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Fragment-based learning of visual object categories in non-human primates.

Kromrey S, Maestri M, Hauffen K, Bart E, Hegdé J - PLoS ONE (2010)

Bottom Line: Recent research has shown that the visual system can use local, informative image fragments of a given object, rather than the whole object, to classify it into a familiar category.We have previously reported, using human psychophysical studies, that when subjects learn new object categories using whole objects, they incidentally learn informative fragments, even when not required to do so.However, the neuronal mechanisms by which we acquire and use informative fragments, as well as category knowledge itself, have remained unclear.

View Article: PubMed Central - PubMed

Affiliation: Brain and Behavior Discovery Institute, Medical College of Georgia, Augusta, Georgia, USA.

ABSTRACT
When we perceive a visual object, we implicitly or explicitly associate it with an object category we know. Recent research has shown that the visual system can use local, informative image fragments of a given object, rather than the whole object, to classify it into a familiar category. We have previously reported, using human psychophysical studies, that when subjects learn new object categories using whole objects, they incidentally learn informative fragments, even when not required to do so. However, the neuronal mechanisms by which we acquire and use informative fragments, as well as category knowledge itself, have remained unclear. Here we describe the methods by which we adapted the relevant human psychophysical methods to awake, behaving monkeys and replicated key previous psychophysical results. This establishes awake, behaving monkeys as a useful system for future neurophysiological studies not only of informative fragments in particular, but also of object categorization and category learning in general.

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The trial paradigm.The animal performed a delayed same-different categorization task while maintaining fixation. After the animal established fixation on a central fixation target (‘+’) within an imaginary ±0.5° window (dashed square in far left frame), two eccentric stimuli were presented sequentially, each followed by a delay. After the second delay, the fixation target was turned off, at which time the animal indicated whether or not the two stimuli belonged to the same category by making a direct saccade to an appropriate saccade target (small blue squares in the far left frame). During the training phase of the study, both the stimuli during a given trial were whole objects. This figure shows a non-matching trial during training. Trials during the testing phase were identical (not shown), except that one of the stimuli during each trial was a fragment presented as a partial view of an object behind a light gray opaque occluder with a corresponding hole in it; the other stimulus in the trial was a whole object. In Experiments 1, 2 and 3, the fragment was presented as the first stimulus in each trial. See Materials and Methods for details.
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pone-0015444-g002: The trial paradigm.The animal performed a delayed same-different categorization task while maintaining fixation. After the animal established fixation on a central fixation target (‘+’) within an imaginary ±0.5° window (dashed square in far left frame), two eccentric stimuli were presented sequentially, each followed by a delay. After the second delay, the fixation target was turned off, at which time the animal indicated whether or not the two stimuli belonged to the same category by making a direct saccade to an appropriate saccade target (small blue squares in the far left frame). During the training phase of the study, both the stimuli during a given trial were whole objects. This figure shows a non-matching trial during training. Trials during the testing phase were identical (not shown), except that one of the stimuli during each trial was a fragment presented as a partial view of an object behind a light gray opaque occluder with a corresponding hole in it; the other stimulus in the trial was a whole object. In Experiments 1, 2 and 3, the fragment was presented as the first stimulus in each trial. See Materials and Methods for details.

Mentions: The experiments consisted of training the monkeys using whole objects and then testing the animals using fragments, in both cases using a delayed same-different categorization task (Fig. 2; see Materials and Methods for details). Since only whole objects, not fragments, were used during training, the animals did not necessarily have to learn the fragments in order to learn the categories. Figure 3 shows the category learning curve of the two animals for class X vs. class Y (see inset). Note that at the start of the training, either animal performed at chance levels, indicating that the specific classes needed to be learned before the animals could classify the objects successfully. After several hundred trials, the performance of both animals was significantly above chance levels (binomial proportions test, p<0.05).


Fragment-based learning of visual object categories in non-human primates.

Kromrey S, Maestri M, Hauffen K, Bart E, Hegdé J - PLoS ONE (2010)

The trial paradigm.The animal performed a delayed same-different categorization task while maintaining fixation. After the animal established fixation on a central fixation target (‘+’) within an imaginary ±0.5° window (dashed square in far left frame), two eccentric stimuli were presented sequentially, each followed by a delay. After the second delay, the fixation target was turned off, at which time the animal indicated whether or not the two stimuli belonged to the same category by making a direct saccade to an appropriate saccade target (small blue squares in the far left frame). During the training phase of the study, both the stimuli during a given trial were whole objects. This figure shows a non-matching trial during training. Trials during the testing phase were identical (not shown), except that one of the stimuli during each trial was a fragment presented as a partial view of an object behind a light gray opaque occluder with a corresponding hole in it; the other stimulus in the trial was a whole object. In Experiments 1, 2 and 3, the fragment was presented as the first stimulus in each trial. See Materials and Methods for details.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2991334&req=5

pone-0015444-g002: The trial paradigm.The animal performed a delayed same-different categorization task while maintaining fixation. After the animal established fixation on a central fixation target (‘+’) within an imaginary ±0.5° window (dashed square in far left frame), two eccentric stimuli were presented sequentially, each followed by a delay. After the second delay, the fixation target was turned off, at which time the animal indicated whether or not the two stimuli belonged to the same category by making a direct saccade to an appropriate saccade target (small blue squares in the far left frame). During the training phase of the study, both the stimuli during a given trial were whole objects. This figure shows a non-matching trial during training. Trials during the testing phase were identical (not shown), except that one of the stimuli during each trial was a fragment presented as a partial view of an object behind a light gray opaque occluder with a corresponding hole in it; the other stimulus in the trial was a whole object. In Experiments 1, 2 and 3, the fragment was presented as the first stimulus in each trial. See Materials and Methods for details.
Mentions: The experiments consisted of training the monkeys using whole objects and then testing the animals using fragments, in both cases using a delayed same-different categorization task (Fig. 2; see Materials and Methods for details). Since only whole objects, not fragments, were used during training, the animals did not necessarily have to learn the fragments in order to learn the categories. Figure 3 shows the category learning curve of the two animals for class X vs. class Y (see inset). Note that at the start of the training, either animal performed at chance levels, indicating that the specific classes needed to be learned before the animals could classify the objects successfully. After several hundred trials, the performance of both animals was significantly above chance levels (binomial proportions test, p<0.05).

Bottom Line: Recent research has shown that the visual system can use local, informative image fragments of a given object, rather than the whole object, to classify it into a familiar category.We have previously reported, using human psychophysical studies, that when subjects learn new object categories using whole objects, they incidentally learn informative fragments, even when not required to do so.However, the neuronal mechanisms by which we acquire and use informative fragments, as well as category knowledge itself, have remained unclear.

View Article: PubMed Central - PubMed

Affiliation: Brain and Behavior Discovery Institute, Medical College of Georgia, Augusta, Georgia, USA.

ABSTRACT
When we perceive a visual object, we implicitly or explicitly associate it with an object category we know. Recent research has shown that the visual system can use local, informative image fragments of a given object, rather than the whole object, to classify it into a familiar category. We have previously reported, using human psychophysical studies, that when subjects learn new object categories using whole objects, they incidentally learn informative fragments, even when not required to do so. However, the neuronal mechanisms by which we acquire and use informative fragments, as well as category knowledge itself, have remained unclear. Here we describe the methods by which we adapted the relevant human psychophysical methods to awake, behaving monkeys and replicated key previous psychophysical results. This establishes awake, behaving monkeys as a useful system for future neurophysiological studies not only of informative fragments in particular, but also of object categorization and category learning in general.

Show MeSH