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Case 1

Case # 1: Harold has several visual deficits. First, he reports that he cannot “see” anything in his right visual field. However, if an object moves within the right visual field, he can say what direction it moved but cannot name the object that moved. Secondly, he is colorblind (dichromatic red-green colorblindness) in his intact left visual field. Based on this limited information, speculate what could be going on in Harold’s brain that would produce such deficits.


While choosing to speculate can be ripe for errors, based on lessons nine and ten teachings, Harold appears to be afflicted with blindsight. In certain sporadic cases, the subject can distinguish movement within the visual field but not identify anything visually within the field at all. This affliction is known as apperceptive visual agnosia, whereby the subject can detect movement but cannot perceive an object as a singular image. From our teachings, it is suspected that individuals afflicted with blind-sight have some damage to newer cortical pathways yet still have older pathways to the superior colliculus intact (The Pennsylvania State University, 2023).

Harold has dichromatic red-green colorblindness in his intact and functioning left visual field. As we have learned from our lectures, the optic nerve consists of ganglion cells that process information from photoreceptors. There are three subtypes of ganglion cells: M, P, and K, representing their associated pathway to the lateral geniculate nucleus (LGN) of the thalamus. In Harold’s case, it appears his red-green colorblindness is related to parvocellular cellular response or the lack thereof. Since this affliction seems to be commonly associated with genetics, one could hypothesize that an insufficient amount of ganglion-type P cells impacts Harold’s ability to interpret colors on the red-green spectrum. To rule this out, more information would be required to complete the case study. At a minimum, the parvocellular pathways seem to be degraded (Freberg, 2018).

Case 2

Jane was in a car accident. The accident damaged the magnocellular pathways in the right hemisphere and the parvocellular pathways in the left hemisphere. What would you imagine her visual performance would be like after the accident?


Jane suffers from magnocellular pathway damage in the right hemisphere of her brain, proximate to a motor vehicle accident. Likely, Jane will have a degraded response to movement and contrast in the right visual field. She will not have substantial degradation of color processing in the field but will likely exhibit difficulty processing low-contrast objects and movement. Damage to her parvocellular pathways in the left hemisphere of her brain will affect her right visual field as parvocellular pathways potentially also impact the red-green color spectrum. In essence, Jane could suffer from significant vision impairment related to motion detection, the contrast of objects, and their associated colors (The Pennsylvania State University, 2023).

Case 3:

Matthew damaged the dorsal pathway of his left hemisphere in a motorcycle accident. What problems do you think he may have due to this damage? Also, he was born without the inhibiting connections of horizontal cells between photoreceptor-bipolar interactions. Thus, his horizontal cells cannot work properly to inhibit surrounding bipolar receptive fields. What types of function would most likely be lost because of this (name it) and what type of deficits would you expect from the loss of this function?


Matthew presents with damage to the dorsal pathway of his left hemisphere proximate to a motorcycle accident. The Dorsal Stream, as noted in our lectures, is responsible for information about visual movement. This pathway is primarily comprised of ganglionic type M cells. This pathway is primarily associated with two regions: the medial temporal and medial superior regions. This region is commonly known as the “how” pathway and is responsible for providing information on how to interact with objects. Damage to the dorsal pathway frequently presents as difficulty detecting motion. Matthew could be diagnosed with Akinetopsia or motion blindness, (The Pennsylvania State University, 2023).

Matthew also presents with a preexisting condition involving inhibiting connections of horizontal cells between photoreceptor-bipolar interactions. Essentially, it appears Matthew was born without horizontal cells which dramatically reduces his ability to depolarize light. Likely, Matthew would have photosensitivity or an acute sensitivity to light, (The Pennsylvania State University, 2023).


Freberg, L. (2018). Discovering Behavioral Neuroscience: An Introduction to Biological Psychology (4th ed.).

The Pennsylvania State University. (2023). Lesson 10, Vision Part II: The Brain and Vision. The Pennsylvania State University.

The Pennsylvania State University. (2023, 03 04). Lesson 9, Vision Part I: The Eye [Lecture Notes]. The Pennsylvania State University.

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