In 2000, monocular vision was restored to M. M., who had been blind between the ages of 3 and 46 ... more In 2000, monocular vision was restored to M. M., who had been blind between the ages of 3 and 46 years. Tests carried out over 2 years following the surgery revealed impairments of 3-D form, object, and face processing and an absence of object- and face-selective blood-oxygen-level-dependent responses in ventral visual cortex. In the present research, we reexamined M. M. to test for experience-dependent recovery of visual function. Behaviorally, M. M. remains impaired in 3-D form, object, and face processing. Accordingly, we found little to no evidence of the category-selective organization within ventral visual cortex typically associated with face, body, scene, or object processing. We did observe remarkably normal object selectivity within lateral occipital cortex, consistent with M. M.'s previously reported shape-discrimination performance. Together, these findings provide little evidence for recovery of high-level visual function after more than a decade of visual experienc...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 9, 2015
Early visual areas have neuronal receptive fields that form a sampling mosaic of visual space, re... more Early visual areas have neuronal receptive fields that form a sampling mosaic of visual space, resulting in a series of retinotopic maps in which the same region of space is represented in multiple visual areas. It is not clear to what extent the development and maintenance of this retinotopic organization in humans depend on retinal waves and/or visual experience. We examined the corticocortical receptive field organization of resting-state BOLD data in normally sighted, early blind, and anophthalmic (in which both eyes fail to develop) individuals and found that resting-state correlations between V1 and V2/V3 were retinotopically organized for all subject groups. These results show that the gross retinotopic pattern of resting-state connectivity across V1-V3 requires neither retinal waves nor visual experience to develop and persist into adulthood. Evidence from resting-state BOLD data suggests that the connections between early visual areas develop and are maintained even in the ...
Here, we examine overlap between tactile and visual motion BOLD responses within the human MT+ co... more Here, we examine overlap between tactile and visual motion BOLD responses within the human MT+ complex. Although several studies have reported tactile responses overlapping with hMT+, many used group average analyses, leaving it unclear whether these responses were restricted to subregions of hMT+. Moreover, previous studies either employed a tactile task or passive stimulation, leaving it unclear whether or not tactile responses in hMT+ are simply the consequence of visual imagery. Here, we carried out a replication of one of the classic papers finding tactile responses in hMT+. We mapped MT and MST in individual subjects using visual field localizers. We then examined responses to tactile motion on the arm, either presented passively or in the presence of a visual task performed at fixation designed to minimize visualization of the concurrent tactile stimulation. To our surprise, without a visual task, we found only weak tactile motion responses in MT (6% of voxels showing tactile...
Congenital blindness leads to large-scale functional and structural reorganization in the occipit... more Congenital blindness leads to large-scale functional and structural reorganization in the occipital cortex, but relatively little is known about the neurochemical changes underlying this cross-modal plasticity. To investigate the effect of complete and early visual deafferentation on the concentration of metabolites in the pericalcarine cortex, 1H magnetic resonance spectroscopy (MRS) was performed in fourteen sighted subjects and five subjects with bilateral anophthalmia, a condition in which both eyes fail to develop. In the pericalcarine cortex, where primary visual cortex is normally located, the proportion of gray matter was significantly greater and levels of choline, glutamate and glutamine, myo-inositol and total creatine were elevated in anophthalmic relative to sighted subjects. Anophthalmia had no effect on the structure or neurochemistry of a sensorimotor cortex control region. More gray matter, combined with high levels of choline and myo-inositol, resembles the profile of the cortex at birth and suggests that the lack of visual input from the eyes might have delayed or arrested the maturation of this cortical region. High levels of choline and glutamate/glutamine are consistent with enhanced excitatory circuits in the anophthalmic occipital cortex, which could reflect a shift towards enhanced plasticity or sensitivity that could in turn mediate or unmask cross-modal responses. Finally, it is possible that the change in function of the occipital results in biochemical profiles that resemble those of auditory, language or somatosensory cortex.
Studies showing that occipital cortex responds to auditory and tactile stimuli after early blindn... more Studies showing that occipital cortex responds to auditory and tactile stimuli after early blindness are often interpreted as demonstrating that early blind subjects "see" auditory and tactile stimuli. However, it is not clear whether these occipital responses directly mediate the perception of auditory/tactile stimuli, or simply modulate or augment responses within other sensory areas. We used fMRI pattern classification to categorize the perceived direction of motion for both coherent and ambiguous auditory motion stimuli. In sighted individuals, perceived motion direction was accurately categorized based on neural responses within the planum temporale (PT) and right lateral occipital cortex (LOC). Within early blind individuals, auditory motion decisions for both stimuli were successfully categorized from responses within the human middle temporal complex (hMT+), but not the PT or right LOC. These findings suggest that early blind responses within hMT+ are associated wi...
The responses of motion mechanisms depend not only on the direction of a stimulus, but also on it... more The responses of motion mechanisms depend not only on the direction of a stimulus, but also on its contrast, coherence and speed. We examined how contrast, coherence and directional selectivity interact by measuring directional tuning psychophysically across a wide range of coherence and contrast levels. We fit data with a simple model that estimated directional tuning bandwidth using contrast and coherence gain parameters that were based on neurophysiological estimates. This model estimated a bandwidth of approximately 90 degrees for directionally selective mechanisms. Bandwidth was invariant across a wide range of contrasts and coherences, as predicted by models of contrast normalization.
Subject Peter Doyle (PD) had congenital bilateral cataracts removed at the age of 43. Pre-operati... more Subject Peter Doyle (PD) had congenital bilateral cataracts removed at the age of 43. Pre-operatively PD's visual acuity was 20/80, with a resolution limit around 15 cpd, and he experienced monocular diplopia with high contrast stimuli. Post-operatively PD's visual acuity improved to approximately 20/40, with a resolution limit around 25 cpd. Using a variety of pre- and post-operative tests we have documented a wide range of neural adaptations to his limited and distorted visual input, and have found a limited amount of post-operative adaptation to his newly improved visual input. These results show that the human visual system is capable of significant adaptation to the particular optical input that is experienced.
The prevention of posterior segment complications of cataract surgery depends on the maintenance ... more The prevention of posterior segment complications of cataract surgery depends on the maintenance of an intact lens capsule and zonular apparatus. The phacoemulsification techniques presented here, including cortical cleaving hydrodissection, hydrodelineation, ultrasound power modulation, and management of the epinucleus and cortex, together with the special techniques presented for management of small pupils and compromised zonule, minimize the risk of damage to the posterior capsule by maximizing control of nuclear disassembly and evacuation. Choo-choo chop and flip phacoemulsification, in particular, provides a management strategy for cataracts of all grades of nuclear hardness whether in the presence of a small pupil or compromised zonule.
Previous brain imaging studies have demonstrated responses to tactile and auditory stimuli in vis... more Previous brain imaging studies have demonstrated responses to tactile and auditory stimuli in visual cortex of blind subjects, suggesting that removal of one sensory modality leads to neural reorganization of the remaining modalities. To investigate whether similar 'cross-modal' plasticity occurs in human auditory cortex, we used functional magnetic resonance imaging (fMRI) to measure visually evoked activity in auditory areas of both early-deafened and hearing individuals. Here we find that deaf subjects exhibit activation in a region of the right auditory cortex, corresponding to Brodmann's areas 42 and 22, as well as in area 41 (primary auditory cortex), demonstrating that early deafness results in the processing of visual stimuli in auditory cortex.
Our goal was to differentiate low and mid level perceptual learning. We used a complex grating di... more Our goal was to differentiate low and mid level perceptual learning. We used a complex grating discrimination task that required observers to combine information across wide ranges of spatial frequency and orientation. Stimuli were 'wicker'-like textures containing two orthogonal signal components of 3 and 9 c/deg. Observers discriminated a 15% spatial frequency shift in these components. Stimuli also contained four noise components, separated from the signal components by at least 45 degrees of orientation or approximately 2 octaves in spatial frequency. In Experiment 1 naive observers were trained for eight sessions with a four-alternative same-different forced choice judgment with feedback. Observers showed significant learning, thresholds dropped to approximately 1/3 of their original value. In Experiment 2 we found that observers showed far less learning when the noise components were not present. Experiment 3 found, unlike many other studies, almost complete transfer o...
Frontiers in Optics 2007/Laser Science XXIII/Organic Materials and Devices for Displays and Energy Conversion, 2007
» View Full Text: Acrobat PDF (15 KB) * * Note that full-text PDFs from conferences typically con... more » View Full Text: Acrobat PDF (15 KB) * * Note that full-text PDFs from conferences typically contain 1-3 pages of content, some or all of which might be an abstract, summary, or miscellaneous items. ... We will describe how the high temporal sensitivity of the visual system allows for ...
Our goal was to examine the plasticity of the human visual system at mid to high levels of visual... more Our goal was to examine the plasticity of the human visual system at mid to high levels of visual processing. It is well understood that early stages of visual processing contain cells tuned for spatial frequency and orientation. However images of real-world objects contain a wide range of spatial frequencies and orientations. We were interested in how different spatial frequencies and orientations are combined. We used a pattern discrimination task -observers were asked to discriminate small changes in a "wickerlike" stimulus consisting of six superimposed sinusoidal gratings. Observers were asked to discriminate a 15% spatial frequency shift in two of these sinusoidal components, which were masked by four noise components. We found large amounts of perceptual learning for this task -over eight sessions of training observers' average percent correct increased by 31%, corresponding to their thresholds dropping to a third of their initial values. Further experiments suggest that learning was based on changes within a mid level stage of processing intermediate between lowlevel analyzers tuned for orientation and spatial frequency and high-level pattern matching or object tuned cells. This mid level stage seems to be "very roughly Fourier" and combines information from individual gratings using probability summation. This stage of processing is also remarkably plastic compared to earlier stages of processing.
ABSTRACT Methods and devices for fitting a visual prosthesis are described. In one of the methods... more ABSTRACT Methods and devices for fitting a visual prosthesis are described. In one of the methods, threshold levels and maximum levels for the electrodes of the prosthesis are determined and a map of brightness to electrode stimulation levels is later formed. A fitting system for a visual prosthesis is also discussed, together with a computer-operated system having a graphical user interface showing visual prosthesis diagnostic screens and visual prosthesis configuration screens.
Lack of visual input early in life results in occipital cortical responses to auditory and tactil... more Lack of visual input early in life results in occipital cortical responses to auditory and tactile stimuli. However, it remains unclear whether cross-modal plasticity also occurs in subcortical pathways. Using functional magnetic resonance imaging, auditory responses were compared across individuals with congenital anophthalmia (absence of eyes), those with early onset (in the first few years of life) blindness and normally sighted individuals. We find that the superior colliculus, a 'visual' subcortical structure, is recruited by the auditory system in congenital and early-onset blindness. Additionally, auditory subcortical responses to monaural stimuli were altered as a result of blindness. Specifically, responses in the auditory thalamus were equally strong to contralateral and ipsilateral stimulation in both groups of blind subjects, whereas sighted controls showed stronger responses to contralateral stimulation. These findings suggest that early blindness results in substantial reorganization of subcortical auditory responses.
Introduction Community-acquired pneumonia remains a common condition worldwide. It is associated ... more Introduction Community-acquired pneumonia remains a common condition worldwide. It is associated with significant morbidity and mortality. The aim of this study was to evaluate conditions that could predict a poor outcome. Design Retrospective analyse of 69 patients admitted to the ICU from 1996 to 2003. Demographic data included age, sex and medical history. Etiologic agents, multiorgan dysfunction, nosocomial infections, SAPS II and PORT scores were recorded for each patient. For statistical analysis we used a t test, chi-square test and Mann-Whitney U test on SPSS ® . A value of P less than 0.05 was considered significant. Results Forty-seven patients were male and 22 patients were female. Mean age was 52 years. Sixty-seven percent had serious pre-morbid conditions including pulmonary disease (34.8%), cardiac problems (36.2%), diabetes (13%) and chronic liver disease (5.8%); 40.6% were smokers, drug abusers or alcohol dependents. Sixtyeight patients required invasive mechanical ventilation. The average length of ventilation was 13.5 days, median 8 days. The mean SAPS II score was 40.14 and the mean PORT score was 141. The mortality rate was 27.5% (SAPS II estimated mortality, 35%). Complications reported were ARDS (40.6%), septic shock (34.8%), acute renal failure (2.9%), cardiac arrest (8.7%) and nosocomial infeccions (46.4%). Mortality rates were higher for previous hepatic (75%) and metabolic (33%) diseases. We found a close association between crude mortality and SAPS II score (P = 0.003) and development of complications (P = 0.0028). Respiratory dysfunction (P = 0.006) and septic shock (P = 0.022) were most significantly related to mortality. No significant differences were founded regarding age, comorbidities, PORT score, etiologic agents, nosocomial infections and length of invasive mechanical ventilation. Conclusions Previous hepatic chronic disease was strictly related to higher mortality as well as isolation of MRSA. ARDS and septic shock predicted a poor outcome. SAPS II score was the best severity indicator of mortality.
As described elsewhere in this special issue, recent advances in neuroimaging over the last decad... more As described elsewhere in this special issue, recent advances in neuroimaging over the last decade have led to a rapid expansion in our knowledge of anatomical and functional correlations within the normal and abnormal human brain. Here, we review how early blindness has been used as a model system for examining the role of visual experience in the development of anatomical connections and functional responses. We discuss how lack of power in group comparisons may provide a potential explanation for why extensive anatomical changes in cortico-cortical connectivity are not observed. Finally we suggest a framework-cortical specialization via hierarchical mixtures of experts-which offers some promise in reconciling a wide range of functional and anatomical data.
Here we describe a method for measuring tonotopic maps and estimating bandwidth for voxels in hum... more Here we describe a method for measuring tonotopic maps and estimating bandwidth for voxels in human primary auditory cortex (PAC) using a modification of the population Receptive Field (pRF) model, developed for retinotopic mapping in visual cortex by Dumoulin and Wandell (2008). The pRF method reliably estimates tonotopic maps in the presence of acoustic scanner noise, and has two advantages over phase-encoding techniques. First, the stimulus design is flexible and need not be a frequency progression, thereby reducing biases due to habituation, expectation, and estimation artifacts, as well as reducing the effects of spatio-temporal BOLD nonlinearities. Second, the pRF method can provide estimates of bandwidth as a function of frequency. We find that bandwidth estimates are narrower for voxels within the PAC than in surrounding auditory responsive regions (non-PAC).
In 2000, monocular vision was restored to M. M., who had been blind between the ages of 3 and 46 ... more In 2000, monocular vision was restored to M. M., who had been blind between the ages of 3 and 46 years. Tests carried out over 2 years following the surgery revealed impairments of 3-D form, object, and face processing and an absence of object- and face-selective blood-oxygen-level-dependent responses in ventral visual cortex. In the present research, we reexamined M. M. to test for experience-dependent recovery of visual function. Behaviorally, M. M. remains impaired in 3-D form, object, and face processing. Accordingly, we found little to no evidence of the category-selective organization within ventral visual cortex typically associated with face, body, scene, or object processing. We did observe remarkably normal object selectivity within lateral occipital cortex, consistent with M. M.'s previously reported shape-discrimination performance. Together, these findings provide little evidence for recovery of high-level visual function after more than a decade of visual experienc...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 9, 2015
Early visual areas have neuronal receptive fields that form a sampling mosaic of visual space, re... more Early visual areas have neuronal receptive fields that form a sampling mosaic of visual space, resulting in a series of retinotopic maps in which the same region of space is represented in multiple visual areas. It is not clear to what extent the development and maintenance of this retinotopic organization in humans depend on retinal waves and/or visual experience. We examined the corticocortical receptive field organization of resting-state BOLD data in normally sighted, early blind, and anophthalmic (in which both eyes fail to develop) individuals and found that resting-state correlations between V1 and V2/V3 were retinotopically organized for all subject groups. These results show that the gross retinotopic pattern of resting-state connectivity across V1-V3 requires neither retinal waves nor visual experience to develop and persist into adulthood. Evidence from resting-state BOLD data suggests that the connections between early visual areas develop and are maintained even in the ...
Here, we examine overlap between tactile and visual motion BOLD responses within the human MT+ co... more Here, we examine overlap between tactile and visual motion BOLD responses within the human MT+ complex. Although several studies have reported tactile responses overlapping with hMT+, many used group average analyses, leaving it unclear whether these responses were restricted to subregions of hMT+. Moreover, previous studies either employed a tactile task or passive stimulation, leaving it unclear whether or not tactile responses in hMT+ are simply the consequence of visual imagery. Here, we carried out a replication of one of the classic papers finding tactile responses in hMT+. We mapped MT and MST in individual subjects using visual field localizers. We then examined responses to tactile motion on the arm, either presented passively or in the presence of a visual task performed at fixation designed to minimize visualization of the concurrent tactile stimulation. To our surprise, without a visual task, we found only weak tactile motion responses in MT (6% of voxels showing tactile...
Congenital blindness leads to large-scale functional and structural reorganization in the occipit... more Congenital blindness leads to large-scale functional and structural reorganization in the occipital cortex, but relatively little is known about the neurochemical changes underlying this cross-modal plasticity. To investigate the effect of complete and early visual deafferentation on the concentration of metabolites in the pericalcarine cortex, 1H magnetic resonance spectroscopy (MRS) was performed in fourteen sighted subjects and five subjects with bilateral anophthalmia, a condition in which both eyes fail to develop. In the pericalcarine cortex, where primary visual cortex is normally located, the proportion of gray matter was significantly greater and levels of choline, glutamate and glutamine, myo-inositol and total creatine were elevated in anophthalmic relative to sighted subjects. Anophthalmia had no effect on the structure or neurochemistry of a sensorimotor cortex control region. More gray matter, combined with high levels of choline and myo-inositol, resembles the profile of the cortex at birth and suggests that the lack of visual input from the eyes might have delayed or arrested the maturation of this cortical region. High levels of choline and glutamate/glutamine are consistent with enhanced excitatory circuits in the anophthalmic occipital cortex, which could reflect a shift towards enhanced plasticity or sensitivity that could in turn mediate or unmask cross-modal responses. Finally, it is possible that the change in function of the occipital results in biochemical profiles that resemble those of auditory, language or somatosensory cortex.
Studies showing that occipital cortex responds to auditory and tactile stimuli after early blindn... more Studies showing that occipital cortex responds to auditory and tactile stimuli after early blindness are often interpreted as demonstrating that early blind subjects "see" auditory and tactile stimuli. However, it is not clear whether these occipital responses directly mediate the perception of auditory/tactile stimuli, or simply modulate or augment responses within other sensory areas. We used fMRI pattern classification to categorize the perceived direction of motion for both coherent and ambiguous auditory motion stimuli. In sighted individuals, perceived motion direction was accurately categorized based on neural responses within the planum temporale (PT) and right lateral occipital cortex (LOC). Within early blind individuals, auditory motion decisions for both stimuli were successfully categorized from responses within the human middle temporal complex (hMT+), but not the PT or right LOC. These findings suggest that early blind responses within hMT+ are associated wi...
The responses of motion mechanisms depend not only on the direction of a stimulus, but also on it... more The responses of motion mechanisms depend not only on the direction of a stimulus, but also on its contrast, coherence and speed. We examined how contrast, coherence and directional selectivity interact by measuring directional tuning psychophysically across a wide range of coherence and contrast levels. We fit data with a simple model that estimated directional tuning bandwidth using contrast and coherence gain parameters that were based on neurophysiological estimates. This model estimated a bandwidth of approximately 90 degrees for directionally selective mechanisms. Bandwidth was invariant across a wide range of contrasts and coherences, as predicted by models of contrast normalization.
Subject Peter Doyle (PD) had congenital bilateral cataracts removed at the age of 43. Pre-operati... more Subject Peter Doyle (PD) had congenital bilateral cataracts removed at the age of 43. Pre-operatively PD's visual acuity was 20/80, with a resolution limit around 15 cpd, and he experienced monocular diplopia with high contrast stimuli. Post-operatively PD's visual acuity improved to approximately 20/40, with a resolution limit around 25 cpd. Using a variety of pre- and post-operative tests we have documented a wide range of neural adaptations to his limited and distorted visual input, and have found a limited amount of post-operative adaptation to his newly improved visual input. These results show that the human visual system is capable of significant adaptation to the particular optical input that is experienced.
The prevention of posterior segment complications of cataract surgery depends on the maintenance ... more The prevention of posterior segment complications of cataract surgery depends on the maintenance of an intact lens capsule and zonular apparatus. The phacoemulsification techniques presented here, including cortical cleaving hydrodissection, hydrodelineation, ultrasound power modulation, and management of the epinucleus and cortex, together with the special techniques presented for management of small pupils and compromised zonule, minimize the risk of damage to the posterior capsule by maximizing control of nuclear disassembly and evacuation. Choo-choo chop and flip phacoemulsification, in particular, provides a management strategy for cataracts of all grades of nuclear hardness whether in the presence of a small pupil or compromised zonule.
Previous brain imaging studies have demonstrated responses to tactile and auditory stimuli in vis... more Previous brain imaging studies have demonstrated responses to tactile and auditory stimuli in visual cortex of blind subjects, suggesting that removal of one sensory modality leads to neural reorganization of the remaining modalities. To investigate whether similar 'cross-modal' plasticity occurs in human auditory cortex, we used functional magnetic resonance imaging (fMRI) to measure visually evoked activity in auditory areas of both early-deafened and hearing individuals. Here we find that deaf subjects exhibit activation in a region of the right auditory cortex, corresponding to Brodmann's areas 42 and 22, as well as in area 41 (primary auditory cortex), demonstrating that early deafness results in the processing of visual stimuli in auditory cortex.
Our goal was to differentiate low and mid level perceptual learning. We used a complex grating di... more Our goal was to differentiate low and mid level perceptual learning. We used a complex grating discrimination task that required observers to combine information across wide ranges of spatial frequency and orientation. Stimuli were 'wicker'-like textures containing two orthogonal signal components of 3 and 9 c/deg. Observers discriminated a 15% spatial frequency shift in these components. Stimuli also contained four noise components, separated from the signal components by at least 45 degrees of orientation or approximately 2 octaves in spatial frequency. In Experiment 1 naive observers were trained for eight sessions with a four-alternative same-different forced choice judgment with feedback. Observers showed significant learning, thresholds dropped to approximately 1/3 of their original value. In Experiment 2 we found that observers showed far less learning when the noise components were not present. Experiment 3 found, unlike many other studies, almost complete transfer o...
Frontiers in Optics 2007/Laser Science XXIII/Organic Materials and Devices for Displays and Energy Conversion, 2007
» View Full Text: Acrobat PDF (15 KB) * * Note that full-text PDFs from conferences typically con... more » View Full Text: Acrobat PDF (15 KB) * * Note that full-text PDFs from conferences typically contain 1-3 pages of content, some or all of which might be an abstract, summary, or miscellaneous items. ... We will describe how the high temporal sensitivity of the visual system allows for ...
Our goal was to examine the plasticity of the human visual system at mid to high levels of visual... more Our goal was to examine the plasticity of the human visual system at mid to high levels of visual processing. It is well understood that early stages of visual processing contain cells tuned for spatial frequency and orientation. However images of real-world objects contain a wide range of spatial frequencies and orientations. We were interested in how different spatial frequencies and orientations are combined. We used a pattern discrimination task -observers were asked to discriminate small changes in a "wickerlike" stimulus consisting of six superimposed sinusoidal gratings. Observers were asked to discriminate a 15% spatial frequency shift in two of these sinusoidal components, which were masked by four noise components. We found large amounts of perceptual learning for this task -over eight sessions of training observers' average percent correct increased by 31%, corresponding to their thresholds dropping to a third of their initial values. Further experiments suggest that learning was based on changes within a mid level stage of processing intermediate between lowlevel analyzers tuned for orientation and spatial frequency and high-level pattern matching or object tuned cells. This mid level stage seems to be "very roughly Fourier" and combines information from individual gratings using probability summation. This stage of processing is also remarkably plastic compared to earlier stages of processing.
ABSTRACT Methods and devices for fitting a visual prosthesis are described. In one of the methods... more ABSTRACT Methods and devices for fitting a visual prosthesis are described. In one of the methods, threshold levels and maximum levels for the electrodes of the prosthesis are determined and a map of brightness to electrode stimulation levels is later formed. A fitting system for a visual prosthesis is also discussed, together with a computer-operated system having a graphical user interface showing visual prosthesis diagnostic screens and visual prosthesis configuration screens.
Lack of visual input early in life results in occipital cortical responses to auditory and tactil... more Lack of visual input early in life results in occipital cortical responses to auditory and tactile stimuli. However, it remains unclear whether cross-modal plasticity also occurs in subcortical pathways. Using functional magnetic resonance imaging, auditory responses were compared across individuals with congenital anophthalmia (absence of eyes), those with early onset (in the first few years of life) blindness and normally sighted individuals. We find that the superior colliculus, a 'visual' subcortical structure, is recruited by the auditory system in congenital and early-onset blindness. Additionally, auditory subcortical responses to monaural stimuli were altered as a result of blindness. Specifically, responses in the auditory thalamus were equally strong to contralateral and ipsilateral stimulation in both groups of blind subjects, whereas sighted controls showed stronger responses to contralateral stimulation. These findings suggest that early blindness results in substantial reorganization of subcortical auditory responses.
Introduction Community-acquired pneumonia remains a common condition worldwide. It is associated ... more Introduction Community-acquired pneumonia remains a common condition worldwide. It is associated with significant morbidity and mortality. The aim of this study was to evaluate conditions that could predict a poor outcome. Design Retrospective analyse of 69 patients admitted to the ICU from 1996 to 2003. Demographic data included age, sex and medical history. Etiologic agents, multiorgan dysfunction, nosocomial infections, SAPS II and PORT scores were recorded for each patient. For statistical analysis we used a t test, chi-square test and Mann-Whitney U test on SPSS ® . A value of P less than 0.05 was considered significant. Results Forty-seven patients were male and 22 patients were female. Mean age was 52 years. Sixty-seven percent had serious pre-morbid conditions including pulmonary disease (34.8%), cardiac problems (36.2%), diabetes (13%) and chronic liver disease (5.8%); 40.6% were smokers, drug abusers or alcohol dependents. Sixtyeight patients required invasive mechanical ventilation. The average length of ventilation was 13.5 days, median 8 days. The mean SAPS II score was 40.14 and the mean PORT score was 141. The mortality rate was 27.5% (SAPS II estimated mortality, 35%). Complications reported were ARDS (40.6%), septic shock (34.8%), acute renal failure (2.9%), cardiac arrest (8.7%) and nosocomial infeccions (46.4%). Mortality rates were higher for previous hepatic (75%) and metabolic (33%) diseases. We found a close association between crude mortality and SAPS II score (P = 0.003) and development of complications (P = 0.0028). Respiratory dysfunction (P = 0.006) and septic shock (P = 0.022) were most significantly related to mortality. No significant differences were founded regarding age, comorbidities, PORT score, etiologic agents, nosocomial infections and length of invasive mechanical ventilation. Conclusions Previous hepatic chronic disease was strictly related to higher mortality as well as isolation of MRSA. ARDS and septic shock predicted a poor outcome. SAPS II score was the best severity indicator of mortality.
As described elsewhere in this special issue, recent advances in neuroimaging over the last decad... more As described elsewhere in this special issue, recent advances in neuroimaging over the last decade have led to a rapid expansion in our knowledge of anatomical and functional correlations within the normal and abnormal human brain. Here, we review how early blindness has been used as a model system for examining the role of visual experience in the development of anatomical connections and functional responses. We discuss how lack of power in group comparisons may provide a potential explanation for why extensive anatomical changes in cortico-cortical connectivity are not observed. Finally we suggest a framework-cortical specialization via hierarchical mixtures of experts-which offers some promise in reconciling a wide range of functional and anatomical data.
Here we describe a method for measuring tonotopic maps and estimating bandwidth for voxels in hum... more Here we describe a method for measuring tonotopic maps and estimating bandwidth for voxels in human primary auditory cortex (PAC) using a modification of the population Receptive Field (pRF) model, developed for retinotopic mapping in visual cortex by Dumoulin and Wandell (2008). The pRF method reliably estimates tonotopic maps in the presence of acoustic scanner noise, and has two advantages over phase-encoding techniques. First, the stimulus design is flexible and need not be a frequency progression, thereby reducing biases due to habituation, expectation, and estimation artifacts, as well as reducing the effects of spatio-temporal BOLD nonlinearities. Second, the pRF method can provide estimates of bandwidth as a function of frequency. We find that bandwidth estimates are narrower for voxels within the PAC than in surrounding auditory responsive regions (non-PAC).
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