Formation of Cortical Fields on a Reduced Cortical Sheet

Huffman, Kelly J.; Molnár, Zoltán; Dellen, Anton van; Kahn, Dianna M.; Blakemore, Colin; Krubitzer, Leah

doi:10.1523/jneurosci.19-22-09939.1999

Cited by 55 publications

(33 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1). Stimuli of 25 psi (1 psi ϭ 6.89 kPa) were delivered at 2 Hz with a somatosensory stimulus generator (BTi, San Diego, CA) by means of four stimulus channels that ended in a plastic bladder clip with a 1-cm diameter.As predicted from microelectrode recording studies of anterior parietal cortex in human and nonhuman primates (8)(9)(10)(11)(12)(13)(14), the representation of the hand was medial and superior to that of the face. This observation has also been made in positronemission tomography (PET) (15) and fMRI (16-18, 4) studies of human somatosensory cortical organization (Fig.…”

mentioning

confidence: 56%

Functional MRI at 1.5 tesla: A comparison of the blood oxygenation level-dependent signal and electrophysiology

Disbrow

Slutsky

Roberts

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

165

View full text Add to dashboard Cite

How well does the functional MRI (fMRI) signal reflect underlying electrophysiology? Despite the ubiquity of the technique, this question has yet to be adequately answered. Therefore, we have compared cortical maps generated based on the indirect blood oxygenation level-dependent signal of fMRI with maps from microelectrode recording techniques, which directly measure neural activity. Identical somatosensory stimuli were used in both sets of experiments in the same anesthetized macaque monkeys. Our results demonstrate that fMRI can be used to determine the topographic organization of cortical fields with 55% concordance to electrophysiological maps. The variance in the location of fMRI activation was greatest in the plane perpendicular to local vessels. An appreciation of the limitations of fMRI improves our ability to use it effectively to study cortical organization. U ntil recently, noninvasive techniques used to image the human brain and its activity were not widely accessible. However, in the past few years, procedures such as functional MRI (fMRI) have become readily available and are used in a wide range of disciplines including Radiology, Psychology, Psychiatry, Neurology, Neurosurgery, and Neuroscience. The investigations undertaken by different groups are diverse and range in scope from understanding complex perceptual and cognitive processes to examining the activity patterns generated from simple sensory stimuli. However, a basic question that has yet to be addressed is: how accurately do changes in the vascular system reflect changes in neural activity (1)?Despite the ubiquity of the technique and the number of inferences that have been made based on its use, there have been few studies that focus on the relationship between the blood oxygenation level-dependent (BOLD; ref.2) signal of fMRI and the underlying neural activity that it is assumed to reflect. Typically, fMRI is based on the hemodynamic response to evoked neural activity. The BOLD signal is derived from the oxygenation state of local hemoglobin. Neural activity requires oxygen, which triggers an increase in local oxy-hemoglobin, resulting in an increase in signal intensity in an active region of cortex (3). Thus, the BOLD signal is an indirect indicator of neural activity with unknown accuracy.Appreciating the link between fMRI and neurophysiology is important not only for the use and interpretation of fMRI, but also when comparing data from humans with the wealth of data gathered using invasive techniques in monkey cortex. The macaque monkey is the most widely studied animal model for human neocortical organization and function. The ability to compare human data directly with an animal model will allow us to extend our understanding of complex human behavior based on detailed neurophysiological and neuroanatomical data from the macaque monkey.We have, therefore, developed a monkey model appropriate for the study of the relationship between the fMRI BOLD signal and the underlying neural activity. We have examined the BOLD response and th...

show abstract

mentioning

confidence: 56%

Functional MRI at 1.5 tesla: A comparison of the blood oxygenation level-dependent signal and electrophysiology

Disbrow

Slutsky

Roberts

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

165

View full text Add to dashboard Cite

show abstract

“…Rather, in this reduced cortical sheet, normal spatial relationships between visual, somatosensory and auditory cortical fields are established. This implies that cortical fields can apparently form in a new location on portions of the cortical sheet that would normally be occupied by a different sensory modality (Huffman et al 1999).…”

Section: Reorganization In the Somatosensory Systemmentioning

confidence: 99%

Reorganization after pre‐ and perinatal brain lesions*

2010

View full text Add to dashboard Cite

The developing human brain can compensate for pre-and perinatally acquired focal lesions more effectively than the adult brain. The mechanisms by which this effective reorganization is achieved vary considerably between different functional systems, reflecting differences in the normal maturation of these systems. In the motor system, descending cortico-spinal motor projections have already reached their spinal target zones at the beginning of the third trimester of pregnancy, with initially bilateral projections from each hemisphere. During normal development, the ipsilateral projections are gradually withdrawn, whereas the contralateral projections persist. When, during this period, a unilateral brain lesion disrupts the cortico-spinal projections of one hemisphere, the ipsilateral projections from the contralesional hemisphere will persist. This allows the contralesional hemisphere to take over motor control over the paretic extremities. Although this mechanism of reorganization is available throughout the pre-and perinatal period, the efficacy of this ipsilateral takeover of motor functions decreases with increasing age at the time of the insult. In the somatosensory system, ascending thalamo-cortical somatosensory projections have not yet reached their cortical target zones at the beginning of the third trimester of pregnancy. Therefore, these projections can still 'react' to brain lesions acquired during this period, and can form 'axonal bypasses' around periventricular white matter lesions to reach their original cortical target areas in the postcentral gyrus. Thus, somatosensory functions can be well preserved even in cases of large periventricular lesions. In contrast, when the postcentral gyrus itself is affected, no signs for reorganization have been observed. Accordingly, somatosensory functions are often poor in these patients. Language functions can be normal even in patients with extensive early left-hemispheric brain lesions. This is achieved by language organization in the right hemisphere, which takes place in brain regions homotopic to the classical left-hemispheric language areas in normal subjects. In patients with periventricular lesions, the degree of right-hemispheric takeover of language functions correlates with the severity of structural damage to facial (and, thus, articulatory) motor projections.

show abstract

“…Although there have been some studies on how robustness emerges in genetic and cellular networks (Barkai and Leibler, 1997;Alon et al, 1999), the question has received only scant attention from neuroscientists. The interplay between plasticity and robustness in the nervous system has been highlighted in an exemplary fashion in marsupials where the removal of up to 75% of the cortical neuroepithelial sheet early in development results in normal relationships between visual, somatosensory, and auditory cortical fields on the remaining cortical sheet (Huffman et al, 1999;Krubitzer and Huffman, 2000).…”

Section: Plasticity and Robustnessmentioning

confidence: 99%

Functional genomics of neural and behavioral plasticity

2002

View full text Add to dashboard Cite

How does the environment, particularly the social environment, influence brain and behavior and what are the underlying physiologic, molecular, and genetic mechanisms? Adaptations of brain and behavior to changes in the social or physical environment are common in the animal world, either as short-term (i.e., modulatory) or as long-term modifications (e.g., via gene expression changes) in behavioral or physiologic properties. The study of the mechanisms and constraints underlying these dynamic changes requires model systems that offer plastic phenotypes as well as a sufficient level of quantifiable behavioral complexity while being accessible at the physiological and molecular level. In this article, I explore how the new field of functional genomics can contribute to an understanding of the complex relationship between genome and environment that results in highly plastic phenotypes. This approach will lead to the discovery of genes under environmental control and provide the basis for the study of the interrelationship between an individual's gene expression profile and its social phenotype in a given environmental context.

show abstract

Formation of Cortical Fields on a Reduced Cortical Sheet

Cited by 55 publications

References 71 publications

Functional MRI at 1.5 tesla: A comparison of the blood oxygenation level-dependent signal and electrophysiology

Functional MRI at 1.5 tesla: A comparison of the blood oxygenation level-dependent signal and electrophysiology

Reorganization after pre‐ and perinatal brain lesions*

Functional genomics of neural and behavioral plasticity

Contact Info

Product

Resources

About