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1.
Curr Biol ; 31(2): 406-412.e3, 2021 01 25.
Artículo en Inglés | MEDLINE | ID: mdl-33157025

RESUMEN

Identifying the plastic and stable components of the visual cortex after retinal loss is an important topic in visual neuroscience and neuro-ophthalmology.1-5 Humans with juvenile macular degeneration (JMD) show significant blood-oxygen-level-dependent (BOLD) responses in the primary visual area (V1) lesion projection zone (LPZ),6 despite the absence of the feedforward signals from the degenerated retina. Our previous study7 reported that V1 LPZ responds to full-field visual stimuli during the one-back task (OBT), not during passive viewing, suggesting the involvement of task-related feedback signals. Aiming to clarify whether visual inputs to the intact retina are necessary for the LPZ responses, here, we measured BOLD responses to tactile and auditory stimuli for both JMD patients and control participants with and without OBT. Participants were instructed to close their eyes during the experiment for the purpose of eliminating retinal inputs. Without OBT, no V1 responses were detected in both groups of participants. With OBT, to the contrary, both stimuli caused substantial V1 responses in JMD patients, but not controls. Furthermore, we also found that the task-dependent activity in V1 LPZ became less pronounced when JMD patients opened their eyes, suggesting that task-related feedback signals can be partially suppressed by residual feedforward signals. Modality-independent V1 LPZ responses only in the task condition suggest that V1 LPZ responses reflect task-related feedback signals rather than reorganized feedforward visual inputs.


Asunto(s)
Enfermedad de Stargardt/fisiopatología , Corteza Visual/fisiopatología , Vías Visuales/fisiopatología , Percepción Visual/fisiología , Estimulación Acústica , Adulto , Edad de Inicio , Anciano , Estudios de Casos y Controles , Retroalimentación Fisiológica , Femenino , Voluntarios Sanos , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Estimulación Luminosa , Retina/patología , Enfermedad de Stargardt/patología , Tacto , Corteza Visual/diagnóstico por imagen , Vías Visuales/diagnóstico por imagen
2.
Neuroimage ; 181: 645-658, 2018 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-29936310

RESUMEN

Diffusion MRI tractography is essential for reconstructing white-matter projections in the living human brain. Yet tractography results miss some projections and falsely identify others. A challenging example is the optic radiation (OR) that connects the thalamus and the primary visual cortex. Here, we tested whether OR tractography can be optimized using quantitative T1 mapping. Based on histology, we proposed that myelin-sensitive T1 values along the OR should remain consistently low compared with adjacent white matter. We found that complementary information from the T1 map allows for increasing the specificity of the reconstructed OR tract by eliminating falsely identified projections. This T1-filtering outperforms other, diffusion-based tractography filters. These results provide evidence that the smooth microstructural signature along the tract can be used as constructive input for tractography. Finally, we demonstrate that this approach can be applied in a case of multiple sclerosis, and generalized to the HCP-available MRI measurements. We conclude that multimodal MRI microstructural information can be used to eliminate spurious tractography results in the case of the OR.


Asunto(s)
Imagen de Difusión Tensora/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Tálamo/anatomía & histología , Corteza Visual/anatomía & histología , Vías Visuales/anatomía & histología , Adolescente , Adulto , Imagen de Difusión Tensora/normas , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador/normas , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/diagnóstico por imagen , Esclerosis Múltiple/patología , Tálamo/diagnóstico por imagen , Corteza Visual/diagnóstico por imagen , Vías Visuales/diagnóstico por imagen , Adulto Joven
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