Biomedical subjects

Ching-Mei Feng

Publications and source records attributed to Ching-Mei Feng.

6 recordsLinked to original sources

PubMed2005

Disparity of activation onset in sensory cortex from simultaneous auditory and visual stimulation: Differences between perfusion and blood oxygenation level-dependent functional magnetic resonance imaging.

PURPOSE: To compare the temporal behaviors of perfusion and blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in the detection of timing differences between distinct brain areas, and determine potential latency differences between stimulus onset and measurable fMRI signal in sensory cortices. MATERIALS AND METHODS: Inversion recovery (IR) spin-echo echo-planar imaging (EPI) and T2*-weighted gradient-echo EPI sequences were used for perfusion- and BOLD-weighted experiments, respectively. Simultaneous auditory and visual stimulations were employed in an event-related (ER) paradigm. Signal time courses were averaged across 40 repeated trials to evaluate the onset of activation and to determine potential differences of activation latency between auditory and visual cortices and between these scanning methods. RESULTS: Temporal differences between visual and auditory areas ranged from 90-200 msec (root-mean-square (RMS) = 134 msec) and from -80 to 930 msec (RMS = 604 msec) in perfusion and BOLD measurements, respectively. The temporal variability detected with BOLD sequences was larger between subjects and was significantly greater than that in the perfusion response (P < 0.04). The measured time to half maximum (TTHM) values for perfusion imaging (visual, 3260 +/- 710 msec; auditory, 3130 +/- 700 msec) were earlier than those in BOLD responses (visual, 3770 +/- 430 msec; auditory, 3360 +/- 460 msec). CONCLUSION: The greater temporal variability between brain areas detected with BOLD could result from differences in the venous contributions to the signal. The results suggest that perfusion methods may provide more accurate timing information of neuronal activities than BOLD-based imaging.

Acoustic Stimulation↗

PubMed2004

CBF changes during brain activation: fMRI vs. PET.

The changes in regional cerebral blood flow (rCBF) associated with the changes in neuronal activity are routinely measured both by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) techniques. However, direct comparison has not been performed to determine similarities and differences of PET and fMRI techniques in determining the rCBF response to brain activation. In the present study, a quantitative comparison of the functional rCBF maps obtained by PET and fMRI are made by performing an activation study in a single group of subjects under precisely controlled conditions and using identical visual stimuli. Twelve healthy volunteers participated in the activation study using the visual checkerboard stimulation with flip frequency at 8 Hz. By selecting the conjunctive pixels which activated on both PET and fMRI maps, the change in rCBF measured by fMRI was 36.95 +/- 2.54%, whereas the value measured by PET was 38.79 +/- 2.63%. Our results have demonstrated that there is no statistically significant difference (P = 0.22) in the measurements of rCBF change between MRI and PET methods.

Algorithms↗

PubMed2004

Is left inferior frontal gyrus a general mechanism for selection?

Converging lines of research in neuroimaging recognize selection as one of the critical functions of prefrontal cortex (e.g., see Annu. Rev. Neurosci. 24, 2001 167). We examined a central thesis of a selection hypothesis (Neuropsychologia 41, 2003 280) that the left inferior frontal gyrus (LIFG) serves as a general mechanism for selecting among competing representations (Annu. Rev. Neurosci. 18, 1995 193). Participants were presented with two sets of letters to remember and then cued to select one set from the two as the target set for subsequent recognition. LIFG showed significantly more activation when the cue elicited a strong need for selection, relative to when it did not, suggesting that the involvement of this area in selection is generalizable beyond semantic retrieval tasks as originally found. This result provides supporting evidence for the selection hypothesis.

Adult↗

PubMed2003

Neural systems of second language reading are shaped by native language.

Reading in a second language (L2) is a complex task that entails an interaction between L2 and the native language (L1). To study the underlying mechanisms, we used functional magnetic resonance imaging (fMRI) to visualize Chinese-English bilinguals' brain activity in phonological processing of logographic Chinese and alphabetic English, two written languages with a sharp contrast in phonology and orthography. In Experiment 1, we found that phonological processing of Chinese characters recruits a neural system involving left middle frontal and posterior parietal gyri, cortical regions that are known to contribute to spatial information representation, spatial working memory, and coordination of cognitive resources as a central executive system. We assume that the peak activation of this system is relevant to the unique feature of Chinese that a logographic character has a square configuration that maps onto a monosyllabic unit of speech. Equally important, when our bilingual subjects performed a phonological task on English words, this neural system was most active, whereas brain areas mediating English monolinguals' fine-grained phonemic analysis, as demonstrated by Experiment 2, were only weakly activated. This suggests that our bilingual subjects were applying their L1 system to L2 reading and that the lack of letter-to-sound conversion rules in Chinese led Chinese readers to being less capable of processing English by recourse to an analytic reading system on which English monolinguals rely. Our brain imaging findings lend strongest support to the idea that language experience tunes the cortex.

Adult↗

PubMed2003

Dynamic changes in the cerebral metabolic rate of O2 and oxygen extraction ratio in event-related functional MRI.

Dynamic changes in the cerebral metabolic rate of oxygen (CMRO(2)) and oxygen extraction ratio (OER) in an event-related functional MRI (ER-fMRI) were measured in this study. Six subjects participated in this study at a magnetic field of 1.9 T. Cerebral blood flow (CBF) and blood oxygenation level-dependent (BOLD) changes were acquired during the brief visual stimulation, and the corresponding changes in CMRO(2) and OER were then determined. The results showed that the maximum relative changes in CMRO(2) and OER were about 10.36 +/- 0.85 and -6.54 +/- 0.55%, respectively, while the maximum changes in CBF and BOLD were approximately 17.35 +/- 1.37 and 1.03 +/- 0.06%, respectively. The CBF, CMRO(2), and OER changes reach their maximum approximately 1 s earlier than the BOLD signal change (4.15 +/- 0.21, 4.16 +/- 0.21, and 4.17 +/- 0.21 s vs 5.12 +/- 0.24 s after stimulation, P < 0.05).

Arousal↗

PubMed2002

Lie detection by functional magnetic resonance imaging.

The accurate detection of deception or lying is a challenge to experts in many scientific disciplines. To investigate if specific cerebral activation characterized feigned memory impairment, six healthy male volunteers underwent functional magnetic resonance imaging with a block-design paradigm while they performed forced-choice memory tasks involving both simulated malingering and under normal control conditions. Malingering that demonstrated the existence and involvement of a prefrontal-parietal-sub-cortical circuit with feigned memory impairment produced distinct patterns of neural activation. Because astute liars feign memory impairment successfully in testing once they understand the design of the measure being employed, our study represents an extremely significant preliminary step towards the development of valid and sensitive methods for the detection of deception.

Adult↗