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Inferotemporal neuron activities and color discrimination with delay

Brain Research
Publication Date
DOI: 10.1016/0006-8993(80)90830-6
  • Konorski'S Task (It)
  • Inferotemporal Cortex Neurons
  • Monkey
  • Color Discrimination With Delay
  • Delayed Matching To Sample Task


Abstract Neuron activity was recorded from the inferotemporal cortex (IT)of rhesus monkeys while they were performing a visual color discrimination task, in which a light (green or red) was illuminated twice with a delay period of 1–5 sec. Two kinds of task were employed. The first was a visual short-term memory task, originally described by Konorski (task I), and the second was its slightly modified version (task II). If the first stimulus (sample) and the second (matching) were the same in color, the monkey pressed one of two levers and if two stimuli were different, the monkey pressed the other. In task I, the matching stimulus signaled ‘GO’ for lever press. In task II, after visual stimuli, another delay period and then auditory stimulus, indicating ‘GO’ for lever press, were added. Out of 101 task related neurons, 57 were recorded during task I and 44 were during task II. Most of these were activated by visual stimuli and these were divided into two classes: ones responding non-differentially to different colors (45 neurons) and the other responding differentially to different colors (37 neurons). In task I, 8 neurons showed increases only after matching stimuli and one increased only after sample stimuli. Out of 33 neurons activated by both stimuli, 20 showed stronger responses to matching stimuli and others showed increase or decrease of equal degree. Out of task II-related neurons, 40 were activated visually during sample and matching periods and 20 showed stronger responses to matching stimuli. It is said that in these task visually activated neurons tended to show stronger responses to matching than to sample stimuli. Activity related to the lever press was not found. It was suggested from these results that the IT neurons were related to a process of visual discrimination, so that a physically identical stimulus which had a different meaning in the behavioral context would be differentiated.

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