Biomedical subjects

E W Pang

Publications and source records attributed to E W Pang.

5 recordsLinked to original sources

PubMed2000

Tracking the development of the N1 from age 3 to adulthood: an examination of speech and non-speech stimuli.

OBJECTIVES: To examine developmental changes in the N1a, N1b and N1c evoked by a tone and a speech consonant (/da/). METHODS: Subjects (n=70 for tones; n=69 for /da/) were grouped into 2 year intervals (age 3-16) and adults. They listened to a tone (2 kHz; 36 ms; 77 dB SL; ISI=600 ms; n=346) or a speech consonant /da/ (female voice recording; 7 ms VOT; 212 ms; 72 dB SL; ISI=600 ms; n=349) while watching a Disney((R)) screensaver. EEG was recorded from 26 electrodes referenced to Cz. An averaged reference was computed off-line. Amplitude and latency data were analyzed with repeated-measures ANOVAs for agexelectrode, and agexN1 component, respectively. RESULTS: Left hemisphere N1a was mature before age 3 whereas the right hemisphere N1a matured around 7-8 years. The vertex N1b showed a parietal distribution which shifted anteriorly with age. The N1c showed age- and stimulus-related changes. The N1c measured over the left hemisphere matured earlier than the N1c over the right hemisphere. The N1c to /da/ matured earlier than that to tones. CONCLUSIONS: Auditory processing undergoes steady and subtle developmental changes. These changes follow different maturational patterns depending on the type of stimuli. The evidence suggests earlier development of the left hemisphere and earlier development of the generators underlying speech processing.

Acoustic Stimulation↗

PubMed1999

Dissociation of the mismatch negativity and processing negativity attentional waveforms with nitrous oxide.

In Näätänen's model of early attention, the role of arousal in influencing the permanent feature detection system (indexed by mismatch negativity [MMN]) and the temporary feature-detection system (indexed by processing negativity [PN]) is unclear. To address this question, we investigated the effects of the anesthetic gas nitrous oxide (N2O) on the MMN and PN. Ten subjects performed a dichotic listening task in which discrimination difficulty and breathing mixture (air or 25% N2O) were manipulated factorially. MMN, PN, N1 and P300 at Fz, Cz, and Pz, as well as reaction time (RT), were measured. N2O had no effect on the PN, but decreased MMN amplitude. As expected, N2O decreased the amplitude of the N1 and P300 and increased the latency of the P300 and RT. The dissociation of MMN and PN by N2O suggests that this agent decreases the ability to detect automatic stimulus change without affecting voluntary selective attention. We interpret these results as indicating that arousal has multidimensional effects on early attentional mechanisms. These dimensions can be differentiated chemically by neurotransmitters in the reticular formation of the brain.

Adult↗

PubMed1999

Developmental changes in early cognitive processes.

The three paradigms presented in this paper demonstrate the value of ERPs in examining the development of early cognitive processes. Although we have presented only three examples, early cognitive processing could be investigated in a wide range of paradigms using ERPs, in normal as well as clinical populations. Clearly, a next step in understanding the age-related changes in these cognitive processes is to employ dipole source localization to examine the involvement of different generators and their maturation. The final conclusion is that developmental studies are important as they can contribute to our understanding of models of processing and of the generators of ERPs, in terms of cognition as well as neuroanatomy. Hence, the models of cognitive processes in adults should include the development of those processes through childhood.

Adult↗

PubMed1998

Mismatch negativity to speech stimuli in 8-month-old infants and adults.

The mismatch negativity (MMN) was measured in 15 normal awake 8-month-old infants and 10 adults to the speech consonants /da/ and /ta/. ERPs were analyzed at 11 electrodes (Fz, Cz, Pz, C3, C4, T3, T4, T5, T6, P3, P4). Four-hundred trials were presented: the /da/ standards with 80% probability and the /ta/ deviants with 20% probability. The ISI was 600 ms. An MMN was observed for both adults and infants but with different scalp distributions. A clear infant MMN was observed only at C3 and T3 electrodes, whereas the adult MMN was present at Fz, Cz, C3, C4 and Pz. A repeated-measures ANOVA on the normalized summed area between 200 and 250 ms revealed an age (adult vs. infant) x electrode interaction. Paired t-tests indicated that adults and infants showed significant differences at the C3, Cz, T3, Pz and T6 electrodes. The adult MMN was largest at Cz and C3 whereas the infant MMN was largest at T3. These data are discussed in terms of possible maturational changes in the MMN.

Adult↗

PubMed1997

Use of nitrous oxide to dissociate the non-specific and specific components of the human auditory N1.

The components of the N1 are thought to be related to sensory functioning (Components 1 and 2) and arousal (Component 3). To provide direct evidence for the involvement of Component 3 in arousal, we hypothesized that it should be more sensitive to the anesthetic gas nitrous oxide (N2O) than Component 1. Using the technique of selective adaptation, 30 blocks of 5 tones were presented at 1 min intervals to 9 subjects who breathed air, 25% and 35% N2O. As hypothesized, the amplitude of Component 3 was significantly reduced in a dose-dependent manner by N2O, but the amplitude of Component 1 was not, although the latter showed some evidence of a decrease at 25% N2O.

Adult↗