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Modulation of ventral prefrontal cortex functional connections reflects the interplay of cognitive processes and stimulus characteristics.

Protzner AB, McIntosh AR - Cereb. Cortex (2008)

Bottom Line: Emerging ideas of brain function emphasize the context-dependency of regional contributions to cognitive operations, where the function of a particular region is constrained by its pattern of functional connectivity.Analysis of right ventral PFC functional connectivity, however, suggested these activity patterns interact.These results underscore the interactive nature of brain processing, where modality-specific and process-specific networks interact for normal cognitive operations.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuropsychology, Toronto Western Hospital and Research Institute, Toronto, M5G 2M9 ON, Canada. protzner@uhnres.utoronto.ca

ABSTRACT
Emerging ideas of brain function emphasize the context-dependency of regional contributions to cognitive operations, where the function of a particular region is constrained by its pattern of functional connectivity. We used functional magnetic resonance imaging to examine how modality of input (auditory or visual) affects prefrontal cortex (PFC) functional connectivity for simple working memory tasks. The hypothesis was that PFC would show contextually dependent changes in functional connectivity in relation to the modality of input despite similar cognitive demands. Participants were presented with auditory or visual bandpass-filtered noise stimuli, and performed 2 simple short-term memory tasks. Brain activation patterns independently mapped onto modality and task demands. Analysis of right ventral PFC functional connectivity, however, suggested these activity patterns interact. One functional connectivity pattern showed task differences independent of stimulus modality and involved ventromedial and dorsolateral prefrontal and occipitoparietal cortices. A second pattern showed task differences that varied with modality, engaging superior temporal and occipital association regions. Importantly, these association regions showed nonzero functional connectivity in all conditions, rather than showing a zero connectivity in one modality and nonzero in the other. These results underscore the interactive nature of brain processing, where modality-specific and process-specific networks interact for normal cognitive operations.

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(A) Singular image for the nonrotated task PLS task demands LV. Brain regions in blue are more active during control tasks, and brain regions in yellow are more active during experimental tasks. White circle indicates the approximate location of the BA 47 seed voxel used in the seed PLS analysis. (B) Hemodynamic response function from the seed voxel circled in (A) (MNI template coordinates: x = 44, y = 32, z = −24). The averaged response for experimental tasks is shown in blue, and averaged response for control tasks are shown in red. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).
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fig3: (A) Singular image for the nonrotated task PLS task demands LV. Brain regions in blue are more active during control tasks, and brain regions in yellow are more active during experimental tasks. White circle indicates the approximate location of the BA 47 seed voxel used in the seed PLS analysis. (B) Hemodynamic response function from the seed voxel circled in (A) (MNI template coordinates: x = 44, y = 32, z = −24). The averaged response for experimental tasks is shown in blue, and averaged response for control tasks are shown in red. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).

Mentions: Within the PFC, we chose our ROI statistically. We used task spatiotemporal partial least squares (task PLS, McIntosh et al. 2004) to identify the PFC voxel whose activity most reliably differentiated experimental from control tasks. This voxel was located in the right inferior frontal gyrus, Brodmann's area (BA) 47 (Montreal Neurological Institute [MNI] coordinate: 44, 32, −12; see circled region in Fig. 3A for approximate seed location). Meta-analyses and review papers of working memory have suggested that ventral PFC, including BA 47, tends to be recruited for maintenance operations (Courtney et al. 1998; D'Esposito et al. 1998; Wager and Smith 2003) which would be a common processing demand for both the temporal sequencing and comparison tasks. We used seed spatiotemporal PLS (seed PLS) to examine the functional connectivity of this prefrontal seed. With this usage of PLS, we analyzed how BA 47 activity correlated across participants with the rest of the brain. PLS can sort the correlations into what is similar, and what is different across tasks. This seed PLS was conducted only on experimental tasks. The control tasks were not included to focus the analysis on the potential dependence of functional connectivity on the varying experimenter manipulated cognitive challenges and modality.


Modulation of ventral prefrontal cortex functional connections reflects the interplay of cognitive processes and stimulus characteristics.

Protzner AB, McIntosh AR - Cereb. Cortex (2008)

(A) Singular image for the nonrotated task PLS task demands LV. Brain regions in blue are more active during control tasks, and brain regions in yellow are more active during experimental tasks. White circle indicates the approximate location of the BA 47 seed voxel used in the seed PLS analysis. (B) Hemodynamic response function from the seed voxel circled in (A) (MNI template coordinates: x = 44, y = 32, z = −24). The averaged response for experimental tasks is shown in blue, and averaged response for control tasks are shown in red. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2665153&req=5

fig3: (A) Singular image for the nonrotated task PLS task demands LV. Brain regions in blue are more active during control tasks, and brain regions in yellow are more active during experimental tasks. White circle indicates the approximate location of the BA 47 seed voxel used in the seed PLS analysis. (B) Hemodynamic response function from the seed voxel circled in (A) (MNI template coordinates: x = 44, y = 32, z = −24). The averaged response for experimental tasks is shown in blue, and averaged response for control tasks are shown in red. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).
Mentions: Within the PFC, we chose our ROI statistically. We used task spatiotemporal partial least squares (task PLS, McIntosh et al. 2004) to identify the PFC voxel whose activity most reliably differentiated experimental from control tasks. This voxel was located in the right inferior frontal gyrus, Brodmann's area (BA) 47 (Montreal Neurological Institute [MNI] coordinate: 44, 32, −12; see circled region in Fig. 3A for approximate seed location). Meta-analyses and review papers of working memory have suggested that ventral PFC, including BA 47, tends to be recruited for maintenance operations (Courtney et al. 1998; D'Esposito et al. 1998; Wager and Smith 2003) which would be a common processing demand for both the temporal sequencing and comparison tasks. We used seed spatiotemporal PLS (seed PLS) to examine the functional connectivity of this prefrontal seed. With this usage of PLS, we analyzed how BA 47 activity correlated across participants with the rest of the brain. PLS can sort the correlations into what is similar, and what is different across tasks. This seed PLS was conducted only on experimental tasks. The control tasks were not included to focus the analysis on the potential dependence of functional connectivity on the varying experimenter manipulated cognitive challenges and modality.

Bottom Line: Emerging ideas of brain function emphasize the context-dependency of regional contributions to cognitive operations, where the function of a particular region is constrained by its pattern of functional connectivity.Analysis of right ventral PFC functional connectivity, however, suggested these activity patterns interact.These results underscore the interactive nature of brain processing, where modality-specific and process-specific networks interact for normal cognitive operations.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuropsychology, Toronto Western Hospital and Research Institute, Toronto, M5G 2M9 ON, Canada. protzner@uhnres.utoronto.ca

ABSTRACT
Emerging ideas of brain function emphasize the context-dependency of regional contributions to cognitive operations, where the function of a particular region is constrained by its pattern of functional connectivity. We used functional magnetic resonance imaging to examine how modality of input (auditory or visual) affects prefrontal cortex (PFC) functional connectivity for simple working memory tasks. The hypothesis was that PFC would show contextually dependent changes in functional connectivity in relation to the modality of input despite similar cognitive demands. Participants were presented with auditory or visual bandpass-filtered noise stimuli, and performed 2 simple short-term memory tasks. Brain activation patterns independently mapped onto modality and task demands. Analysis of right ventral PFC functional connectivity, however, suggested these activity patterns interact. One functional connectivity pattern showed task differences independent of stimulus modality and involved ventromedial and dorsolateral prefrontal and occipitoparietal cortices. A second pattern showed task differences that varied with modality, engaging superior temporal and occipital association regions. Importantly, these association regions showed nonzero functional connectivity in all conditions, rather than showing a zero connectivity in one modality and nonzero in the other. These results underscore the interactive nature of brain processing, where modality-specific and process-specific networks interact for normal cognitive operations.

Show MeSH