scholarly journals Fine-scale activity patterns in high-level visual areas encode the category of invisible objects

2008 ◽  
Vol 8 (15) ◽  
pp. 10-10 ◽  
Author(s):  
P. Sterzer ◽  
J. D. Haynes ◽  
G. Rees
Keyword(s):  
Activity Patterns ◽  
Fine Scale ◽  
Visual Areas ◽  
High Level

scholarly journals Shared and Independent Neural Representation Between Visual Perception and Mental Imagery

2021 ◽  
Author(s):  
Yingying Huang ◽  
Frank Pollick ◽  
Ming Liu ◽  
Delong Zhang
Keyword(s):  
Visual Perception ◽  
Mental Imagery ◽  
Activity Patterns ◽  
Neural Representation ◽  
Gabor Features ◽  
Visual Areas ◽  
Neural Substrate ◽  
Early Visual Cortex ◽  
Human Participants ◽  
Insight Into

Abstract Visual mental imagery and visual perception have been shown to share a hierarchical topological visual structure of neural representation. Meanwhile, many studies have reported a dissociation of neural substrate between mental imagery and perception in function and structure. However, we have limited knowledge about how the visual hierarchical cortex involved into internally generated mental imagery and perception with visual input. Here we used a dataset from previous fMRI research (Horikawa & Kamitani, 2017), which included a visual perception and an imagery experiment with human participants. We trained two types of voxel-wise encoding models, based on Gabor features and activity patterns of high visual areas, to predict activity in the early visual cortex (EVC, i.e., V1, V2, V3) during perception, and then evaluated the performance of these models during mental imagery. Our results showed that during perception and imagery, activities in the EVC could be independently predicted by the Gabor features and activity of high visual areas via encoding models, which suggested that perception and imagery might share neural representation in the EVC. We further found that there existed a Gabor-specific and a non-Gabor-specific neural response pattern to stimuli in the EVC, which were shared by perception and imagery. These findings provide insight into mechanisms of how visual perception and imagery shared representation in the EVC.

scholarly journals A data‐driven approach to stimulus selection reveals an image‐based representation of objects in high‐level visual areas

2019 ◽  
Vol 40 (16) ◽  
pp. 4716-4731 ◽  
Author(s):  
David D. Coggan ◽  
Afrodite Giannakopoulou ◽  
Sanah Ali ◽  
Burcu Goz ◽  
David M. Watson ◽  
...  
Keyword(s):  
Data Driven ◽  
Stimulus Selection ◽  
Visual Areas ◽  
Data Driven Approach ◽  
High Level

Sequentially Adapted Flow-Based PEBI Grids for Reservoir Simulation

SPE Journal ◽  
2006 ◽  
Vol 11 (03) ◽  
pp. 317-327 ◽  
Author(s):  
Martin Mlacnik ◽  
Louis J. Durlofsky ◽  
Zoltan E. Heinemann
Keyword(s):  
Reservoir Simulation ◽  
Large Body ◽  
Structural Features ◽  
Flow In Porous Media ◽  
Fine Scale ◽  
Reservoir Properties ◽  
Fine Grid ◽  
Grid Coarsening ◽  
Grid Optimization ◽  
High Level

Summary A technique for the sequential generation of perpendicular-bisectional (PEBI) grids adapted to flow information is presented and applied. The procedure includes a fine-scale flow solution, the generation of an initial streamline-isopotential grid, grid optimization, and upscaling. The grid optimization is accomplished through application of a hybrid procedure with gradient and Laplacian smoothing steps, while the upscaling is based on a global-local procedure that makes use of the global solution used in the grid-determination step. The overall procedure is successfully applied to a complex channelized reservoir model involving changing well conditions. The gridding and upscaling procedures presented here may also be suitable for use with other types of structured or unstructured grid systems. Introduction Modern geological and geostatistical tools provide highly detailed descriptions of the spatial variation of reservoir properties, resulting in fine-grid models consisting of 107 to 108 gridblocks. As a consequence of this high level of detail, these models cannot be used directly in numerical reservoir simulators, but need to be coarsened significantly. Coarsening requires the averaging of rock parameters from the fine scale to the coarse scale. This process is referred to as upscaling. For simulation of flow in porous media, the upscaling of permeability is of particular interest. A large body of literature exists on this topic; for a comprehensive review of existing techniques, see Durlofsky (2005). To preserve as much of the geological information of the fine grid as possible, the grid coarsening should not be performed uniformly, but with more refinement in areas that are expected to have large impact on the flow, including structural features, such as faults. Although grid-generation techniques based on purely static, nonflow-based considerations have been shown to produce reasonable results(Garcia et al. 1992), the application of flow-based grids is often preferable. Flow-based grids require the solution of some type of fine-scale problem. They are then constructed by exploiting the information obtained from streamlines (and possibly isopotentials) either directly or indirectly. Depending on the type of grid used, points will be defined as cell vertices or nodes, resulting in either a corner-point geometry or point-distributed grid. Several gridding techniques for reservoir simulation have been introduced along these lines, as we now discuss.

Activity patterns and fine-scale resource partitioning in the gregarious Kihansi spray toadNectophrynoides asperginisin captivity

Zoo Biology ◽  
2014 ◽  
pp. n/a-n/a
Author(s):  
Alfan A. Rija ◽  
Ezekiel M. Goboro ◽  
Kuruthumu A. Mwamende ◽  
Abubakari Said ◽  
Edward M. Kohi ◽  
...  
Keyword(s):  
Resource Partitioning ◽  
Activity Patterns ◽  
Fine Scale

Winter activity patterns of females in two moose populations

1989 ◽  
Vol 67 (6) ◽  
pp. 1516-1522 ◽  
Author(s):  
Göran Cederlund ◽  
Roger Bergström ◽  
Finn Sandegren
Keyword(s):  
Food Availability ◽  
Activity Pattern ◽  
Average Length ◽  
Activity Patterns ◽  
Body Motion ◽  
Active Time ◽  
Low Level ◽  
Winter Activity ◽  
Radio Signals ◽  
High Level

Data on activity patterns of nine radio-tagged female moose (Alces alces) in an area with a high level of nutrition (Grimsö) and seven radio-tagged female moose in an area with a low level of nutrition (Furudal) are presented. The study was done during January–May in 1982–1986 at Grimsö and in 1986 in Furudal, comprising 6063 and 4136 h of recording, respectively. The character of the radio signals allowed separation of active (any kind of body motion, mainly movements) and inactive (a motionless state, mainly in lying position) bouts. The 24-h activity pattern was similar between the two areas during all winter months. Active bouts showed a polyphasic pattern with prominent peaks around sunrise and sunset. The average active time per 24-h interval varied (30–50%) through the winter months, and increased rapidly in April and May. The average length of active bouts was similar in both areas during midwinter (60–70 min) but developed more rapidly in April and May among moose at Grimsö. The moose at Furudal rested for longer periods than those at Grimsö, and in both areas bouts became shorter towards spring (around 120 min). The moose at Grimsö kept the number of bouts per 24-h interval almost unchanged throughout winter (11.0–11.9), while the number consistently increased at Furudal (9.9–12.7 bouts per 24-h interval). Differences in activity pattern are discussed in relation to food availability and overbrowsing.

scholarly journals Characterization of turbulence and validation of fine-scale parametrization in the Mediterranean Sea during BOUM experiment

2011 ◽  
Vol 8 (5) ◽  
pp. 8961-8998 ◽  
Author(s):  
Y. Cuypers ◽  
P. Bouruet-Aubertot ◽  
C. Marec ◽  
J.-L. Fuda
Keyword(s):  
Energy Dissipation ◽  
Mediterranean Sea ◽  
Fine Scale ◽  
Data Set ◽  
Mean Values ◽  
The Mediterranean ◽  
Microstructure Measurements ◽  
High Level ◽  
Anticyclonic Eddies

Abstract. One main purpose of BOUM experiment was to give evidence of the possible impact of submesoscale dynamics on biogeochemical cycles. To this aim physical as well as biogeochemical data were collected along a zonal transect through the western and eastern basins. Along this transect 3 day fixed point stations were performed within anticyclonic eddies during which microstructure measurements were collected over the first 100 m. We focus here on the characterization of turbulent mixing induced by internal wave breaking. The analysis of microstructure measurements revealed a high level of turbulence in the seasonal pycnocline and a moderate level below with energy dissipation mean values of the order of 10−6 W kg−1 and 10−8 W kg−1, respectively. Fine-scale parameterizations developed to mimic energy dissipation produced by internal wavebreaking were then tested against these direct measurements. Once validated a parameterization has been applied to infer energy dissipation and mixing over the whole data set, thus providing an overview over a latitudinal section of the Mediterranean sea. The results evidence a significant increase of dissipation at the top and base of eddies associated with strong near inertial waves. Vertical turbulent diffusivity is increased both in these regions and in the weakly stratified eddy core.

scholarly journals Locomotion-dependent remapping of distributed cortical networks

2018 ◽  
Author(s):  
Kelly B. Clancy ◽  
Ivana Orsolic ◽  
Thomas D. Mrsic-Flogel
Keyword(s):  
Activity Patterns ◽  
Local Area ◽  
Local Network ◽  
Brain State ◽  
Dorsal Cortex ◽  
Cortical Networks ◽  
V1 Neurons ◽  
State Dependent ◽  
Visual Areas ◽  
Sensory Cortices

AbstractThe interactions between areas of the neocortex are fluid and state-dependent, but how individual neurons couple to cortex-wide network dynamics remains poorly understood. We correlated the spiking of individual neurons in primary visual (V1) and retrosplenial (RSP) cortex to activity across dorsal cortex, recorded simultaneously by calcium imaging. Individual neurons were correlated with distinct and reproducible patterns of activity across the cortical surface; while some fired predominantly with their local area, others coupled to activity in subsets of distal areas. The extent of distal coupling was predicted by how strongly neurons correlated with the local network. Changes in brain state triggered by locomotion re-structured how neurons couple to cortical activity patterns: running strengthened affiliations of V1 neurons with visual areas, while strengthening distal affiliations of RSP neurons with sensory cortices. Thus, individual neurons within a cortical area can independently engage in different cortical networks depending on the animal's behavioral state.

scholarly journals Shared experience, shared memory: a common structure for brain activity during naturalistic recall

2016 ◽  
Author(s):  
Janice Chen ◽  
Yuan Chang Leong ◽  
Kenneth A Norman ◽  
Uri Hasson
Keyword(s):  
Brain Activity ◽  
Activity Patterns ◽  
Real Life ◽  
Angular Gyrus ◽  
Striking Similarity ◽  
Daily Lives ◽  
Common Structure ◽  
Medial Cortex ◽  
Memory Representations ◽  
High Level

Our daily lives revolve around sharing experiences and memories with others. When different people recount the same events, how similar are their underlying neural representations? In this study, participants viewed a fifty-minute audio-visual movie, then verbally described the events while undergoing functional MRI. These descriptions were completely unguided and highly detailed, lasting for up to forty minutes. As each person spoke, event-specific spatial patterns were reinstated (movie-vs.-recall correlation) in default network, medial temporal, and high-level visual areas; moreover, individual event patterns were highly discriminable and similar between people during recollection (recall-vs.-recall similarity), suggesting the existence of spatially organized memory representations. In posterior medial cortex, medial prefrontal cortex, and angular gyrus, activity patterns during recall were more similar between people than to patterns elicited by the movie, indicating systematic reshaping of percept into memory across individuals. These results reveal striking similarity in how neural activity underlying real-life memories is organized and transformed in the brains of different people as they speak spontaneously about past events.

scholarly journals FFA and OFA encode distinct types of face identity information

2020 ◽  
Author(s):  
Maria Tsantani ◽  
Nikolaus Kriegeskorte ◽  
Katherine Storrs ◽  
Adrian Lloyd Williams ◽  
Carolyn McGettigan ◽  
...  
Keyword(s):  
Brain Activity ◽  
Activity Patterns ◽  
Brain Regions ◽  
Image Encoding ◽  
Low Level ◽  
Social Traits ◽  
Face Area ◽  
Face Similarity ◽  
And Gender ◽  
High Level

AbstractFaces of different people elicit distinct functional MRI (fMRI) patterns in several face-selective brain regions. Here we used representational similarity analysis to investigate what type of identity-distinguishing information is encoded in three face-selective regions: fusiform face area (FFA), occipital face area (OFA), and posterior superior temporal sulcus (pSTS). We used fMRI to measure brain activity patterns elicited by naturalistic videos of famous face identities, and compared their representational distances in each region with models of the differences between identities. Models included low-level to high-level image-computable properties and complex human-rated properties. We found that the FFA representation reflected perceived face similarity, social traits, and gender, and was well accounted for by the OpenFace model (deep neural network, trained to cluster faces by identity). The OFA encoded low-level image-based properties (pixel-wise and Gabor-jet dissimilarities). Our results suggest that, although FFA and OFA can both discriminate between identities, the FFA representation is further removed from the image, encoding higher-level perceptual and social face information.

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