Neuropsychological studies have suggested differences in the cortical representations of verbs an... more Neuropsychological studies have suggested differences in the cortical representations of verbs and nouns. Assessment of word-class specific deficits often relies on picture naming with different sets of images used for action and object naming. Such a setup may be problematic in neuroimaging studies, as the perception of the image and the actual differences in retrieving verbs or nouns become intertwined. To address this issue, we investigated how different sets of images affect the pattern of activation in action and object naming. In the present fMRI experiment, healthy volunteers silently performed both action and object naming from action images, and object naming from object-only images. A similar network of cortical areas was activated in all three conditions, including bilateral occipitotemporal and parietal regions, and left frontal cortex. With action images, noun retrieval enhanced activation in bilateral parietal and right frontal cortex, areas previously associated with visual search and attention. Increased activation in the left posterior parietal cortex during this condition also suggests that naming an object in the context of action emphasizes motor-based properties of objects. Action images, regardless of whether verbs or nouns were named, evoked stronger activation than object-only images in the posterior middle temporal cortex bilaterally, the left temporoparietal junction, and the left frontal cortex, a network previously identified in processing of action knowledge. The strong influence of perceptual input on neural activation associated with noun vs. verb naming can in part explain discrepancies in previous lesion and functional neuroimaging studies on the processing of nouns and verbs.
Specific language impairment is associated with enduring problems in language-related functions. ... more Specific language impairment is associated with enduring problems in language-related functions. We followed the spatiotemporal course of cortical activation in SLI using magnetoencephalography. In the experiment, children with normal and impaired language development heard spoken real words and pseudowords presented only once or two times in a row. In typically developing children, the activation in the bilateral superior temporal cortices was attenuated to the second presentation of the same word. In SLI children, this repetition effect was nearly nonexistent in the left hemisphere. Furthermore, the activation was equally strong to words and pseudowords in SLI children whereas in the typically developing children the left hemisphere activation persisted longer for pseudowords than words. Our results indicate that the short-term maintenance of linguistic activation that underlies spoken word recognition is defective in SLI particularly in the left language-dominant hemisphere. The unusually rapid decay of speechevoked activation can contribute to impaired vocabulary growth.
There is an increasing interest to integrate electrophysiological and hemodynamic measures for ch... more There is an increasing interest to integrate electrophysiological and hemodynamic measures for characterizing spatial and temporal aspects of cortical processing. However, an informative combination of responses that have markedly different sensitivities to the underlying neural activity is not straightforward, especially in complex cognitive tasks. Here, we used parametric stimulus manipulation in magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) recordings on the same subjects, to study effects of noise on processing of spoken words and environmental sounds. The added noise influenced MEG response strengths in the bilateral supratemporal auditory cortex, at different times for the different stimulus types. Specifically for spoken words, the effect of noise on the electrophysiological response was remarkably nonlinear. Therefore, we used the singlesubject MEG responses to construct parametrization for fMRI data analysis and obtained notably higher sensitivity than with conventional stimulus--based parametrization. fMRI results showed that partly different temporal areas were involved in noise-sensitive processing of words and environmental sounds. These results indicate that cortical processing of sounds in background noise is stimulus specific in both timing and location and provide a new functionally meaningful platform for combining information obtained with electrophysiological and hemodynamic measures of brain function.
Human utterances demonstrate temporal patterning, also referred to as rhythm. While simple oromot... more Human utterances demonstrate temporal patterning, also referred to as rhythm. While simple oromotor behaviors (e.g., chewing) feature a salient periodical structure, conversational speech displays a time-varying quasi-rhythmic pattern. Quantification of periodicity in speech is challenging. Unimodal spectral approaches have highlighted rhythmic aspects of speech. However, speech is a complex multimodal phenomenon that arises from the interplay of articulatory, respiratory, and vocal systems. The present study addressed the question of whether a multimodal spectral approach, in the form of coherenceanalysis between electromyographic (EMG) and acoustic signals, would allow one to characterize rhythm in natural speech more efficiently than a unimodal analysis. The main experimental task consisted of speech production at three speaking rates; a simple oromotor task served as control. The EMG–acoustic coherence emerged as a sensitive means of tracking speech rhythm, whereas spectral analysis of either EMG or acoustic amplitude envelope alone was less informative. Coherence metrics seem to distinguish and highlight rhythmic structure in natural speech.
Tactile sensory memory is needed to infer shape or motion from the spatiotemporal pattern of sens... more Tactile sensory memory is needed to infer shape or motion from the spatiotemporal pattern of sensory input during manual exploration.
Neuropsychological studies have suggested differences in the cortical representations of verbs an... more Neuropsychological studies have suggested differences in the cortical representations of verbs and nouns. Assessment of word-class specific deficits often relies on picture naming with different sets of images used for action and object naming. Such a setup may be problematic in neuroimaging studies, as the perception of the image and the actual differences in retrieving verbs or nouns become intertwined. To address this issue, we investigated how different sets of images affect the pattern of activation in action and object naming. In the present fMRI experiment, healthy volunteers silently performed both action and object naming from action images, and object naming from object-only images. A similar network of cortical areas was activated in all three conditions, including bilateral occipitotemporal and parietal regions, and left frontal cortex. With action images, noun retrieval enhanced activation in bilateral parietal and right frontal cortex, areas previously associated with visual search and attention. Increased activation in the left posterior parietal cortex during this condition also suggests that naming an object in the context of action emphasizes motor-based properties of objects. Action images, regardless of whether verbs or nouns were named, evoked stronger activation than object-only images in the posterior middle temporal cortex bilaterally, the left temporoparietal junction, and the left frontal cortex, a network previously identified in processing of action knowledge. The strong influence of perceptual input on neural activation associated with noun vs. verb naming can in part explain discrepancies in previous lesion and functional neuroimaging studies on the processing of nouns and verbs.
Specific language impairment is associated with enduring problems in language-related functions. ... more Specific language impairment is associated with enduring problems in language-related functions. We followed the spatiotemporal course of cortical activation in SLI using magnetoencephalography. In the experiment, children with normal and impaired language development heard spoken real words and pseudowords presented only once or two times in a row. In typically developing children, the activation in the bilateral superior temporal cortices was attenuated to the second presentation of the same word. In SLI children, this repetition effect was nearly nonexistent in the left hemisphere. Furthermore, the activation was equally strong to words and pseudowords in SLI children whereas in the typically developing children the left hemisphere activation persisted longer for pseudowords than words. Our results indicate that the short-term maintenance of linguistic activation that underlies spoken word recognition is defective in SLI particularly in the left language-dominant hemisphere. The unusually rapid decay of speechevoked activation can contribute to impaired vocabulary growth.
There is an increasing interest to integrate electrophysiological and hemodynamic measures for ch... more There is an increasing interest to integrate electrophysiological and hemodynamic measures for characterizing spatial and temporal aspects of cortical processing. However, an informative combination of responses that have markedly different sensitivities to the underlying neural activity is not straightforward, especially in complex cognitive tasks. Here, we used parametric stimulus manipulation in magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) recordings on the same subjects, to study effects of noise on processing of spoken words and environmental sounds. The added noise influenced MEG response strengths in the bilateral supratemporal auditory cortex, at different times for the different stimulus types. Specifically for spoken words, the effect of noise on the electrophysiological response was remarkably nonlinear. Therefore, we used the singlesubject MEG responses to construct parametrization for fMRI data analysis and obtained notably higher sensitivity than with conventional stimulus--based parametrization. fMRI results showed that partly different temporal areas were involved in noise-sensitive processing of words and environmental sounds. These results indicate that cortical processing of sounds in background noise is stimulus specific in both timing and location and provide a new functionally meaningful platform for combining information obtained with electrophysiological and hemodynamic measures of brain function.
Human utterances demonstrate temporal patterning, also referred to as rhythm. While simple oromot... more Human utterances demonstrate temporal patterning, also referred to as rhythm. While simple oromotor behaviors (e.g., chewing) feature a salient periodical structure, conversational speech displays a time-varying quasi-rhythmic pattern. Quantification of periodicity in speech is challenging. Unimodal spectral approaches have highlighted rhythmic aspects of speech. However, speech is a complex multimodal phenomenon that arises from the interplay of articulatory, respiratory, and vocal systems. The present study addressed the question of whether a multimodal spectral approach, in the form of coherenceanalysis between electromyographic (EMG) and acoustic signals, would allow one to characterize rhythm in natural speech more efficiently than a unimodal analysis. The main experimental task consisted of speech production at three speaking rates; a simple oromotor task served as control. The EMG–acoustic coherence emerged as a sensitive means of tracking speech rhythm, whereas spectral analysis of either EMG or acoustic amplitude envelope alone was less informative. Coherence metrics seem to distinguish and highlight rhythmic structure in natural speech.
Tactile sensory memory is needed to infer shape or motion from the spatiotemporal pattern of sens... more Tactile sensory memory is needed to infer shape or motion from the spatiotemporal pattern of sensory input during manual exploration.
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Papers by R. Salmelin