The Effects of Corpus Callosum Severance on Visual Perception: Juan’s Case

QUESTION

Juan as a young boy suffered from chronic epileptic seizures, and had a procedure done to sever his corpus callosum. He is shown an object that is flashed only to the right side of a computer screen. How will he be able to report the image that was shown? Selected answer will be automatically saved. For keyboard navigation, press up/down arrow keys to select an answer. a he will be able to draw it with his left hand. b he will be able to name it out loud. c he will be able to name it and draw it with his left hand. d he will be unable to report what was shown

ANSWER

The Effects of Corpus Callosum Severance on Visual Perception: Juan’s Case

Introduction

This essay explores the case of Juan, who underwent a procedure to sever his corpus callosum due to chronic epileptic seizures during his childhood. The corpus callosum is a bundle of nerve fibers that connects the two hemispheres of the brain, facilitating communication between them. By examining the consequences of corpus callosum severance, particularly in relation to visual perception, we can better understand how this procedure impacts Juan’s ability to report visual stimuli.

The Role of the Corpus Callosum in Visual Perception

The corpus callosum plays a critical role in integrating and sharing information between the left and right hemispheres of the brain. When an object is presented to one side of the visual field, the information is initially processed by the opposite hemisphere. In individuals with an intact corpus callosum, this information is rapidly transmitted to the other hemisphere, allowing for a cohesive perception of the visual stimulus.

Impact of Corpus Callosum Severance on Visual Perception

In Juan’s case, the severance of his corpus callosum disrupts the communication between the hemispheres. When an object is flashed only to the right side of a computer screen, the visual information is processed by the left hemisphere. However, due to the severed corpus callosum, the information cannot be transmitted to the right hemisphere for holistic perception and subsequent verbal reporting.

Juan’s Ability to Report the Shown Object

Based on the understanding of corpus callosum severance, Juan will be unable to verbally report the image that was shown when it is presented solely to the right visual field. The left hemisphere, which is responsible for language processing in most individuals, lacks access to the visual information. Therefore, Juan will not be able to name the object out loud (option B).

Alternative Modes of Reporting

Interestingly, although Juan cannot verbally report the image, studies have shown that individuals with a severed corpus callosum can demonstrate partial awareness of the stimuli through non-verbal means. In this context, Juan may still be able to draw the object using his left hand (option A). Since the left hand is primarily controlled by the right hemisphere, which processed the visual information, Juan may exhibit a form of “alien hand syndrome” where his left hand performs actions without conscious control. This phenomenon allows him to depict the image through drawing.

Conclusion

The severance of Juan’s corpus callosum has significant implications for his visual perception and reporting abilities. While he cannot verbally name the object shown when presented only to the right visual field, he may still demonstrate partial awareness and non-verbal reporting through drawing using his left hand. This case highlights the intricate role of the corpus callosum in facilitating interhemispheric communication and emphasizes the importance of understanding its functional consequences in individuals who have undergone such procedures. Further research on corpus callosum severance and its impact on perception can contribute to our understanding of brain function and inform therapeutic interventions for individuals like Juan.