Biomedical subjects

Johanna Pekkola

Publications and source records attributed to Johanna Pekkola.

7 recordsLinked to original sources

PubMed2007

Human brain activity associated with audiovisual perception and attention.

Coherent perception of objects in our environment often requires perceptual integration of auditory and visual information. Recent behavioral data suggest that audiovisual integration depends on attention. The current study investigated the neural basis of audiovisual integration using 3-Tesla functional magnetic resonance imaging (fMRI) in 12 healthy volunteers during attention to auditory or visual features, or audiovisual feature combinations of abstract stimuli (simultaneous harmonic sounds and colored circles). Audiovisual attention was found to modulate activity in the same frontal, temporal, parietal and occipital cortical regions as auditory and visual attention. In addition, attention to audiovisual feature combinations produced stronger activity in the superior temporal cortices than attention to only auditory or visual features. These modality-specific areas might be involved in attention-dependent perceptual binding of synchronous auditory and visual events into coherent audiovisual objects. Furthermore, the modality-specific temporal auditory and occipital visual cortical areas showed attention-related modulations during both auditory and visual attention tasks. This result supports the proposal that attention to stimuli in one modality can spread to encompass synchronously presented stimuli in another modality.

Adolescent↗

PubMed2006

Attention to visual speech gestures enhances hemodynamic activity in the left planum temporale.

Observing a speaker's articulatory gestures can contribute considerably to auditory speech perception. At the level of neural events, seen articulatory gestures can modify auditory cortex responses to speech sounds and modulate auditory cortex activity also in the absence of heard speech. However, possible effects of attention on this modulation have remained unclear. To investigate the effect of attention on visual speech-induced auditory cortex activity, we scanned 10 healthy volunteers with functional magnetic resonance imaging (fMRI) at 3 T during simultaneous presentation of visual speech gestures and moving geometrical forms, with the instruction to either focus on or ignore the seen articulations. Secondary auditory cortex areas in the bilateral posterior superior temporal gyrus and planum temporale were active both when the articulatory gestures were ignored and when they were attended to. However, attention to visual speech gestures enhanced activity in the left planum temporale compared to the situation when the subjects saw identical stimuli but engaged in a nonspeech motion discrimination task. These findings suggest that attention to visually perceived speech gestures modulates auditory cortex function and that this modulation takes place at a hierarchically relatively early processing level.

Adult↗

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

Processing of audiovisual speech in Broca's area.

We investigated cerebral processing of audiovisual speech stimuli in humans using functional magnetic resonance imaging (fMRI). Ten healthy volunteers were scanned with a 'clustered volume acquisition' paradigm at 3 T during observation of phonetically matching (e.g., visual and acoustic /y/) and conflicting (e.g., visual /a/ and acoustic /y/) audiovisual vowels. Both stimuli activated the sensory-specific auditory and visual cortices, along with the superior temporal, inferior frontal (Broca's area), premotor, and visual-parietal regions bilaterally. Phonetically conflicting vowels, contrasted with matching ones, specifically increased activity in Broca's area. Activity during phonetically matching stimuli, contrasted with conflicting ones, was not enhanced in any brain region. We suggest that the increased activity in Broca's area reflects processing of conflicting visual and acoustic phonetic inputs in partly disparate neuron populations. On the other hand, matching acoustic and visual inputs would converge on the same neurons.

Adult↗

PubMed2005

Primary auditory cortex activation by visual speech: an fMRI study at 3 T.

Recent studies have yielded contradictory evidence on whether visual speech perception (watching articulatory gestures) can activate the human primary auditory cortex. To circumvent confounds due to inter-individual anatomical variation, we defined our subjects' Heschl's gyri and assessed blood oxygenation-dependent signal changes at 3 T within this confined region during visual speech perception and observation of moving circles. Visual speech perception activated Heschl's gyri in nine subjects, with activation in seven of them extending to the area of primary auditory cortex. Activation was significantly stronger during visual speech perception than during observation of the moving circles. Further, a significant hemisphere by stimulus interaction occurred, suggesting left Heschl's gyrus specialization for visual speech processing.

Adult↗

PubMed2005

Modulation of auditory cortex activation by sound presentation rate and attention.

We studied the effects of sound presentation rate and attention on auditory supratemporal cortex (STC) activation in 12 healthy adults using functional magnetic resonance imaging (fMRI) at 3 T. The sounds (200 ms in duration) were presented at steady rates of 0.5, 1, 1.5, 2.5, or 4 Hz while subjects either had to focus their attention to the sounds or ignore the sounds and attend to visual stimuli presented with a mean rate of 1 Hz. Consistent with previous observations, we found that both increase in stimulation rate and attention to sounds enhanced activity in STC bilaterally. Further, we observed larger attention effects with higher stimulation rates. This interaction of attention and presentation rate has not been reported previously. In conclusion, our results show both rate-dependent and attention-related modulations of STC indicating that both factors should be controlled, or at least addressed, in fMRI studies of auditory processing.

Acoustic Stimulation↗

PubMed2003

Localized pericochlear hypoattenuating foci at temporal-bone thin-section CT in pediatric patients: nonpathologic differential diagnostic entity?

PURPOSE: To evaluate the prevalence of localized hypoattenuating areas in the cochlear otic capsule at temporal-bone thin-section computed tomography (CT) in pediatric patients and correlate the findings with clinical information. MATERIALS AND METHODS: Temporal-bone thin-section CT images obtained in 73 patients aged 0-9 years (20 Austrian, 53 Finnish; 36 female and 37 male patients) were evaluated for the presence of localized hypoattenuating foci in the region of the fissula ante fenestram of the otic capsule. Clinical information collected for all patients was also evaluated. The data were analyzed with a logistic regression model. RESULTS: Hypoattenuating areas in the region of the fissula ante fenestram were observed in 23 of 73 patients (32%). Hypoattenuating foci were substantially more prevalent in patients younger than 3 years than in those 3 years or older (odds ratio, 0.14; 95% CI: 0.04, 0.52; P =.001). The prevalence did not differ between sexes or according to clinical diagnosis. Only three of the 23 patients with hypoattenuating foci had clinical findings suggestive of otosclerosis, and none had osteogenesis imperfecta. After adjustment for age and sex, the finding was more prevalent among the Finnish patients (odds ratio, 5.4; 95% CI: 1.19, 24.52; P =.02) than among the Austrian patients. CONCLUSION: Hypoattenuating areas in the region of the fissula ante fenestram in the otic capsule at thin-section CT are prevalent among children younger than 3 years in the absence of clinical evidence of otosclerosis or osteogenesis imperfecta and appear in children up to 9 years old.

Child↗