Biomedical subjects

Jeremy P Young

Publications and source records attributed to Jeremy P Young.

3 recordsLinked to original sources

PubMed2005

Simulating activations with cytoarchitecture.

Cytoarchitectonic delineation of areas in post-mortem human brains provides the precise location of these areas. It has been possible to study the size and location of areas between post-mortem brains with multi-subject cytoarchitectonic data. If the structure-function relationship is assumed to be a one-to-one mapping for the purposes of inter-subject variability, then functional areas in the cortex will also adhere to the structure, and therefore, the location and size of cytoarchitectonic areas in the brain. Thus, it is possible to use the cytoarchitectonic data as being representative of the size and location of functional activations. Under this assumption, we simulated activations in cytoarchitectonic areas from ten post-mortem brains in this study. We then treated these data as we would a normal PET experiment. The purpose of this study is to demonstrate a standard PET image analysis on a simulated ten-subject PET study using cytoarchitecture to localize the activations. By doing so, we simulate activations with real inter-subject variability with the size and location of each area. Significant activations were obtained for activations simulated in areas 3a and 3b. A voxel-wise conjunction between simulated data and experimental data was made to better determine the underlying areas activated by the experimental tasks. This study presents a novel technique for demonstrating the effect of standard image analysis on the location and size of simulated activations as determined by cytoarchitectonic data from multiple subjects. Furthermore, this technique has been applied to better determine the underlying areas activated in an experiment.

Adult↗

PubMed2004

Somatotopy and attentional modulation of the human parietal and opercular regions.

The somatotopical organization of the postcentral gyrus is well known, but less is known about the somatotopical organization of area 2, the somatosensory association areas in the postparietal cortex, and the parietal operculum. The extent to which these areas are modulated by attention is also poorly understood. For these reasons, we measured the BOLD signal when rectangular parallelepipeds of varying shape were presented to the immobile right hand or right foot of 10 subjects either discriminating these or just being stimulated. Activation areas in each subject were mapped against cytoarchitectural probability maps of area 2, IP1, and IP2 along the intraparietal sulcus and the parietal opercular areas OP1-OP4. In area 2, the somatotopical representation of the hand and foot were distinctly separate, whereas there was considerable overlap in IP1 and no clear evidence of separate representations in OP1, OP4, and IP2. The overlap of hand and foot representations increased in the following order: area 3a, 3b, 1, 2, IP1, OP4, IP2, and OP1. There were significant foot representations but no hand representations in right (ipsilateral) areas 3a, 3b, and 1. Shape discrimination using the foot as opposed to stimulation enhanced the signal in OP4 bilaterally, whereas discrimination with the hand enhanced the signal bilaterally in area 2, IP1, and IP2. These results indicate that somatosensory areas in humans are arranged from strong somatotopy into no somatotopy in the following order: 3a, 3b, 1, 2, IP1, OP4, IP2, and OP1. Higher order areas such as IP1, IP2, and OP4 showed task-related attentional enhancement.

Adult↗

PubMed2003

Regional cerebral blood flow correlations of somatosensory areas 3a, 3b, 1, and 2 in humans during rest: a PET and cytoarchitectural study.

The concept of functional connectivity relies on the assumption that cortical areas that are directly anatomically connected will show correlations in regional blood flow (rCBF) or regional metabolism. We studied correlations of rCBF of cytoarchitectural areas 3a, 3b, 1, and 2 in the brains of 37 subjects scanned with PET during a rest condition. The cytoarchitectural areas, delineated from 10 postmortem brains with statistical methods, were transformed into the same standard anatomical format as the resting PET images. In areas 3a, 3b, and 1, somatotopically corresponding regions were intercorrelated. Area 2 was correlated with the dorsal pre-motor area. These results were in accordance with the somatosensory connectivity in macaque monkeys. In contrast, we also found correlations between areas 3b and 1 with area 4a, and SMA, and among the left and right hand sector of areas 3a, 3b, and 1. Furthermore, there were no correlations between areas 3b, 1, and 2 with SII or other areas in the parietal operculum, nor of other areas known to be directly connected with areas 3a, 3b, 1, and 2 in macaques. This indicates that rCBF correlations between cortical areas during the rest state only partly reflect their connectivity and that this approach lacks sensitivity and is prone to reveal spurious or indirect connectivity.

Adult↗