Patients With Hemianopsia, Essay Example

The Effect of Arm Positions on the Visual Ability in Patients with Hemianopsia

Schendel and Robertson presented a study where they hypothesized that a patient that was suffering from hemianopsia, the loss of vision in a half of the visual field was able to improve his vision. The study proposed that extending the arm on the affected side of the body activates the bimodal visual-tactile neurons, and these neurons enable the brain to detect the visual stimuli in the Hemianopic field (Schendel & Robertson, 2004). This study brings about a number of questions and comments about the brain, cognitive systems in humans, research and the importance of how readers interpret research results. The authors were satisfied that the study improved the subject’s vision; however, a further study revealed that arm position does not affect the visual ability in patients with hemianopsia.

The study Schendel and Robertson presented consisted of only one subject. The subject suffered a stroke that left him with severe left hemianopsia. They conducted two baseline sessions in the study. The left arm was placed in the lap of the subject and another session where the left arm was extended out front of him. The subject was asked to detect the computerized visual symbol that appeared on the screen (Schendel & Robertson, 2004). They requested that the subject not to guess where the dot would be without first seeing it. The results of the study indicated the subject was able to improve his affected visual field when his left arm was extended out (Schendel & Robertson, 2004).

The results of this study bring attention to relevant and important factors when it comes to research studies and interpreting the results. A significant research study starts with an appropriate population of participants who share the same or very similar characteristics. The population is representative of the conditions/issues being researched. In the study for the contralesional visual field by Schendel and Robertson, they did not select a relevant population to consider for the arm test. They selected only one individual to study, and presented findings for all to consider. There was not any mention of why the study consisted of only one individual. If the authors wanted to conduct a valid study, they should have chosen a small sample of the population diagnosed with hemianopsia or a group of all patients suffering from hemianopsia (Bordens, 2008). The study produced a relatively low external validity because it did not correctly produce a sample of participants who were representative of the whole and made a generalization of the results about all hemianopsia patients regardless of participating in the study (Bordens, 2008). The sample was biased. There was not a valid sample to make these hypothesized results.

Besides the sample size that was utilized in the study, there were other issues that made the study unreliable. The participant was not an atypical patient diagnosed with hemianopsia. Based on the methods employed in the study, the participant did not perform well enough to conclude he had spared visual ability in his various blind spots (Smith, et.al, 2008). There was also insufficient monitoring of fixation in the visual field mapping that could easily dismiss the claims that attenuate visual loss. Matter of fact it was a stronger probability that the subject guessed on the responses because of the insufficient monitoring (Smith, et.al, 2008).

The study by Schendel and Robertson further extenuated the need for the reader to be cautious of interpreting the results of studies. Smith, Lane and Schenk conducted a similar study to Schendel and Robertson’s to detect the effect of arm position on visual ability in hemianopic patients because they wanted to validate the results of the study. Smith, Lane and Schenk solved some of the problems with the earlier study by utilizing five participants, subjects with dense hemianopsia; utilizing a fixation that was monitored with a manual Tuebinger Perimeter and video-based eye-tracking. The case study by Smith’s group concluded that the positioning of the arm close to the visual stimuli did not influence visual perception in the hemianopic field (Smith, 2008).

According to Smith et al. (2008), Arm position does not improve the visual ability but it will direct the subject’s attention to the affected field. Patients with some residual vision could benefit from the attention attracted by arm movement. The detection mechanism on the degraded stimulus was improved when spatial attention was given to the perceived area.  Smith et al. suggestion was consistent with a previous study (Reed, Grubb, & Steele, 2006) found that when subjects were moving their hands and fingers the spatial attention shifted towards the same visual field where the arm was presented.

Schendel and Robertson reported that bimodal visual-tactile neurons have been found in some frontal and parietal areas and in parts of subcritical nuclei in particular the putamen. These areas match with some anatomical regions that discussed on the attention networks theory. This may explain Schendel and Robertson consideration of the bimodal neurons. While attention modulation is the best explanation for the WM patient improvement in the Schendel and Robertson study, there is no evidence that proves that attention networks improves the visual ability in patients with hemianopsia.  Further studies are needed to determine the attention effects on the hemianopic patients after strokes.

So the reader of the case study needs to keep in mind whether or not the study is evidenced-based. An evidence-based study consists of clinical case study that utilizes measurements and analysis protocols that are supported by systematic evaluation. In addition, the study should be able to accomplish the goals of research which are to describe, explain and predict events that relate to the phenomenon and to control the variables that may affect the results (Bordens, 2008).

In Ruz (2006) study that attempted to explain the functions of the brain’s “attention” mechanisms. The general scientific principles of the brain’s attention are described in three networks: alerting, orienting and executive. Alerting network is responsible for the recognition of the alert state by generating a chemical reaction in response to expect incoming stimulus (Ruz, 2006). The integrated areas of the right parietal and frontal hemispheres may be responsible for altering network. The orienting network that selects the stimuli from the sensory inputs has also been reported in Ruz study. The voluntary responses are managed by areas in the superior parietal lobe, frontal eye fields, superior colliculus, and some nuclei in the thalamus. The reflexive or automatic alterations in attention produced by the appearance of unexpected stimuli at different locations appear to be decided by activations in the temporo-parietal junction (Ruz, 2006).

Conclusion

Schendel and Robertson attempted to make a case that a patient diagnosed with hemianopsia can improve his visual ability when his arm is placed in a certain position. The study; however, only provided some insight into the brain, how it works and the cognitive systems in humans. The study failed to solidify the actual results of the study because it did not appear to be a well produced and thoroughly presented research study.

References

Bordens, K. S., & Abbott, B. B. (2008). Research design and methods: A process approach (7^th ed.). New York: McGraw-Hill. ISBN-13: 9780073129068

Mechsner, F. (2004). A Psychological Approach to Human Voluntary Movements. Journal of Motor Behavior, 36(4), 355-370.

Ruz, M. (2006). Let the Brain Explain the Mind: the Case of Attention. Philosophical Psychology, 19(4), 495-505.

Smith, D., Lane, A & Schenk, T (2008). Arm Position Does Not Attenuate Visual Loss in Patients with Homonymous Field Deficits. Neuropsychologia, 46, 2320-2325.