%0 Journal Article %J Journal of Neurophysiology %D 2004 %T Using Neuronal Latency to Determine Sensory–Motor Processing Pathways in Reaction Time Tasks %A DiCarlo, James J. %A Maunsell, John H. R. %K Action Potentials %K Afferent %K Animal %K Animals %K Behavior %K Macaca mulatta %K Male %K Models %K Motor Neurons %K Neural Pathways %K Neurological %K Neurons %K Photic Stimulation %K Psychomotor Performance %K Reaction Time %K Task Performance and Analysis %K Temporal Lobe %K Time Factors %K Visual Fields %X

We describe a new technique that uses the timing of neuronal and behavioral responses to explore the contributions of individual neurons to specific behaviors. The approach uses both the mean neuronal latency and the trial-by-trial covariance between neuronal latency and behavioral response. Reliable measurements of these values were obtained from single-unit recordings made from anterior inferotemporal (AIT) cortex and the frontal eye fields (FEF) in monkeys while they performed a choice reaction time task. These neurophysiological data show that the responses of AIT neurons and some FEF neurons have little covariance with behavioral response, consistent with a largely "sensory" response. The responses of another group of FEF neurons with longer mean latency covary tightly with behavioral response, consistent with a largely "motor" response. A very small fraction of FEF neurons had responses consistent with an intermediate position in the sensory-motor pathway. These results suggest that this technique is a valuable tool for exploring the functional organization of neuronal circuits that underlie specific behaviors.

 

%B Journal of Neurophysiology %V 93 %P 2974 - 2986 %8 11/2004 %G eng %U https://www.physiology.org/doi/10.1152/jn.00508.2004 %N 5 %! Journal of Neurophysiology %R 10.1152/jn.00508.2004 %0 Journal Article %J Journal of Neurophysiology %D 2003 %T Anterior Inferotemporal Neurons of Monkeys Engaged in Object Recognition Can be Highly Sensitive to Object Retinal Position %A DiCarlo, James J. %A Maunsell, John H. R. %K Action Potentials %K Animals %K Depth Perception %K Electrophysiology %K Eye Movements %K Form Perception %K Macaca mulatta %K Male %K Neurons %K Pattern Recognition %K Photic Stimulation %K Psychomotor Performance %K Retina %K Temporal Lobe %K Time Factors %K Visual %K Visual Fields %K Visual Perception %X

Visual object recognition is computationally difficult because changes in an object'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'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.

 

%B Journal of Neurophysiology %V 89 %P 3264 - 3278 %8 01/2003 %G eng %U https://www.physiology.org/doi/10.1152/jn.00358.2002 %N 6 %! Journal of Neurophysiology %R 10.1152/jn.00358.2002 %0 Journal Article %J Nature Neuroscience %D 2000 %T Form representation in monkey inferotemporal cortex is virtually unaltered by free viewing %A DiCarlo, James J. %A Maunsell, John H. R. %K Animals %K Conditioning %K Fixation %K Form Perception %K Macaca mulatta %K Male %K Neurons %K Ocular %K Pattern Recognition %K Photic Stimulation %K Psychology %K Saccades %K Temporal Lobe %K Visual %K Visual Cortex %X

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.

%B Nature Neuroscience %V 3 %P 814 - 821 %8 01/2000 %G eng %U http://www.nature.com/articles/nn0800_814 %N 8 %! Nat Neurosci %R 10.1038/77722