Human Brain Regions Involved in Visual Discriminations

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 298-298
Author(s):  
G A Orban
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Brain Regions ◽  
Orientation Discrimination ◽  
National Academy Of Sciences ◽  
Temporal Comparison ◽  
Dot Motion ◽  
Speed Discrimination ◽  
Academy Of Sciences ◽  
Visual Discriminations

We have used simple visual discriminations as a tool to investigate the human visual system with PET and fMRI. In discrimination tasks, stimuli in which an attribute is defined by a cue are presented in a position in the visual field and the subjects compare the stimuli with each other or with a standard. We have manipulated each of these four aspects. Manipulation of stimulus position engages visuo-spatial attention mechanisms in parietal and frontal cortex (Vandenberghe et al, 1996 Brain119 1263 – 1276; 1997 Journal of Neuroscience in press). Manipulation of the cue has revealed the kinetic occipital (KO) region involved in the processing of kinetic contours (Orban et al, 1995 Proceedings of the National Academy of Sciences of the USA92 993 – 997; Dupont et al, 1997 Cerebral Cortex in press). Using luminance-defined patterns presented centrally and contrasting successive orientation discrimination with identification we have demonstrated the involvement of right fusiform cortex in temporal comparison of orientation (Orban et al, 1997 European Journal of Neurosciences9 246 – 259). The same region is involved in spatial comparison of orientation as well as in temporal comparison of speed and direction of random-dot motion. This set of experiments shows that processing in the human visual system depends not only on the attribute used but also on the nature of the task to be performed. The direction and speed discrimination experiments also reveal the involvement of the lingual motion area in these tasks, but surprisingly very little involvement of human MT/V5.

Task-invariant Brain Responses to the Social Value of Faces

2011 ◽  
Vol 23 (10) ◽  
pp. 2766-2781 ◽  
Author(s):  
Alexander Todorov ◽  
Christopher P. Said ◽  
Nikolaas N. Oosterhof ◽  
Andrew D. Engell
Keyword(s):  
Brain Regions ◽  
Parametric Model ◽  
Social Value ◽  
National Academy Of Sciences ◽  
Brain Responses ◽  
The Social ◽  
The Face ◽  
Approach Avoidance ◽  
Face Stimuli ◽  
Academy Of Sciences

In two fMRI experiments (n = 44) using tasks with different demands—approach–avoidance versus one-back recognition decisions—we measured the responses to the social value of faces. The face stimuli were produced by a parametric model of face evaluation that reduces multiple social evaluations to two orthogonal dimensions of valence and power [Oosterhof, N. N., & Todorov, A. The functional basis of face evaluation. Proceedings of the National Academy of Sciences, U.S.A., 105, 11087–11092, 2008]. Independent of the task, the response within regions of the occipital, fusiform, and lateral prefrontal cortices was sensitive to the valence dimension, with larger responses to low-valence faces. Additionally, there were extensive quadratic responses in the fusiform gyri and dorsal amygdala, with larger responses to faces at the extremes of the face valence continuum than faces in the middle. In all these regions, participants' avoidance decisions correlated with brain responses, with faces more likely to be avoided evoking stronger responses. The findings suggest that both explicit and implicit face evaluation engage multiple brain regions involved in attention, affect, and decision making.

scholarly journals Recurrence is required to capture the representational dynamics of the human visual system

2019 ◽  
Vol 116 (43) ◽  
pp. 21854-21863 ◽  
Author(s):  
Tim C. Kietzmann ◽  
Courtney J. Spoerer ◽  
Lynn K. A. Sörensen ◽  
Radoslaw M. Cichy ◽  
Olaf Hauk ◽  
...  
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Network Models ◽  
Brain Regions ◽  
Ventral Stream ◽  
Causality Analysis ◽  
Neural Network Models ◽  
Object Processing ◽  
Time Resolved ◽  
Feedback Connections

The human visual system is an intricate network of brain regions that enables us to recognize the world around us. Despite its abundant lateral and feedback connections, object processing is commonly viewed and studied as a feedforward process. Here, we measure and model the rapid representational dynamics across multiple stages of the human ventral stream using time-resolved brain imaging and deep learning. We observe substantial representational transformations during the first 300 ms of processing within and across ventral-stream regions. Categorical divisions emerge in sequence, cascading forward and in reverse across regions, and Granger causality analysis suggests bidirectional information flow between regions. Finally, recurrent deep neural network models clearly outperform parameter-matched feedforward models in terms of their ability to capture the multiregion cortical dynamics. Targeted virtual cooling experiments on the recurrent deep network models further substantiate the importance of their lateral and top-down connections. These results establish that recurrent models are required to understand information processing in the human ventral stream.

Human Brain Regions Involved in Direction Discrimination

1998 ◽  
Vol 79 (5) ◽  
pp. 2749-2765 ◽  
Author(s):  
L. Cornette ◽  
P. Dupont ◽  
A. Rosier ◽  
S. Sunaert ◽  
P. Van Hecke ◽  
...  
Keyword(s):  
Visual System ◽  
Human Brain ◽  
Motion Detection ◽  
Human Visual System ◽  
Brain Regions ◽  
Successive Discrimination ◽  
Functional Specialization ◽  
Direction Discrimination ◽  
Cortical Regions ◽  
The Right

Cornette, L., P. Dupont, A. Rosier, S. Sunaert, P. Van Hecke, J. Michiels, L. Mortelmans, and G. A. Orban. Human brain regions involved in direction discrimination. J. Neurophysiol. 79: 2749–2765, 1998. To obtain further evidence for the functional specialization and task-dependent processing in the human visual system, we used positron emission tomography to compare regional cerebral blood flow in two direction discrimination tasks and four control tasks. The stimulus configuration, which was identical in all tasks, included the motion of a random dot pattern, dimming of a fixation point, and a tone burst. The discrimination tasks comprised the identification of motion direction and successive direction discrimination. The control tasks were motion detection, dimming detection, tone detection, and passive viewing. There was little difference in the activation patterns evoked by the three detection tasks except for decreased activity in the parietal cortex during the detection of a tone. Thus attention to a nonvisual stimulus modulated different visual cortical regions nonuniformly. Comparison of successive discrimination with motion detection yielded significant activation in the right fusiform gyrus, right lingual gyrus, right frontal operculum, left inferior frontal gyrus, and right thalamus. The fusiform and opercular activation sites persisted even after subtracting direction identification from successive discrimination, indicating their involvement in temporal comparison. Functional magnetic resonance imaging (fMRI) experiments confirmed the weak nature of the activation of human MT/V5 by successive direction discrimination but also indicated the involvement of an inferior satellite of human MT/V5. The fMRI experiments moreover confirmed the involvement of human V3A, lingual, and parietal regions in successive discrimination. Our results provide further evidence for the functional specialization of the human visual system because the cortical regions involved in direction discrimination partially differ from those involved in orientation discrimination. They also support the principle of task-dependent visual processing and indicate that the right fusiform gyrus participates in temporal comparison, irrespective of the stimulus attribute.

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