Monocular Occlusion on Spatial Attention - Research Paper Example

? Monocular occlusion on Spatial Attention Clinical psychology is a field in psychology that specializes with treating mental illnesses and disorders like abnormal behavior and psychiatric problems. This field of psychology integrates treatment of complicated human problems and psychological sciences through experimentation. Clinical psychology concerns itself with understanding, relieving and preventing psychologically based dysfunction and stress. It aims to promote personal development and subjective well-being of those affected. In some countries, clinical psychology is regulated as health care job. Experimental clinical psychology gives someone a diverse opportunity to apply theory and research methods that allow someone to test the practical application of these methods. Experiments are conducted to test the suitability of a theory in treating a known disorder and it efficacy in healing that individual. Experimental psychology studies and investigate what causes abnormal behavior and its treatment. Cross sectional and longitudinal designs are some of the most commonly used study designs for identifying causes of illnesses. Case reports and randomized clinical trials (RCTs) are some of the treatment evaluation designs used, and RCTs have become benchmark tools in biomedical research. Majority of studies involved in clinical psychology experiments derive their inferences from observation. Some experts claim that RCTs are impractical or impossible in some circumstances, but they remain extremely useful tools when conducting an experiment. This paper’s objective is to highlight an experiment on clinical psychology and its relevance in today’s ongoing development in clinical psychology. This study is going to focus its attention on the effects of monocular eye patching on attention biases in normal subjects. Introduction Single eye viewing has an effect on how people perceive images in their line of sight and the dominance of one eye over the other. This affects patients who have suffered trauma to the head. When ordinary respondents differentiate vertical lines using both eyes, they illustrate that a distant attention bias by bisecting lines away from their body (Cattaneo & Vecchi, 2011). In a viewing experiment, it was found that most participants who were right eye dominant, had relatively closer bisections and a reduced far bias when they only used their right eye. This was compared with the results garnered when their right eyes were covered, and it is necessary to note that these subjects were all right eye dominant. The group that was “left eye” dominant had relatively closer bisections and a reduced far bias. In the Hemi-spatial placement experiment, hemispheric engagement was manipulated by having participants perform a similar task in right and left Hemi-space. It was established that right eye dominant subjects had a reduced far bias in right Hemi-space relative to left Hemi-space. The left eye dominant subjects showed the opposite pattern while having a diminished far bias in the left Hemi-space. In concluding, spatial representation influenced performance more for the non-dominant eye than left or right dominant eyes, for both groups. The result suggested that single eye viewing is associated with preferential activation of attention systems in the contra-lateral hemisphere. The results showed that right eye dominant subjects have right hemispheres biased towards far space. Eye dominance relates to hemispheric specialization for attention (Cattaneo & Vecchi, 2011). Hemispheric injury may induce an attention bias and a failure to report, orient or respond to meaningful stimuli in the contralesional space, which is termed as unilateral spatial neglect. Lesions caused by various forms inflammation on cortical structures like the hypothalamus, thalamus, basal ganglia, intramlaminar nuclei, midbrain tegmentum, cingulate Gyrus, prefrontal cortex, parietal cortex and occipital cortex. Any disorder on these areas can cause unilateral spatial neglect (Howard, 2012). In human patients, patching the ipsilesional eye can be used to manupulate the activity of contra-lesional colliculus and the corresponding hemisphere on the same side. This reduces the activity of the contra-lesional colliculus and hemisphere while restoring the balance of attention and decrease the severity of neglect. Stimulation of the eye that remains open results in increased activation of the ipsilesional hemisphere. This experiment sets out to investigate whether single eye patching can influence activation of lateralized attentional system. It also seeks to establish if it would be possible to induce an opposite hemispheric asymmetries by patching up alternative eyes. The assumption would be that attentional systems contra-lateral to the viewing eye would be relatively activated with attentional systems contra-lateral to the covered up eye (Demetriou & Raftopoulos, 2004). The effects of the single eye viewing on attentional biases were tested by asking normal subjects to bisect radial lines. This was carried out at the intersection of transverse planes with either one or the other eye covered up. Having normal subjects bisect radial lines, their performance is less likely to reach ceiling levels that could obscure the effects of attentional variables. Coupled to this, the extent of monocular horizontal fields is different for the two eyes while that for a vertical field is identical. Consistent differences between the effects of the right eye patching and left eye patching in normal subjects could support the notion that covering the eye produces asymmetric activation of the hemispheres (Taub et al, 2012). Eye dominance was also considered as a factor that could identify whether monocular produces an attentional bias link with visual laterality preferences (Taub et al, 2012). Viewing Experiment Seventeen undergraduate university student volunteers participated in the experimental study. The study requires that all participants be native English speakers for the purposes of ensuring clear and concise communication between the subjects and test conductors. All were screened for any history of brain injury and potential learning disorders. Sighting eye dominance was determined for each subject using a modification of the Porta test (Healy & Proctor, 2003) and a hole in the hand test. In the Porta test, participants were asked to extend one of their arms and align their index finger vertically to the corner of the room with both of their eyes open. They were then told to close one eye or the other alternately and report which eye closure caused the largest alignment distortion. The dominant eye was the one that caused the more change in alignment (Healy & Proctor, 2003). The hole in the hand test is also another way of determining the dominant eye. It is performed by asking the participants to make a small hole between their outstretched hands and look at a small object. They were then asked to move their hands towards their face without losing view of the feature of interest. The eye they brought their hands back to, without losing sight of the object was recorded as the dominant eye. The participants were classified as the right eye dominant if they registered as right eye dominant on both tests and the left dominant were classified the same way. Those subjects with mixed eye dominance by showing inconsistent results in both tests were excluded from the experiment. Of the seventeen subjects, ten were right eye dominant, five were left eye dominant, and two were mixed eye dominant (Healy & Proctor, 2003). The test also required that the participants be classified as right or left handed for writing. Apparatus Black lines of 2.5 mm width were printed on 220 ? 280 mm white paper, one line per sheet. Parallel orientation of the lines was done to the long axis of the paper and was centered on the page, both horizontally and vertically. The lines were of five different line lengths; 2, 4, 8, 16 and 22 cm. A black, opaque eye patch was used to obscure vision in one eye. Method The participants were required to sit at a table where they were asked to bisect lines that were put before them. Lines were oriented in the radial/vertical direction in the transverse plane. Each subject was asked to bisect twenty-five lines with each eye. One set of twenty-five lines consisted of five examples of each line length that were intermixed in a semi-randomized fashion. While wearing an eye patch on one eye, subjects bisected the first set of twenty-five lines and the second set of lines while wearing the patch over the other eye. Counter balancing, of eye patches, was done across participants to ensure that half the subjects bisected the lines with their left eyes first, and the other half with their right eye first. Results Bisection error of the lines was measured to the accuracy of 0.5 mm from the true midpoint. A positive value was arbitrarily attached to errors that were distal or beyond the midpoint and errors that were proximal to the midpoint were given a negative value. The standard deviations and means were calculated for each line length and each participant’s eye condition. An analysis of variance (ANOVA) was done on repeated measurements of data. Mean errors made at each line length (2, 4, 8, 16 and 22) were used to come up with the subject factors including the eye used (left or right). The in between subject factors were for the eye dominance groups i.e. right eye or left eye dominant subjects. The analysis revealed a considerable main effect of line, an indication that subjects made increasingly positive errors with increasing line size as expected for radial line bisections in normal subjects F (4, 12) = 6.64, P = 0.005. The experiment did not reveal a main effect for an eye, which was a sign of the effect of the single eye patching independent of eye preference. This did not change the error bias in a consistent manner. There was a substantial eye by group interaction F (4, 12) = 7.32, P = 0.003. This interaction indicates that subjects who were “left eye” dominant performed better, making smaller positive errors and bisecting the lines relatively nearer to their body. Subjects who were right eye dominant performed better making smaller errors and bisecting the line nearer to their bodies. From the experiment, all the individuals who made greater far errors when looking from the right eye relative to the left eye were found to belong in the left eye dominant group. Discussion Previous experiments have shown normal subjects having a consistent attentional bias on the radial bisection task. The effect is proportional to line length such that greater absolute errors towards the far end of the line are made with increasing line lengths. The portion of a line to which greater attention is allocated appears longer than an equal length of line to which attention is not directed (Catteneo & Vecchi, 2011). When participants bisect towards the far end of the line, they are apparently attending more to the far end line and overestimating its length. They could also be conversely focusing less to the near end of the line and underrating its length (Catteneo & Vecchi, 2011). This experiment also replicates these same general findings in normal subjects. In this experiment, the participants were required to bisect radial lines further away from the true centre. It is assumed that in doing so, they were allocating more attention to the far portion of the line compared with the near portions of the line than the far portions. The results, in this analysis, show that monocular vision systematically influences bias on the radial line bisection task. Basing the experiment’s expectations on this postulate, subjects using their right eye were expected to be relatively biased toward near space and that subjects using the left eye would be relatively biased towards far space. According to the results garnered from this experiment, it was found that right eye dominant participants had a better favoritism in using the left eye. This could have been caused the activation of the near biased left biased hemisphere. Left eye dominant subjects had a reversal of this pattern, which demonstrated a greater far bias using their right eye than the left eye. The reversal of bias in the left eye dominant subjects could signify that they have a hemispheric organization for spatial attention to close (Werner & Chalupa, 2004). Further studies through research have indicated that these differences are not related to the refractive index or retinal differences but to the central processing (Adelman, 2012). The differences in performance can be attributed to activation of contra-lateral attention systems preferentially of different hemispherical activation to account for the differences observed between different eyes used. An alternate hypothesis can be attributed to the difference in performance between use of the non-dominant and dominant eye may be related to differences in the defining aspects of dominant and non-dominant eyes, independent of differential hemispheric activation of attentional systems. This experiment can be used to study and treat injuries and lesions to parts of the brain concerned with vision like occipital lobe. Damages to the right hemisphere through stroke can be treated using monocular vision therapeutics. References Cattaneo, Zaira and Vecchi, T. (2011). Blind Vision: The Neuroscience of Visual Impairment. Massachusetts: MIT Press. Howard, I. P. (2012) Perceiving in Depth, Volume 3: other Mechanisms of depth Perception. Illustrated Edition. London: Oxford University Press. Demetriou, A and Raftopoulos, A. (2012). Cognitive Development Change: Theories, Models and Measurement. Illustrated Edition. London: Cambridge University Press. Taub, M. B, Bartuccio, M and Maino, D. (2012). Visual Diagnosis and Care of the Patient with Special Needs. London: Lippincott Williams & Wilkins. Healy, A. F and Proctor, R. W. (2003). Handbook of Psychology, Experimental Psychology. New York: John Wiley & Sons. Wilson, M. E, Saunders, R. A and Trivedi, R. H. (2009). Pediatric Ophthalmology: Current Thought and Practical Guide. Springer. Werner, J. S and Chalupa, L. M. (2004). The Visual Neuroscience. 2nd Illustrated Edition. Massachusetts: MIT Press. Adelman, J. S. (2012). Visual Word Recognition Volume 2: Meaning and Context, Individuals and Development, Volume 2. Psychology Press. Appendix An analysis on the variance was done on the data set using the subject factors in ANOVA test because this is the most appropriate way of determining the true variances in a data set. This method helps eliminate any bias in data set that could have been obtained through experimental procedure. Test conductor or test subject bias is eliminated by using subject factor in ANOVA. Read More