Neuronal activity of primate putamen during categorical perception of somaesthetic stimuli

Merchant, Hugo; Oros-Ruíz, Socorro; Crespo, Patricia; Zainos, Antonio

doi:10.1097/00001756-199505090-00016

Cited by 28 publications

(19 citation statements)

References 16 publications

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“…This differential activity actually was observed only during the comparison stimuli, which would be expected if animals based their decisions exclusively on the second stimulus. Similar responses have been recorded from monkeys trained to categorize the speed of tactile motion on the basis of a single stimulus; some neurons from M1 cortex (E. Salinas and R. Romo, unpublished results), the supplementary motor area (Romo et al, 1993, and the putamen (Romo et al, 1995;Merchant et al, 1997) reflect the sensory decision process in their activity. Werner (1980) has clearly stated the distinctions between the different questions that can be asked about the magnitude of a sensation.…”

Section: Discussionmentioning

confidence: 59%

Discrimination in the Sense of Flutter: New Psychophysical Measurements in Monkeys

et al. 1997

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Humans and monkeys have similar capacities to discriminate the frequencies of mechanical sinusoids delivered to their hands in the range that corresponds to the sense of flutter . Previous studies showed that monkeys can discriminate whether comparison stimuli are higher or lower in frequency than a base stimulus that does not vary from trial to trial during an experiment. We verified this result in two monkeys trained in this manner. To confirm that these animals were able to discriminate, we tested them in a variant of the task in which the frequency of the base stimulus changed randomly from trial to trial. The monkeys failed to discriminate in this new testing mode; instead they seemed to categorize the comparison stimuli, ignoring the base stimulus. After further training in the randomized base condition, the two monkeys learned to discriminate accurately. We then explored how the stimulation parameters affected performance. We found that animals could discriminate accurately with stimulus durations as short as 250 msec, with interstimulus intervals as long as 10 sec, with 50% differences between base and comparison stimulus amplitudes or when stimulated on a different finger. Performance did not degrade in these conditions, even though the monkeys had never been trained or tested under them. The results show that monkeys may try to categorize rather than discriminate when the task allows either strategy, although they are capable of performing true discriminations very robustly. These findings have important implications for investigating the neuronal processes underlying sensory discrimination. Key words: flutter; psychophysics; discrimination; categorization; monkeys; vibrotactile stimuliAn important problem in sensory physiology is the isolation of the neural codes that explain the capacity of a subject to make detections and discriminations of sensory stimuli. In this respect, LaMotte and Mountcastle (1975) and Mountcastle et al. (1990) have made a number of important observations in a sensory modality called the sense of flutter. They determined that both humans and monkeys have similar capacities for detecting and discriminating the frequencies of mechanical sinusoids delivered to their hands. The aim of those studies was to discover how the neural code of primary somatosensory cortex (S1) is related to somesthetic performance in the sense of flutter. In the task they designed, animals had to indicate whether the frequency of a comparison stimulus was lower or higher than a base stimulus that did not vary in frequency from trial to trial during a run. The results revealed a set of neurons with quickly adapting properties, the activity of which was entrained by the stimuli, firing in phase with the oscillatory signal. These neurons responded identically to the two stimuli, they did so even during passive stimulation, and their activities seemed unrelated to any kind of comparison process that presumably takes place during discrimination. Mountcastle and colleagues (1990) concluded that the neuronal s...

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Section: Discussionmentioning

confidence: 59%

Discrimination in the Sense of Flutter: New Psychophysical Measurements in Monkeys

et al. 1997

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“…In COVIS, associations between stimuli and category labels are learned via changes in synaptic strength between pyramidal cells in visual association areas and medium spiny cells in the striatum. A large set of diverse results support this general model (for a review see, e.g., Ashby & Ennis, 2006), including single-cell recording studies in monkeys showing that striatal medium spiny cells develop category-specific responses after extensive categorization training (Merchant, Zainos, Hernandez, Salinas, & Romo, 1997; Romo, Merchant, Ruiz, Crespo, & Zainos, 1995; Romo, Merchant, Zainos, & Hernandez, 1997). Some of the characteristics associated with the neural architecture of the COVIS stimulus-to-label association are roughly consistent with the empirical findings reported here.…”

Section: Discussionmentioning

confidence: 88%

Category label and response location shifts in category learning

Maddox

Glass

O’Brien

et al. 2009

Psychological Research

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The category shift literature suggests that rule-based classification, an important form of explicit learning, is mediated by two separate learned associations: a stimulus-to-label association that associates stimuli and category labels, and a label-to-response association that associates category labels and responses. Three experiments investigate whether information–integration classification, an important form of implicit learning, is also mediated by two separate learned associations. Participants were trained on a rule-based or an information–integration categorization task and then the association between stimulus and category label, or between category label and response location was altered. For rule-based categories, and in line with previous research, breaking the association between stimulus and category label caused more interference than breaking the association between category label and response location. However, no differences in recovery rate emerged. For information–integration categories, breaking the association between stimulus and category label caused more interference and led to greater recovery than breaking the association between category label and response location. These results provide evidence that information–integration category learning is mediated by separate stimulus-to-label and label-to-response associations. Implications for the neurobiological basis of these two learned associations are discussed.

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“…In human stroke patients, delusions of parasitosis often occur following lesions of right temporoparietal cortex, thalamus and putamen (Huber et al , 2008). Putamen strongly influences visuotactile perception (Graziano and Gross, 1993; Ladavas et al , 1998; Romo et al , 1995; Yoo et al , 2003), it contains bimodal cells with visual and tactile receptive fields, which help to encode the location of sensory stimuli mainly near the face. These cells project to parietal (ventral intraparietal cortex), primary somatosensory and pre-motor cortices (Graziano and Gross, 1993; Ladavas et al , 1998).…”

Section: Explaining Delusion Contentmentioning

confidence: 99%

Toward a neurobiology of delusions

Corlett

Taylor

Wang³

et al. 2010

Progress in Neurobiology

352

380

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Delusions are the false and often incorrigible beliefs that can cause severe suffering in mental illness. We cannot yet explain them in terms of underlying neurobiological abnormalities. However, by drawing on recent advances in the biological, computational and psychological processes of reinforcement learning, memory, and perception it may be feasible to account for delusions in terms of cognition and brain function. The account focuses on a particular parameter, prediction error – the mismatch between expectation and experience – that provides a computational mechanism common to cortical hierarchies, frontostriatal circuits and the amygdala as well as parietal cortices. We suggest that delusions result from aberrations in how brain circuits specify hierarchical predictions, and how they compute and respond to prediction errors. Defects in these fundamental brain mechanisms can vitiate perception, memory, bodily agency and social learning such that individuals with delusions experience an internal and external world that healthy individuals would find difficult to comprehend. The present model attempts to provide a framework through which we can build a mechanistic and translational understanding of these puzzling symptoms.

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Neuronal activity of primate putamen during categorical perception of somaesthetic stimuli

Cited by 28 publications

References 16 publications

Discrimination in the Sense of Flutter: New Psychophysical Measurements in Monkeys

Discrimination in the Sense of Flutter: New Psychophysical Measurements in Monkeys

Category label and response location shifts in category learning

Toward a neurobiology of delusions

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