Background: The anterior cingulate cognitive division (ACcd) plays a central role in attentional processing by: 1) modulating stimulus selection (i.e., focusing attention) and/or 2) mediating ...response selection. We hypothesized that ACcd dysfunction might therefore contribute to producing core features of attention-deficit/hyperactivity disorder (ADHD), namely inattention and impulsivity. ADHD subjects have indeed shown performance deficits on the Color Stroop, an attentional/cognitive interference task known to recruit the ACcd. Recently, the Counting Stroop, a Stroop-variant specialized for functional magnetic resonance imaging (fMRI), produced ACcd activation in healthy adults. In the present fMRI study, the Counting Stroop was used to examine the functional integrity of the ACcd in ADHD.
Methods: Sixteen unmedicated adults from two groups (8 with ADHD and 8 matched control subjects) performed the Counting Stroop during fMRI.
Results: While both groups showed an interference effect, the ADHD group, in contrast to control subjects, failed to activate the ACcd during the Counting Stroop. Direct comparisons showed ACcd activity was significantly higher in the control group. ADHD subjects did activate a frontostriatal-insular network, indicating ACcd hypoactivity was not caused by globally poor neuronal responsiveness.
Conclusions: The data support a hypothesized dysfunction of the ACcd in ADHD.
Dyspnea (shortness of breath, breathlessness) is a major and disabling symptom of heart and lung disease. The representation of dyspnea in the cerebral cortex is unknown. In the first study designed ...to explore the central neural structures underlying perception of dyspnea, we evoked the perception of severe 'air hunger' in healthy subjects by restraining ventilation below spontaneous levels while holding arterial oxygen and carbon dioxide levels constant. PET revealed that air hunger activated the insular cortex. The insula is a limbic structure also activated by visceral stimuli, temperature, taste, nausea and pain. Like dyspnea, such perceptions underlie behaviors essential to homeostasis and survival.
The cortical mechanisms associated with conscious object recognition were studied using functional magnetic resonance imaging (fMRI). Participants were required to recognize pictures of masked ...objects that were presented very briefly, randomly and repeatedly. This design yielded a gradual accomplishment of successful recognition. Cortical activity in a ventrotemporal visual region was linearly correlated with perception of object identity. Therefore, although object recognition is rapid, awareness of an object's identity is not a discrete phenomenon but rather associated with gradually increasing cortical activity. Furthermore, the focus of the activity in the temporal cortex shifted anteriorly as subjects reported an increased knowledge regarding identity. The results presented here provide new insights into the processes underlying explicit object recognition, as well as the analysis that takes place immediately before and after recognition is possible.
Stereopsis, the perception of depth from small differences between the images in the two eyes, provides a rich model for investigating the cortical construction of surfaces and space. Although ...disparity-tuned cells have been found in a large number of areas in macaque visual cortex, stereoscopic processing in these areas has never been systematically compared using the same stimuli and analysis methods. In order to examine the global architecture of stereoscopic processing in primate visual cortex, we studied fMRI activity in alert, fixating human and macaque subjects. In macaques, we found strongest activation to near/far compared to zero disparity in areas V3, V3A, and CIPS. In humans, we found strongest activation to the same stimuli in areas V3A, V7, the V4d topolog (V4d-topo), and a caudal parietal disparity region (CPDR). Thus, in both primate species a small cluster of areas at the parieto-occipital junction appears to be specialized for stereopsis.
1 Speech and Hearing Sciences Program, Massachusetts Institute of Technology-Harvard Division of Health Sciences and Technology, Cambridge, Massachusetts 02139; 2 Massachusetts General ...Hospital-Nuclear Magnetic Resonance Center, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts 02129; 3 Electrical and Computer Engineering/Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907-2035; 4 Cognitive Science Department, University of California-San Diego, La Jolla, California 92093; 5 Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts 02115; and 6 Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114
Submitted 13 December 2002;
accepted in final form 7 November 2003
Functional neuroimaging experiments have revealed an organization of frequency-dependent responses in human auditory cortex suggestive of multiple tonotopically organized areas. Numerous studies have sampled cortical responses to isolated narrow-band stimuli, revealing multiple locations in auditory cortex at which the position of response varies systematically with frequency content. Because appropriate anatomical or functional grouping of these distinct frequency-dependent responses is uncertain, the number and location of tonotopic mappings within human auditory cortex remains unclear. Further, sampling does not address whether the observed mappings exhibit continuity as a function of position. This functional magnetic resonance imaging study used frequency-swept stimuli to identify progressions of frequency sensitivity across the cortical surface. The center-frequency of narrow-band, amplitude-modulated noise was slowly swept between 125 and 8,000 Hz. The latency of response relative to sweep onset was determined for each cortical surface location. Because frequency varied systematically with time, response latency indicated the frequency to which a location was maximally sensitive. Areas of cortex exhibiting a progressive change in response latency with position were considered tonotopically organized. There exist two main findings. First, six progressions of frequency sensitivity (i.e., tonotopic mappings) were repeatably observed in the superior temporal plane. Second, the locations of the higher- and lower-frequency endpoints of these progressions were approximately congruent with regions reported to be most responsive to discrete higher- and lower-frequency stimuli. Based on these findings and previous anatomical work, we propose a correspondence between these progressions and anatomically defined cortical areas, suggesting that five areas in human auditory cortex exhibit at least six tonotopic organizations.
Address for reprint requests and other correspondence: T. M. Talavage, 465 Northwestern Ave., Purdue University, West Lafayette, IN 47907-2035 (E-mail: tmt{at}ecn.purdue.edu ).
The global gene expression profiles for 67 human lung tumors representing 56 patients were examined by using 24,000-element cDNA microarrays. Subdivision of the tumors based on gene expression ...patterns faithfully recapitulated morphological classification of the tumors into squamous, large cell, small cell, and adenocarcinoma. The gene expression patterns made possible the subclassification of adenocarcinoma into subgroups that correlated with the degree of tumor differentiation as well as patient survival. Gene expression analysis thus promises to extend and refine standard pathologic analysis.
The experiments presented in this report were designed to test the hypothesis that visual working memory for spatial stimuli and for object stimuli recruits separate neuronal networks in prefrontal ...cortex. We acquired BOLD fMRI data from subjects while they compared each serially presented stimulus to the one that had appeared two or three stimuli previously. Three experiments failed to reject the null hypothesis that prefrontal cortical activity associated with spatial working memory performance cannot be dissociated from prefrontal cortical activity associated with nonspatial working memory performance. Polymodal regions of parietal cortex (inferior and superior parietal lobules), as well as cortex surrounding the superior frontal sulcus (and encompassing the frontal eye fields), also demonstrated equivalent levels of activation in the spatial and object conditions. Posterior cortical regions associated with the ventral visual processing stream (portions of lingual, fusiform, and inferior temporal gyri), however, demonstrated greater object than spatial working memory-related activity, particularly when stimuli varied only along spatial or featural dimensions. These experiments, representing fMRI studies of spatial and object working memory in which the testing procedure and the stimuli were identical in the two conditions, suggest that domain-specific visual working memory processing may be mediated by posterior regions associated with domain-specific sensory processing.
For more widespread clinical use advanced imaging methods such as relative cerebral blood volume must be both accurate and repeatable. The aim of this study was to determine the repeatability of ...relative CBV measurements in newly diagnosed glioblastoma multiforme by using several of the most commonly published estimation techniques.
The relative CBV estimates were calculated from dynamic susceptibility contrast MR imaging in double-baseline examinations for 33 patients with treatment-naïve and pathologically proved glioblastoma multiforme (men = 20; mean age = 55 years). Normalized and standardized relative CBV were calculated by using 6 common postprocessing methods. The repeatability of both normalized and standardized relative CBV, in both tumor and contralateral brain, was examined for each method with metrics of repeatability, including the repeatability coefficient and within-subject coefficient of variation. The minimum sample size required to detect a parameter change of 10% or 20% was also determined for both normalized relative CBV and standardized relative CBV for each estimation method.
When ordered by the repeatability coefficient, methods using postprocessing leakage correction and ΔR2*(t) techniques offered superior repeatability. Across processing techniques, the standardized relative CBV repeatability in normal-appearing brain was comparable with that in tumor (P = .31), yet inferior in tumor for normalized relative CBV (P = .03). On the basis of the within-subject coefficient of variation, tumor standardized relative CBV estimates were less variable (13%-20%) than normalized relative CBV estimates (24%-67%). The minimum number of participants needed to detect a change of 10% or 20% is 118-643 or 30-161 for normalized relative CBV and 109-215 or 28-54 for standardized relative CBV.
The ΔR2* estimation methods that incorporate leakage correction offer the best repeatability for relative CBV, with standardized relative CBV being less variable and requiring fewer participants to detect a change compared with normalized relative CBV.
Background
Psychological factors are known to significantly modulate itch in patients suffering from chronic itch. Itch is also highly susceptible to both placebo and nocebo (negative placebo) ...effects. Brain activity likely supports nocebo‐induced itch, but is currently unknown.
Methods
We collected functional MRI (fMRI) data from atopic dermatitis (AD) patients, in a within‐subject design, and contrast brain response to nocebo saline understood to be allergen vs open‐label saline control. Exploratory analyses compared results to real allergen itch response and placebo responsiveness, evaluated in the same patients.
Results
Nocebo saline produced greater itch than open saline control (P < 0.01). Compared to open saline, nocebo saline demonstrated greater fMRI response in caudate, dorsolateral prefrontal cortex (dlPFC), and intraparietal sulcus (iPS) – brain regions important for cognitive executive and motivational processing. Exploratory analyses found that subjects with greater dlPFC and caudate activation to nocebo‐induced itch also demonstrated greater dlPFC and caudate activation, respectively, for real allergen itch. Subjects reporting greater nocebo‐induced itch also demonstrated greater placebo reduction of allergen‐evoked itch, suggesting increased generalized modulation of itch perception.
Conclusions
Our study demonstrates the capacity of nocebo saline to mimic both the sensory and neural effects of real allergens and provides an insight to the brain mechanisms supporting nocebo‐induced itch in AD, thus aiding our understanding of the role that expectations and other psychological factors play in modulating itch perception in chronic itch patients.
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