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Network Modeling for Functional Magnetic Resonance Imaging (fMRI) Signals during Ultra-Fast Speech Comprehension in Late-Blind Listeners.

Dietrich S, Hertrich I, Ackermann H - PLoS ONE (2015)

Bottom Line: Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension.By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1.Taken together, right V1 might facilitate the "parsing" of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

View Article: PubMed Central - PubMed

Affiliation: Department of General Neurology, Hertie Institute for Clinical Brain Research, Center for Neurology, University of Tübingen, Hoppe-Seyler-Str. 3, D-72076 Tübingen, Germany.

ABSTRACT
In many functional magnetic resonance imaging (fMRI) studies blind humans were found to show cross-modal reorganization engaging the visual system in non-visual tasks. For example, blind people can manage to understand (synthetic) spoken language at very high speaking rates up to ca. 20 syllables/s (syl/s). FMRI data showed that hemodynamic activation within right-hemispheric primary visual cortex (V1), bilateral pulvinar (Pv), and left-hemispheric supplementary motor area (pre-SMA) covaried with their capability of ultra-fast speech (16 syllables/s) comprehension. It has been suggested that right V1 plays an important role with respect to the perception of ultra-fast speech features, particularly the detection of syllable onsets. Furthermore, left pre-SMA seems to be an interface between these syllabic representations and the frontal speech processing and working memory network. So far, little is known about the networks linking V1 to Pv, auditory cortex (A1), and (mesio-) frontal areas. Dynamic causal modeling (DCM) was applied to investigate (i) the input structure from A1 and Pv toward right V1 and (ii) output from right V1 and A1 to left pre-SMA. As concerns the input Pv was significantly connected to V1, in addition to A1, in blind participants, but not in sighted controls. Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension. By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1. Taken together, right V1 might facilitate the "parsing" of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

No MeSH data available.


Model specification.Model comparison was performed on family-level inferences: Models were subgrouped into four families specified by (Family 1) coupling between V1/A1 and SMA, (Family 2) coupling between A1 and SMA, (Family 3) coupling between V1 and SMA, and (Family 4) those with/without coupling between A1 and SMA, but without any connection to/from Pv/V1. Within the families, models consisted of either (i) bidirectional, (ii) absent, or (iii) unidirectional connectivity regarding the Pv/V1 coupling to/from the remaining areas. Furthermore, unidirectional models were configured hierarchically in the way that Pv projected forward to A1/V1 which again projected forward to SMA. Backward projections were only defined with respect to bidirectional models, not in an unidirectional way. A priori, driving input on Pv/A1, bidirectional A1-V1, and absent Pv-pre-SMA connectivity was assumed.
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pone.0132196.g003: Model specification.Model comparison was performed on family-level inferences: Models were subgrouped into four families specified by (Family 1) coupling between V1/A1 and SMA, (Family 2) coupling between A1 and SMA, (Family 3) coupling between V1 and SMA, and (Family 4) those with/without coupling between A1 and SMA, but without any connection to/from Pv/V1. Within the families, models consisted of either (i) bidirectional, (ii) absent, or (iii) unidirectional connectivity regarding the Pv/V1 coupling to/from the remaining areas. Furthermore, unidirectional models were configured hierarchically in the way that Pv projected forward to A1/V1 which again projected forward to SMA. Backward projections were only defined with respect to bidirectional models, not in an unidirectional way. A priori, driving input on Pv/A1, bidirectional A1-V1, and absent Pv-pre-SMA connectivity was assumed.

Mentions: Hypothesizing the recruitment of the secondary visual pathway (see Fig 1), A1 and Pv were considered as driving input regions, whereas pre-SMA was modeled as an area with higher cortical functions. Both input regions (A1, Pv) were specified to be driven by forward and backward moderately speech (both speech rates: 8 and 16 syl/s). Connections between A1 and V1 were assumed to be bidirectional, but no direct Pv-pre-SMA connections were included (peak location within Pv was found to be within the inferior lateral region and, thus, hypothesized to interact with sensory rather than frontal cortex). The resulting models were assigned to four “families” as shown in Fig 3 (Fam. 1: coupling between V1/A1 and SMA; Fam. 2: coupling between A1 and SMA; Fam. 3: coupling between V1 and SMA; Fam. 4: no connections to/from Pv and V1). Models of each family consisted of either bidirectional, absent, or unidirectional connectivity regarding the Pv/V1 coupling to/from the remaining areas. Furthermore, unidirectional models were configured hierarchically in the way that Pv (subcortical) projected forward to A1/V1 (sensory cortex) which again projected forward to SMA (higher cognitive area). Backward projections were only defined for bidirectional, but not in case of unidirectional connections (Fig 3).


Network Modeling for Functional Magnetic Resonance Imaging (fMRI) Signals during Ultra-Fast Speech Comprehension in Late-Blind Listeners.

Dietrich S, Hertrich I, Ackermann H - PLoS ONE (2015)

Model specification.Model comparison was performed on family-level inferences: Models were subgrouped into four families specified by (Family 1) coupling between V1/A1 and SMA, (Family 2) coupling between A1 and SMA, (Family 3) coupling between V1 and SMA, and (Family 4) those with/without coupling between A1 and SMA, but without any connection to/from Pv/V1. Within the families, models consisted of either (i) bidirectional, (ii) absent, or (iii) unidirectional connectivity regarding the Pv/V1 coupling to/from the remaining areas. Furthermore, unidirectional models were configured hierarchically in the way that Pv projected forward to A1/V1 which again projected forward to SMA. Backward projections were only defined with respect to bidirectional models, not in an unidirectional way. A priori, driving input on Pv/A1, bidirectional A1-V1, and absent Pv-pre-SMA connectivity was assumed.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492787&req=5

pone.0132196.g003: Model specification.Model comparison was performed on family-level inferences: Models were subgrouped into four families specified by (Family 1) coupling between V1/A1 and SMA, (Family 2) coupling between A1 and SMA, (Family 3) coupling between V1 and SMA, and (Family 4) those with/without coupling between A1 and SMA, but without any connection to/from Pv/V1. Within the families, models consisted of either (i) bidirectional, (ii) absent, or (iii) unidirectional connectivity regarding the Pv/V1 coupling to/from the remaining areas. Furthermore, unidirectional models were configured hierarchically in the way that Pv projected forward to A1/V1 which again projected forward to SMA. Backward projections were only defined with respect to bidirectional models, not in an unidirectional way. A priori, driving input on Pv/A1, bidirectional A1-V1, and absent Pv-pre-SMA connectivity was assumed.
Mentions: Hypothesizing the recruitment of the secondary visual pathway (see Fig 1), A1 and Pv were considered as driving input regions, whereas pre-SMA was modeled as an area with higher cortical functions. Both input regions (A1, Pv) were specified to be driven by forward and backward moderately speech (both speech rates: 8 and 16 syl/s). Connections between A1 and V1 were assumed to be bidirectional, but no direct Pv-pre-SMA connections were included (peak location within Pv was found to be within the inferior lateral region and, thus, hypothesized to interact with sensory rather than frontal cortex). The resulting models were assigned to four “families” as shown in Fig 3 (Fam. 1: coupling between V1/A1 and SMA; Fam. 2: coupling between A1 and SMA; Fam. 3: coupling between V1 and SMA; Fam. 4: no connections to/from Pv and V1). Models of each family consisted of either bidirectional, absent, or unidirectional connectivity regarding the Pv/V1 coupling to/from the remaining areas. Furthermore, unidirectional models were configured hierarchically in the way that Pv (subcortical) projected forward to A1/V1 (sensory cortex) which again projected forward to SMA (higher cognitive area). Backward projections were only defined for bidirectional, but not in case of unidirectional connections (Fig 3).

Bottom Line: Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension.By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1.Taken together, right V1 might facilitate the "parsing" of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

View Article: PubMed Central - PubMed

Affiliation: Department of General Neurology, Hertie Institute for Clinical Brain Research, Center for Neurology, University of Tübingen, Hoppe-Seyler-Str. 3, D-72076 Tübingen, Germany.

ABSTRACT
In many functional magnetic resonance imaging (fMRI) studies blind humans were found to show cross-modal reorganization engaging the visual system in non-visual tasks. For example, blind people can manage to understand (synthetic) spoken language at very high speaking rates up to ca. 20 syllables/s (syl/s). FMRI data showed that hemodynamic activation within right-hemispheric primary visual cortex (V1), bilateral pulvinar (Pv), and left-hemispheric supplementary motor area (pre-SMA) covaried with their capability of ultra-fast speech (16 syllables/s) comprehension. It has been suggested that right V1 plays an important role with respect to the perception of ultra-fast speech features, particularly the detection of syllable onsets. Furthermore, left pre-SMA seems to be an interface between these syllabic representations and the frontal speech processing and working memory network. So far, little is known about the networks linking V1 to Pv, auditory cortex (A1), and (mesio-) frontal areas. Dynamic causal modeling (DCM) was applied to investigate (i) the input structure from A1 and Pv toward right V1 and (ii) output from right V1 and A1 to left pre-SMA. As concerns the input Pv was significantly connected to V1, in addition to A1, in blind participants, but not in sighted controls. Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension. By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1. Taken together, right V1 might facilitate the "parsing" of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

No MeSH data available.