Joseph Madsen - Academia.edu (original) (raw)
Papers by Joseph Madsen
NeuroImage, Jan 25, 2015
Noninvasive localization of brain function is used to understand and treat neurological disease, ... more Noninvasive localization of brain function is used to understand and treat neurological disease, exemplified by pre-operative fMRI mapping prior to neurosurgical intervention. The principal approach for generating these maps relies on brain responses evoked by a task and, despite known limitations, has dominated clinical practice for over 20years. Recently, pre-operative fMRI mapping based on correlations in spontaneous brain activity has been demonstrated, however this approach has its own limitations and has not seen widespread clinical use. Here we show that spontaneous and task-based mapping can be performed together using the same pre-operative fMRI data, provide complimentary information relevant for functional localization, and can be combined to improve identification of eloquent motor cortex. Accuracy, sensitivity, and specificity of our approach are quantified through comparison with electrical cortical stimulation mapping in eight patients with intractable epilepsy. Broad...
Journal of Neurophysiology, 2014
Visual recognition takes a small fraction of a second and relies on the cascade of signals along ... more Visual recognition takes a small fraction of a second and relies on the cascade of signals along the ventral visual stream. Given the rapid path through multiple processing steps between photoreceptors and higher visual areas, information must progress from stage to stage very quickly. This rapid progression of information suggests that fine temporal details of the neural response may be important to the brain's encoding of visual signals. We investigated how changes in the relative timing of incoming visual stimulation affect the representation of object information by recording intracranial field potentials along the human ventral visual stream while subjects recognized objects whose parts were presented with varying asynchrony. Visual responses along the ventral stream were sensitive to timing differences between parts as small as 17 ms. In particular, there was a strong dependency on the temporal order of stimulus presentation, even at short asynchronies. This sensitivity to the order of stimulus presentation provides evidence that the brain may use differences in relative timing as a means of representing information.
Surgical Neurology, 1992
A cavernous angioma of the posterior fossa dura was discovered incidentally on neuroimaging studi... more A cavernous angioma of the posterior fossa dura was discovered incidentally on neuroimaging studies. The clinical and pathologic features of this lesion are described. Although it has been reported to arise in the posterior fossa and the tentorium cerebelli, we present the first case of such a malformation arising from the dura of the posterior fossa.
Proceedings of the National Academy of Sciences, 1999
The purine nucleoside inosine has been shown to induce axon outgrowth from primary neurons in cul... more The purine nucleoside inosine has been shown to induce axon outgrowth from primary neurons in culture through a direct intracellular mechanism. For this study, we investigated the effects of inosine in vivo by examining whether it would stimulate axon growth after a unilateral transection of the corticospinal tract. Inosine applied with a minipump to the rat sensorimotor cortex stimulated intact pyramidal cells to undergo extensive sprouting of their axons into the denervated spinal cord white matter and adjacent neuropil. Axon growth was visualized by anterograde tracing with biotinylated dextran amine and by immunohistochemistry with antibodies to GAP-43. Thus, inosine, a naturally occurring metabolite without known side effects, might help to restore essential circuitry after injury to the central nervous system.
Pediatric Neurosurgery, 1997
Cellular use of small organic solutes known as organic osmolytes for regulation of the volume of ... more Cellular use of small organic solutes known as organic osmolytes for regulation of the volume of the cell is a universal biological phenomenon. During swelling, cells open an anion channel which allows for efflux of these solutes. This channel is known as the volume-sensitive organic osmolyte/anion channel (VSOAC). Anion channels with properties identical to VSOAC were found in human brain cells obtained following pediatric neurosurgical procedures. The tissues examined included tumors as well as putatively normal gray and white matter astrocytes. The cells activated an anion conductance when swollen by hypotonic shock. Baseline currents in these cells were generally small and increased up to 30-fold within 10 min following the onset of swelling. The anion channel activated by swelling was outwardly rectified and inactivated by depolarization, both characteristic of the VSOAC. These observations indicate that human glial cells and tumor cells activate VSOAC following cellular swelling. This suggests that organic osmolyte efflux can be modulated during brain swelling by pharmaceuticals which modulate VSOAC.
Journal of Neurophysiology, 2012
The cerebral cortex needs to maintain information for long time periods while at the same time be... more The cerebral cortex needs to maintain information for long time periods while at the same time being capable of learning and adapting to changes. The degree of stability of physiological signals in the human brain in response to external stimuli over temporal scales spanning hours to days remains unclear. Here, we quantitatively assessed the stability across sessions of visually selective intracranial field potentials (IFPs) elicited by brief flashes of visual stimuli presented to 27 subjects. The interval between sessions ranged from hours to multiple days. We considered electrodes that showed robust visual selectivity to different shapes; these electrodes were typically located in the inferior occipital gyrus, the inferior temporal cortex, and the fusiform gyrus. We found that IFP responses showed a strong degree of stability across sessions. This stability was evident in averaged responses as well as single-trial decoding analyses, at the image exemplar level as well as at the category level, across different parts of visual cortex, and for three different visual recognition tasks. These results establish a quantitative evaluation of the degree of stationarity of visually selective IFP responses within and across sessions and provide a baseline for studies of cortical plasticity and for the development of brain-machine interfaces.
The Journal of Comparative Neurology, 1997
The hippocampal formation has been one of the most extensively studied cortical regions in rats, ... more The hippocampal formation has been one of the most extensively studied cortical regions in rats, yet little is known about the anatomical connections of the hippocampus in primates, especially humans. With the use of an antibody against the calcium-binding protein, calbindin-D28K, in normal autopsy tissue and the neuronal tracers biocytin or biotinylated dextrans in in vitro slice preparations from tissue removed during surgery for intractable epilepsy, we examined the human hippocampal mossy fiber pathway. The injections of biocytin into the dentate granule cell layer labeled neurons in a Golgi-like manner, revealing the presence of basal dendrites on about 30% of the granule cells. The granule cell axons, the mossy fibers, initially formed a diffuse plexus of fibers in the polymorphic layer before organizing into fiber fascicles in the hilar pyramidal region. These fiber fascicles were much more prominent rostrally than caudally. Within the hilus and proximal portions of the extrahilar CA3 field, the mossy fibers ran through the pyramidal cell layer, and while near the transition to field CA2, the fibers turned superficially and crossed the pyramidal layer to run in the stratum lucidum. All of these features, seen following injections of tracer into hippocampal slices from the brains of epileptics, were confirmed by calbindin-staining of mossy fibers in normal brains. Biocytin-labeled mossy fiber axons revealed two characteristic types of enlargements: small varicosities and larger expansions. The expansions were found throughout the neuropil and were highly irregular, diaminobenzidine-dense profiles that had pleiomorphic modes of attachment to the parent axon. Electron microscopic images of these biocytin labeled expansions revealed that they were large synaptic boutons bearing asymmetric synapses. This study indicates that the human mossy fiber pathway shows some minor deviations from the rodent brain but little difference from monkeys. We argue that these changes mirror a phylogenetic growth of the CA3 pyramidal neurons (subfield CA3c) into the hilus rather than an evolutionary change of the mossy fiber pathway. This growth of subfield CA3c and the increase in mossy fibers running through the pyramidal layer (and a presumed accompanying increase in proximal basal dendritic contacts) may reflect a growing role of the projection from the dentate granule cells to subfield CA3c and from there to field CA1 in the primate hippocampus.
Journal of the American Pharmacists Association, 2006
To propose a paradigm shift in the role of the pharmacist by encouraging pharmacists&... more To propose a paradigm shift in the role of the pharmacist by encouraging pharmacists' involvement in the achievement and maintenance of healthy lifestyles in their patients, thus reducing the need for long-term medications. Peer-reviewed medical literature, contemporary lay literature, news releases from health organizations/associations, United States health standards, and professional experiences of the authors. Our current paradigm for the management of chronic disease is malaligned. The medications we use are helpful for many patients with chronic disorders, but they are not curative and leave many individuals with unwanted adverse effects that are often treated with additional medication. The more effective approach to managing many patients with chronic diseases induced through unhealthy lifestyles would be to eat properly, exercise to maintain ideal body weight, and abstain from harmful substances. Managing the root causes of chronic disease would eliminate most of the unhealthy consequences and perhaps reduce the need for long-term medication. Pharmacists have the knowledge and capacity to assist in this endeavor. Influencing patients to achieve ideal body weight through proper diet and exercise, encouraging people to stay well, and then helping them to keep well are roles for the pharmacist. If pharmacists made wellness and disease prevention part of their practices, they would have greater impact on improving patients' overall health. Without treating the primary cause of a condition and only treating the symptoms of unhealthy lifestyles, we are in many ways "spitting into the wind."
Epilepsy Research, 2014
Objective: To investigate the correlation between spike propagation represented by spatiotemporal... more Objective: To investigate the correlation between spike propagation represented by spatiotemporal source analysis of magnetoencephalographic (MEG) spikes and surgical outcome in patients with temporal lobe epilepsy. Methods: Thirty-seven patients were divided into mesial (n = 27) and non-mesial (n = 10) groups based on the presurgical evaluation. In each patient, ten ipsilateral spikes were averaged, and spatiotemporal source maps of the averaged spike were obtained by using minimum norm estimate. Regions of interest (ROIs) were created including temporoparietal, inferior frontal, mesial temporal, anterior and posterior part of the lateral temporal cortex. We extracted activation values from the source maps and the threshold was set at half of the maximum activation at the peak latency. The leading and propagated areas of the spike were defined as those ROIs with activation reaching the threshold at the earliest and at the peak latencies, respectively. Surgical outcome was assessed based on Engel's classification. Binary variables Abbreviations: MEG, magnetoencephalography; IEEG, intracranial electroencephalography; MPRAGE, magnetization-prepared rapid acquisition gradient echo; MNE, minimum norm estimate; ROI, region of interest.
NeuroImage, Jan 25, 2015
Noninvasive localization of brain function is used to understand and treat neurological disease, ... more Noninvasive localization of brain function is used to understand and treat neurological disease, exemplified by pre-operative fMRI mapping prior to neurosurgical intervention. The principal approach for generating these maps relies on brain responses evoked by a task and, despite known limitations, has dominated clinical practice for over 20years. Recently, pre-operative fMRI mapping based on correlations in spontaneous brain activity has been demonstrated, however this approach has its own limitations and has not seen widespread clinical use. Here we show that spontaneous and task-based mapping can be performed together using the same pre-operative fMRI data, provide complimentary information relevant for functional localization, and can be combined to improve identification of eloquent motor cortex. Accuracy, sensitivity, and specificity of our approach are quantified through comparison with electrical cortical stimulation mapping in eight patients with intractable epilepsy. Broad...
Journal of Neurophysiology, 2014
Visual recognition takes a small fraction of a second and relies on the cascade of signals along ... more Visual recognition takes a small fraction of a second and relies on the cascade of signals along the ventral visual stream. Given the rapid path through multiple processing steps between photoreceptors and higher visual areas, information must progress from stage to stage very quickly. This rapid progression of information suggests that fine temporal details of the neural response may be important to the brain's encoding of visual signals. We investigated how changes in the relative timing of incoming visual stimulation affect the representation of object information by recording intracranial field potentials along the human ventral visual stream while subjects recognized objects whose parts were presented with varying asynchrony. Visual responses along the ventral stream were sensitive to timing differences between parts as small as 17 ms. In particular, there was a strong dependency on the temporal order of stimulus presentation, even at short asynchronies. This sensitivity to the order of stimulus presentation provides evidence that the brain may use differences in relative timing as a means of representing information.
Surgical Neurology, 1992
A cavernous angioma of the posterior fossa dura was discovered incidentally on neuroimaging studi... more A cavernous angioma of the posterior fossa dura was discovered incidentally on neuroimaging studies. The clinical and pathologic features of this lesion are described. Although it has been reported to arise in the posterior fossa and the tentorium cerebelli, we present the first case of such a malformation arising from the dura of the posterior fossa.
Proceedings of the National Academy of Sciences, 1999
The purine nucleoside inosine has been shown to induce axon outgrowth from primary neurons in cul... more The purine nucleoside inosine has been shown to induce axon outgrowth from primary neurons in culture through a direct intracellular mechanism. For this study, we investigated the effects of inosine in vivo by examining whether it would stimulate axon growth after a unilateral transection of the corticospinal tract. Inosine applied with a minipump to the rat sensorimotor cortex stimulated intact pyramidal cells to undergo extensive sprouting of their axons into the denervated spinal cord white matter and adjacent neuropil. Axon growth was visualized by anterograde tracing with biotinylated dextran amine and by immunohistochemistry with antibodies to GAP-43. Thus, inosine, a naturally occurring metabolite without known side effects, might help to restore essential circuitry after injury to the central nervous system.
Pediatric Neurosurgery, 1997
Cellular use of small organic solutes known as organic osmolytes for regulation of the volume of ... more Cellular use of small organic solutes known as organic osmolytes for regulation of the volume of the cell is a universal biological phenomenon. During swelling, cells open an anion channel which allows for efflux of these solutes. This channel is known as the volume-sensitive organic osmolyte/anion channel (VSOAC). Anion channels with properties identical to VSOAC were found in human brain cells obtained following pediatric neurosurgical procedures. The tissues examined included tumors as well as putatively normal gray and white matter astrocytes. The cells activated an anion conductance when swollen by hypotonic shock. Baseline currents in these cells were generally small and increased up to 30-fold within 10 min following the onset of swelling. The anion channel activated by swelling was outwardly rectified and inactivated by depolarization, both characteristic of the VSOAC. These observations indicate that human glial cells and tumor cells activate VSOAC following cellular swelling. This suggests that organic osmolyte efflux can be modulated during brain swelling by pharmaceuticals which modulate VSOAC.
Journal of Neurophysiology, 2012
The cerebral cortex needs to maintain information for long time periods while at the same time be... more The cerebral cortex needs to maintain information for long time periods while at the same time being capable of learning and adapting to changes. The degree of stability of physiological signals in the human brain in response to external stimuli over temporal scales spanning hours to days remains unclear. Here, we quantitatively assessed the stability across sessions of visually selective intracranial field potentials (IFPs) elicited by brief flashes of visual stimuli presented to 27 subjects. The interval between sessions ranged from hours to multiple days. We considered electrodes that showed robust visual selectivity to different shapes; these electrodes were typically located in the inferior occipital gyrus, the inferior temporal cortex, and the fusiform gyrus. We found that IFP responses showed a strong degree of stability across sessions. This stability was evident in averaged responses as well as single-trial decoding analyses, at the image exemplar level as well as at the category level, across different parts of visual cortex, and for three different visual recognition tasks. These results establish a quantitative evaluation of the degree of stationarity of visually selective IFP responses within and across sessions and provide a baseline for studies of cortical plasticity and for the development of brain-machine interfaces.
The Journal of Comparative Neurology, 1997
The hippocampal formation has been one of the most extensively studied cortical regions in rats, ... more The hippocampal formation has been one of the most extensively studied cortical regions in rats, yet little is known about the anatomical connections of the hippocampus in primates, especially humans. With the use of an antibody against the calcium-binding protein, calbindin-D28K, in normal autopsy tissue and the neuronal tracers biocytin or biotinylated dextrans in in vitro slice preparations from tissue removed during surgery for intractable epilepsy, we examined the human hippocampal mossy fiber pathway. The injections of biocytin into the dentate granule cell layer labeled neurons in a Golgi-like manner, revealing the presence of basal dendrites on about 30% of the granule cells. The granule cell axons, the mossy fibers, initially formed a diffuse plexus of fibers in the polymorphic layer before organizing into fiber fascicles in the hilar pyramidal region. These fiber fascicles were much more prominent rostrally than caudally. Within the hilus and proximal portions of the extrahilar CA3 field, the mossy fibers ran through the pyramidal cell layer, and while near the transition to field CA2, the fibers turned superficially and crossed the pyramidal layer to run in the stratum lucidum. All of these features, seen following injections of tracer into hippocampal slices from the brains of epileptics, were confirmed by calbindin-staining of mossy fibers in normal brains. Biocytin-labeled mossy fiber axons revealed two characteristic types of enlargements: small varicosities and larger expansions. The expansions were found throughout the neuropil and were highly irregular, diaminobenzidine-dense profiles that had pleiomorphic modes of attachment to the parent axon. Electron microscopic images of these biocytin labeled expansions revealed that they were large synaptic boutons bearing asymmetric synapses. This study indicates that the human mossy fiber pathway shows some minor deviations from the rodent brain but little difference from monkeys. We argue that these changes mirror a phylogenetic growth of the CA3 pyramidal neurons (subfield CA3c) into the hilus rather than an evolutionary change of the mossy fiber pathway. This growth of subfield CA3c and the increase in mossy fibers running through the pyramidal layer (and a presumed accompanying increase in proximal basal dendritic contacts) may reflect a growing role of the projection from the dentate granule cells to subfield CA3c and from there to field CA1 in the primate hippocampus.
Journal of the American Pharmacists Association, 2006
To propose a paradigm shift in the role of the pharmacist by encouraging pharmacists&... more To propose a paradigm shift in the role of the pharmacist by encouraging pharmacists' involvement in the achievement and maintenance of healthy lifestyles in their patients, thus reducing the need for long-term medications. Peer-reviewed medical literature, contemporary lay literature, news releases from health organizations/associations, United States health standards, and professional experiences of the authors. Our current paradigm for the management of chronic disease is malaligned. The medications we use are helpful for many patients with chronic disorders, but they are not curative and leave many individuals with unwanted adverse effects that are often treated with additional medication. The more effective approach to managing many patients with chronic diseases induced through unhealthy lifestyles would be to eat properly, exercise to maintain ideal body weight, and abstain from harmful substances. Managing the root causes of chronic disease would eliminate most of the unhealthy consequences and perhaps reduce the need for long-term medication. Pharmacists have the knowledge and capacity to assist in this endeavor. Influencing patients to achieve ideal body weight through proper diet and exercise, encouraging people to stay well, and then helping them to keep well are roles for the pharmacist. If pharmacists made wellness and disease prevention part of their practices, they would have greater impact on improving patients' overall health. Without treating the primary cause of a condition and only treating the symptoms of unhealthy lifestyles, we are in many ways "spitting into the wind."
Epilepsy Research, 2014
Objective: To investigate the correlation between spike propagation represented by spatiotemporal... more Objective: To investigate the correlation between spike propagation represented by spatiotemporal source analysis of magnetoencephalographic (MEG) spikes and surgical outcome in patients with temporal lobe epilepsy. Methods: Thirty-seven patients were divided into mesial (n = 27) and non-mesial (n = 10) groups based on the presurgical evaluation. In each patient, ten ipsilateral spikes were averaged, and spatiotemporal source maps of the averaged spike were obtained by using minimum norm estimate. Regions of interest (ROIs) were created including temporoparietal, inferior frontal, mesial temporal, anterior and posterior part of the lateral temporal cortex. We extracted activation values from the source maps and the threshold was set at half of the maximum activation at the peak latency. The leading and propagated areas of the spike were defined as those ROIs with activation reaching the threshold at the earliest and at the peak latencies, respectively. Surgical outcome was assessed based on Engel's classification. Binary variables Abbreviations: MEG, magnetoencephalography; IEEG, intracranial electroencephalography; MPRAGE, magnetization-prepared rapid acquisition gradient echo; MNE, minimum norm estimate; ROI, region of interest.