Haeil Park

A Piece of the Action: Modulation of Sensory-Motor Regions by Action Idioms and Metaphors

The idea that the conceptual system draws on sensory and motor systems has received considerable experimental support in recent years. Whether the tight coupling between sensory-motor and conceptual systems is modulated by factors such as context or task demands is a matter of controversy. Here, we tested the context sensitivity of this coupling by using action verbs in three different types of sentences in an fMRI study: literal action, apt but non-idiomatic action metaphors, and action idioms. Abstract sentences served as a baseline. The result showed involvement of sensory-motor areas for literal and metaphoric action sentences, but not for idiomatic ones. A trend of increasing sensory-motor activation from abstract to idiomatic to metaphoric to literal sentences was seen. These results support a gradual abstraction process whereby the reliance on sensory-motor systems is reduced as the abstractness of meaning as well as conventionalization is increased, highlighting the context sensitive nature of semantic processing.

Effects of GM-CSF on the neural progenitor cells

Granulocyte macrophage colony stimulating factor (GM-CSF) is a potent hematopoietic cytokine, which stimulates stem cell proliferation in the bone marrow. We now report that GM-CSF receptors expressed on neural progenitor cells and can mediate a biological response in cells to treat with GM-CSF treated neural progenitor cells exhibited a proliferative response and a marked decrease in terminal differentiation to mature neuron or astrocytes. GM-CSF treatment also suppressed neural progenitor cell apoptosis. These findings suggest that GM-CSF can stimulate the proliferation and inhibit the apoptosis of neural progenitor cells to expand the progenitor population, and that GM-CSF has a potential role in neural development or repair.

Reorganization of neural circuits in the blind on diffusion direction analysis

The neural reorganization of the visual cortex of early blind individuals was evaluated using voxel-by-voxel analysis of diffusion tensor images with regard to the diffusion direction, diffusion anisotropy and diffusivity. Reduced anisotropy and increased diffusivity was found mainly in the visual pathways of 18 early blind individuals as opposed to 25 sighted individuals. Alteration of the diffusion direction was detected not only in the visual pathways but also in nonvisual pathways such as the u fibers of the parietal lobe, the sagittal striatum, the pulvinar and the inferior and superior longitudinal fasciculi. The alteration of regional diffusion direction, reduced anisotropy and increased diffusivity in early blind individuals imply the neural reorganization for functional adaptation to the loss of visual input during the early development period.

Neural correlates in the processing of phoneme-level complexity in vowel production.

We investigated how articulatory complexity at the phoneme level is manifested neurobiologically in an overt production task. fMRI images were acquired from young Korean-speaking adults as they pronounced bisyllabic pseudowords in which we manipulated phonological complexity defined in terms of vowel duration and instability (viz., COMPLEX: /tiɯi/ >> MID-COMPLEX: /tiye/ >> SIMPLE: /tii/). Increased activity in the left inferior frontal gyrus (Brodmann Areas (BA) 44 and 47), supplementary motor area and anterior insula was observed for the articulation of COMPLEX sequences relative to MID-COMPLEX; this was the case with the articulation of MID-COMPLEX relative to SIMPLE, except that the pars orbitalis (BA 47) was dominantly identified in the Brocas area. The differentiation indicates that phonological complexity is reflected in the neural processing of distinct phonemic representations, both by recruiting brain regions associated with retrieval of phonological information from memory and via articulatory rehearsal for the production of COMPLEX vowels. In addition, the finding that increased complexity engages greater areas of the brain suggests that brain activation can be a neurobiological measure of articulo-phonological complexity, complementing, if not substituting for, biomechanical measurements of speech motor activity.

Everyday conversation requires cognitive inference: Neural bases of comprehending implicated meanings in conversations

In ordinary conversations, literal meanings of an utterance are often quite different from implicated meanings and the inference about implicated meanings is essentially required for successful comprehension of the speakers utterances. Inference of finding implicated meanings is based on the listeners assumption that the conversational partner says only relevant matters according to the maxim of relevance in Grices theory of conversational implicature. To investigate the neural correlates of comprehending implicated meanings under the maxim of relevance, a total of 23 participants underwent an fMRI task with a series of conversational pairs, each consisting of a question and an answer. The experimental paradigm was composed of three conditions: explicit answers, moderately implicit answers, and highly implicit answers. Participants were asked to decide whether the answer to the Yes/No question meant Yes or No. Longer reaction time was required for the highly implicit answers than for the moderately implicit answers without affecting the accuracy. The fMRI results show that the left anterior temporal lobe, left angular gyrus, and left posterior middle temporal gyrus had stronger activation in both moderately and highly implicit conditions than in the explicit condition. Comprehension of highly implicit answers had increased activations in additional regions including the left inferior frontal gyrus, left medial prefrontal cortex, left posterior cingulate cortex and right anterior temporal lobe. The activation results indicate involvement of these regions in the inference process to build coherence between literally irrelevant but pragmatically associated utterances under the maxim of relevance. Especially, the left anterior temporal lobe showed high sensitivity to the level of implicitness and showed increased activation for highly versus moderately implicit conditions, which imply its central role in inference such as semantic integration. The right hemisphere activation, uniquely found in the anterior temporal lobe for highly implicit utterances, suggests its competence for integrating distant concepts in implied utterances under the relevance principle.

Activation of the occipital cortex and deactivation of the default mode network during working memory in the early blind.

Although blind people heavily depend on working memory to manage daily life without visual information, it is not clear yet whether their working memory processing involves functional reorganization of the memory-related cortical network. To explore functional reorganization of the cortical network that supports various types of working memory processes in the early blind, we investigated activation differences between 2-back tasks and 0-back tasks using fMRI in 10 congenitally blind subjects and 10 sighted subjects. We used three types of stimulus sequences: words for a verbal task, pitches for a non-verbal task, and sound locations for a spatial task. When compared to the sighted, the blind showed additional activations in the occipital lobe for all types of stimulus sequences for working memory and more significant deactivation in the posterior cingulate cortex of the default mode network. The blind had increased effective connectivity from the default mode network to the left parieto-frontal network and from the occipital cortex to the right parieto-frontal network during the 2-back tasks than the 0-back tasks. These findings suggest not only cortical plasticity of the occipital cortex but also reorganization of the cortical network for the executive control of working memory.

Consonant chords stimulate higher EEG gamma activity than dissonant chords

We examined the perceptions of consonant and dissonant chords to test auditory coherent percepts that are related to gamma oscillation. Consonant chords have coherent auditory properties due to the physical relationships of their components, in contrast to dissonant chords. EEGs were measured on 18 subjects with no musical expertise while they listened to consonant chords, dissonant chords, and single-note sounds and counted the number of single tones they heard. Induced gamma band activity was observed over the right brain hemisphere 170ms after the onset of stimuli. The induced gamma activity was significantly increased while listening to consonant chords as compared to dissonant chords. Our results suggest that the neural activity of the gamma frequency bands may reflect an auditory coherent percept generated from physical relationships of sounds.

Different hemispheric specializations for pitch and audioverbal working memory

Critical times of involvement of areas important to working memory were examined both with pitch and audioverbal N-back tasks using single-pulse transcranial magnetic stimulation (TMS). TMS was administered to 12 healthy participants over dorsolateral prefrontal and inferior parietal regions in each hemisphere at four different times after stimulus onset (250, 450, 650, and 850u2009ms). For the pitch N-back task, interference with working memory, as evidenced by a significant increase in reaction time, was observed with TMS over the right hemisphere regions. In contrast, for the audioverbal N-back task, TMS resulted in significantly increased reaction time only for left inferior parietal TMS delivered 450u2009ms after stimulus onset. These results imply different hemispheric specializations for pitch and audioverbal working memory.

Multi-jet atmospheric glow plasma for PCB desmear process

Summary form only given. The plasma desmear process is widely used in the printed circuit board industry. During drilling, drill bits become heated resulting in the melting and smearing of the epoxy-resin base material across the inner-layer copper surfaces within the hole barrel to which subsequent through-hole plating must connect. If not corrected, the smear would constitute a dielectric layer between the inner-layer copper surfaces and the plated copper, and the circuit would be defective. In order to effectively remove the residual smear like epoxy resin base material commonly found on the micro-via blind holes after drilling. We invented the multi-jet atmospheric glow plasma system and have compared the effect of micro-via blind holes desmearing at low pressure with that of a multi-jet atmospheric glow plasma source at atmospheric pressure. A multi-jet atmospheric glow plasma system with the radio frequency generated hollow cathodes was used for the PCB desmear process which operated in atmospheric pressure. The size of the proto-type system is 180 by 60 mm. The electrode comprises 100 hollow cathodes with flowing gas and the distance of both electrodes is adjustable between 1 and 10 mm. However, the construction perfectly enables further scaling up. The forward RF-power to sustain the discharge at atmospheric pressure can be as low as 12 W. Using this multi-jet atmospheric glow plasma source, we have successfully verified a possibility to ignite and maintain an atmospheric pressure discharge in He and He + O/sub 2/ in the RF powered multi-cylindrical hollow cathodes with inner diameter of 500 /spl mu/m. The discharge is stable, volume filling, silent, with no streamer. Our results show that residual smear can be effectively removed by a He + O/sub 2/ plasma, If it is performed under optimum process condition. The optimum process conditions for the removal of residual smear existing on the micro-via blind holes are the plasma exposure time of I min and the RF-power of 80 W. On the other hand, the highest efficiency of the residual smear clearing was achieved for a low-pressure plasma exposure time of 1 min and RF-power of 40 W. In both experiments, the higher O/sub 2/ content in the He plasma, the residual smear of micro-via blind holes effectively removed. As a result, the multi-jet atmospheric glow plasma source may substantially save coats by avoiding investment of the vacuum equipment and may bring a number of interesting applications in large area cold atmospheric plasma processing.