Have you ever found yourself struggling to understand an image without being able to? Have you tried perhaps to find some similarity between what you see and some well-known object, in an attempt to make sense of that image that you had never seen before? You may have experienced this sensation for a moment, for example, when looking at a magnetic resonance or an ultrasound image for the first time; or when looking at an abstract painting whose title induces you to strive towards recognizing a specific object in it.
Visual agnosia is an acquired perceptual disorder caused by brain damage, in which the affected person is unable to recognize previously known visual stimuli, despite preservation of at least some sensation (there is no blindness) [1] and despite being able to recognize the same stimuli through other senses, such as touch or hearing.
These individuals can see, but they cannot understand what they see. This occurs either when the brain fails to produce a single, coherent image from the visual features of the object present, what is called apperceptive visual agnosia. Or when, despite being able to form an image (percept), it cannot be associated with anything already known, and so no meaning can be assigned to what the visual information is or to its function. This second case is known as associative visual agnosia [1, 2].
TYPES OF VISUAL AGNOSIA
In apperceptive visual agnosia, due to a failure to form a coherent percept, individuals cannot identify the shape of objects and so have trouble recognizing the differences between similar objects, copying a drawing of these simple shapes, or mentally reconstructing forms [1].
In associative visual agnosia, individuals can correctly perceive shapes, but they cannot interpret them. Individuals can match similar figures and copy a drawing, but cannot associate shapes with objects [1] (e.g., associating a rectangle with a book, or a glove with a hand).
Poppelreuter Test (superimposed figures) used in the assessment of visual agnosia. People with apperceptive agnosia are not able to identify the different line drawings of objectse.g., cannot color the individual items or trace the outlines of the figures.) People with associative agnosia can correctly identify the different figures but cannot recognize the objects.
In addition, visual agnosia can selectively affect the recognition of different types of stimuli, such as objects (visual object agnosia), colors (color agnosia or achromatognosia), words (gnostic alexia), faces (prosopagnosia) or it can affect the integration of the elements of a complex stimulus (simultaneous agnosia or simultagnosia). [1,3]
Seeing Without Recognizing: How Is This Possible?
The specificity of these disorders is best understood if one considers the hierarchical manner in which our nervous system processes images.
Visual information is processed both in parallel (the photoreceptors in the retina transmit simultaneously different types of visual information, such as levels of light intensity, wavelengths, colors, etc.) and in series (from the retina via the thalamus to the cerebral cortex). [4]
At an early stage of serial processing, features such as the shape and structure of the stimulus are processed; but if a lesion occurs in the brain areas involved in this task, a specific type of blindness (called cortical blindness) can occur [2].
At higher stages of visual recognition, visual features are integrated into coherent object representations, and meaning is also assigned to objects [2]. Thus, localized brain lesions affecting higher levels of processing can alter these particular aspects of perception without altering sensory ability, and as a result, the person with agnosia can see the object but cannot interpret it.
On the other hand, that there is a disorder such as prosopagnosia (agnosia for faces) speaks to the importance (evolutionarily speaking) of the recognition of this specific type of stimulus for our survival, given that nature has entrusted its processing to a specific part of the brain.
NeuronUP has developed many useful exercises for improving gnosis with various stimuli, including faces. Click here to see them.
By: Lidia García Pérez
Translated by Silvia Duque
BIBLIOGRAPHY
- Ardila, A. y Rosselli, M. (2007). Neuropsicología clínica. México, D. F.: El Manual Moderno.
- Fernández-Guinea, S. (2011). Apraxias y agnosias. En Bruna, O., Roig, T., Puyuelo, M., Junqué, C. y Rueano, A. (Eds.). Rehabilitación neuropsicológica: intervención y práctica clínica (p. 83-108). Barcelona: ElsevierMasson.
- Portellano, J. A. (2010). Introducción a la neuropsicología. Madrid: McGraw Hill.
- Kandel, E. R., Schwartz, J. H., Jessell, T. M., & Agud Aparicio, J. L. (2001). Principios de neurociencia(4a ed., 1a ed. en español.). Madrid: McGraw-Hill.
Lidia García Pérez
Latest posts by Lidia García Pérez (see all)
- Confabulations (Vol. II): theoretical models - February 5, 2019
- Confabulations (Vol. I): classification, neuropathology and cognitive mechanisms - January 29, 2019
- The cognitive mechanisms of errorless learning - October 23, 2018
Artículo muy interesante. ¿Tenéis algún juego para trabajar gnosias visuales en niños?
Hola Sara, gracias por tu comentario y por tu pregunta,
En primer lugar conviene aclarar que neuronUP es una herramienta de rehabilitación neurocognitiva, pensada para ser manejada por profesionales de la neurorrehabilitación. En este sentido, dispone de ejercicios para entrenar las gnosias (o las agnosias) de pacientes con alguna alteración cognitiva, los cuales son altamente personalizables ya que el profesional puede variar en ellos diversos parámetros en función del perfil del paciente (edad, perfil cognitivo y psicológico) y en función del objetivo terapéutico.
Por tanto, puesto que son ejercicios personalizables en múltiples dimensiones sí se pueden utilizar con niños, como con personas de cualquier edad; pero el criterio para su personalización y en general su uso, ha de llevarlo a cabo un profesional con formación en evaluación y rehabilitación neuropsicológicas, que pueda establecer previamente el perfil neuropsicológico del paciente (que en el caso de los niños, considerará de forma especialmente relevante su nivel de funcionamiento intelectual, madurativo y del lenguaje, entre otras funciones cognitivas) y en función de ello, que pueda establecer también cuáles son los objetivos terapéuticos a plantear en cada sesión de trabajo con la herramienta.
Si eres profesional de la neurorrehabilitación puedes adquirir de forma gratuita la demo de neuronUP y durante 10 días explorar sus posibilidades: https://www.neuronup.com/es/request/demo/ext/1
Espero haberte resuelto la duda, muchas gracias por tu interés,
Lidia GP –
This is an extremely interesting article on a topic that I was up until now unaware of. I suspect that there are indeed games for kids and adults alike that can help with this condition
Thank you very much for your comments Chris,
Regarding what you comment on the games, my opinion is that it depends on the goals you have. In other words, if the objectivl is just to stimulate the gnosis of healthy young children (for example at school or at home), any age-adjusted game takes this aspect into account: intense colors, shapes and textures, sounds, all stimulate perception, which develops in the first ages. Thus, games intended for young children (especially 0-2 years) often take this in consideration.
On the other hand, if your interest is to help people (children or adults) with agnosia or other problems due to adquired brain damage, my recommendation is they be evaluated and rehabilitated by brain injury care professionals.
Regards,
Lidia GP-
les he leido un grandioso articulo para mi!. Mi caso es que mi madre tiene 92 años, y ha empezado a reclamarme que la ropa que tiene y tendidos y cobijas no son los que ella a tenido y que yo se la he cambiado!, se vovio un gran problema y no se que hacer!, entiendo en el artículo que se ha generado un daño cerebral de orden neuroronal. Cómo me ayudan para que ella no reclame cosas que no son? mil gracias
Hola Nestor,
Gracias por tus palabras y por compartir con nosotros tu preocupación. Desde NeuronUP te recomendamos que asistas con tu madre a un especialista que le pueda diagnosticar. Te mandamos mucho ánimo.
¡Un saludo y gracias de nuevo!
Me parece que la información del artículo es muy útil. Los test psicométricos son instrumentos útiles de
evaluación, pero tienen que aplicarse e interpretarse por un especialista,
de manera opuesta podríamos caer en el error de hacer malas interpretaciones de los resultados y hacer una selección equivocada de un candidato.
Te agradezco mucho por la información.
Gracias a tí por tu comentario, María
Un saludo,
Lidia GP-