Biomedical subjects

A Kujala

Publications and source records attributed to A Kujala.

5 recordsLinked to original sources

PubMed2001

Long-term memory traces facilitate short-term memory trace formation in audition in humans.

Long-term memory traces of one's native language have an effect on the short-term memory traces formed by phonemes, Nature 385 (1997) 432. We investigated whether they also affect the number of stimulus repetitions needed to form an adequate memory trace used in the elicitation of the mismatch negativity (MMN), an event-related response to a change in an ongoing sound stream. We recorded MMNs to infrequent stimuli occurring in trains of prototype and non-prototype phonemes, matched in their physical distances, and in trains of sinusoidal tones. We found that the number of standards needed to produce a prominent MMN was smaller for native-language prototype phonemes than to non-prototype phonemes, suggesting a faster trace development.

Adult↗

PubMed2001

Phonological aspects of word recognition as revealed by high-resolution spatio-temporal brain mapping.

We describe, for the first time, the use of high-resolution event-related brain potentials (hrERP) to identify the spatio-temporal characteristics of neural systems involved in phonological analysis. Subjects studied a visual word/non-word that was followed by the brief presentation of a prime letter (e.g. House, M) with the instruction to anticipate the word/non-word formed by replacing the word's first letter with the prime letter. After the prime letter, an auditory target word/non-word was presented that either matched/mismatched expectations (e.g., Mouse/Barn). ERPs were recorded to the onset of the auditory targets and scalp topographical maps were derived for the phonological mismatch negativity (PMN). The PMN reflected phonological analysis and examination of the peak topography revealed that the response was characterized by a prominent frontal, right-asymmetrical distribution. Spatial de-blurring (using current source density maps) indicated that the PMN scalp topography resulted primarily from an active left anterior source. The current results provide the initial evidence for the localization of the intra-cranial generator(s) involved in phonological analysis.

Acoustic Stimulation↗

PubMed2000

Harmonic partials facilitate pitch discrimination in humans: electrophysiological and behavioral evidence.

The effect of the spectral tone structure on pre-attentive and attentive pitch discrimination was investigated. The mismatch negativity (MMN) component was recorded from reading subjects to pitch changes of identical magnitude in pure tones with only one sinusoidal frequency component and in spectrally rich tones with two additional harmonic partials. In a separate condition, subjects were asked to indicate detection of pitch change by a button press. The MMN was elicited with a larger amplitude and shorter latency by change in spectrally rich tones than by change in pure tones. Furthermore, the subjects' behavioral responses were more accurate for spectrally rich tones than for sinusoidal tones. Together these data indicate that pre-attentive and attentive pitch discrimination is facilitated with spectrally rich sounds in comparison to pure sinusoidal tones.

Adolescent↗

PubMed1999

Electromagnetic responses of the human auditory cortex generated by sensory-memory based processing of tone-frequency changes.

Event-related brain potentials (ERPs) and magnetoencephalographic (MEG) responses to infrequent ('deviant') tones occurring among frequent ('standard') tones of different pitch were compared with responses to rare tones presented alone. The subjects were to ignore the tones. Deviant tones elicited the mismatch negativity (MMN) and its MEG counterpart (MMNm), while the rare tones delivered alone elicited a larger N1 and its MEG counterpart (N1m) than did standard tones. Source modeling of MEG responses indicated a difference in auditory-cortex source locations between the MMNm to deviant tones and the enhanced N1m to the rare tones presented alone. Thus, the MMN/MMNm is elicited by infrequent sounds only when they occur among frequent sounds. This supports the idea that a sensory-memory trace formed in the auditory cortex by preceding repetitive sounds is a necessary precondition for MMN/MMNm elicitation.

Acoustic Stimulation↗

PubMed1999

Functional specialization of the human auditory cortex in processing phonetic and musical sounds: A magnetoencephalographic (MEG) study.

Functional specialization of the human auditory cortex in processing phonetic vs musical sounds was investigated. While subjects watched a silent self-selected movie, they were presented with sequences consisting of frequent and infrequent phonemes (/e/ and /o/, respectively) or chords (A major and A minor, respectively). The subjects' brain responses to these sounds were recorded with a 122-channel whole-head magnetometer. The data indicated that within the right hemisphere, the magnetoencephalographic (MEG) counterpart MMNm of the mismatch negativity (MMN) elicited by an infrequent chord change was stronger than the MMNm elicited by a phoneme change. Within the left hemisphere, the MMNm strength for a chord vs phoneme change did not significantly differ. Furthermore, the MMNm sources for the phoneme and chord changes were posterior to the P1m sources generated at or near the primary auditory areas. In addition, the MMNm source for a phoneme change was superior to that for the chord change in both hemispheres. The data thus provide evidence for spatially distinct cortical areas in both hemispheres specialized in representing phonetic and musical sounds.

Acoustic Stimulation↗