Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm

Desjardins, Samuel; Braun, Claude M. J.

doi:10.1016/j.actpsy.2005.07.003

Cited by 6 publications

(10 citation statements)

References 29 publications

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“…9 According to the known histologic pattern of the CC, through-CC cortical presentations (homotopic stimulations) yielded faster reaction times than heterotopic stimulations. 10 Given extensive axonal degeneration and atrophy within the CC in MS, structural connectivity–related homotopy changes are likely. DTI has been particularly useful in determining the microstructural axonal degeneration in white matter tracts such as the CC by use of quantitative scalar indices such as mean diffusivity and FA.…”

mentioning

confidence: 99%

Functional Homotopic Changes in Multiple Sclerosis with Resting-State Functional MR Imaging

Zhou

Milham

Zuo

et al. 2013

AJNR Am J Neuroradiol

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BACKGROUND AND PURPOSE CC is extensively involved in MS with interhemispheric dysfunction. The purpose of this study was to determine whether interhemispheric correlation is altered in MS by use of a recently developed RS-fMRI homotopy technique and whether these homotopic changes correlate with CC pathology. MATERIALS AND METHODS Twenty-four patients with relapsing-remitting MS and 24 age-matched healthy volunteers were studied with RS-fMRI and DTI acquired at 3T. The Pearson correlation of each pair of symmetric interhemispheric voxels of RS-fMRI time-series data was performed to compute VMHC, and z-transformed for subsequent group-level analysis. In addition, 5 CC segments in the midsagittal area and DTI-derived FA were measured to quantify interhemispheric microstructural changes and correlate with global and regional VMHC in MS. RESULTS Relative to control participants, patients with MS exhibited an abnormal homotopic pattern with decreased VMHC in the primary visual, somatosensory, and motor cortices and increased VMHC in several regions associated with sensory processing and motor control including the insula, thalamus, pallidum, and cerebellum. The global VMHC correlates moderately with the average FA of the entire CC for all participants in both groups (r = 0.3; P = .03). CONCLUSIONS Our data provide preliminary evidence of the potential usefulness of VMHC analyses for the detection of abnormalities of interhemispheric coordination in MS. We demonstrated that the whole-brain homotopic RS-fMRI pattern was altered in patients with MS, which was partially associated with the underlying structural degenerative changes of CC measured with FA.

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confidence: 99%

Functional Homotopic Changes in Multiple Sclerosis with Resting-State Functional MR Imaging

Zhou

Milham

Zuo

et al. 2013

AJNR Am J Neuroradiol

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“…They predicted that placing two stimuli to be discriminated in an oblique rather than a horizontal axis (relative to the meridian) on a computer screen (see Figure 1 for an illustration) should present a cost in RT significantly greater in bilateral stimulation conditions (requiring inter-hemispheric integration) than in unilateral stimulation conditions (not requiring inter-hemispheric integration). They obtained precisely that pattern, significantly, in two distinct experiments (Braun et al, 2011, Experiment 1;Desjardins & Braun, 2006). Stated more technically, the interaction between bilateral/unilateral stimulation and horizontal/oblique stimulus-pair location, relative to the meridian, was significant, as predicted.…”

Section: Callosal Homotopymentioning

confidence: 72%

“…The first has been termed the callosal homotopy mechanism by Desjardins et al (2006) and was supported by the appropriate interaction of Bilateral/Unilateral Stimulation and Stimulus Pair Axis Orientation, significant as predicted in both experiments. This demonstrates that the idea of this mechanism is supported with stimuli having no intrinsic orientation (Experiment 1) and with full balancing of any kind of orientation of the fixation stimulus, the target stimuli and the stimulus fields or quadrants (Experiment 2).…”

Section: Discussionmentioning

confidence: 86%

“…In all three of the relevant experiments of Braun, Desjardins and colleagues (Braun et al, 2011;Desjardins & Braun, 2006), the callosal homotopy effect was non-significantly greater with the squares than the discs. In the case of the squares, the contours of the stimulus had a "cardinal" orientation (relative to the meridian).…”

Section: Purposes Of the Present Investigationmentioning

confidence: 90%

“…Using this line of reasoning, Desjardins and Braun (2006) and Braun et al (2011) tried to determine whether tachistoscopic visual stimulation and collection of RTs would reveal such an effect. They predicted that placing two stimuli to be discriminated in an oblique rather than a horizontal axis (relative to the meridian) on a computer screen (see Figure 1 for an illustration) should present a cost in RT significantly greater in bilateral stimulation conditions (requiring inter-hemispheric integration) than in unilateral stimulation conditions (not requiring inter-hemispheric integration).…”

Section: Callosal Homotopymentioning

confidence: 99%

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Inter-hemispheric dynamics revealed by reaction time in the Dimond paradigm

Leblanc-Sirois

Braun

2015

Quarterly Journal of Experimental Psychology

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The Dimond paradigm (DP) consists of tachistoscopically presenting two stimuli to be discriminated--either both stimuli in a single visual hemifield or one in each. The DP has recently been implemented using predecessors to index homotopy of the callosal fibre projection with reaction time (RT) as the dependent measure. Using simple perceptual discrimination tasks, it has recently been reported that the advantage of the unilateral stimulation condition significantly decreases with practice. This effect has been interpreted as being due to the plasticity of the callosal network. Two experiments were designed to replicate these two little-known effects, namely callosal homotopy and callosal network plasticity. In addition, new evidence of another type of callosal network plasticity, termed "callosal network dispatching", was sought by introducing double manipulation of orientations of both stimulus-contours and inter-stimulus arrays to the DP. Strong support for the callosal homotopy and callosal network plasticity effects was obtained. In addition, evidence for a "callosal network dispatcher" effect accrued.

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