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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 modality LV. On the singular image, time from stimulus onset, expressed in seconds, is indicated on the y-axis of the singular image. The approximate location of the axial slice in MNI atlas space is indicated on the x-axis. Voxels in the image are highlighted according to the magnitude of the ratio of their parameter estimate to the bootstrap-estimated standard error (bootstrap ratio). The singular image is superimposed on a T1-weighted MRI template. On the singular image, brain regions in blue are more active during visual tasks, and brain regions in yellow are more active during auditory tasks. (B) HRF from BA 22, identified in the modality LV as more active during the visual tasks (MNI template coordinates: x = 68, y = −40, z = 12). Auditory tasks are shown in blue and visual in red to emphasize that change in response was greater for auditory than visual tasks. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).
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fig2: (A) Singular image for the nonrotated task PLS modality LV. On the singular image, time from stimulus onset, expressed in seconds, is indicated on the y-axis of the singular image. The approximate location of the axial slice in MNI atlas space is indicated on the x-axis. Voxels in the image are highlighted according to the magnitude of the ratio of their parameter estimate to the bootstrap-estimated standard error (bootstrap ratio). The singular image is superimposed on a T1-weighted MRI template. On the singular image, brain regions in blue are more active during visual tasks, and brain regions in yellow are more active during auditory tasks. (B) HRF from BA 22, identified in the modality LV as more active during the visual tasks (MNI template coordinates: x = 68, y = −40, z = 12). Auditory tasks are shown in blue and visual in red to emphasize that change in response was greater for auditory than visual tasks. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).

Mentions: The LV that showed the strongest effect was the contrast between auditory and visual tasks (modality LV, Fig. 2A, see Table 1 for a list of local maxima). Dominant negative saliences (related to increased activation during visual tasks) were located in left middle frontal gyrus (BA 46), right medial frontal gyrus (BA 8), bilateral superior temporal gyrus (BA 22), left superior parietal lobe (BA 7), right cuneus (BA 19), and bilateral cerebellum. Dominant positive weights (related to increased activation during auditory tasks) were located in right caudate, bilateral middle temporal cortex (BA 21b and 22r), right precentral gyrus (BA 6), and right thalamus.


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 modality LV. On the singular image, time from stimulus onset, expressed in seconds, is indicated on the y-axis of the singular image. The approximate location of the axial slice in MNI atlas space is indicated on the x-axis. Voxels in the image are highlighted according to the magnitude of the ratio of their parameter estimate to the bootstrap-estimated standard error (bootstrap ratio). The singular image is superimposed on a T1-weighted MRI template. On the singular image, brain regions in blue are more active during visual tasks, and brain regions in yellow are more active during auditory tasks. (B) HRF from BA 22, identified in the modality LV as more active during the visual tasks (MNI template coordinates: x = 68, y = −40, z = 12). Auditory tasks are shown in blue and visual in red to emphasize that change in response was greater for auditory than visual tasks. 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

fig2: (A) Singular image for the nonrotated task PLS modality LV. On the singular image, time from stimulus onset, expressed in seconds, is indicated on the y-axis of the singular image. The approximate location of the axial slice in MNI atlas space is indicated on the x-axis. Voxels in the image are highlighted according to the magnitude of the ratio of their parameter estimate to the bootstrap-estimated standard error (bootstrap ratio). The singular image is superimposed on a T1-weighted MRI template. On the singular image, brain regions in blue are more active during visual tasks, and brain regions in yellow are more active during auditory tasks. (B) HRF from BA 22, identified in the modality LV as more active during the visual tasks (MNI template coordinates: x = 68, y = −40, z = 12). Auditory tasks are shown in blue and visual in red to emphasize that change in response was greater for auditory than visual tasks. Responses are expressed as percent change from stimulus onset (T = 0) and are averaged across subjects (±SE).
Mentions: The LV that showed the strongest effect was the contrast between auditory and visual tasks (modality LV, Fig. 2A, see Table 1 for a list of local maxima). Dominant negative saliences (related to increased activation during visual tasks) were located in left middle frontal gyrus (BA 46), right medial frontal gyrus (BA 8), bilateral superior temporal gyrus (BA 22), left superior parietal lobe (BA 7), right cuneus (BA 19), and bilateral cerebellum. Dominant positive weights (related to increased activation during auditory tasks) were located in right caudate, bilateral middle temporal cortex (BA 21b and 22r), right precentral gyrus (BA 6), and right thalamus.

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