Hubel and Wiesel’s research surrounding area V1 of the primary visual cortex provided one of the first descriptions of the receptive fields in mammals. By flashing various lines along the receptive field, Hubel and Wiesel were able to classify cortical neurons into two distinct groups; simple and complex (Hubel & Wiesel, 1963). The use of manually mapping the receptive fields with simple dots, lines and edges meant that they not only discovered orientation tuning in single neurons, but also described the columnar organisation of ocular dominance and orientation preferences in the cerebral cortex (Ringach, 2004). Although Hubel and Wiesel’s findings were an extreme advance in our understanding of the visual cortex (Wurtz, 2009), it became apparent that there were cells in the visual system that responded to stimuli far more complicated than orientated lines meaning that the cells in area V1 were much more modifiable than Hubel and Wiesel had suggested. In this essay, Hubel and Wiesel’s classic receptive field shall be discussed along with reasons as to why it can no longer offer us a satisfactory explanation into visual perception. First to be discussed are the specific types of cells which were defined in Hubel and Wiesel’s classic experiment into the striate cortex.
Hubel and Wiesel defined the classic receptive field as a restricted region of the visual cortex. If a specific stimulus fell into this area, this may drive the cell to evoke action potential responses (Zipser, Lamme & Schiller, 1996). By shining orientated slits of light into the cat’s eye, they were able to discover that each cell had its own specific stimulus requirements (Barlow, 1982). Different cells differed from each other in many ways; some preferred a spe...
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...och, C. (2013). Brain cells for grandmother. Retrieved on February 20, 2014 from https://www2.le.ac.uk/centres/csn/Publications/scientificamerican0213- 30.pdf
Ringach, D. L. (2004). Mapping receptive fields in primary visual cortex. Journal of Physiology, 558, 717-728.
Rossi, A. F., Desimone, R., & Ungerleider, L. G. (2001). Contextual modulation in primary visual cortex of macaques. The Journal of Neuroscience, 21, 1698-1709.
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Wurtz, R. H. (2009). Recounting the impact of Hubel and Wiesel. The Journal of Physiology, 587, 2817-2823
Zipser, K., Lamme, V. A. F., & Schiller, P. H. (1996). Contextual modulation in primary visual cortex. The Journal of Neuroscience, 16, 7376-7389.
The ultimate goal for a system of visual perception is representing visual scenes. It is generally assumed that this requires an initial ‘break-down’ of complex visual stimuli into some kind of “discrete subunits” (De Valois & De Valois, 1980, p.316) which can then be passed on and further processed by the brain. The task thus arises of identifying these subunits as well as the means by which the visual system interprets and processes sensory input. An approach to visual scene analysis that prevailed for many years was that of individual cortical cells being ‘feature detectors’ with particular response-criteria. Though not self-proclaimed, Hubel and Wiesel’s theory of a hierarchical visual system employs a form of such feature detectors. I will here discuss: the origins of the feature detection theory; Hubel and Wiesel’s hierarchical theory of visual perception; criticism of the hierarchical nature of the theory; an alternative theory of receptive-field cells as spatial frequency detectors; and the possibility of reconciling these two theories with reference to parallel processing.
According to Dr. Vilayanur Ramachandran, in his movie “Secrets of the Mind,” our vision system is divided into two parts, one with our eyes, and the other with our brain. He also says that there are two different pathways in which our brain uses to “see.” One of these pathways, he calls the evolutionary new pathway (the more sophisticated pathway) in which our eyes see, then the information is sent to the thalamus, and eventually entering the visual cortex of the brain. This pathway is the conscious part of seeing. The other pathway Dr. Ramachandran says is more prominent, as well as evolutionarily primitive. An iguana uses this system of seeing. In this second pathway, information enters through the eyes, and then is sent to the brain stem, which in turn relays the information to the higher center of the brain. Dr. Ramachandran says that this second system is used to orientate our eyes to look at things, especially movement. Dr. Ramachandran has looked at patients with what is known as blind-sight to form his hypothesis.
Sajda P. & Finkle, L.H. (1995) Intermediate Visual Representations and the Construction of Surface Perception. Journal of Cognitive Neuroscience, 7, 267-291.
A camera lens focuses patterns of light onto film which records the image exactly. If the lens is out of focus or partially covered, a b lurry or obscured picture will result. The film is a recording device, it does not interpret and select what it portrays. Images from a camera are objective in a very literal sense. Seeing, however, is not such a seamless process. Our eyes work similarly to a camera in that they have a lens which focuses a real image on our retina, a light sensitive sheet of cells. This retinal image is a portrayal of the world as it truly is. The image which we see, however, is not this image. By considering a normal vis ual property as well as an uncommon ocular disorder the process of formulating our visual sense will be investigated. There is a difference between the picture recorded on film and that recorded by our brains. For purposes of this paper, the term "retina l image" is used as an analogy to a photographic image (one without interpretation by the brain). The phrase "brain image" refers to the retinal image post-brain interpretation. The brain image is the image which would be described by the person, the imag e which is thought of as seeing.
There are a limited number of ways to discover and understand how the human mind works and reacts to things. One can not sit and directly observe the brain and eye working together (James, Schneider & Rodgers, 1994). The concept behind mental rotation of images tries to do this by measuring reaction times as the angular disparity of an object increases. Thus, demonstrating the time it takes for the eye and brain to make a connection when presented with a stimulus. Though our experiment was solely limited to calculating reaction times to mental rotations of images, Wohlschlager and Wohlschlager (1998) took this concept one step further to see if mental object rotation and manual object rotation shared a common thought process in our brain.
Ratey, John J., and Albert M. Galaburda. A User's Guide to the Brain: Perception, Attention, and
Vision is often taken for granted and often over-looked for its marvelous intricacies. The brain processes the information it is given very quickly with immense synchrony. MIT graduate student, Bhavin R. Sheth relates a fine illustraton. “Mr. Sheth compares vision to an orchestra, where clusters of cells in different parts of the brain cooperate to process different
30 different areas of the brain helps to process color, light, form, and motion to create a single
Lee, T. S., Yang, C. F., Romero, R. D., & Mumford, D. (2002). Neural activity in early visual
Lissauer (1890) made an important distinction between Apperceptive and Associative Agnosia. He found that Apperceptive recognition can occur without acuity or other sensory functions whereas associative cannot. Ettlinger (1956) can follow on with his research sh...
S.A. Clark, T. A. (1988). Receptive fields in the body-surface map in adult cortex defined by temporally correlated inputs. Nature, 332.
Kandel, E. R., J. H. Schwarz, and T. M. Jessel. Principles of Neural Science. 3rd ed. Elsevier. New York: 1991.
Our objective for this lab was to learn more about the distribution and capabilities of sensory cells. In Table 1, the mean for the angle stimulus detected was 78° and the mean for the angle color detected was 58°. The results from the table indicated that I was able to detect an object was near before I was able to detect the color of the object. Being able to detect an object before detecting the objects’ color could be explained by the type of photoreceptors located in the center and periphery of the retina. Based on my results from Table 1, I was able to conclude that the photoreceptor that is most common in the center of my eye is cone cells. I was able to conclude this due to the mean angle to which color was detected. Thus, the photoreceptor most common in the periphery would be the rod cells.
In this lab we apply the technique known as a two point discrimination test. This test will allow us to determine which regions of the skin are best able to discriminate between two simultaneous sensory impulses. According to (Haggard et al. 2007), tactile discrimination depends on the size of the receptive fields located on the somatosensory neurons. However receptive fields for other types of sensations are located elsewhere. For vision we find that the receptive fields are located inside the visual cortex, and for hearing we find receptive fields in the auditory cortex. The ability for the body to discriminate two points depends on how well that area of the body is innervated with neurons; and thus conferring to the size of the receptive fields (Haggard et al. 2007). It is important to note that the size of the receptive field generally decreases in correlation to higher innervations. As was seen in the retinal receptive fields, the peripheries of tissue had contained larger receptive fields (Hartline, 1940). In our test we hypothesized that the finger region will be able to discriminate better than the forearm. This means that they will be much more innervated with neurons than the forearm, and likewise contain smaller receptive fields. This also means that convergence is closer to a 1:1 ratio, and is less the case the farther from the fingers we go. We also think that the amount of convergence is varied with each individual. We will test to see if two people will have different interpretations of these results.
There are many different Visual Perception principles in perception. The main principles are Gestalt. Gestalt is a German word meaning 'form' or 'shape'. Gestalt psychologists formulated a series of principles that describe how t...