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Papers by michael paradiso

Neuronale Mechanismen der Emotion

Spektrum Akademischer Verlag eBooks, 2009

Neuronale Mechanismen der Emotion

Springer eBooks, 2009

Neurowissenschaften

Spektrum Akademischer Verlag eBooks, 2009

Vision Research, May 1, 1996

The luminance of a squnrewave grating was modulated in a manner such that every other stripe temp... more The luminance of a squnrewave grating was modulated in a manner such that every other stripe temporally varied between bright and dark and the intervening stripes had constant luminance. This produces brightmess induction in the constant stripes, roughly in antiphase to the luminance modulation. We used this stimulus as a probe to explore the temporal properties of brightness induction and the mechanisms detelmainln~ perceived brightness. Over a range of spatial frequencies we measured: (1) the highest temporal frequency at which brightness induction occurs; (2) the magnitude of Induced brightness; and (3) the temporal phase of the induced brightness modulation. We find that brightness induction ceases with lumInance modulation above a cutoff temporal frequency that depends on spatial frequency. The magnitude of induced brightness modulation is greatest at low spatial frequencies and low temporal frequencies. Induced brightness lags behind the luminance modulation and this phase lag increJtses as spatial frequency decreases. All of these findings can be understood as consequences of an Induction process that takes longer to complete as the induction region increases in size.

Das auditorische und das vestibuläre System

Kapitel 11 beschaftigt sich mit zwei sensorischen Systemen, die sehr unterschiedliche Funktionen,... more Kapitel 11 beschaftigt sich mit zwei sensorischen Systemen, die sehr unterschiedliche Funktionen, aber uberraschende Ubereinstimmungen in Bau und Funktionsweise haben: mit dem Gehorsinn, der auch als auditorischer Sinn bezeichnet wird, und dem vom vestibularen System vermittelten Gleichgewichtssinn. Horen ist ein wichtiger Teil unseres bewussten Erlebens, wahrend wir den ganzen Tag hindurch unser Gleichgewichtssystem einsetzen, ohne weiter daruber nachzudenken. In diesem Kapitel werden die Mechanismen in Ohr und Gehirn untersucht, die Schallwellen in der Umgebung in aussagekraftige neuronale Signale und Kopfbewegungen in ein Gefuhl dafur umwandelt, wo im Raum man sich befindet. Diese Transformationen werden in Stufen statt in einem einzigen Schritt ausgefuhrt. Im Hirnstamm und im Thalamus werden die von den Rezeptoren kommenden Signale integriert, bevor sie schlieslich den auditorischen und den vestibularen Cortex erreichen.

Gehirnrhythmen und Schlaf

Thema von Kapitel 19 sind Systeme, die die Rhythmen des Gehirns erzeugen: sowohl die schnellen el... more Thema von Kapitel 19 sind Systeme, die die Rhythmen des Gehirns erzeugen: sowohl die schnellen elektrischen Rhythmen wahrend der Schlaf- und Wachphasen als auch die langsamen circadianen Rhythmen, denen die Kontrolle von Hormonen, Korpertemperatur, der Wachheit und des Stoffwechsels unterliegt. Das Vorderhirn, insbesondere die Groshirnrinde, produziert eine Reihe rascher elektrischer Rhythmen, die leicht messbar sind und eng mit interessanten Verhaltensweisen, einschlieslich Schlaf, korrelieren. Zuerst wird das Elektroenzephalogramm (EEG) diskutiert, weil es die klassische Methode ist, um Hirnrhythmen aufzuzeichnen, und weil es fur die Diskussion von Schlaf grundlegend ist. Schlaf wird ausfuhrlich behandelt, weil er so komplex und allgegenwartig ist – und weil er uns so sehr am Herzen liegt. Schlieslich wird das Wissen uber die inneren Zeitgeber zusammengefasst, die Vigilanz, Hormonausschuttung, Korpertemperatur und Stoffwechsel steuern.

Neuronale Mechanismen der Emotion

Gegenstand von Kapitel 18 sind die neuronalen Systeme, denen eine Schlusselrolle fur das Erleben ... more Gegenstand von Kapitel 18 sind die neuronalen Systeme, denen eine Schlusselrolle fur das Erleben und den Ausdruck von Emotionen zugeschrieben wird. Dabei liegt das Hauptaugenmerk auf Furcht, Angst, Wut und Aggression. Um sich die Bedeutung von Emotionen bewusst zu machen, sollte man sich einmal das Leben ohne sie vorstellen. Ohne die alltaglichen Hochs und Tiefs, die jeder kennt, ware das Leben eine leere, eintonige Existenz ohne jede Bedeutung. Der Ausdruck von Gefuhlen macht zweifellos einen grosen Teil des Menschseins aus. Auserirdische in Science-Fiction-Filmen haben zwar oft menschliche Zuge, sie wirken aber trotzdem unmenschlich, weil sie keine Gefuhle zeigen.

Das Auge

Neurowissenschaften, 2009

Frontiers in Integrative Neuroscience, Jan 14, 2019

Approximately three times per second, human visual perception is interrupted by a saccadic eye mo... more Approximately three times per second, human visual perception is interrupted by a saccadic eye movement. In addition to taking the eyes to a new location, several lines of evidence suggest that the saccades play multiple roles in visual perception. Indeed, it may be crucial that visual processing is informed about movements of the eyes in order to analyze visual input distinctly and efficiently on each fixation and preserve stable visual perception of the world across saccades. A variety of studies has demonstrated that activity in multiple brain areas is modulated by saccades. The hypothesis tested here is that these signals carry significant information that could be used in visual processing. To test this hypothesis, local field potentials (LFPs) were simultaneously recorded from multiple electrodes in macaque primary visual cortex (V1); support vector machines (SVMs) were used to classify the peri-saccadic LFPs. We find that LFPs in area V1 carry information that can be used to distinguish neural activity associated with fixations from saccades, precisely estimate the onset time of fixations, and reliably infer the directions of saccades. This information may be used by the brain in processes including visual stability, saccadic suppression, receptive field (RF) remapping, fixation amplification, and trans-saccadic visual perception.

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.

The complex spatial topography of attentional modulation in macaque V4

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.

A performance deficit at the site of attentional cueing

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.

Neuronale Mechanismen der Emotion

Spektrum Akademischer Verlag eBooks, 2009

Neuronale Mechanismen der Emotion

Springer eBooks, 2009

Neurowissenschaften

Spektrum Akademischer Verlag eBooks, 2009

Vision Research, May 1, 1996

The luminance of a squnrewave grating was modulated in a manner such that every other stripe temp... more The luminance of a squnrewave grating was modulated in a manner such that every other stripe temporally varied between bright and dark and the intervening stripes had constant luminance. This produces brightmess induction in the constant stripes, roughly in antiphase to the luminance modulation. We used this stimulus as a probe to explore the temporal properties of brightness induction and the mechanisms detelmainln~ perceived brightness. Over a range of spatial frequencies we measured: (1) the highest temporal frequency at which brightness induction occurs; (2) the magnitude of Induced brightness; and (3) the temporal phase of the induced brightness modulation. We find that brightness induction ceases with lumInance modulation above a cutoff temporal frequency that depends on spatial frequency. The magnitude of induced brightness modulation is greatest at low spatial frequencies and low temporal frequencies. Induced brightness lags behind the luminance modulation and this phase lag increJtses as spatial frequency decreases. All of these findings can be understood as consequences of an Induction process that takes longer to complete as the induction region increases in size.

Das auditorische und das vestibuläre System

Kapitel 11 beschaftigt sich mit zwei sensorischen Systemen, die sehr unterschiedliche Funktionen,... more Kapitel 11 beschaftigt sich mit zwei sensorischen Systemen, die sehr unterschiedliche Funktionen, aber uberraschende Ubereinstimmungen in Bau und Funktionsweise haben: mit dem Gehorsinn, der auch als auditorischer Sinn bezeichnet wird, und dem vom vestibularen System vermittelten Gleichgewichtssinn. Horen ist ein wichtiger Teil unseres bewussten Erlebens, wahrend wir den ganzen Tag hindurch unser Gleichgewichtssystem einsetzen, ohne weiter daruber nachzudenken. In diesem Kapitel werden die Mechanismen in Ohr und Gehirn untersucht, die Schallwellen in der Umgebung in aussagekraftige neuronale Signale und Kopfbewegungen in ein Gefuhl dafur umwandelt, wo im Raum man sich befindet. Diese Transformationen werden in Stufen statt in einem einzigen Schritt ausgefuhrt. Im Hirnstamm und im Thalamus werden die von den Rezeptoren kommenden Signale integriert, bevor sie schlieslich den auditorischen und den vestibularen Cortex erreichen.

Gehirnrhythmen und Schlaf

Thema von Kapitel 19 sind Systeme, die die Rhythmen des Gehirns erzeugen: sowohl die schnellen el... more Thema von Kapitel 19 sind Systeme, die die Rhythmen des Gehirns erzeugen: sowohl die schnellen elektrischen Rhythmen wahrend der Schlaf- und Wachphasen als auch die langsamen circadianen Rhythmen, denen die Kontrolle von Hormonen, Korpertemperatur, der Wachheit und des Stoffwechsels unterliegt. Das Vorderhirn, insbesondere die Groshirnrinde, produziert eine Reihe rascher elektrischer Rhythmen, die leicht messbar sind und eng mit interessanten Verhaltensweisen, einschlieslich Schlaf, korrelieren. Zuerst wird das Elektroenzephalogramm (EEG) diskutiert, weil es die klassische Methode ist, um Hirnrhythmen aufzuzeichnen, und weil es fur die Diskussion von Schlaf grundlegend ist. Schlaf wird ausfuhrlich behandelt, weil er so komplex und allgegenwartig ist – und weil er uns so sehr am Herzen liegt. Schlieslich wird das Wissen uber die inneren Zeitgeber zusammengefasst, die Vigilanz, Hormonausschuttung, Korpertemperatur und Stoffwechsel steuern.

Neuronale Mechanismen der Emotion

Gegenstand von Kapitel 18 sind die neuronalen Systeme, denen eine Schlusselrolle fur das Erleben ... more Gegenstand von Kapitel 18 sind die neuronalen Systeme, denen eine Schlusselrolle fur das Erleben und den Ausdruck von Emotionen zugeschrieben wird. Dabei liegt das Hauptaugenmerk auf Furcht, Angst, Wut und Aggression. Um sich die Bedeutung von Emotionen bewusst zu machen, sollte man sich einmal das Leben ohne sie vorstellen. Ohne die alltaglichen Hochs und Tiefs, die jeder kennt, ware das Leben eine leere, eintonige Existenz ohne jede Bedeutung. Der Ausdruck von Gefuhlen macht zweifellos einen grosen Teil des Menschseins aus. Auserirdische in Science-Fiction-Filmen haben zwar oft menschliche Zuge, sie wirken aber trotzdem unmenschlich, weil sie keine Gefuhle zeigen.

Das Auge

Neurowissenschaften, 2009

Frontiers in Integrative Neuroscience, Jan 14, 2019

Approximately three times per second, human visual perception is interrupted by a saccadic eye mo... more Approximately three times per second, human visual perception is interrupted by a saccadic eye movement. In addition to taking the eyes to a new location, several lines of evidence suggest that the saccades play multiple roles in visual perception. Indeed, it may be crucial that visual processing is informed about movements of the eyes in order to analyze visual input distinctly and efficiently on each fixation and preserve stable visual perception of the world across saccades. A variety of studies has demonstrated that activity in multiple brain areas is modulated by saccades. The hypothesis tested here is that these signals carry significant information that could be used in visual processing. To test this hypothesis, local field potentials (LFPs) were simultaneously recorded from multiple electrodes in macaque primary visual cortex (V1); support vector machines (SVMs) were used to classify the peri-saccadic LFPs. We find that LFPs in area V1 carry information that can be used to distinguish neural activity associated with fixations from saccades, precisely estimate the onset time of fixations, and reliably infer the directions of saccades. This information may be used by the brain in processes including visual stability, saccadic suppression, receptive field (RF) remapping, fixation amplification, and trans-saccadic visual perception.

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.

The complex spatial topography of attentional modulation in macaque V4

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.

A performance deficit at the site of attentional cueing

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.