Biomedical subjects

Joel R Meyer

Publications and source records attributed to Joel R Meyer.

9 recordsLinked to original sources

PubMed2005

Larger deficits in brain networks for response inhibition than for visual selective attention in attention deficit hyperactivity disorder (ADHD).

BACKGROUND: Brain activation differences between 12 control and 12 attention deficit hyperactivity disorder (ADHD) children (9- to 12-year-olds) were examined on two cognitive tasks during functional magnetic resonance imaging (fMRI). METHOD: Visual selective attention was measured with the visual search of a conjunction target (red triangle) in a field of distracters and response inhibition was measured with a go/no-go task. RESULTS: There were limited group differences in the selective attention task, with control children showing significantly greater intensity of activation in a small area of the superior parietal lobule region of interest. There were large group differences in the response inhibition task, with control children showing significantly greater intensity of activation in fronto-striatal regions of interest including the inferior, middle, superior and medial frontal gyri as well as the caudate nucleus and globus pallidus. CONCLUSION: The widespread hypoactivity for the ADHD children on the go/no-go task is consistent with the hypothesis that response inhibition is a specific deficit in attention deficit hyperactivity disorder.

Attention↗

PubMed2005

Simultaneous assessment of motor and language areas with a single functional MR imaging paradigm: feasibility.

The purpose of this study was to test a hybrid multitask paradigm in healthy subjects and in a patient at preoperative functional magnetic resonance (MR) imaging. In this new paradigm, tasks related to different centers of brain function (motor and language) are performed in alternation during a single functional MR imaging examination, without the typical rest period, to improve time efficiency without compromising the quality of activation maps. The institutional review board approved the study, and all participants gave informed prior consent. The study complied with the Health Insurance Portability and Accountability Act. Seven healthy right-handed volunteers (four men, three women; age range, 22-40 years) were studied first. In both individual and group analyses, there was no statistically significant difference in results between assessment with the multitask design and that with the traditional block design. An advantage of the new paradigm was substantial time savings because the subject was engaged during the entire examination. Finally, the multitask design was tested in a patient undergoing preoperative evaluation, with similar results; therefore, use of the multitask design is feasible in a clinical setting.

Adult↗

PubMed2004

Brain-behavior correlation in children depends on the neurocognitive network.

We examined brain-behavior correlations in 12 children (age range 9.3 to 11.7 years) during a selective attention task that required the visual search of a conjunction of features and during a response inhibition task that required the inhibition of a pre-potent response during "no-go" blocks. We found that the association between performance in these tasks and brain activation as measured by functional magnetic resonance imaging (fMRI) depended on the neurocognitive network. Specifically, better performance during the no-go task was associated with greater activation in the response inhibition network including the prefrontal cortex and basal ganglia. In contrast, better performance during the visual search task was associated with less activation in the selective attention network including superior parietal lobule and lateral premotor cortex. These results show that the relation of performance to the magnitude of neural activation is complex and may display differential relationships based on the cognitive domain, anatomical region, and perhaps also developmental stage.

Attention↗

PubMed2004

Development of brain mechanisms for processing orthographic and phonologic representations.

Developmental differences in the neurocognitive networks for lexical processing were examined in 15 adults and 15 children (9- to 12-year-olds) using functional magnetic resonance imaging (fMRI). The lexical tasks involved spelling and rhyming judgments in either the visual or auditory modality. These lexical tasks were compared with nonlinguistic control tasks involving judgments of line patterns or tone sequences. The first main finding was that adults showed greater activation than children during the cross-modal lexical tasks in a region proposed to be involved in mapping between orthographic and phonologic representations. The visual rhyming task, which required conversion from orthography to phonology, produced greater activation for adults in the angular gyrus. The auditory spelling task, which required the conversion from phonology to orthography, also produced greater activation for adults in the angular gyrus. The greater activation for adults suggests they may have a more elaborated posterior heteromodal system for mapping between representational systems. The second main finding was that adults showed greater activation than children during the intra-modal lexical tasks in the angular gyrus. The visual spelling and auditory rhyming did not require conversion between orthography and phonology for correct performance but the adults showed greater activation in a system implicated for this mapping. The greater activation for adults suggests that they have more interactive convergence between representational systems during lexical processing.

Acoustic Stimulation↗

PubMed2003

Relation between brain activation and lexical performance.

Functional magnetic resonance imaging (fMRI) was used to determine whether performance on lexical tasks was correlated with cerebral activation patterns. We found that such relationships did exist and that their anatomical distribution reflected the neurocognitive processing routes required by the task. Better performance on intramodal tasks (determining if visual words were spelled the same or if auditory words rhymed) was correlated with more activation in unimodal regions corresponding to the modality of sensory input, namely the fusiform gyrus (BA 37) for written words and the superior temporal gyrus (BA 22) for spoken words. Better performance in tasks requiring cross-modal conversions (determining if auditory words were spelled the same or if visual words rhymed), on the other hand, was correlated with more activation in posterior heteromodal regions, including the supramarginal gyrus (BA 40) and the angular gyrus (BA 39). Better performance in these cross-modal tasks was also correlated with greater activation in unimodal regions corresponding to the target modality of the conversion process (i.e., fusiform gyrus for auditory spelling and superior temporal gyrus for visual rhyming). In contrast, performance on the auditory spelling task was inversely correlated with activation in the superior temporal gyrus possibly reflecting a greater emphasis on the properties of the perceptual input rather than on the relevant transmodal conversions.

Acoustic Stimulation↗

PubMed2003

Neural development of selective attention and response inhibition.

Brain activation differences between 12 children (9- to 12-year-olds) and 12 adults (20- to 30-year-olds) were examined on two cognitive tasks during functional magnetic resonance imaging (fMRI). Spatial selective attention was measured with the visual search for a conjunction target (red triangle) in a field of distracters and response inhibition was measured with a go no-go task. There were small developmental differences in the selective attention task, with children showing greater activation than adults in the anterior cingulate and thalamus. There were large developmental differences in the response inhibition task, with children showing greater activation than adults in a fronto-striatal network including middle cingulate, medial frontal gyrus, medial aspects of bilateral superior frontal gyrus, and the caudate nucleus on the left. Children also showed greater bilateral activation for the response inhibition task in posterior cingulate, thalamus and the hippocampo-amygdaloid region. The extensive developmental differences on the response inhibition task are consistent with the prolonged maturation of the fronto-striatal network.

Adult↗

PubMed2002

Modality independence of word comprehension.

Functional magnetic resonance imaging (fMRI) was used to examine the functional anatomy of word comprehension in the auditory and visual modalities of presentation. We asked our subjects to determine if word pairs were semantically associated (e.g., table, chair) and compared this to a reference task where they were asked to judge whether word pairs rhymed (e.g., bank, tank). This comparison showed task-specific and modality-independent activation for semantic processing in the heteromodal cortices of the left inferior frontal gyrus (BA 46, 47) and left middle temporal gyrus (BA 21). There were also modality-specific activations in the fusiform gyrus (BA 37) for written words and in the superior temporal gyrus (BA 22) for spoken words. Our findings are consistent with the hypothesis that word form recognition (lexical encoding) occurs in unimodal cortices and that heteromodal brain regions in the anterior as well as posterior components of the language network subserve word comprehension (semantic decoding).

Adult↗

PubMed2002

Functional anatomy of intra- and cross-modal lexical tasks.

Functional magnetic resonance imaging (fMRI) was used to examine lexical processing in normal adults (20-35 years). Two tasks required only intramodal processing (spelling judgments with visual input and rhyming judgments with auditory input) and two tasks required cross-modal processing between phonologic and orthographic representations (spelling judgments with auditory input and rhyming judgments with visual input). Each task led to greater activation in the unimodal association area concordant with the modality of input, namely fusiform gyrus (BA 19, 37) for written words and superior temporal gyrus (BA 22, 42) for spoken words. Cross-modal tasks generated greater activation in posterior heteromodal regions including the supramarginal and angular gyri (BA 40, 39). Cross-modal tasks generated additional activation in unimodal areas representing the target of conversion, superior temporal gyrus for visual rhyming and fusiform gyrus for auditory spelling. Our findings suggest that the fusiform gyrus processes orthographic word forms, the superior temporal gyrus processes phonologic word forms, and posterior heteromodal regions are involved in the conversion between orthography and phonology.

Adult↗

PubMed2002

Imaging the cerebrovascular tree in the cadaveric head for planning surgical strategy.

OBJECTIVE: The objective of the study was to identify whether an integration of cadaveric dissections with preoperative imaging information may enable a better understanding of pathological anatomy, especially vascular lesions, and thus allow for greater precision in surgical planning. METHODS: We selected a computed tomographic contrast agent and experimentally determined the proportion of it that could mix compatibly with the silicone compound. The resultant mixture was injected into the cerebrovascular systems of six fresh human cadaveric heads. The specimens underwent computed tomography for the purpose of digital virtual exposures in parallel with laboratory dissections performed on these specimens. RESULTS: The 1:8 ratio of contrast agent to silicone rubber was determined to be appropriate for both computed tomography and subsequent laboratory dissection of the specimens. The blood vessels in computed tomographic scans demonstrated a higher attenuation than surrounding soft tissues. The opacity consistency of the injected vessels was a critical parameter for a clear three-dimensional rendering of the vascular structures in the natural surroundings of the skull base. Static and dynamic three-dimensional images of the cadaveric vascular tree were obtained as viewed through surgical corridors of various skull base approaches. CONCLUSION: We demonstrated a new cadaveric preparation model for imaging and dissection. This model allows for static and dynamic three-dimensional examination of the surgical anatomy from a neurosurgeon's perspective. It may facilitate the study of cerebrovascular system morphology/pathology in relation to the skull base as a tool for surgical planning.

Brain↗