michael paradiso - Academia.edu (original) (raw)
Papers by michael paradiso
The Journal of Neuroscience, Jul 15, 1999
Brightness changes can be induced in a static gray field by modulating the luminance of surroundi... more Brightness changes can be induced in a static gray field by modulating the luminance of surrounding areas. We used this induction phenomenon to investigate the neural representation of perceived brightness. Extracellular recordings were made in striate cortex, the lateral geniculate nucleus (LGN), and the optic tract of anesthetized cats using stimuli that produced brightness induction. While a cell's receptive field (RF) was covered by uniform gray illumination, the luminance of rectangular flanking regions was modulated sinusoidally in time, inducing brightness changes in the RF. We looked for a correspondence between the modulation of a cell's response and stimulus conditions that did or did not produce perceptual changes in brightness. We found that the responses of retinal ganglion cell axons in the optic tract were never correlated with brightness. On the other hand, many neurons in striate cortex and a small fraction in the LGN responded in a phase-locked manner at the temporal frequency of the flank modulation, even though the flanks were 3-7°beyond the edges of the RF. Only in striate cortex were cells found that had responses correlated with brightness under all stimulus conditions. These findings suggest that brightness information is explicitly represented in the responses of neurons in striate cortex as part of a neural representation of object surfaces.
Journal of Vision, Aug 1, 2004
Visual Neuroscience, 2018
Neurons in visual areas of the brain are generally characterized by the increase in firing rate t... more Neurons in visual areas of the brain are generally characterized by the increase in firing rate that occurs when a stimulus is flashed on in the receptive field. However, neurons also increase their firing rate when a stimulus is turned off. These "termination responses" or "after-discharges" that occur with flashed stimuli have been observed in area V1 and they may be important for vision as stimulus terminations have been shown to influence visual perception. The goal of the present study was to determine the strength of termination responses in the more natural situation in which eye movements move a stimulus out of a receptive field. We find that termination responses do occur in macaque V1 when termination results from a saccadic eye movement, but they are smaller in amplitude compared to flashed-off stimuli. Further, there are termination responses even in the absence of visual stimulation. These findings demonstrate that termination responses are a component of naturalistic vision. They appear to be based on both visual and non-visual signals in visual cortex. We speculate that the weakening of termination responses might be a neural correlate of saccadic suppression, the loss of perceptual sensitivity around the time of saccades.
Journal of Neurophysiology, Jul 1, 2012
Vision in natural situations is different from the paradigms generally used to study vision in th... more Vision in natural situations is different from the paradigms generally used to study vision in the laboratory. In natural vision, stimuli usually appear in a receptive field as the result of saccadic eye movements rather than suddenly flashing into view. The stimuli themselves are rich with meaningful and recognizable objects rather than simple abstract patterns. In this study we examined the sensitivity of neurons in macaque area V1 to saccades and to complex background contexts. Using a variety of visual conditions, we find that natural visual response patterns are unique. Compared with standard laboratory situations, in more natural vision V1 responses have longer latency, slower time course, delayed orientation selectivity, higher peak selectivity, and lower amplitude. Furthermore, the influences of saccades and background type (complex picture vs. uniform gray) interact to give a distinctive, and presumably more natural, response pattern. While in most of the experiments natural images were used as background, we find that similar synthetic unnatural background stimuli produce nearly identical responses (i.e., complexity matters more than "naturalness"). These findings have important implications for our understanding of vision in more natural situations. They suggest that with the saccades used to explore complex images, visual context ("surround effects") would have a far greater effect on perception than in standard experiments with stimuli flashed on a uniform background. Perceptual thresholds for contrast and orientation should also be significantly different in more natural situations. primary visual cortex; natural vision; orientation selectivity; temporal aspects of visual processing; visual context and saccades
Nature Neuroscience, Nov 1, 1998
Ample evidence suggests that primary visual cortex is involved in the perception of form, and the... more Ample evidence suggests that primary visual cortex is involved in the perception of form, and there is increasing evidence that it may also be important in the perception of surfaces. Perceptual qualities of surfaces, such as brightness, are based on extensive integration of information throughout the visual field. In primary visual cortex, we found that the responses of neurons to surfaces were also influenced by the intensity and organization of light in large portions of the visual field. Interactions with surrounding stimuli typically extended 10 to 20 degrees beyond a cell's receptive field, the same spatial scale as perceptual interactions. Moreover, there were both facilitatory and inhibitory influences, just as there are additive and subtractive perceptual interactions. Surprisingly, influences from outside the receptive field obtained with surface stimuli did not reliably correlate with influences recorded with gratings. These properties suggest that the underlying neuronal interactions may serve as the fundamental building blocks of surface perception.
Journal of Vision, Mar 16, 2010
Current Opinion in Neurobiology, Apr 1, 2002
Abbreviations 2-DG 2-deoxyglucose FEF frontal eye field fMRI functional magnetic resonance imagin... more Abbreviations 2-DG 2-deoxyglucose FEF frontal eye field fMRI functional magnetic resonance imaging LGN lateral geniculate nucleus MST medial superior temporal area MT middle temporal area PET positron emission tomography rTMS repetitive TMS TE temporal visual area TMS transcranial magnetic stimulation V1 primary visual cortex V2 second visual area
Progress in Brain Research, 2005
To conduct well-controlled studies of visual processing in the laboratory, deviations from natura... more To conduct well-controlled studies of visual processing in the laboratory, deviations from natural visual situations must generally be employed. In some regards, the reduced visual paradigms typically used are adequate for providing an accurate description of visual representations. However, the use of fixation paradigms and stimuli isolated within a receptive field may underestimate the richness of visual processing in area V1. Experiments ranging from lightness encoding and perception to paradigms involving natural scenes and saccades used to examine the relationship between V1 activity and perception are reviewed in this chapter. Using more complex and natural visual stimulation, V1 responses have been detected that are significantly different from responses obtained in more reduced paradigms. A feature common to the findings of different experiments is that the scale of the activated neural population and circuitry appears to play a key role in the correlation between V1 activity and perception. More complex and natural visual stimulation brings into play extra-receptive field modulatory input not involved with stimulation localized to the receptive field. The results suggest that rather than subtly sculpting the response, modulatory input coming from intra-and/or intercortical sources is fundamental in establishing perceptual response patterns in natural visual situations.
Journal of Neurophysiology, Feb 1, 2008
Natural vision takes place within the context of rich varied stimuli and frequent eye movements. ... more Natural vision takes place within the context of rich varied stimuli and frequent eye movements. In the present study, we examined the way that scene complexity and saccades combine to sculpt the temporal response patterns of V1 neurons. To bridge the gap between conventional and free viewing experiments, we compared responses of neurons across four paradigms ranging from less to more natural. An optimal bar stimulus was either flashed into a receptive field (RF) or brought into it via saccade, and was embedded in either a natural scene or a uniform gray background. Responses to a flashed bar tended to be higher with a uniform rather than natural background. The most novel result reported here is that responses evoked by stimuli brought into the RF via saccades were enhanced, compared to the same stimuli flashed during steady fixation. No single factor appears to account entirely for this surprising effect, but there were small contributions from fixational saccades and residual activity carried over from the previous fixation. We also found a negative correlation with cells' response "history", in that a larger response on one fixation was associated with a lower response on the subsequent fixation. The effects of the natural background and saccades exhibited a significant non-linear interaction, with the suppressive effects of the natural background less for stimuli entering RFs with saccades. Together, these results suggest that even responses to standard optimal stimuli are difficult to predict under conditions similar to natural vision, and further demonstrate the importance of naturalistic experimental paradigms to the study of visual processing in V1.
Neurowissenschaften, 2009
tSo. OECL ASSIFICATION / DOWNGRADING
Indispensable depuis plus de 20 ans, l'ouvrage Neurosciences, a la decouverte du cerveau est ... more Indispensable depuis plus de 20 ans, l'ouvrage Neurosciences, a la decouverte du cerveau est la reference incontestee pour l'initiation et la formation aux sciences du cerveau. Cette 4e edition met en lumiere des avancees majeures si bien qu'une refonte complete de la plupart des textes s'est imposee. L'ouvrage mene le lecteur dans un monde fascinant ou les progres des connaissances, allies a l'essor de technologies innovantes, ont permis en particulier de mieux comprendre les mecanismes de certaines maladies neurologiques et psychiatriques, ont revele les bases des processus attentionnels et celles de la memoire et ont mene a la decouverte des mecanismes du langage. Les auteurs sont animes par la volonte de rendre toujours accessibles les donnees les plus complexes et multiplient les ressources pedagogiques : l'iconographie abondante (dont des schemas tres didactiques) renforce l'expose ; la rubrique "Les voies de la decouverte" propose au ...
Kapitel 23 erlautert die Mechanismen, die wahrend der Gehirnentwicklung fur die richtigen Verknup... more Kapitel 23 erlautert die Mechanismen, die wahrend der Gehirnentwicklung fur die richtigen Verknupfungen zwischen den Neuronen sorgen. Hier soll die Gehirnentwicklung noch einmal betrachtet werden, aber dieses Mal werden wir uns darauf konzentrieren, wie im Laufe der Reifung des Gehirns Verbindungen ausgebildet und modifiziert werden. Es wird sich herausstellen, dass die Verschaltung im Gehirn grostenteils durch genetische Programme bestimmt wird. Sie ermoglichen es den Axonen, die richtigen Bahnen und Ziele zu finden. Ein signifikanter Anteil der endgultigen Verschaltung beruht aber auch auf sensorischen Informationen aus unserer Umwelt, die wir in der fruhen Kindheit aufnehmen. Auf diese Weise leisten sowohl Gene als auch Umwelt ihren Beitrag zur endgultigen Struktur und Funktion des Nervensystems.
Journal of Neurophysiology, 2006
Important information was inadvertently omitted from the legends of Figs. 2 and 4. This informati... more Important information was inadvertently omitted from the legends of Figs. 2 and 4. This information is presented here. Figure 2: lesion designations at bottom right ("LS Lesion" and "AES & LS Lesion") should read "rLS Lesion" and "AES & rLS lesion," respectively. All lesions are shown on the right hemisphere for illustrative purposes. Figure 4: all receptive fields are plotted on the right hemifield for illustrative purposes.
Tienda online donde Comprar Neurociencia. La Exploracion Del Cerebro 4a Ed. al precio 88,78 € de ... more Tienda online donde Comprar Neurociencia. La Exploracion Del Cerebro 4a Ed. al precio 88,78 € de Mark F. Bear | Barry W. Connors | Michael A. Paradiso, tienda de Libros de Medicina, Libros de Neurologia - Neurociencia
Neurowissenschaften, 2009
Neurowissenschaften, 2009
Neurowissenschaften, 2009
The Journal of Neuroscience, Jul 15, 1999
Brightness changes can be induced in a static gray field by modulating the luminance of surroundi... more Brightness changes can be induced in a static gray field by modulating the luminance of surrounding areas. We used this induction phenomenon to investigate the neural representation of perceived brightness. Extracellular recordings were made in striate cortex, the lateral geniculate nucleus (LGN), and the optic tract of anesthetized cats using stimuli that produced brightness induction. While a cell's receptive field (RF) was covered by uniform gray illumination, the luminance of rectangular flanking regions was modulated sinusoidally in time, inducing brightness changes in the RF. We looked for a correspondence between the modulation of a cell's response and stimulus conditions that did or did not produce perceptual changes in brightness. We found that the responses of retinal ganglion cell axons in the optic tract were never correlated with brightness. On the other hand, many neurons in striate cortex and a small fraction in the LGN responded in a phase-locked manner at the temporal frequency of the flank modulation, even though the flanks were 3-7°beyond the edges of the RF. Only in striate cortex were cells found that had responses correlated with brightness under all stimulus conditions. These findings suggest that brightness information is explicitly represented in the responses of neurons in striate cortex as part of a neural representation of object surfaces.
Journal of Vision, Aug 1, 2004
Visual Neuroscience, 2018
Neurons in visual areas of the brain are generally characterized by the increase in firing rate t... more Neurons in visual areas of the brain are generally characterized by the increase in firing rate that occurs when a stimulus is flashed on in the receptive field. However, neurons also increase their firing rate when a stimulus is turned off. These "termination responses" or "after-discharges" that occur with flashed stimuli have been observed in area V1 and they may be important for vision as stimulus terminations have been shown to influence visual perception. The goal of the present study was to determine the strength of termination responses in the more natural situation in which eye movements move a stimulus out of a receptive field. We find that termination responses do occur in macaque V1 when termination results from a saccadic eye movement, but they are smaller in amplitude compared to flashed-off stimuli. Further, there are termination responses even in the absence of visual stimulation. These findings demonstrate that termination responses are a component of naturalistic vision. They appear to be based on both visual and non-visual signals in visual cortex. We speculate that the weakening of termination responses might be a neural correlate of saccadic suppression, the loss of perceptual sensitivity around the time of saccades.
Journal of Neurophysiology, Jul 1, 2012
Vision in natural situations is different from the paradigms generally used to study vision in th... more Vision in natural situations is different from the paradigms generally used to study vision in the laboratory. In natural vision, stimuli usually appear in a receptive field as the result of saccadic eye movements rather than suddenly flashing into view. The stimuli themselves are rich with meaningful and recognizable objects rather than simple abstract patterns. In this study we examined the sensitivity of neurons in macaque area V1 to saccades and to complex background contexts. Using a variety of visual conditions, we find that natural visual response patterns are unique. Compared with standard laboratory situations, in more natural vision V1 responses have longer latency, slower time course, delayed orientation selectivity, higher peak selectivity, and lower amplitude. Furthermore, the influences of saccades and background type (complex picture vs. uniform gray) interact to give a distinctive, and presumably more natural, response pattern. While in most of the experiments natural images were used as background, we find that similar synthetic unnatural background stimuli produce nearly identical responses (i.e., complexity matters more than "naturalness"). These findings have important implications for our understanding of vision in more natural situations. They suggest that with the saccades used to explore complex images, visual context ("surround effects") would have a far greater effect on perception than in standard experiments with stimuli flashed on a uniform background. Perceptual thresholds for contrast and orientation should also be significantly different in more natural situations. primary visual cortex; natural vision; orientation selectivity; temporal aspects of visual processing; visual context and saccades
Nature Neuroscience, Nov 1, 1998
Ample evidence suggests that primary visual cortex is involved in the perception of form, and the... more Ample evidence suggests that primary visual cortex is involved in the perception of form, and there is increasing evidence that it may also be important in the perception of surfaces. Perceptual qualities of surfaces, such as brightness, are based on extensive integration of information throughout the visual field. In primary visual cortex, we found that the responses of neurons to surfaces were also influenced by the intensity and organization of light in large portions of the visual field. Interactions with surrounding stimuli typically extended 10 to 20 degrees beyond a cell's receptive field, the same spatial scale as perceptual interactions. Moreover, there were both facilitatory and inhibitory influences, just as there are additive and subtractive perceptual interactions. Surprisingly, influences from outside the receptive field obtained with surface stimuli did not reliably correlate with influences recorded with gratings. These properties suggest that the underlying neuronal interactions may serve as the fundamental building blocks of surface perception.
Journal of Vision, Mar 16, 2010
Current Opinion in Neurobiology, Apr 1, 2002
Abbreviations 2-DG 2-deoxyglucose FEF frontal eye field fMRI functional magnetic resonance imagin... more Abbreviations 2-DG 2-deoxyglucose FEF frontal eye field fMRI functional magnetic resonance imaging LGN lateral geniculate nucleus MST medial superior temporal area MT middle temporal area PET positron emission tomography rTMS repetitive TMS TE temporal visual area TMS transcranial magnetic stimulation V1 primary visual cortex V2 second visual area
Progress in Brain Research, 2005
To conduct well-controlled studies of visual processing in the laboratory, deviations from natura... more To conduct well-controlled studies of visual processing in the laboratory, deviations from natural visual situations must generally be employed. In some regards, the reduced visual paradigms typically used are adequate for providing an accurate description of visual representations. However, the use of fixation paradigms and stimuli isolated within a receptive field may underestimate the richness of visual processing in area V1. Experiments ranging from lightness encoding and perception to paradigms involving natural scenes and saccades used to examine the relationship between V1 activity and perception are reviewed in this chapter. Using more complex and natural visual stimulation, V1 responses have been detected that are significantly different from responses obtained in more reduced paradigms. A feature common to the findings of different experiments is that the scale of the activated neural population and circuitry appears to play a key role in the correlation between V1 activity and perception. More complex and natural visual stimulation brings into play extra-receptive field modulatory input not involved with stimulation localized to the receptive field. The results suggest that rather than subtly sculpting the response, modulatory input coming from intra-and/or intercortical sources is fundamental in establishing perceptual response patterns in natural visual situations.
Journal of Neurophysiology, Feb 1, 2008
Natural vision takes place within the context of rich varied stimuli and frequent eye movements. ... more Natural vision takes place within the context of rich varied stimuli and frequent eye movements. In the present study, we examined the way that scene complexity and saccades combine to sculpt the temporal response patterns of V1 neurons. To bridge the gap between conventional and free viewing experiments, we compared responses of neurons across four paradigms ranging from less to more natural. An optimal bar stimulus was either flashed into a receptive field (RF) or brought into it via saccade, and was embedded in either a natural scene or a uniform gray background. Responses to a flashed bar tended to be higher with a uniform rather than natural background. The most novel result reported here is that responses evoked by stimuli brought into the RF via saccades were enhanced, compared to the same stimuli flashed during steady fixation. No single factor appears to account entirely for this surprising effect, but there were small contributions from fixational saccades and residual activity carried over from the previous fixation. We also found a negative correlation with cells' response "history", in that a larger response on one fixation was associated with a lower response on the subsequent fixation. The effects of the natural background and saccades exhibited a significant non-linear interaction, with the suppressive effects of the natural background less for stimuli entering RFs with saccades. Together, these results suggest that even responses to standard optimal stimuli are difficult to predict under conditions similar to natural vision, and further demonstrate the importance of naturalistic experimental paradigms to the study of visual processing in V1.
Neurowissenschaften, 2009
tSo. OECL ASSIFICATION / DOWNGRADING
Indispensable depuis plus de 20 ans, l'ouvrage Neurosciences, a la decouverte du cerveau est ... more Indispensable depuis plus de 20 ans, l'ouvrage Neurosciences, a la decouverte du cerveau est la reference incontestee pour l'initiation et la formation aux sciences du cerveau. Cette 4e edition met en lumiere des avancees majeures si bien qu'une refonte complete de la plupart des textes s'est imposee. L'ouvrage mene le lecteur dans un monde fascinant ou les progres des connaissances, allies a l'essor de technologies innovantes, ont permis en particulier de mieux comprendre les mecanismes de certaines maladies neurologiques et psychiatriques, ont revele les bases des processus attentionnels et celles de la memoire et ont mene a la decouverte des mecanismes du langage. Les auteurs sont animes par la volonte de rendre toujours accessibles les donnees les plus complexes et multiplient les ressources pedagogiques : l'iconographie abondante (dont des schemas tres didactiques) renforce l'expose ; la rubrique "Les voies de la decouverte" propose au ...
Kapitel 23 erlautert die Mechanismen, die wahrend der Gehirnentwicklung fur die richtigen Verknup... more Kapitel 23 erlautert die Mechanismen, die wahrend der Gehirnentwicklung fur die richtigen Verknupfungen zwischen den Neuronen sorgen. Hier soll die Gehirnentwicklung noch einmal betrachtet werden, aber dieses Mal werden wir uns darauf konzentrieren, wie im Laufe der Reifung des Gehirns Verbindungen ausgebildet und modifiziert werden. Es wird sich herausstellen, dass die Verschaltung im Gehirn grostenteils durch genetische Programme bestimmt wird. Sie ermoglichen es den Axonen, die richtigen Bahnen und Ziele zu finden. Ein signifikanter Anteil der endgultigen Verschaltung beruht aber auch auf sensorischen Informationen aus unserer Umwelt, die wir in der fruhen Kindheit aufnehmen. Auf diese Weise leisten sowohl Gene als auch Umwelt ihren Beitrag zur endgultigen Struktur und Funktion des Nervensystems.
Journal of Neurophysiology, 2006
Important information was inadvertently omitted from the legends of Figs. 2 and 4. This informati... more Important information was inadvertently omitted from the legends of Figs. 2 and 4. This information is presented here. Figure 2: lesion designations at bottom right ("LS Lesion" and "AES & LS Lesion") should read "rLS Lesion" and "AES & rLS lesion," respectively. All lesions are shown on the right hemisphere for illustrative purposes. Figure 4: all receptive fields are plotted on the right hemifield for illustrative purposes.
Tienda online donde Comprar Neurociencia. La Exploracion Del Cerebro 4a Ed. al precio 88,78 € de ... more Tienda online donde Comprar Neurociencia. La Exploracion Del Cerebro 4a Ed. al precio 88,78 € de Mark F. Bear | Barry W. Connors | Michael A. Paradiso, tienda de Libros de Medicina, Libros de Neurologia - Neurociencia
Neurowissenschaften, 2009
Neurowissenschaften, 2009
Neurowissenschaften, 2009