Biomedical subjects

J-B Poline

Publications and source records attributed to J-B Poline.

5 recordsLinked to original sources

PubMed2004

Coordinate-based versus structural approaches to brain image analysis.

A basic issue in neurosciences is to look for possible relationships between brain architecture and cognitive models. The lack of architectural information in magnetic resonance images, however, has led the neuroimaging community to develop brain mapping strategies based on various coordinate systems without accurate architectural content. Therefore, the relationships between architectural and functional brain organizations are difficult to study when analyzing neuroimaging experiments. This paper advocates that the design of new brain image analysis methods inspired by the structural strategies often used in computer vision may provide better ways to address these relationships. The key point underlying this new framework is the conversion of the raw images into structural representations before analysis. These representations are made up of data-driven elementary features like activated clusters, cortical folds or fiber bundles. Two classes of methods are introduced. Inference of structural models via matching across a set of individuals is described first. This inference problem is illustrated by the group analysis of functional statistical parametric maps (SPMs). Then, the matching of new individual data with a priori known structural models is described, using the recognition of the cortical sulci as a prototypical example.

Brain↗

PubMed2004

Letter binding and invariant recognition of masked words: behavioral and neuroimaging evidence.

Fluent readers recognize visual words across changes in case and retinal location, while maintaining a high sensitivity to the arrangement of letters. To evaluate the automaticity and functional anatomy of invariant word recognition, we measured brain activity during subliminal masked priming. By preceding target words with an unrelated prime, a repeated prime, or an anagram made of the same letters, we separated letter-level and whole-word codes. By changing the case and the retinal location of primes and targets, we evaluated the invariance of those codes. Our results indicate that an invariant binding of letters into words is achieved unconsciously through a series of increasingly invariant stages in the left occipito-temporal pathway.

Adult↗

PubMed2003

Brain imaging of language plasticity in adopted adults: can a second language replace the first?

Do the neural circuits that subserve language acquisition lose plasticity as they become tuned to the maternal language? We tested adult subjects born in Korea and adopted by French families in childhood; they have become fluent in their second language and report no conscious recollection of their native language. In behavioral tests assessing their memory for Korean, we found that they do not perform better than a control group of native French subjects who have never been exposed to Korean. We also used event-related functional magnetic resonance imaging to monitor cortical activations while the Korean adoptees and native French listened to sentences spoken in Korean, French and other, unknown, foreign languages. The adopted subjects did not show any specific activations to Korean stimuli relative to unknown languages. The areas activated more by French stimuli than by foreign stimuli were similar in the Korean adoptees and in the French native subjects, but with relatively larger extents of activation in the latter group. We discuss these data in light of the critical period hypothesis for language acquisition.

Adoption↗

PubMed2002

Estimating the delay of the fMRI response.

We propose a fast, efficient, general, simple, valid, and robust method of estimating and making inference about the delay of the fMRI response modeled as a temporal shift of the hemodynamic response function (HRF). We estimate the shift unbiasedly using two optimally chosen basis functions for a spectrum of time shifted HRFs. This is done at every voxel, to create an image of estimated delays and their standard deviations. This can be used to compare delays for the same stimulus at different voxels, or for different stimuli at the same voxel. Our method is compared to other alternatives and validated on an fMRI data set from an experiment in pain perception.

Brain↗

PubMed2002

Bilateral hemispheric alteration of memory processes in right medial temporal lobe epilepsy.

OBJECTIVE: Functional MRI (fMRI ) was used to investigate right medial temporal lobe epilepsy (RTLE) effects on verbal memory. METHODS: BOLD fMRI data were collected from seven right sided MTLE patients (RTLE) and compared with the data previously acquired from seven left sided MTLE patients (LTLE) and 10 control subjects. Twenty two contiguous images covering the whole brain were acquired using an EPI echoplanar sequence. Subjects were instructed to learn a list of 17 words, and to recall it immediately and at 24 hours interval. Group analyses were performed using SPM96. RESULTS: RTLE patients retrieval performances were significantly impaired as compared with the performance of control subjects. As compared with control subjects and LTLE patients, RTLE patients exhibited a different pattern of hemispheric activations and a global decrease in left hemisphere functional activity. CONCLUSION: MTLE cannot be considered as a model of pure well lateralised hippocampal dysfunction. The verbal memory impairment depicted in RTLE patients may be considered as the witness of a bilateral impairment of the neuroanatomical circuits subserving memory.

Adolescent↗