Abnormal Functional Activation During a Simple Word Repetition Task: A PET Study of Adult Dyslexics
Journal of Cognitive Neuroscience
The Neural Circuitry Involved in the Reading of German Words and Pseudowords: A PET Study
Journal of Cognitive Neuroscience
Conceptual Processing during the Conscious Resting State: A Functional MRI Study
Journal of Cognitive Neuroscience
Functional Neuroanatomy of the Semantic System: Divisible by What?
Journal of Cognitive Neuroscience
Dissociating Reading Processes on the Basis of Neuronal Interactions
Journal of Cognitive Neuroscience
Development of Brain Mechanisms for Processing Orthographic and Phonologic Representations
Journal of Cognitive Neuroscience
Neuroimaging Studies of Word and Pseudoword Reading: Consistencies, Inconsistencies, and Limitations
Journal of Cognitive Neuroscience
Functional MRI and the Study of Human Consciousness
Journal of Cognitive Neuroscience
Journal of Cognitive Neuroscience
Commentary on "Functional MRI and the Study of Human Consciousness" by Daniel Lloyd
Journal of Cognitive Neuroscience
Focusing on the Big Picture with fMRI: Consciousness and Temporal Flux
Journal of Cognitive Neuroscience
Sensitivity and Uniformity in Detecting Motion Artifacts
Neural Information Processing
Journal of Cognitive Neuroscience
Hi-index | 0.00 |
The effect of stimulus rate and its interaction with stimulus type on brain activity during reading was investigated using functional magnetic resonance imaging (fMRI). This (i) enabled the segregation of brain regions showing differential responses, (ii) identified the optimum experimental design parameters for maximizing sensitivity, and (iii) allowed us to evaluate further the sources of discrepancy between positron emission tomography (PET) and fMRI signals. The effect of visual word rate has already been investigated in a previous PET study. However, rate effects can be very different in PET and fMRI, as seen in previous studies of auditory word processing. In this work, we attempt to replicate rate-sensitive activations observed with PET using fMRI. Our objective was to characterize the discrepancies in regionally specific ratesensitive effects between the two imaging modalities. Subjects were presented with words and pseudowords at varying rates while performing a silent reading task. The analysis specifically identified regions showing (i) an effect of stimulus rate on brain activity during reading; (ii) modulation of this effect by word type; and (iii) increased activity during reading relative to rest, but with no dependence on stimulus rate. The results identified similar effects of rate for words and pseudowords (no interactions between rate and word type reached significance). Irrespective of word type, strong positive linear effects of rate (i.e., activity increasing with rate) were detected in visual areas, right superior temporal gyrus, and bilateral precentral gyrus. These findings replicate the results of the previous PET study, confirming that activation in regions associated with visual processing and response generation increases with the number of stimuli. Likewise, we detected rate-independent effects reported in the previous PET study in bilateral anterior middle temporal, inferior frontal, and superior parietal regions. These results differentiate the functionally specific responses in rate-dependent and rate-independent areas. However, for negative effects of rate, fMRI did not replicate the effects seen in PET, suggesting some form of hemodynamic "rectification." The discussion focuses on differences between evoked rCBF and BOLD signals.