Biomedical subjects

Anu Kujala

Publications and source records attributed to Anu Kujala.

8 recordsLinked to original sources

PubMed2006

Training in Morse code enhances involuntary attentional switching to acoustic frequency: Evidence from ERPs.

This study examined the possibility that learning Morse code could result in cortical changes in processing of physical acoustic features, as indexed by the mismatch negativity (MMN) and P3a components of the auditory event-related potential (ERP). ERPs were recorded in 9 subjects who were learning Morse code. The subjects were presented with auditory stimuli at 3 different times relative to their training (before, during and after). These stimuli were presented within an auditory 'oddball' paradigm, with repetitive standard stimuli interspersed by one of three infrequent deviant stimuli (duration, frequency or SOA). The data showed that there was a significant increase in the P3a only for frequency deviants as a function of training, whereas the MMN response was not affected by the training. These data are interpreted in terms of an attentional switching to unfamiliar changes that participants would not expect among the signals that they would grow to anticipate while receiving Morse code.

Acoustic Stimulation↗

PubMed2005

Short-term memory functions of the human fetus recorded with magnetoencephalography.

Studies in fetuses and in prematurely born infants show that auditory discriminative skills are present prior to birth. The magnetic fields generated by the fetal brain activity pass the maternal tissues and, despite their weakness, can be detected externally using MEG. Recent studies on the auditory evoked magnetic responses show that the fetal brain responds to sound onset. In contrast, higher-level auditory skills, such as those involving discriminative and memory functions, were not so far studied in fetuses with MEG. Here we show that fetal responses related to discriminating sounds can be recorded, implicating that the auditory change-detection system is functional. These results open new views to developmental neuroscience by enabling one to determine the sensory capabilities as well as the extent and accuracy of the short-term memory system of the fetus, and, further, to follow the development of these crucial processes.

Adult↗

PubMed2004

Speech-sound discrimination in neonates as measured with MEG.

Magnetic brain responses to speech sounds were measured in 10 healthy neonates. The stimulation consisted of a frequent vowel sound [a:] with a steady pitch contour, which was occasionally replaced by the vowel [i:] with a steady pitch, or the vowel [a:] with a rising pitch, manifesting a change of intonation. The magnetic mismatch-negativity response (MMNm) was obtained and successfully modelled to the speech sound quality change in all infants and to the intonation change in 6 infants. The present results indicate that auditory-cortex speech-sound discrimination may well be studied with magnetic recordings as early as in newborn infants.

Acoustic Stimulation↗

PubMed2004

Activation in the anterior left auditory cortex associated with phonological analysis of speech input: localization of the phonological mismatch negativity response with MEG.

The spatio-temporal dynamics of cortical activation underlying auditory word recognition, particularly its phonological stage, was studied with whole-head magnetoencephalography (MEG). Subjects performed a visuo-auditory priming task known to evoke the phonological mismatch negativity (PMN) response that is elicited by violations of phonological expectancies. Words and non-words were presented in separate conditions. In each of the 318 trials, the subjects first saw a word/non-word (e.g., 'cat') that was soon followed by a prime letter (e.g., 'h'). Their task was to replace mentally the sound of the first letter of the word/non-word with the prime letter, thus resulting in a new word/non-word (e.g., 'hat'). Finally, an auditory word/non-word either matching or mismatching with the anticipated item was presented. In most subjects, a PMNm followed by a later, N400m-like negativity was obtained in the left hemisphere to the mismatching auditory stimuli. A similar response pattern was obtained in the right hemisphere only in a few subjects. Source localization of the N1m, an index of acoustic analysis, and the PMNm and N400m-like responses was performed using L1 minimum-norm estimation. In the left hemisphere, the PMNm source for the words was significantly more anterior than the source of the N400m-like response; for the non-words, the PMNm source was significantly more anterior than the sources of the N1m and the N400m-like response. These results suggest that the left-hemisphere neuronal networks involved in sub-lexical phonological analysis are at least partly different from those responsible for the earlier (acoustic) and later (whole item) processing of speech input.

Acoustic Stimulation↗

PubMed2004

From symbols to sounds: visual symbolic information activates sound representations.

Expectations on forthcoming sounds can speed up responding to environmental changes and can, thus, be a basis for successful adaptation. The present study investigated event-related brain potential (ERP) effects in situations where particular sounds were predicted on the basis of preceding visual information. Subjects had to map scorelike visual symbols to corresponding sounds. The sounds could be either congruent or occasionally incongruent with the corresponding symbol. When the auditory stimulation was incongruent with the visual information, a brain response was elicited starting as early as about 100 ms from the onset of the auditory stimulus. It had a bilateral frontal distribution and a polarity inversion at the mastoids compatible with the assumption of sources in auditory cortex. These results suggest that the auditory system can establish a representation of an expected stimulus on the basis of visual symbolic information.

Acoustic Stimulation↗

PubMed2003

Auditory magnetic responses of healthy newborns.

We recorded magnetic brain activity from healthy human newborns when they heard frequency changes in an otherwise repetitive sound stream. We were able to record the magnetic counterpart of the mismatch negativity (MMN) previously described only with electric recordings in infants. The results show that these recordings are possible, although still challenging due to the small head size and head movements. The modelling of the neural sources underlying the recorded responses suggests cortical sources in the temporal lobes.

Acoustic Stimulation↗

PubMed2003

Plastic cortical changes induced by learning to communicate with non-speech sounds.

With Morse code, an acoustic message is transmitted using combinations of tone patterns rather than the spectrally and temporally complex speech sounds that constitute the spoken language. Using MEG recordings of the mismatch negativity (MMN, an index of permanent auditory cortical representations of native language speech sounds), we probed the dominant hemisphere for the developing Morse code representations in adult Morse code learners. Initially, the MMN to the Morse coded syllables was, on average, stronger in the hemisphere opposite to the one dominant for the MMN to native language speech sounds. After a training period of 3 months, the pattern reversed, however: the mean Morse code MMN became lateralized to the hemisphere that was predominant for the speech-sound MMN. This suggests that memory traces for the Morse coded acoustic language units develop within the hemisphere that already accommodates the permanent traces for natural speech sounds. These plastic changes manifest, presumably, the close associations formed between the neural representations of the tone patterns and phonemes.

Acoustic Stimulation↗

PubMed2002

Context modulates processing of speech sounds in the right auditory cortex of human subjects.

Using whole-head magnetoencephalography, we studied how context affects processing of speech sounds by recording the magnetic counterpart (MMNm) of the mismatch negativity (MMN) event-related potential, which is elicited in the auditory cortex by a contrast between infrequent and frequent auditory stimuli. In Experiment 1, in the right, but not in the left, hemisphere auditory cortex, a contrast of consonant-vowel syllables elicited a stronger MMNm when presented within a word context than when occurring alone. Further, in Experiment 2, these same syllable contrasts were processed in the right auditory cortex more strongly when embedded in a non-speech sound context than when presented alone. This facilitation thus was insensitive to the phonetic and semantic features of the context but might nevertheless reflect the participation of the right hemisphere in speech perception.

Acoustic Stimulation↗