@article {15, title = {Neural dynamics at successive stages of the ventral visual stream are consistent with hierarchical error signals.}, journal = {eLife}, volume = {7}, year = {2018}, month = {11/2018}, abstract = {

Ventral visual stream neural responses are dynamic, even for static image presentations. However, dynamical neural models of visual cortex are lacking as most progress has been made modeling static, time-averaged responses. Here, we studied population neural dynamics during face detection across three cortical processing stages. Remarkably,~30 milliseconds after the initially evoked response, we found that neurons in intermediate level areas decreased their responses to typical configurations of their preferred face parts relative to their response for atypical configurations even while neurons in higher areas achieved and maintained a preference for typical configurations. These hierarchical neural dynamics were inconsistent with standard feedforward circuits. Rather, recurrent models computing prediction errors between stages captured the observed temporal signatures. This model of neural dynamics, which simply augments the standard feedforward model of online vision, suggests that neural responses to static images may encode top-down prediction errors in addition to bottom-up feature estimates.

}, keywords = {Animals, Brain Mapping, Face, Humans, Macaca mulatta, Models, Neurological, Neurons, Pattern Recognition, Photic Stimulation, Reaction Time, Visual, Visual Cortex, Visual Perception}, issn = {2050-084X}, doi = {10.7554/eLife.42870}, url = {https://elifesciences.org/articles/42870https://cdn.elifesciences.org/articles/42870/elife-42870-v2.pdf}, author = {Issa, Elias B and Cadieu, Charles F and DiCarlo, James J} } @article {99, title = {Anterior Inferotemporal Neurons of Monkeys Engaged in Object Recognition Can be Highly Sensitive to Object Retinal Position}, journal = {Journal of Neurophysiology}, volume = {89}, year = {2003}, month = {01/2003}, pages = {3264 - 3278}, abstract = {

Visual object recognition is computationally difficult because changes in an object\&$\#$39;s position, distance, pose, or setting may cause it to produce a different retinal image on each encounter. To robustly recognize objects, the primate brain must have mechanisms to compensate for these variations. Although these mechanisms are poorly understood, it is thought that they elaborate neuronal representations in the inferotemporal cortex that are sensitive to object form but substantially invariant to other image variations. This study examines this hypothesis for image variation resulting from changes in object position. We studied the effect of small differences (+/-1.5 degrees ) in the retinal position of small (0.6 degrees wide) visual forms on both the behavior of monkeys trained to identify those forms and the responses of 146 anterior IT (AIT) neurons collected during that behavior. Behavioral accuracy and speed were largely unaffected by these small changes in position. Consistent with previous studies, many AIT responses were highly selective for the forms. However, AIT responses showed far greater sensitivity to retinal position than predicted from their reported receptive field (RF) sizes. The median AIT neuron showed a approximately 60\% response decrease between positions within +/-1.5 degrees of the center of gaze, and 52\% of neurons were unresponsive to one or more of these positions. Consistent with previous studies, each neuron\&$\#$39;s rank order of target preferences was largely unaffected across position changes. Although we have not yet determined the conditions necessary to observe this marked position sensitivity in AIT responses, we rule out effects of spatial-frequency content, eye movements, and failures to include the RF center. To reconcile this observation with previous studies, we hypothesize that either AIT position sensitivity strongly depends on object size or that position sensitivity is sharpened by extensive visual experience at fixed retinal positions or by the presence of flanking distractors.

}, keywords = {Action Potentials, Animals, Depth Perception, Electrophysiology, Eye Movements, Form Perception, Macaca mulatta, Male, Neurons, Pattern Recognition, Photic Stimulation, Psychomotor Performance, Retina, Temporal Lobe, Time Factors, Visual, Visual Fields, Visual Perception}, issn = {0022-3077}, doi = {10.1152/jn.00358.2002}, url = {https://www.physiology.org/doi/10.1152/jn.00358.2002}, author = {DiCarlo, James J. and Maunsell, John H. R.} } @article {105, title = {Form representation in monkey inferotemporal cortex is virtually unaltered by free viewing}, journal = {Nature Neuroscience}, volume = {3}, year = {2000}, month = {01/2000}, pages = {814 - 821}, abstract = {

How are objects represented in the brain during natural behavior? Visual object recognition in primates is thought to depend on the inferotemporal cortex {(IT).} In most neurophysiological studies of {IT,} monkeys hold their direction of gaze fixed while isolated visual stimuli are presented (controlled viewing). However, during natural behavior, primates visually explore cluttered environments by changing gaze direction several times each second (free viewing). We examined the effect of free viewing on {IT} neuronal responses in monkeys engaged in a form-recognition task. By making small, real-time stimulus adjustments, we produced nearly identically retinal stimulation during controlled and free viewing. Nearly 90\% of neuronal responses were unaffected by free viewing, and average stimulus selectivity was unchanged. Thus, neuronal representations that likely underlie form recognition are virtually unaltered by free viewing.

}, keywords = {Animals, Conditioning, Fixation, Form Perception, Macaca mulatta, Male, Neurons, Ocular, Pattern Recognition, Photic Stimulation, Psychology, Saccades, Temporal Lobe, Visual, Visual Cortex}, issn = {1097-6256}, doi = {10.1038/77722}, url = {http://www.nature.com/articles/nn0800_814}, author = {DiCarlo, James J. and Maunsell, John H. R.} }