Two distinct neural networks for semantic access during visual word recognition

s / Neuroscience Research 58S (2007) S1–S244 S173 P2-h20 Behavioral responses to frequency modulated sounds in Mongolian gerbils: Upward FM versus downward FM Yuki Nagata Department of knowledge Engineering and Computer Sciences, Doshisha University, Kyoto, Japan It is known that Mongolian gerbils (Meriones unguicultus) have communication calls that are mainly frequency modulated (FM) sounds. They vocalize downward FM (dFM) sounds more often than upward FM (uFM) sounds in low frequency range (<16 kHz). We considered that gerbils could perceive small differences between the dFM rates, since they use different types of dFM sounds in daily life. We compared behavioral responses to dFM sounds with those to uFM sounds by using GO/NOGO discrimination tasks. Gerbils were trained to discriminate FM sounds (dFM sound and uFM sound) from constant frequency (CF) sounds. After training was completed, test stimuli with different FM rates were presented to gerbils. As a result, the go response decreased as the FM rate decreased in the cace of dFM sounds. However, gerbils did not appear to discriminate differences within uFM sounds. Research fund: Grant to RCAST at Doshisha University from MEXT, Innovative Cluster Creation Project by MEXT P2-h21 Phonological and lexico-semantic processing during kanji word reading: An MEG study Qiang Wei1,2, Aya Ihara1, Tomoe Hayakawa1,3, Tsutomu Murata1, Norio Fujimaki1,2 1 Biological ICT Group, National Institute of Information and Communications Technology, Kobe, Japan; 2 Department of Brain Science and Engineering, Kyushu Institute of Technology, Kitakyushu, Japan; 3 Department of Psychology, Teikyo University, Tokyo, Japan We measured neural activities including the effect of phonological information on the lexico-semantic process during silent reading of kanji homophone words by using MEG. Subjects were presented prime-target word pairs that consisted of two kanji characters. The primes were phonologically same as or different from the following target words, or pseudo-characters. The neural activation differed between conditions in the left posterior superior temporal and inferior parietal areas, and became weaker by the phonological repetition. Furthermore, activity was larger for different condition in the anterior temporal lobe, and for same condition in Broca’s area, as compared with the other two conditions at 400–500 ms. Our results suggest that the phonological information influences the lexico-semantic process even under the strong constraint of orthographic information. P2-h22 Two distinct neural networks for semantic access during visual word recognition Hyeonjeong Jeong1, Motoaki Sugiura1,2, Yuko Sassa1,4, Tadao Miyamoto3, Kaoru Horie3, Shigeru Sato3, Ryuta Kawashima1 1 Department of Functional Brain Imaging, Tohoku University, Sendai, Japan; 2 Department of Cortical Research, NIPS, Japan; 3 Graduate School of International Cultural Studies, Tohoku University, Japan; 4 RISTEX, JST, Japan To investigate how Japanese efficiently access the meanings of written words in the brain, this study employed a two-by-two factorial design that manipulates both word types (Kanji vs. Kana) and task types (semantic vs. phonological). Two main findings emerged. First, differential semantic – phonological activation was significantly greater for Kanji than Kana in the left inferior temporal gyrus, left parahippocampal gyrus, left hippocampus, left caudate and right anterior fusiform gyrus. This finding suggests that these areas constitute the direct pathway from orthography to semantic system. Second, differential semantic – phonological activation was greater for Kana than Kanji in the left inferior occipital gyrus. This indicates that these areas are involved in reading through phonological mediation prior to accessing the semantic system. P2-h23 IFG activity in observing music performance Masumi Wakita1,2 1 Primate Research Institute, Kyoto University, Aichi, Japan; 2 Japan Science Technology Agency, Japan Broca’s area is involved in processing of hierarchical sensory and motor structures, and is activated when subjects are observing practiced actions. The current study was conducted on the hypothesis that the response of this region while viewing a structured action, such as music performance, would be influenced by the experience of observers. To this end, healthy right-handed adult participants were exposed to hand movements playing either ‘Twinkle, twinkle, little star’ or ‘Mary had a little lamb’ that was paired with its piano sounds either in a congruent or in an incongruent fashion. The subjects were asked to determine which music the hand was performing independent of the heard sounds. Cortical activity was measured using a near-infrared spectroscopy. Consequently, Broca’s area of the expert subjects showed higher activity in the incongruent condition requiring a higher processing load although all the subjects answered the song names correctly. Thus, Broca’s area is assumed to be involved in transforming a sequence of discrete actions into unified meaningful performance. Research fund: 21c COE (A14), JST, Nakayama Fundation for Human Science P2-h24 Early GABA function regulates sensory critical period during birdsong learning Yoko Yazaki-Sugiyama1,2, Jason Kushner3, Neal A Hessler2,3, Takao K Hensch1,2 1 CREST, JST, Osaka, Japan; 2 Neuronal Circuit Dev, RIKEN BSI, Wako, Japan; 3 Vocal Behabior Mech, RIKEN BSI, Wako, Japan Neural circuits are shaped by experience during restricted critical periods in early life. In mouse visual cortex, this timing is triggered by the maturation of inhibitory function. Here, we tested whether the principle also applies to another widely studied system, birdsong learning. Male zebra finches were injected into the ventricle with the positive GABAA receptor modulator diazepam (DZ) or vehicle control for 4 consecutive days before the critical period (∼20 days post-hatch). Birds in which inhibitory function was briefly accelerated suffered long-lasting learning deficits (>120 days) across several parameters: delayed singing onset, reduced song consistency or similarity to the tutors’ songs. Rate of motor learning was not affected. Premature closure of the sensory acquisition phase was instead implicated using a sequential, dual-tutoring paradigm, as well as by neuroanatomical consequences of early DZ treatment. Taken together, inhibitory circuits may generally influence the timing of developmental critical periods. Research fund: CREST P2-h25 Flexible word order in Japanese and its effects on frontal activation: A NIRS study Y. Nishimura1, K. Sugisaki2, N. Hattori2, Y. Inokuchi2, Y. Nishimura1, M. Ogawa2, Y. Okazaki1,3, W. Taki1, T. Yamamoto1, E. Yoshida2, Seiki Ayano2 1 Division of Neuroscience, Mie University Graduate School of Medicine, Mie, Japan; 2 Faculty of Humanity and Social Sciences, Mie University, Mie, Japan; 3 Tokyo Metropolitan Matsuzawa Hospital, Tokyo, Japan Japanese has flexible word order. In order to determine the basic word order in Japanese, oxy-hemoglobin concentration (oxyHb) changes in the frontal region were monitored by a 52-channel near-infrared spectroscopy (NIRS) in 32 right-handed healthy males during Subject (whyS/Swhy) and Object (SOV/OSV) Scrambling Conditions. The results have shown that while oxyHb changes in the sentences with Object Scrambling Condition (OSV) were significantly larger than that in the non-scrambled sentences (SOV) in the left frontal lobe, such effects cannot be observed in the case of Subject Scrambling Condition. These findings suggest that while OSV is derived from the basic order of SOV, there is no such derivational relationship between whyS and Swhy: both of these constitute the basic order. Research fund: This research was supported in part by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (#17320062).