Effect of mother's voice on neonatal respiratory activity and EEG delta amplitude.

While the influence of the mother's voice on neonatal heart-rate response and its relevant activity on cerebral cortex and the autonomic nervous system (ANS) are well known, few studies have assessed its influence on respiratory activity. We investigated the relationship among the respiration rate, the delta wave amplitudes through electroencephalography, and the basal state of ANS through the respiratory variability index while 22 full-term neonates hear their mother's voice and an unknown voice. It was found that when respiratory variability was large, a transient (<5 s) change in respiration rates was observed in response to an unknown voice, while a greater increase in the delta wave amplitude was observed in the frontal lobe than the parietal one in response to the mother's voice. Conversely, when respiratory variability was small, a sustained increase (>10 s) in respiration rates was observed in response to the mother's voice, while a greater increase in the delta wave amplitude was found in both the frontal and parietal lobes. These results suggest that the basal state of ANS influences the latency of increases in respiration rates. Furthermore, induced by the mother's voice, transient increases in respiration rates are reduced in association with frontal lobe activity, and sustained increases in respiration rates are promoted in association with frontal and parietal lobe activities.

Prefrontal Function Engaging in External-Focused Attention in 5- to 6-Month-Old Infants: A Suggestion for Default Mode Network.

The present study used functional near-infrared spectroscopy (fNIRS) to measure 5- to 6-month-old infants' hemodynamic response in the prefrontal cortex (PFC) to visual stimuli differing in saliency and social value. Nineteen Japanese 5- to 6-month-old infants watched video clips of Peek-a-Boo (social signal) performed by an anime character (AC) or a human, and hand movements without social signal performed by an AC. The PFC activity of infants was measured by 22-channel fNIRS, while behaviors including looking time were recorded simultaneously. NIRS data showed that infants' hemodynamic responses in the PFC generally decreased due to these stimuli, and the decrease was most prominent in the frontopolar (FP), covering medial PFC (MPFC), when infants were viewing Peek-a-Boo performed by an AC. Moreover, the decrease was more pronounced in the dorsolateral PFC (DLPFC) when infants were viewing Peek-a-Boo performed by an AC than by a human. Accordingly, behavioral data revealed significantly longer looking times when Peek-a-Boo was performed by an AC than by a human. No significant difference between Peek-a-Boo and non-Peek-a-Boo conditions was observed in either measure. These findings indicate that infants at this age may prefer stimuli with more salient features, which may be more effective in attracting their attentions. In conjunction with our previous findings on responses to self-name calling in infants of similar age, we hypothesize that the dynamic function of the MPFC and its vicinity (as part of default mode network (DMN): enhanced by self-focused stimuli, attenuated by externally focused stimuli), which is consistently observed in adults, may have already emerged in 5- to 6-month-old infants.

[Developmental changes of rapid automatized naming and Hiragana reading of Japanese in elementary-school children].

Two hundred and seven Japanese elementary school children aged from 6 (Grade 1) to 12 (Grade 6) years old were tested for their abilities to name numbers and pictured objects along with reading Hiragana characters and words. These children all showed typical development and their classroom teachers judged that they were not having any problems with reading or writing. The children were randomly divided into two groups, the first group was assigned to two naming tasks;the rapid automatized naming (RAN) of "numbers" and "pictured objects," the second group was assigned to two rapid alternative stimulus (RAS) naming tasks using numbers and pictured objects. All children were asked to perform two reading tasks that were written in Hiragana script: single mora reading task and four syllable word reading task. The total articulation time for naming and reading and performance in terms of accuracy were measured for each task. Developmental changes in these variables were evaluated. The articulation time was significantly longer for the first graders, and it gradually shortened as they moved through to the upper grades in all tasks. The articulation time reached a plateau in the 5th grade for the number naming, while gradual change continued after drastic change in the lower grades for the pictured object naming. The articulation times for the single mora reading and RAN of numbers correlated strongly. The articulation time for the RAS naming was significantly longer compared to that for the RAN, though there were very few errors. The RAS naming showed the highest correlation with the four syllable word reading. This study demonstrated that the performance in rapid automatized naming of numbers and pictures were closely related with performance on reading tasks. Thus Japanese children with reading disorders such as developmental dyslexia should also be evaluated for rapid automatized naming.

[Developmental changes in reading ability of Japanese elementary school children--analysis of 4 kana reading tasks].

Five hundred and twenty-eight Japanese elementary school children aged from 6 (Grade 1) to 12 (Grade 6) were tested for their abilities to read Hiragana characters, words, and short sentences. They were typically developing children whom the classroom teachers judged to have no problems with reading and writing in Japanese. Each child was asked to read four tasks which were written in Hiragana script: single mora reading task, four syllable non-word reading task, four syllable word reading task, and short sentence reading task. The total articulation time for reading and performance in terms of accuracy were measured for each task. Developmental changes in these variables were evaluated. The articulation time was significantly longer for the first graders, and it gradually shortened as they moved through to the upper grades in all tasks. The articulation time reached a plateau in the 4th grade for the four syllable word and short sentence reading tasks, while it did so for the single mora and four syllable non-word reading tasks in the 5th grade. The articulation times for the four syllable word and short sentence reading tasks correlated strongly. There were very few clear errors for all tasks, and the number of such errors significantly changed between the school grades only for the single mora and four syllable word reading tasks. It was noted that more than half of the children read the beginning portion of the word or phrase twice or more, in order to read it accurately, and developmental changes were also seen in this pattern of reading. This study revealed that the combination of these reading tasks may function as a screening test for reading disorders such as developmental dyslexia in children below the age of ten or eleven years old.

Lexical processing during saccades in text comprehension.

We asked whether people process words during saccades when reading sentences. Irwin (1998) demonstrated that such processing occurs when words are presented in isolation. In our experiment, participants read part of a sentence ending in a high- or low-frequency target word and then made a long (40 degrees) or short (10 degrees) saccade to the rest of the sentence. We found a frequency effect on the target word and the first word after the saccade, but the effect was greater for short than for long saccades. Readers therefore performed more lexical processing during long saccades than during short ones. Hence, lexical processing takes place during saccades in text comprehension.