An essential feature of human memory is the capacity to assess confidence in one's own memory performance, but the neural mechanisms underlying the process of determining confidence in memory performance have not yet been isolated. Using functional magnetic resonance imaging, we examined both the process of confidence assessment and the subjective level of high or low confidence expressed during this process.
This paper describes a neural model of speech acquisition and production that accounts for a wide range of acoustic, kinematic, and neuroimaging data concerning the control of speech movements. The model is a neural network whose components correspond to regions of the cerebral cortex and cerebellum, including premotor, motor, auditory, and somatosensory cortical areas. Computer simulations of the model verify its ability to account for compensation to lip and jaw perturbations during speech.
Verbal declarative memory is one of the most reliably impaired cognitive functions in schizophrenia. Important issues are whether the problem is reversible, and which brain regions underlie improvement. We showed previously that glucose administration improved declarative memory in patients with schizophrenia, and sought in this pilot study to identify whether glucose affects the location or degree of activation of brain regions involved in a verbal encoding task.
Behavioral evidence supports a dissociation between response selection (RS; stimulus-to-response [S-R] mapping) and perceptual discrimination (PD): The former may be subject to a central processing bottleneck, whereas the latter is not (Pashler, 1994). We previously (Jiang & Kanwisher, 2003) identified a set of frontal and parietal regions involved in RS as those that produce a stronger signal when subjects follow a difficult S-R mapping rule than an easy mapping rule.
In many situations, people can only compute one stimulus-to-response mapping at a time, suggesting that response selection constitutes a "central processing bottleneck" in human information processing. Using fMRI, we tested whether common or distinct brain regions were involved in response selection across visual and auditory inputs, and across spatial and nonspatial mapping rules. We isolated brain regions involved in response selection by comparing two conditions that were identical in perceptual input and motor output, but differed in the complexity of the mapping rule.
Perfusion-weighted magnetic resonance imaging (PWI) has been proposed as an attractive non-invasive tool for evaluating cerebral haemodynamics. Quantitative maps of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP) and various other haemodynamic parameters can be obtained. Recent advances in hard- and software made PWI available for clinical routine. Although PWI became common in adult neuroradiology, it remains challenging in pediatric neuroradiology.
Infants with an inhibited temperament tend to develop into children who avoid people, objects, and situations that are novel or unfamiliar, whereas uninhibited children spontaneously approach novel persons, objects, and situations. Behavioral and physiological features of these two temperamental categories are moderately stable from infancy into early adolescence and have been hypothesized to be due, in part, to variation in amygdalar responses to novelty.
Novel word learning is central to the flexibility inherent in the human language capacity. Word learning may partially depend on long-term memory formation during the assembly of phonological representations from orthographic inputs. In the present study, event-related functional magnetic resonance imaging (fMRI) examined the contributions of phonological control-a component of the verbal working memory system-to phonological assembly and word learning.
BACKGROUND AND PURPOSE: Cerebral microinfarcts (CMI) are important contributors to vascular cognitive impairment. Magnetic resonance imaging diffusion-weighted imaging (DWI) hyperintensities have been suggested to represent acute CMI. We aim to describe a mathematical method for estimating total number of CMI based on the presence of incidental DWI lesions.
Simultaneous positron emission tomography and magnetic resonance imaging (PET-MR) is an innovative and promising imaging modality that is generating substantial interest in the medical imaging community, while offering many challenges and opportunities. In this study, we investigated whether MR surface coils need to be accounted for in PET attenuation correction. Furthermore, we integrated motion correction, attenuation correction, and point spread function modeling into a single PET reconstruction framework.
