scholarly journals Position information encoded by population activity in hierarchical visual areas

2016 ◽  
Author(s):  
Kei Majima ◽  
Paul Sukhanov ◽  
Tomoyasu Horikawa ◽  
Yukiyasu Kamitani
Keyword(s):  
Brain Area ◽  
Receptive Fields ◽  
Population Level ◽  
Support Vector ◽  
Population Activity ◽  
Position Information ◽  
Low Level ◽  
Horizontal Dimension ◽  
Visual Areas ◽  
High Level

AbstractNeurons in high-level visual areas respond to more complex visual features with broader receptive fields (RFs) compared to those in low-level visual areas. Thus, high-level visual areas are generally considered to carry less information regarding the position of seen objects in the visual field. However, larger RFs may not imply loss of position information at the population level. Here, we evaluated how accurately the position of a seen object could be predicted (decoded) from activity patterns in each of six representative visual areas with different RF sizes (V1–V4, LOC, and FFA). We collected fMRI responses while human subjects viewed a ball randomly moving in a two-dimensional field. To estimate population RF sizes of individual fMRI voxels, RF models were fitted for individual voxels in each brain area. The voxels in higher visual areas showed larger estimated RFs than those in lower visual areas. Then, the ball’s position in a separate session was predicted by maximum likelihood regression (support vector regression, SVR) to predict the position. We found that regardless of the difference in RF size, all visual areas showed similar prediction accuracies, especially on the horizontal dimension. Higher areas showed slightly lower accuracies on the vertical dimension, which appears to be attributed to the narrower spatial distributions of the RFs centers. The results suggest that much of position information is preserved in population activity through the hierarchical visual pathway regardless of RF sizes, and is potentially available in later processing for recognition and behavior.Significance statementHigh-level ventral visual areas are thought to achieve position invariance with larger receptive fields at the cost of the loss of precise position information. However, larger receptive fields may not imply loss of position information at the population level. Here, multivoxel fMRI decoding reveals that high-level visual areas are predictive of an object’s position with similar accuracies to low-level visual areas, especially on the horizontal dimension, preserving the information potentially available for later processing.

scholarly journals Level Dependence of Contextual Modulation in Auditory Cortex

2008 ◽  
Vol 99 (4) ◽  
pp. 1616-1627 ◽  
Author(s):  
Ben Scholl ◽  
Xiang Gao ◽  
Michael Wehr
Keyword(s):  
Auditory Cortex ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Stimulus Context ◽  
Contextual Modulation ◽  
Sensory Stimuli ◽  
Low Contrast ◽  
Low Level ◽  
High Level ◽  
Contextual Interactions

Responses of cortical neurons to sensory stimuli within their receptive fields can be profoundly altered by the stimulus context. In visual and somatosensory cortex, contextual interactions have been shown to change sign from facilitation to suppression depending on stimulus strength. Contextual modulation of high-contrast stimuli tends to be suppressive, but for low-contrast stimuli tends to be facilitative. This trade-off may optimize contextual integration by cortical cells and has been suggested to be a general feature of cortical processing, but it remains unknown whether a similar phenomenon occurs in auditory cortex. Here we used whole cell and single-unit recordings to investigate how contextual interactions in auditory cortical neurons depend on the relative intensity of masker and probe stimuli in a two-tone stimulus paradigm. We tested the hypothesis that relatively low-level probes should show facilitation, whereas relatively high-level probes should show suppression. We found that contextual interactions were primarily suppressive across all probe levels, and that relatively low-level probes were subject to stronger suppression than high-level probes. These results were virtually identical for spiking and subthreshold responses. This suggests that, unlike visual cortical neurons, auditory cortical neurons show maximal suppression rather than facilitation for relatively weak stimuli.

scholarly journals High-Low Level Support Vector Regression Prediction Approach (HL-SVR) for Data Modeling with Input Parameters of Unequal Sample Sizes

2021 ◽  
pp. 2150029
Author(s):  
Maolin Shi ◽  
Liye Lv ◽  
Zhenggang Guo ◽  
Wei Sun ◽  
Xueguan Song ◽  
...  
Keyword(s):  
Support Vector Regression ◽  
Data Modeling ◽  
Support Vector ◽  
Sample Sizes ◽  
Low Level ◽  
Input Parameters ◽  
High Level ◽  
Prediction Approach ◽  
Larger Sample ◽  
Unequal Sample Sizes

Support vector regression (SVR) has been widely used to reduce the high computational cost of computer simulation. SVR assumes the input parameters have equal sample sizes, but unequal sample sizes are often encountered in engineering practices. To solve this issue, a new prediction approach based on SVR, namely as high-low level SVR approach (HL-SVR) is proposed for data modeling of input parameters of unequal sample sizes in this paper. The proposed approach consists of low-level SVR models for the input parameters of larger sample sizes and high-level SVR model for the input parameters of smaller sample sizes. For each training point of the input parameters of smaller sample sizes, one low-level SVR model is built based on its corresponding input parameters of larger sample sizes and their responses of interest. The high-level SVR model is built based on the obtained responses from the low-level SVR models and the input parameters of smaller sample sizes. A number of numerical examples are used to validate the performance of HL-SVR. The experimental results indicate that HL-SVR can produce more accurate prediction results than SVR. The proposed approach is applied to the stress analysis of dental implant, in which the structural parameters have massive samples but the material of implant can only be selected from Ti and its alloys. The obtained prediction results of the HL-SVR approach are much better than SVR. The proposed approach can be used for the design, optimization, and analysis of engineering systems with input parameters of unequal sample sizes.

scholarly journals Temporal evolution of both premotor and motor cortical tuning properties reflect changes in limb biomechanics

2015 ◽  
Vol 113 (7) ◽  
pp. 2812-2823 ◽  
Author(s):  
Aaron J. Suminski ◽  
Philip Mardoum ◽  
Timothy P. Lillicrap ◽  
Nicholas G. Hatsopoulos
Keyword(s):  
Primary Motor Cortex ◽  
Rhesus Macaques ◽  
Premotor Cortex ◽  
Population Level ◽  
Motor Command ◽  
Bimodal Distribution ◽  
Biomechanical Properties ◽  
Reaching Task ◽  
Low Level ◽  
High Level

A prevailing theory in the cortical control of limb movement posits that premotor cortex initiates a high-level motor plan that is transformed by the primary motor cortex (MI) into a low-level motor command to be executed. This theory implies that the premotor cortex is shielded from the motor periphery, and therefore, its activity should not represent the low-level features of movement. Contrary to this theory, we show that both dorsal (PMd) and ventral premotor (PMv) cortexes exhibit population-level tuning properties that reflect the biomechanical properties of the periphery similar to those observed in M1. We recorded single-unit activity from M1, PMd, and PMv and characterized their tuning properties while six rhesus macaques performed a reaching task in the horizontal plane. Each area exhibited a bimodal distribution of preferred directions during execution consistent with the known biomechanical anisotropies of the muscles and limb segments. Moreover, these distributions varied in orientation or shape from planning to execution. A network model shows that such population dynamics are linked to a change in biomechanics of the limb as the monkey begins to move, specifically to the state-dependent properties of muscles. We suggest that, like M1, neural populations in PMd and PMv are more directly linked with the motor periphery than previously thought.

Human brain activity during mental imagery exhibits signatures of inference in a hierarchical generative model

2018 ◽  
Author(s):  
Jesse Breedlove ◽  
Ghislain St-Yves ◽  
Cheryl Olman ◽  
Thomas Naselaris
Keyword(s):  
Mental Imagery ◽  
Human Subjects ◽  
Brain Activity ◽  
Generative Model ◽  
Formal Structure ◽  
Low Level ◽  
Visual Encoding ◽  
Visual Areas ◽  
High Level ◽  
Echo Effect

Humans have long wondered about the function of mental imagery and its relationship to vision. Although visual representations are utilized during imagery, the computations they subserve are unclear. Building on a theory that treats vision as inference about the causes of sensory stimulation in an internal generative model, we propose that mental imagery is inference about the sensory consequences of predicted or remembered causes. The relation between these complementary inferences yields a relation between the brain activity patterns associated with imagery and vision. We show that this relation has the formal structure of an echo that makes encoding of imagined stimuli in low-level visual areas resemble the encoding of seen stimuli in higher areas. To test for evidence of this echo effect we developed imagery encoding models—a new tool for revealing how imagined stimuli are encoded in brain activity. We estimated imagery encoding models from brain activity measured with fMRI while human subjects imagined complex visual stimuli, and then compared these to visual encoding models estimated from a matched viewing experiment. Consistent with an echo effect, imagery encoding models in low-level visual areas exhibited decreased spatial frequency preference and larger, more foveal receptive fields, thus resembling visual encoding models in high-level visual areas where imagery and vision appeared to be almost interchangeable. Our findings support an interpretation of mental imagery as a predictive inference that is conditioned on activity in high-level visual cortex, and is related to vision through shared dependence on an internal model of the visual world.

scholarly journals Position Information Encoded by Population Activity in Hierarchical Visual Areas

eNeuro ◽  
2017 ◽  
Vol 4 (2) ◽  
pp. ENEURO.0268-16.2017 ◽  
Author(s):  
Kei Majima ◽  
Paul Sukhanov ◽  
Tomoyasu Horikawa ◽  
Yukiyasu Kamitani
Keyword(s):  
Population Activity ◽  
Position Information ◽  
Visual Areas

scholarly journals Neuroimaging Findings on Amodal Completion: A Review

i-Perception ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 204166951984004 ◽  
Author(s):  
Jordy Thielen ◽  
Sander E. Bosch ◽  
Tessa M. van Leeuwen ◽  
Marcel A. J. van Gerven ◽  
Rob van Lier
Keyword(s):  
Computational Models ◽  
Amodal Completion ◽  
Lateral Occipital Complex ◽  
Low Level ◽  
Face Area ◽  
Perceptual Completion ◽  
Visual Areas ◽  
High Level ◽  
Partially Occluded ◽  
Retinal Information

Amodal completion is the phenomenon of perceiving completed objects even though physically they are partially occluded. In this review, we provide an extensive overview of the results obtained from a variety of neuroimaging studies on the neural correlates of amodal completion. We discuss whether low-level and high-level cortical areas are implicated in amodal completion; provide an overview of how amodal completion unfolds over time while dissociating feedforward, recurrent, and feedback processes; and discuss how amodal completion is represented at the neuronal level. The involvement of low-level visual areas such as V1 and V2 is not yet clear, while several high-level structures such as the lateral occipital complex and fusiform face area seem invariant to occlusion of objects and faces, respectively, and several motor areas seem to code for object permanence. The variety of results on the timing of amodal completion hints to a mixture of feedforward, recurrent, and feedback processes. We discuss whether the invisible parts of the occluded object are represented as if they were visible, contrary to a high-level representation. While plenty of questions on amodal completion remain, this review presents an overview of the neuroimaging findings reported to date, summarizes several insights from computational models, and connects research of other perceptual completion processes such as modal completion. In all, it is suggested that amodal completion is the solution to deal with various types of incomplete retinal information, and highly depends on stimulus complexity and saliency, and therefore also give rise to a variety of observed neural patterns.

Temporal trends and socioeconomic differences in the incidence of left-sided valvular heart disease in Denmark

2020 ◽  
Author(s):  
Lene von Kappelgaard ◽  
Gunnar Gislason ◽  
Michael Davidsen ◽  
Ann-Dorthe Zwisler ◽  
Knud Juel
Keyword(s):  
Heart Disease ◽  
Valvular Heart Disease ◽  
Temporal Trends ◽  
Population Level ◽  
Incidence Rates ◽  
Ageing Population ◽  
Socioeconomic Differences ◽  
Low Level ◽  
Medium Level ◽  
High Level

Abstract Aims Due to an ageing population and increasing survival from concurrent diseases, the burden of left-sided degenerative valvular heart disease is expected to increase over time. This study aims at determining the temporal trends in incidence rates at the population level and examines whether there are socioeconomic differences. Methods and results A total of 133 209 patients were identified with a first-time diagnosis of aortic stenosis (AS), mitral regurgitation (MR), or aortic regurgitation (AR) in the Danish National Patient Registry in the 2000–17 period. Incidence rates (per 100 000 person-years) doubled over the period for AS (57 in 2000–02; 114 in 2015–17) and for AR (22 in 2000–02; 41 in 2015–17) and remained the same for MR (38 in both 2000–02 and 2015–17). Incidence rates increased rapidly with increasing age, most markedly for AS. Men had a higher risk of being affected [relative risk (RR) 1.69 for AS, 1.19 for MR, 1.35 for AR]. Compared to high-level education, patients with medium- and low-level education had a higher risk of being affected (RR 1.18 for AS medium level and 1.47 for AS low level; 1.03 for MR medium level and 1.14 for MR low level; 1.03 for AR medium level and 1.18 for AR low level). Conclusions For AS and AR, the incidence rates doubled, while the incidence rates remained at the same level for MR. The risk of being affected increased with advanced age and male gender. Patients with low-level education had a higher risk of being affected compared to patients with high-level education, especially among patients with AS.

Teknik Data Mining Dalam Clustering Produksi Susu Segar Di Indonesia Dengan Algoritma K-Means

2019 ◽  
Vol 1 (1) ◽  
pp. 31-39
Author(s):  
Ilham Safitra Damanik ◽  
Sundari Retno Andani ◽  
Dedi Sehendro
Keyword(s):  
Data Mining ◽  
Milk Production ◽  
Clustering Algorithm ◽  
Clustering Method ◽  
Data Mining Techniques ◽  
Low Level ◽  
Fresh Milk ◽  
Nutritional Needs ◽  
High Level ◽  
Level Cluster

Milk is an important intake to meet nutritional needs. Both consumed by children, and adults. Indonesia has many producers of fresh milk, but it is not sufficient for national milk needs. Data mining is a science in the field of computers that is widely used in research. one of the data mining techniques is Clustering. Clustering is a method by grouping data. The Clustering method will be more optimal if you use a lot of data. Data to be used are provincial data in Indonesia from 2000 to 2017 obtained from the Central Statistics Agency. The results of this study are in Clusters based on 2 milk-producing groups, namely high-dairy producers and low-milk producing regions. From 27 data on fresh milk production in Indonesia, two high-level provinces can be obtained, namely: West Java and East Java. And 25 others were added in 7 provinces which did not follow the calculation of the K-Means Clustering Algorithm, including in the low level cluster.

Determinants of Abuse of the Bodies of the Dead

2019 ◽  
pp. 71-77
Author(s):  
Margarita Khomyakova
Keyword(s):  
Low Income ◽  
Criminal Code ◽  
Value Judgments ◽  
Legal Norms ◽  
Low Level ◽  
Medical Institutions ◽  
Specific Object ◽  
The Subject ◽  
The Dead ◽  
High Level

The author analyzes definitions of the concepts of determinants of crime given by various scientists and offers her definition. In this study, determinants of crime are understood as a set of its causes, the circumstances that contribute committing them, as well as the dynamics of crime. It is noted that the Russian legislator in Article 244 of the Criminal Code defines the object of this criminal assault as public morality. Despite the use of evaluative concepts both in the disposition of this norm and in determining the specific object of a given crime, the position of criminologists is unequivocal: crimes of this kind are immoral and are in irreconcilable conflict with generally accepted moral and legal norms. In the paper, some views are considered with regard to making value judgments which could hardly apply to legal norms. According to the author, the reasons for abuse of the bodies of the dead include economic problems of the subject of a crime, a low level of culture and legal awareness; this list is not exhaustive. The main circumstances that contribute committing abuse of the bodies of the dead and their burial places are the following: low income and unemployment, low level of criminological prevention, poor maintenance and protection of medical institutions and cemeteries due to underperformance of state and municipal bodies. The list of circumstances is also open-ended. Due to some factors, including a high level of latency, it is not possible to reflect the dynamics of such crimes objectively. At the same time, identification of the determinants of abuse of the bodies of the dead will reduce the number of such crimes.

scholarly journals Methionine Diet Evoked Hyperhomocysteinemia Causes Hippocampal Alterations, Metabolomics Plasma Changes and Behavioral Pattern in Wild Type Rats

2021 ◽  
Vol 22 (9) ◽  
pp. 4961
Author(s):  
Maria Kovalska ◽  
Eva Baranovicova ◽  
Dagmar Kalenska ◽  
Anna Tomascova ◽  
Marian Adamkov ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Brain Area ◽  
Critical Role ◽  
Cerebrovascular Diseases ◽  
Behavioral Pattern ◽  
Cell Physiology ◽  
Male Wistar Rats ◽  
High Level ◽  
Hippocampal Alterations ◽  
The Impact

L-methionine, an essential amino acid, plays a critical role in cell physiology. High intake and/or dysregulation in methionine (Met) metabolism results in accumulation of its intermediate(s) or breakdown products in plasma, including homocysteine (Hcy). High level of Hcy in plasma, hyperhomocysteinemia (hHcy), is considered to be an independent risk factor for cerebrovascular diseases, stroke and dementias. To evoke a mild hHcy in adult male Wistar rats we used an enriched Met diet at a dose of 2 g/kg of animal weight/day in duration of 4 weeks. The study contributes to the exploration of the impact of Met enriched diet inducing mild hHcy on nervous tissue by detecting the histo-morphological, metabolomic and behavioural alterations. We found an altered plasma metabolomic profile, modified spatial and learning memory acquisition as well as remarkable histo-morphological changes such as a decrease in neurons’ vitality, alterations in the morphology of neurons in the selective vulnerable hippocampal CA 1 area of animals treated with Met enriched diet. Results of these approaches suggest that the mild hHcy alters plasma metabolome and behavioural and histo-morphological patterns in rats, likely due to the potential Met induced changes in “methylation index” of hippocampal brain area, which eventually aggravates the noxious effect of high methionine intake.

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