Experience-dependent representation of visual categories in parietal cortex

Freedman, David J.; Assad, John A.

doi:10.1038/nature05078

Cited by 481 publications

(567 citation statements)

References 27 publications

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“…First, occipitotemporal, parietal, and motor regions were engaged early (first component) in processing. This is consistent with the role of occipitotemporal regions in the processing of visual forms (Ostwald et al, 2008), and parietal and motor regions in perceptual categorization (Freedman and Assad, 2006) and stimulus-response association processes (Toni et al, 2001). Second, processes related to perceptual judgments (i.e., associated with the second component) engaged prefrontal regions, consistent with the role of prefrontal cortex in categorization and adaptive cognitive processes (Miller, 2000;Duncan, 2001).…”

Section: Eeg-informed Fmri Mapping Of Regions Of Interestsupporting

confidence: 81%

“…Recent studies suggest that learning alters later decision-related processes thought to reweight the contributions of early sensory representations (Dosher and Lu, 1999;Li et al, 2004;Law and Gold, 2008;Jacobs, 2009). Our findings suggest that learning modifies early recurrent processing (Roelfsema and van Ooyen, 2005;Roelfsema, 2006) within higher visual and parietal areas engaged in the integration (Ostwald et al, 2008) and categorization (Freedman and Assad, 2006) of global visual forms. Specifically, our findings showing that learning modulates shape processing in higher occipitotemporal regions (LO) sheds light on the contested role of temporal cortex in visual learning.…”

Section: Discussionmentioning

confidence: 73%

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Learning Acts on Distinct Processes for Visual Form Perception in the Human Brain

Mayhew

Li²,

Kourtzi³

2012

J. Neurosci.

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Learning is known to facilitate our ability to detect targets in clutter and optimize brain processes for successful visual recognition. Previous brain-imaging studies have focused on identifying spatial patterns (i.e., brain areas) that change with learning, implicating occipitotemporal and frontoparietal areas. However, little is known about the interactions within this network that mediate learningdependent improvement in complex perceptual tasks (i.e., discrimination of visual forms in clutter). Here we take advantage of the complementary high spatial and temporal resolution of simultaneous EEG-fMRI to identify the learning-dependent changes in spatiotemporal brain patterns that mediate enhanced behavioral sensitivity in the discrimination of global forms after training. We measured the observers' choices when discriminating between concentric and radial patterns presented in noise before and after training. Similarly, we measured the choices of a pattern classifier when predicting each stimulus from EEG-fMRI signals. By comparing the performance of human observers and classifiers, we demonstrated that learning alters sensitivity to visual forms and EEG-fMRI activation patterns related to distinct visual recognition processes. In particular, behavioral improvement after training was associated with changes in (1) early processes involved in the integration of global forms in higher occipitotemporal and parietal areas, and (2) later processes related to categorical judgments in frontal circuits. Thus, our findings provide evidence that learning acts on distinct visual recognition processes and shapes feedforward interactions across brain areas to support performance in complex perceptual tasks.

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Section: Eeg-informed Fmri Mapping Of Regions Of Interestsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 73%

Learning Acts on Distinct Processes for Visual Form Perception in the Human Brain

Mayhew

Li²,

Kourtzi³

2012

J. Neurosci.

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“…Such "number neurons" abstractly represent the number of items across space, time, and modalities (15,16,17). Number neurons have also been traced indirectly in the human brain using functional MRI (fMRI) (18,19).However, because neurons can be trained to represent behaviorally meaningful categories (20,21,22), it has been argued (23) that the presence of previously described number neurons in trained animals might be a product of intense learning, rather than a reflection of a spontaneous number sense. For the same reason, the coding scheme for numerosity has been debated (23): Is the spontaneous neuronal code for numerosity a summation code, as evidenced by monotonic discharges as a function of quantity (14,24), or a labeled-line code as witnessed by numerosity-selective neurons tuned to preferred numerosities analogous to those found in monkeys performing numerical tasks (25,26)?…”

mentioning

confidence: 99%

Neuronal correlates of a visual “sense of number” in primate parietal and prefrontal cortices

Viswanathan

Nieder

2013

Proc. Natl. Acad. Sci. U.S.A.

150

148

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"Sense of number" refers to the classical idea that we perceive the number of items (numerosity) intuitively. However, whether the brain signals numerosity spontaneously, in the absence of learning, remains unknown; therefore, we recorded from neurons in the ventral intraparietal sulcus and the dorsolateral prefrontal cortex of numerically naive monkeys. Neurons in both brain areas responded maximally to a given number of items, showing tuning to a preferred numerosity. Numerosity was encoded earlier in area ventral intraparietal area, suggesting that numerical information is conveyed from the parietal to the frontal lobe. Visual numerosity is thus spontaneously represented as a perceptual category in a dedicated parietofrontal network. This network may form the biological foundation of a spontaneous number sense, allowing primates to intuitively estimate the number of visual items.association cortices | quantity | single-unit recording T he classical idea of a "sense of number" (1,2) suggests that we and animals are endowed with the faculty to perceive the number of items (i.e., numerosity) intuitively. Numerosity might be a perceptual category provided by hard-wired sensory brain processes, without the need to learn what numerosity refers to. Supporting this hypothesis, numerosity is represented by an approximate nonverbal system that allows wild animals (3,4), prelinguistic infants(5,6), and innumerate humans (7,8) to readily estimate set size. Evidence that the brain is set up to assess visual numerosity spontaneously was recently provided by psychophysical and computational experiments: numerosity-just like color or perceptual categories like faces-in humans is susceptible to adaptation (9,10), and is extracted en passant by computational network models (11).So far, the neuronal foundations of a perceptual number sense were never tested because all experiments done so far were performed in animals that learned to discriminate numerosity (12)(13)(14). Work with behaviorally trained nonhuman primates identified a cortical network with individual neurons in the prefrontal (PFC) and posterior parietal cortex (PPC) selectively responding to the number of items. Such "number neurons" abstractly represent the number of items across space, time, and modalities (15,16,17). Number neurons have also been traced indirectly in the human brain using functional MRI (fMRI) (18,19).However, because neurons can be trained to represent behaviorally meaningful categories (20,21,22), it has been argued (23) that the presence of previously described number neurons in trained animals might be a product of intense learning, rather than a reflection of a spontaneous number sense. For the same reason, the coding scheme for numerosity has been debated (23): Is the spontaneous neuronal code for numerosity a summation code, as evidenced by monotonic discharges as a function of quantity (14,24), or a labeled-line code as witnessed by numerosity-selective neurons tuned to preferred numerosities analogous to those found in monkeys perform...

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“…In agreement with the view that detections are discriminations of a stimulus from noise (11), elegant studies by Romo and coworkers (12, 13) reported neurons actively encoding the decision about the stimulus presence. The decision about stimulus absence, however, was represented as a default (baseline) neuronal response (12-16) for action-based detection decisions.When dissociated from action preparation or studied in a report-independent framework, decisions can be seen as distinct processes that are encoded as abstract categories (17)(18)(19). In a dotmotion discrimination task, neurons in the lateral intraparietal area were shown to encode the abstract decision about motion directions independently from how they signaled the associated motor response (20).…”

mentioning

confidence: 99%

“…When dissociated from action preparation or studied in a report-independent framework, decisions can be seen as distinct processes that are encoded as abstract categories (17)(18)(19). In a dotmotion discrimination task, neurons in the lateral intraparietal area were shown to encode the abstract decision about motion directions independently from how they signaled the associated motor response (20).…”

mentioning

confidence: 99%

Active encoding of decisions about stimulus absence in primate prefrontal cortex neurons

Merten

Nieder

2012

Proc. Natl. Acad. Sci. U.S.A.

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Judging the presence or absence of a stimulus is likely the most basic perceptual decision. A fundamental difference of detection tasks in contrast to discrimination tasks is that only the stimulus presence decision can be inferred from sensory evidence, whereas the alternative decision about stimulus absence lacks sensory evidence by definition. Detection decisions have been studied in an intentional, action-based framework, in which decisions were regarded as intentions to pursue particular actions. These studies have found that only stimulus-present decisions are actively encoded by neurons, whereas the decision about the absence of a stimulus does not affect default neuronal responses. We tested whether this processing mechanism also holds for abstract detection decisions that are dissociated from motor preparation. We recorded single-neuron activity from the prefrontal cortex (PFC) of monkeys performing a visual detection task that forced a reportindependent decision. We not only found neurons that actively encoded the subjective decision of monkeys about the presence of a stimulus, but also cells responding actively for the decision about the absence of stimuli. These results suggest that abstract detection decisions are processed in a different way compared with the previously reported action-based decisions. In a report-independent framework, neuronal networks seem to generate a second set of neurons actively encoding the absence of sensory stimulation, thus translating decisions into abstract categories. This mechanism may allow the brain to "buffer" a decision in a nonmovement-related framework.perceptual detection | abstract decision | single-cell recordings | rhesus monkey P erceptual decisions are choices among alternatives based on sensory information. To arrive at distinct choices, sensory input has to be classified into behaviorally meaningful categories. The detection of a stimulus (decision about its presence or absence) is the most basic form of a perceptual decision. The peculiarity of detection decisions is that only one choice alternative can be based on sensory evidence, whereas the alternative decision about stimulus absence lacks sensory information. How does the brain arrive at categorical stimulus-absent and stimuluspresent decisions when only one response category (stimuluspresent) can rely on sensory input?The neuronal underpinnings of perceptual decisions have been studied extensively in an intentional, action-based framework (1-3). Here, decisions are regarded as intensions to choose among actions associated with the stimuli (1, 4). Decision-related neurons showed activity encoding the process of converting sensory information (5-7) or cognitive cues (8-10) into choices. In agreement with the view that detections are discriminations of a stimulus from noise (11), elegant studies by Romo and coworkers (12, 13) reported neurons actively encoding the decision about the stimulus presence. The decision about stimulus absence, however, was represented as a default (baseline) neuronal res...

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Experience-dependent representation of visual categories in parietal cortex

Cited by 481 publications

References 27 publications

Learning Acts on Distinct Processes for Visual Form Perception in the Human Brain

Learning Acts on Distinct Processes for Visual Form Perception in the Human Brain

Neuronal correlates of a visual “sense of number” in primate parietal and prefrontal cortices

Active encoding of decisions about stimulus absence in primate prefrontal cortex neurons

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