RESUMEN
Deficits of convergence and accommodation are common following traumatic brain injury, including mild traumatic brain injury, although the mechanism and localization of these deficits have been unclear and supranuclear control of the near-vision response has been incompletely understood. We describe a patient who developed profound instability of the near-vision response with inability to maintain convergence and accommodation following mild traumatic brain injury, who was identified to have a structural lesion on brain MRI in the pulvinar of the caudal thalamus, the pretectum, and the rostral superior colliculus. We discuss the potential relationship between posttraumatic clinical near-vision response deficits and the MRI lesion in this patient. We further propose that the MRI lesion location, specifically the rostral superior colliculus, participates in neural integration for convergence holding, given its proven anatomic connections with the central mesencephalic reticular formation and C-group medial rectus motoneurons in the oculomotor nucleus, which project to extraocular muscle nontwitch fibers specialized for fatigue-resistant, slow, tonic activity such as vergence holding.NEW & NOTEWORTHY Supranuclear control of the near-vision response has been incompletely understood to date. We propose, based on clinical and anatomic evidence, functional pathways for vergence that participate in the generation of the near triad, "slow vergence," and vergence holding.
Asunto(s)
Acomodación Ocular/fisiología , Conmoción Encefálica/fisiopatología , Convergencia Ocular/fisiología , Trastornos de la Motilidad Ocular/fisiopatología , Colículos Superiores/fisiopatología , Trastornos de la Visión/fisiopatología , Conmoción Encefálica/complicaciones , Conmoción Encefálica/patología , Femenino , Humanos , Persona de Mediana Edad , Neurociencias , Trastornos de la Motilidad Ocular/etiología , Área Pretectal/lesiones , Pulvinar/lesiones , Colículos Superiores/lesiones , Trastornos de la Visión/etiologíaRESUMEN
Posterior thalamic pulvinar nuclei have been implicated in different aspects of spatial attention, but their exact role in humans remain unclear. Most neuropsychological studies of attention deficits after pulvinar lesion have concerned single patients or small samples. Here we examined a group of 13 patients with focal damage to posterior thalamus on a visual search task with faces, allowing us to test several hypotheses concerning pulvinar function in controlling attention to visually salient or emotionally significant stimuli. Our results identified two subgroups of thalamic patients with distinct patterns of attentional responsiveness to emotional and colour features in face targets. One group with lesions located in anterior and ventral portions of thalamus showed intact performance, with a normal facilitation of visual search for faces with emotional (fearful or happy) expressions on both side of space, similar to healthy controls. By contrast, a second group showed a slower and poorer detection of face targets, most severe for neutral faces, but with a paradoxically enhanced facilitation by both colour and emotional features. This second group had lesions centred on the pulvinar, involving mainly the dorso-medial sectors in patients showing enhanced effects of colour features, but extending to more dorso-lateral sectors in those with enhanced effects of emotional features. These findings reveal that pulvinar nuclei are not critical for orienting attention to emotionally or visually salient features, but instead provide new evidence in support of previous hypotheses suggesting an important role in controlling attention in visual scenes with distracting information.
Asunto(s)
Emociones , Expresión Facial , Desempeño Psicomotor , Pulvinar/lesiones , Percepción Visual/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Atención , Percepción de Color , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Trastornos de la Percepción , Estimulación Luminosa , Núcleos Talámicos Posteriores/diagnóstico por imagen , Núcleos Talámicos Posteriores/lesiones , Núcleos Talámicos Posteriores/patología , Pulvinar/diagnóstico por imagen , Pulvinar/patología , Tiempo de Reacción , Percepción Social , Campos Visuales , Adulto JovenRESUMEN
The pulvinar is an important structure for visual attention function. Spatial and temporal attention was examined in three patients with varying pulvinar lesions. Spatial and temporal deficits were dissociable. The patient with anterior damage showed strong spatial but not temporal attention deficits, while the patient with posterior damage showed clear temporal attention deficits, but much reduced spatial problems. A third patient with intermediate damage showed intermediate behaviours. These findings are discussed within the scope of models of visual attention in which the pulvinar facilitates communication between different brain areas: depending upon the specifics of pulvinar damage, communication with different cortical areas may be degraded, thereby producing distinct patterns of deficit.
Asunto(s)
Atención , Trastornos de la Percepción/diagnóstico , Pulvinar/lesiones , Percepción Espacial , Percepción del Tiempo , Adulto , Anciano , Movimientos Oculares , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Pruebas NeuropsicológicasRESUMEN
We present a unique case demonstrating contributions of the pulvinar in response to visual threat. Substantial evidence demonstrates that the amygdala contributes to the emotion of fear and the response to threat. Traditionally, two routes to amygdala activation have been distinguished: a "slow cortical" route through visual and association cortex and a "fast subcortical" route through the thalamus. The pulvinar nucleus of the thalamus is well connected to the amygdala, suggesting that pulvinar damage might interfere with amygdala activation and response to threat. We tested this possibility in patient SM, who suffered complete loss of the left pulvinar. We measured interference from threatening images on goal-directed behavior. In SM's ipsilesional field, threatening images slowed responses more than pleasant images did. This interference decreased rapidly over time. In contrast, in SM's contralesional field, interference from threatening images was initially absent and then increased rather than decreased over time. Processing through the pulvinar therefore plays a significant role in generating response to visual threat. We suggest that, with disruption of the subcortical route to the amygdala, briefly presented images were not fully processed for threat. The reemergence of interference over time may reflect contributions of a slower route.
Asunto(s)
Amígdala del Cerebelo/fisiología , Miedo/fisiología , Vías Nerviosas/fisiología , Desempeño Psicomotor/fisiología , Pulvinar/lesiones , Percepción Visual/fisiología , Humanos , Imagen por Resonancia Magnética , Pulvinar/fisiología , Campos Visuales/fisiologíaRESUMEN
In 3 patients with unilateral pulvinar lesions, we tested the pulvinar's role in selective attention processing. Each patient completed four variants of a flanker interference task in which they reported the color of a square of a specified size while ignoring an irrelevant flanker that appeared either contralesionally or ipsilesionally to the target. The main finding was that when target location was not known and target and flanker were associated with competing responses, reaction times to contralesional targets were longer than those to ipsilesional targets. Our findings suggest that pulvinar damage produces a contralesional deficit in response competition.
Asunto(s)
Atención , Hemorragia Intracraneal Hipertensiva/fisiopatología , Destreza Motora , Reconocimiento Visual de Modelos , Pulvinar/fisiopatología , Percepción Visual , Daño Encefálico Crónico/etiología , Daño Encefálico Crónico/fisiopatología , Femenino , Área de Dependencia-Independencia , Lateralidad Funcional , Humanos , Masculino , Persona de Mediana Edad , Desempeño Psicomotor , Pulvinar/lesiones , Tiempo de Reacción , Campos VisualesRESUMEN
Inhibition of return (IOR) is a mechanism whereby the attentional system favors novel locations by inhibiting already scanned ones. An important question is what the neural structures are involved. Recently, we studied a patient with damage to the superior colliculus (SC) and concluded that the SC generates IOR. However, it is possible that IOR is generated beyond the colliculus, for example, by the pulvinar. In this paper we tested three patients with unilateral damage to the pulvinar and demonstrated that the pulvinar is not necessary for IOR generation, providing additional support to the suggestion that the SC generates IOR. In addition, since we used monocular presentation, we were able to furnish behavioral evidence for nasal-temporal asymmetrical representation of visual input in the pulvinar.
Asunto(s)
Inhibición Psicológica , Pulvinar/lesiones , Pulvinar/fisiología , Tálamo/fisiología , Análisis de Varianza , Femenino , Lateralidad Funcional/fisiología , Humanos , Masculino , Persona de Mediana Edad , Inhibición Neural/fisiología , Estimulación Luminosa/métodos , Tiempo de Reacción/fisiología , Reproducibilidad de los Resultados , Colículos Superiores/fisiología , Campos Visuales/fisiologíaRESUMEN
We report a patient with unilateral damage to the rostral part of the pulvinar who was impaired in localizing stimuli in the inferior visual field contralateral to the lesion and who made errors in the binding of shape and color in that quadrant. The findings demonstrate the importance of the pulvinar in spatial coding and provide support for the function of the thalamus in binding of features. They also provide evidence for a homology between the visual field maps of the inferior and lateral subdivisions of the pulvinar in monkeys and in humans, such that the inferior visual field is represented in the rostral part of the nucleus.