@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 {110, title = {Structure of Receptive Fields in Area 3b of Primary Somatosensory Cortex in the Alert Monkey}, journal = {The Journal of Neuroscience}, volume = {18}, year = {1998}, month = {04/1998}, pages = {2626 - 2645}, abstract = {

We investigated the two-dimensional structure of area 3b neuronal receptive fields (RFs) in three alert monkeys. Three hundred thirty neurons with RFs on the distal fingerpads were studied with scanned, random dot stimuli. Each neuron was stimulated continuously for 14 min, yielding 20,000 response data points. Excitatory and inhibitory components of each RF were determined with a modified linear regression algorithm. Analyses assessing goodness-of-fit, repeatability, and generality of the RFs were developed. Two hundred forty-seven neurons yielded highly repeatable RF estimates, and most RFs accounted for a large fraction of the explainable response of each neuron. Although the area 3b RF structures appeared to be continuously distributed, certain structural generalities were apparent. Most RFs (94\%) contained a single, central region of excitation and one or more regions of inhibition located on one, two, three, or all four sides of the excitatory center. The shape, area, and strength of excitatory and inhibitory RF regions ranged widely. Half the RFs contained almost evenly balanced excitation and inhibition. The findings indicate that area 3b neurons act as local spatiotemporal filters that are maximally excited by the presence of particular stimulus features. We believe that form and texture perception are based on high-level representations and that area 3b is an intermediate stage in the processes leading to these representations. Two possibilities are considered: (1) that these high-level representations are basically somatotopic and that area 3b neurons amplify some features and suppress others, or (2) that these representations are highly transformed and that area 3b effects a step in the transformation.

}, keywords = {Afferent, Animals, Data Interpretation, Electrophysiology, Female, Macaca mulatta, Male, Neural Inhibition, Neurons, Reproducibility of Results, Somatosensory Cortex, Statistical, Touch}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.18-07-02626.1998}, url = {http://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.18-07-02626.1998}, author = {DiCarlo, James J. and Johnson, Kenneth O. and Hsiao, Steven S.} } @article {116, title = {Marking microelectrode penetrations with fluorescent dyes}, journal = {Journal of Neuroscience Methods}, volume = {64}, year = {1996}, month = {01/1996}, pages = {75 - 81}, abstract = {

Fluorescent dyes were used to mark and identify the tracks left by extracellular microelectrodes in neurophysiological experiments. Forty-two penetrations were made into the postcentral gyrus of 3 Macaque monkeys with electrodes coated with 1 of 5 fluorescent dyes (Dil, DiO, DiI-C5, PyPO, and Fast Blue). The electrodes were driven at rates ranging from 10 to 1000 \μm/min, to a depth of about 4000 \μm, where a small electrolytic lesion was made. Histological sections were viewed under fluorescent optics and the electrode tracks were reconstructed from the dye traces. Fluorescent traces (width 50\–400 \μm) were observed in 41 of 42 penetrations with 24 traces extending to the lesion site. Of the electrodes driven in less than 3 h, those coated with DiI (88) and DiI-C5 (88) left a trace to the lesion site, while 57\% (47) of the DiO, 40\% (25) of the Fast Blue and only 11\% (19) of the PyPO tracks were fully marked.

This method of marking penetrations can be used with any extracellular recording configuration, does not require tissue sections to be processed or stained, does not require electrical lesions, and causes no detectable tissue damage. Because the dyes fluoresce at different wavelengths, closely spaced tracks can be uniquely identified.

}, keywords = {Animals, Brain, Electrophysiology, Fluorescent Dyes, Macaca mulatta, Microelectrodes, Neurosciences}, issn = {01650270}, doi = {10.1016/0165-0270(95)00113-1}, url = {https://linkinghub.elsevier.com/retrieve/pii/0165027095001131}, author = {DiCarlo, James J. and Lane, John W. and Hsiao, Steven S. and Johnson, Kenneth O.} }