antagonist, or MPEP, a metabotropic glutamate receptor 5 antagonist that indirectly inhibits NMDAR function, normalized social interaction. This social rescue was accompanied by normalization of NMDAR function and plasticity in the hippocampus and neuronal firing in the medial prefrontal cortex. These results, together with the reduced NMDAR function implicated in social impairments, suggest that deviation of NMDAR function in either direction leads to social deficits and that correcting the deviation has beneficial effects525411Nsciescopu
Individual differences in dynamic criterion shifts during perceptual decision-making
No full text학위논문 (석사)-- 서울대학교 대학원 : 뇌인지과학과, 2013. 2. 이상훈.Perceptual decision-making involves placing an optimal criterion on the axis of encoded sensory evidence to maximize outcomes for choices. Optimal criterion setting becomes critical particularly when neural representations of sensory inputs are noisy and feedbacks for perceptual choices vary over time in an unpredictable manner. Here, we first induced shifts in criteria by adopting stochastically generated reverse feedbacks, so that subjects sometimes received false feedbacks even for responses they should have gotten correct. Using a reinforcement-learning model, we captured subjects behavior and we investigated rationale for optimal criteria placement, or lack of, in individuals. Utilizing the estimates of model parameters, specifically the shift rate for criteria and subjects sensitivity, we identified the optimal regime. We demonstrate that optimal decision-making is closely correlated with the subjects sensitivity and shift rate. There was a systematic trade-off between the two parameters indicating that sensitivity and shift rate reciprocate, allowing for optimal decision-making in complex environments.Introduction 1
Materials and Methods 3
Results 13
Discussion 23
References 27
Abstract (Korean) 34Maste
Excitatory synapses and gap junctions cooperate to improve Pv neuronal burst firing and cortical social cognition in Shank2-mutant mice
No full text© 2021, The Author(s).NMDA receptor (NMDAR) and GABA neuronal dysfunctions are observed in animal models of autism spectrum disorders, but how these dysfunctions impair social cognition and behavior remains unclear. We report here that NMDARs in cortical parvalbumin (Pv)-positive interneurons cooperate with gap junctions to promote high-frequency (>80 Hz) Pv neuronal burst firing and social cognition. Shank2–/– mice, displaying improved sociability upon NMDAR activation, show impaired cortical social representation and inhibitory neuronal burst firing. Cortical Shank2–/– Pv neurons show decreased NMDAR activity, which suppresses the cooperation between NMDARs and gap junctions (GJs) for normal burst firing. Shank2–/– Pv neurons show compensatory increases in GJ activity that are not sufficient for social rescue. However, optogenetic boosting of Pv neuronal bursts, requiring GJs, rescues cortical social cognition in Shank2–/– mice, similar to the NMDAR-dependent social rescue. Therefore, NMDARs and gap junctions cooperate to promote cortical Pv neuronal bursts and social cognition.11Nsciescopu
P2-17: Individual Differences in Dynamic Criterion Shifts during Perceptual Decision Making
No full textPerceptual decision-making involves placing an optimal criterion on the axis of encoded sensory evidence to maximize outcomes for choices. Optimal criterion setting becomes critical particularly when neural representations of sensory inputs are noisy and feedbacks for perceptual choices vary over time in an unpredictable manner. Here we monitored time courses of decision criteria that are adopted by human subjects while abruptly shifting the criterion of stochastic feedback to perceptual choices with certain amounts in an unpredictable direction and at an unpredictable point of time. Subjects viewed a brief (0.3 s), thin (.07 deg) annulus around the fixation and were forced to judge whether the annulus was smaller or larger than an unknown boundary. We estimated moment-to-moment criteria by fitting a cumulative Gaussian function to the data within a sliding window of trials that are locked to a shift in feedback criterion. Unpredictable shifts in feedback criterion successfully induced shifts in actual decision criterion towards an optimal criterion for many of subjects, but with time delay and amount of shifts varying across individual subjects. There were disproportionately more numbers of overshooters (reaching and then surpassing the optimal criterion required) than undershooters (subpar reach, with a significant anti-correlation with sensory sensitivity). To find a mechanism that generates these individual differences, we developed a dynamic criterion learning model by modifying a reinforcement learning model, which assumes that a criterion is adjusted every trial by a weighted discrepancy between actual and expected rewards
Austin Papers: Series II, Part I, 1794-1817
No full textCopy of transcript for a letter addressed to Issac Tomlinson and Co. or Issac Tomlinson and Sons, in which the author explains taking out loans in order to transport goods
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