The slowness principle provides a natural hypothesis for the functional organization of visual cortex and possibly also other sensory areas.
This difference in time scales leads to the central idea of the slowness principle: By finding and extracting slowly varying output signals from the quickly varying input signal we seek to recover the underlying external causes of the sensory input. Representation of the environment in the brain should vary on a slow If it is to explicitly represent the original visual elements, the internal Single pixel in a video camera, are sensitive to very small changes in the environment, and thus vary on a much faster time scale ( Figure 2). Like the responses of individual retinal receptors or the gray-scale values of a On the other hand, the primary sensory signal, For example, behaviourally relevant visual elements (objects and their attributes) are visible for extended periods of time and change with time in a continuous fashion, on a time scale of seconds. Using these regularities as a guide, the brain is able to form a meaningful representation of its environment.Īt the heart of the slowness principle is one of these regularities, namely that external causes are persistent in time. An important idea in the field is that objects in the world have common structure, which results in statistical regularities in the sensory input. Problem of reconstructing the external causes of the sensory input to allow generation of adequate behaviour (see AlHacen, Alī al-Ḥasan ibn al-Ḥasan ibn al-Haytham, 10th century, cited in Smith, 2001 Helmholtz, 1910).įor example, when looking at a picture on a computer screen, we see the objects that are present on it and their relative position in the image, rather than the color of the individual pixels.Īn active area of research in computational neuroscience is concerned with the way the brain learns to form a representation of these external causes from raw sensory input. In other words, the brain may use this insight to learn the transformation that maps the blue traces into the green ones.įrom a computational point of view, one can think of perception as the Since objects in the world are persistent and their appearance changes mostly in a continuous way, these high-level signals change smoothly over time, which can be leveraged to extract them from the sensory input in an unsupervised way. To produce meaningful behavior, the brain needs to reconstruct the high-level signals regarding, for instance, the monkey's presence and position (green traces). While the information about the monkey is contained in their activity, it is distributed in a non-linear way over millions of receptors. As observers, we experience this visual scene only through the activity of sensory receptors in the retina, whose response is comparable to raw measurements of light intensity in localized parts the visual field (blue traces).
#Thebrain version 9 beata features movie
The movie strip (top) represents a natural visual scene, in which a monkey stands up from a suspended rope, then leaves the field of view to the left. Figure 2: Illustration of the slowness principle.
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