Biomedical subjects

Teija Kujala

Publications and source records attributed to Teija Kujala.

At least 19 recordsLinked to original sources

PubMed2006

Auditory cortical change detection in adults with Asperger syndrome.

The present study investigated whether auditory deficits reported in children with Asperger syndrome (AS) are also present in adulthood. To this end, event-related potentials (ERPs) were recorded from adults with AS for duration, pitch, and phonetic changes in vowels, and for acoustically matched non-speech stimuli. These subjects had enhanced mismatch negativity (MMN) amplitudes particularly for pitch and duration deviants, indicating enhanced sound-discrimination abilities. Furthermore, as reflected by the P3a, their involuntary orienting was enhanced for changes in non-speech sounds, but tended to be deficient for changes in speech sounds. The results are consistent with those reported earlier in children with AS, except for the duration-MMN, which was diminished in children and enhanced in adults.

Acoustic Stimulation↗

PubMed2006

The mismatch negativity in cognitive and clinical neuroscience: theoretical and methodological considerations.

Mismatch negativity (MMN) component of the event-related brain potentials has become popular in cognitive and clinical brain research during the recent years. It is an early response to a violation of an auditory rule such as an infrequent change in the physical feature of a repetitive sound. There is a lot of evidence on the association of the MMN parameters and behavioral discrimination ability, although this relationship is not always straight-forward. Since the MMN reflects sound discrimination accuracy, it can be used for probing how well different groups of individuals perceive sound differences, and how training or remediation affects this ability. In the present review, we first introduce some of the essential MMN findings in probing sound discrimination, memory, and their deficits. Thereafter, issues which need to be taken into account in MMN investigations as well as new improved recording paradigms are discussed.

Auditory Perception↗

PubMed2006

Group intervention changes brain activity in bilingual language-impaired children.

This investigation assessed the effectiveness of a phonological intervention program on the brain functioning of bilingual Finnish 6- to 7-year-old preschool children diagnosed with specific language impairment (SLI). The intervention program was implemented by preschool teachers to small groups of children including children with SLI. A matched group of other bilingual children with SLI received a physical exercise program and served as a control group. Auditory evoked magnetic fields were measured before and after the intervention with an oddball paradigm. The brain activity recordings were followed by a behavioral discrimination test. Our results show that, in children with SLI, the positive intervention effect is reflected in plastic changes in the brain activity of the left and right auditory cortices.

Adaptation, Physiological↗

PubMed2005

Perception of matching and conflicting audiovisual speech in dyslexic and fluent readers: an fMRI study at 3 T.

We presented phonetically matching and conflicting audiovisual vowels to 10 dyslexic and 10 fluent-reading young adults during "clustered volume acquisition" functional magnetic resonance imaging (fMRI) at 3 T. We further assessed co-variation between the dyslexic readers' phonological processing abilities, as indexed by neuropsychological test scores, and BOLD signal change within the visual cortex, auditory cortex, and Broca's area. Both dyslexic and fluent readers showed increased activation during observation of phonetically conflicting compared to matching vowels within the classical motor speech regions (Broca's area and the left premotor cortex), this activation difference being more extensive and bilateral in the dyslexic group. The between-group activation difference in conflicting > matching contrast reached significance in the motor speech regions and in the left inferior parietal lobule, with dyslexic readers exhibiting stronger activation than fluent readers. The dyslexic readers' BOLD signal change co-varied with their phonological processing abilities within the visual cortex and Broca's area, and to a lesser extent within the auditory cortex. We suggest these findings as reflecting dyslexic readers' greater use of motor-articulatory and visual strategies during phonetic processing of audiovisual speech, possibly to compensate for their difficulties in auditory speech perception.

Acoustic Stimulation↗

PubMed2005

The discrimination of and orienting to speech and non-speech sounds in children with autism.

The present study aimed to find out how different stages of cortical auditory processing (sound encoding, discrimination, and orienting) are affected in children with autism. To this end, auditory event-related potentials (ERP) were studied in 15 children with autism and their controls. Their responses were recorded for pitch, duration, and vowel changes in speech stimuli, and for corresponding changes in the non-speech counterparts of the stimuli, while the children watched silent videos and ignored the stimuli. The responses to sound repetition were diminished in amplitude in the children with autism, reflecting impaired sound encoding. The mismatch negativity (MMN), an ERP indexing sound discrimination, was enhanced in the children with autism as far as pitch changes were concerned. This is consistent with earlier studies reporting auditory hypersensitivity and good pitch-processing abilities, as well as with theories proposing enhanced perception of local stimulus features in individuals with autism. The discrimination of duration changes was impaired in these children, however. Finally, involuntary orienting to sound changes, as reflected by the P3a ERP, was more impaired for speech than non-speech sounds in the children with autism, suggesting deficits particularly in social orienting. This has been proposed to be one of the earliest symptoms to emerge, with pervasive effects on later development.

Acoustic Stimulation↗

PubMed2005

The role of blind humans' visual cortex in auditory change detection.

Several studies using brain imaging have demonstrated occipital-cortex activation in blind individuals during tactile and auditory tasks, suggesting that the visual cortex deprived of its normal input has adopted a new role in information processing. So far, however, at what stages of information processing and to which perceptual sub-processes this applies remains unclear. We determined the auditory functions of this cortical region in early-blind humans by means of functional magnetic resonance imaging. We found that these areas were not activated by the mere presence of sound, but were involved in the attentive processing of changes in the auditory environment, which is important in detecting potentially dangerous or other important events in the surroundings, for example.

Acoustic Stimulation↗

PubMed2005

Disruption of immediate memory and brain processes: an auditory ERP protocol.

An event-related potential (ERP) protocol is described that can be used to investigate those sound-evoked neural processes that may be implicated in disrupting immediate memory. Conventional electroencephalogram (EEG) is recorded during the performance of a task that involves ignoring irrelevant sounds while trying to hold in memory lists of numbers. Specific bioelectric measures are made to prevent the contamination of recordings by the movements of articulators. An approach is also outlined which controls the timing of ERP components to sounds with different envelopes. Using this approach, it has been shown that the neural processes involved in the elicitation of the auditory N1 ERP response may be involved in the disruption of memory for serial order produced by irrelevant sound.

Acoustic Stimulation↗

PubMed2005

Magnetic fields evoked by speech sounds in preschool children.

OBJECTIVE: Our objective was to study how well the auditory evoked magnetic fields (EF) reflect the behavioral discrimination of speech sounds in preschool children, and if they reveal the same information as simultaneously recorded evoked potentials (EP). METHODS: EFs and EPs were recorded in 11 preschool children (mean age 6 years 9 months) using an oddball paradigm with two sets of speech stimuli consisting both of one standard and two deviants. After the brain activity recording, children were tested on behavioural discrimination of the same stimuli presented in pairs. RESULTS: There was a mismatch negativity (MMN) calculated from difference curves and its magnetic counterpart MMNm measured from the original responses only to those deviants, which were behaviourally easiest to discriminate from the standards. In addition, EF revealed significant differences between the locations of the activation depending on the hemisphere and stimulus properties. CONCLUSIONS: EF, in addition to reflecting the sound-discrimination accuracy in a similar manner as EP, also reflected the spatial differences in activation of the temporal lobes. SIGNIFICANCE: These results suggest that both EPs and EFs are feasible for investigating the neural basis of sound discrimination in young children. The recording of EFs with its high spatial resolution reveals information on the location of the activated neural sources.

Acoustic Stimulation↗

PubMed2005

Long-term exposure to occupational noise alters the cortical organization of sound processing.

OBJECTIVE: Long-term exposure to noise may cause an altered hemispheric lateralization of speech processing even in silent conditions. We examined whether this lateralization shift is speech specific or occurs also for other sounds. METHODS: Brain responses from 10 healthy noise-exposed workers (>5 years) and 10 matched controls were recorded with a 32-channel electroencephalogram in two conditions, one including standard and deviant speech sounds, the other non-speech sounds, with novel sounds in both. RESULTS: The deviant-sound elicited mismatch negativity (MMN) was larger to non-speech than speech sounds in control subjects, while it did not differ between the sound types in the noise-exposed subjects. Moreover, the MMN to speech sounds was lateralized to the right hemisphere in exposed workers, while it was left-hemisphere predominant in control subjects. No group topography difference was found for non-speech sounds. The deviant sounds that were close in formant space to the standards elicited a longer MMN latency in both speech and non-speech conditions in exposed subjects than controls. No group differences were found for cortical responses to novel sounds. CONCLUSIONS: Long-term noise exposure altered the strength and the hemispheric organization of speech-sound discrimination and decreased the speed of sound-change processing. SIGNIFICANCE: Subpathological changes in cortical responses to sounds may occur even in subjects without a peripheral damage but continuously exposed to noisy auditory environments.

Adult↗

PubMed2005

Diagnostic subgroups of developmental dyslexia have different deficits in neural processing of tones and phonemes.

The present study addressed auditory processing in 8-11-year-old children with developmental dyslexia by means of event-related brain potentials (ERP). Cortical sound reception was evaluated by recording N250 responses to syllables and tones and cortical sound discrimination by analyzing the mismatch negativity (MMN) to syllable and tone changes. We found that both cortical sound reception and sound discrimination were impaired in dyslexic children. The analysis of the data obtained from two dyslexic subgroups, Dyslexics-1 being impaired in non-word reading (or both non-word and frequent word reading) and Dyslexics-2 in frequent word reading but not in non-word reading, revealed that the MMN was specifically diminished in the latter group whereas it was normal-like in Dyslexics-1. However, no differences were found between these subgroups in sound reception as indicated by the responses elicited by the standard stimuli. These results show that different diagnostic subgroups of dyslexics have different patterns of auditory processing deficits as suggested by similarly impaired sound reception in both dyslexic groups and the sound-discrimination impairment specific to one of the groups.

Acoustic Stimulation↗

PubMed2004

The processing of speech and non-speech sounds in aphasic patients as reflected by the mismatch negativity (MMN).

This study compared the discrimination of speech and non-speech sounds in left-hemisphere stroke patients with aphasia and healthy controls by recording event-related potentials (ERPs) and behavioural responses. It was found that the mismatch negativity (MMN) amplitude for vowel and duration changes in speech sounds was diminished in the patients. In contrast, there was no significant difference between the groups in the MMN for comparable frequency and duration changes in non-speech sounds. In the behavioural session, the patients were slower than the control subjects in discriminating duration changes of both types of sounds. These results suggest that left-hemisphere lesions have differential effects on the discrimination of speech and acoustic features indicating that they have separate neural substrates.

Acoustic Stimulation↗

PubMed2004

Comparison of blind and sighted participants' performance in a letter recognition working memory task.

The performance in letter recognition of 21 blind participants was compared with that of 16 age-matched sighted participants in an n-back working memory task. Blind participants were tested tactually with series of raised letters and Braille characters, and sighted participants tactually with series of raised letters and visually with series of letters presented on a computer screen. With this approach, we wanted to compare the tactual performances by trained (blind) and non-trained (sighted) participants, and tactual and visual performances by trained (blind and sighted, respectively) participants. Increments of mnemonic load increased the number of incorrect responses significantly in all n-back tasks. As expected, the blind participants outperformed the sighted ones statistically significantly in the tactile raised letters n-back task. The sighted participants produced significantly fewer incorrect responses in the visual task than the blind participants in the raised letters task, whereas there was no such difference between sighted subjects' visual performance and blind subjects' tactile performance in the Braille task. These results demonstrate the degree and limits to which everyday practice develops perceptual skills either in persons without sensory deficits (vision and visual environment), or persons with severe sensory loss (blindness and tactile environment). The performance level of blind persons relying on their tactile skills is just about the same as that of sighted subjects relying on their visual skills.

Adult↗

PubMed2004

Automatic and controlled processing of acoustic and phonetic contrasts.

Changes in the temporal properties of the speech signal provide important cues for phoneme identification. An impairment or inability to detect such changes may adversely affect one's ability to understand spoken speech. The difference in meaning between the Finnish words tuli (fire) and tuuli (wind), for example, lies in the difference between the duration of the vowel /u/. Detecting changes in the temporal properties of the speech signal, therefore, is critical for distinguishing between phonemes and identifying words. In the current study, we tested whether detection of changes in speech sounds, in native Finnish speakers, would vary as a function of the position within the word that the informational changes occurred (beginning, middle, or end) by evaluating how length contrasts in segments of three-syllable Finnish pseudo-words and their acoustic correlates were discriminated. We recorded a combination of cortical components of event-related brain potentials (MMN, N2b, P3b) along with behavioral measures of the perception of the same sounds. It was found that speech sounds were not processed differently than non-speech sounds in the early stages of auditory processing indexed by MMN. Differences occurred only in later stages associated with controlled processes. The effects of position and attention on speech and non-speech stimuli are discussed.

Acoustic Stimulation↗

PubMed2004

Word-specific cortical activity as revealed by the mismatch negativity.

Neurophysiological brain activity evoked by individual spoken words and pseudowords was recorded and the mismatch negativity (MMN), an automatic index of experience-dependent auditory memory traces, was calculated. Consistent with earlier reported results, the MMN response to word-final syllables was enhanced compared with that elicited by the same syllables placed in a pseudoword context. Here we now demonstrate that the enhancement of the MMN elicited by two individual words showed different scalp topographies. The early word-specific brain activity is consistent with the assumption that the memory traces activated by individual words are carried by large neuronal ensembles that differ in their distributions over the cortex. Current source estimates localized the between-word differences in the right hemisphere and in parieto-occipital left-hemispheric areas. The differential brain responses to individual words appeared as early as approximately 100 ms after the recognition points of the words, suggesting that their specific memory traces become active almost immediately after the information in the acoustic input is sufficient for word identification.

Adult↗

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↗

PubMed2004

Long-term exposure to noise impairs cortical sound processing and attention control.

Long-term exposure to noise impairs human health, causing pathological changes in the inner ear as well as other anatomical and physiological deficits. Numerous individuals are daily exposed to excessive noise. However, there is a lack of systematic research on the effects of noise on cortical function. Here we report data showing that long-term exposure to noise has a persistent effect on central auditory processing and leads to concurrent behavioral deficits. We found that speech-sound discrimination was impaired in noise-exposed individuals, as indicated by behavioral responses and the mismatch negativity brain response. Furthermore, irrelevant sounds increased the distractibility of the noise-exposed subjects, which was shown by increased interference in task performance and aberrant brain responses. These results demonstrate that long-term exposure to noise has long-lasting detrimental effects on central auditory processing and attention control.

Adult↗

PubMed2003

Native and foreign vowel discrimination as indexed by the mismatch negativity (MMN) response.

The development of a new vowel category was studied by measuring both automatic mismatch negativity and conscious behavioural target discrimination. Three groups, nai;ve Finns, advanced Finnish students of English, and native speakers of English, were presented with one pair of Finnish and three pairs of English synthetic vowels. The aim was to determine whether the advanced student group would show native-like responses to the unfamiliar vowel contrasts of the target language. The results suggest that learning in classroom environment may not lead to the formation of new long-term native-like memory traces.

Adolescent↗

PubMed2003

Auditory discrimination after left-hemisphere stroke: a mismatch negativity follow-up study.

BACKGROUND AND PURPOSE: We sought to determine the recovery of cortical auditory discrimination in aphasic, left-hemisphere-stroke patients by using an electrophysiological response called mismatch negativity (MMN) and speech-comprehension tests. METHODS: MMN in 8 left-hemisphere stroke patients was recorded in response to duration and frequency changes in a repetitive, harmonically rich tone 4 and 10 days and again 3 and 6 months after their first unilateral stroke. Eight age-matched, healthy persons served as control subjects. RESULTS: At 4 days after stroke onset, patients' sound discrimination was impaired in their left hemisphere, as suggested by attenuated MMNs, especially to right-ear stimuli. At 3 months after stroke, however, MMN to the right-ear duration change had significantly increased and was of normal size. A significant change for the frequency MMN was found for left-ear stimuli between 3 and 6 months after stroke. During the follow-up period, progressive improvement in speech-comprehension tests was also observed. Furthermore, there was a significant correlation between the change in the duration MMN amplitude and the Boston Diagnostic Aphasia Examination speech-comprehension test from 10 days to 3 months after stroke. CONCLUSIONS: These results suggest that the MMN can be used as an index of the recovery of auditory discrimination.

Acoustic Stimulation↗