agnosia visual - Visual Agnosia

Visual Agnosia: Seeing Without Recognition

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).

agnosia visual - Visual Agnosia

 

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

  1. Ardila, A. y Rosselli, M. (2007). Neuropsicología clínica. México, D. F.: El Manual Moderno.
  2. 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.
  3. Portellano, J. A. (2010). Introducción a la neuropsicología. Madrid: McGraw Hill.
  4. 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.
Summary
Agnosia visual (o no entender lo que estás viendo)
Article Name
Agnosia visual (o no entender lo que estás viendo)
Description
¿Alguna vez te has descubierto intentando comprender una imagen sin conseguirlo? Hoy explicamos el concepto de agnosia visual y sus tipos. Ver sin entender.
Author
Publisher Name
NeuronUP
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Lidia García Pérez

Lidia García Pérez

Licenciada en Psicología (Universidad Complutense de Madrid),Máster en Evaluación y Rehabilitación Neuropsicológicas (Universidad Camilo José Cela) y Máster en Neurociencia (Universidad Autónoma de Madrid).
Lidia García Pérez

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4 thoughts on “Visual Agnosia: Seeing Without Recognition

  1. Sara Gómez martinez Sunday May 21st, 2017 at 11:15 AM

    Artículo muy interesante. ¿Tenéis algún juego para trabajar gnosias visuales en niños?

    • Lidia
      Lidia Monday May 22nd, 2017 at 01:06 PM

      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 –

  2. chris Tuesday May 23rd, 2017 at 09:13 AM

    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

  3. Lidia
    Lidia Tuesday May 23rd, 2017 at 03:37 PM

    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-

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