|Year : 2019 | Volume
| Issue : 4 | Page : 192-195
A comparative study of visual attention in hearing impaired and normal schoolgoing children
Renu Thakur1, Jaikishan Jayakumar2, Sangeeta Pant3
1 Chitkara School of Health Sciences, Chitkara University, Rajpura, Punjab, India
2 Center for Computational Brain Research, Indian Institute of Technology, Chennai, Tamil Nadu, India
3 Chitkara College of Education, Chitkara University, Rajpura, Punjab, India
|Date of Submission||20-Feb-2019|
|Date of Acceptance||10-Jun-2019|
|Date of Web Publication||4-Dec-2019|
Dr. Renu Thakur
Chitkara School of Health Sciences, Chitkara University, Rajpura - 140 401, Punjab
Source of Support: None, Conflict of Interest: None
Background: Enhanced visual attention is one of the major documented effects in auditory deprivation. However, in parallel, it has been shown that the congenitally deaf show deficits in their temporal processing. Aim: In this study, we aimed to study the parameters of visual attention. Materials and Methods: The speed of processing of divided attention (using the symbol digit modality test [SDMT]) and the central attention with attentional blink (AB) using a commercially available App, the BrainBaseline App. We tested these parameters of visual attention in students who are congenitally hearing impaired and those with normal hearing. Results: The measure of visual attention (error scores) using the SDMT did not show any significant differences between the congenitally hearing impaired and the students with normal hearing. However, we report significant differences in the processing speeds of divided attention and the error rates in the AB test between the congenitally hearing impaired and the normal with the hearing impaired having slower speeds of processing but making less errors in AB test. Conclusion: This finding probably indicates the redistribution or allocation of available brain resources as a result of sensory deprivation.
Keywords: Attention, attentional blink, hearing impaired, symbol-digit modalities test, visuospatial attention
|How to cite this article:|
Thakur R, Jayakumar J, Pant S. A comparative study of visual attention in hearing impaired and normal schoolgoing children. Indian J Otol 2019;25:192-5
| Introduction|| |
Living in an overwhelmingly rich and complex world, we are constantly bombarded with large amounts of sensory information through multiple channels such as vision, audition, and olfaction from our surrounding environment. Our ability to contextually select only the relevant information from the multitude of information entering the brain for e.g., via the visual pathway; is called attention. Visual attention is ability to focus consciousness on a task; which is eventually important for visual information. Visual attention can be elaborated as (a) Focus execute (ability to focus on target) (b) Sustain (ability to maintain over period of time) (c) Shift (ability to shift from one to another task) (d) Encode (digit span). There is no unique location in the brain which is responsible for visual attention. There are different selections processes take place at different stages of the visual pathways and feature integration which involves several areas of cerebral hemispheres, which is again suggesting that attention is not a separate and sovereign system, but a set of differentiated selection processes.
Audio visual integration in the brain guides attention in a much more efficient manner than single sensory modalities., What effect does one sensory deprivation have on the attentional mechanisms is still unknown. In this study, we report basic parameters of visual attention in hearing impaired individuals and compare them with normal controls.
Children with hearing impairment are often reported to be inattentive and easily distracted. This may be a reflection of how they allocate attention resources, as well as other factors such as linguistic competence and teacher parent attributions, as opposed to a state of inattentiveness and attention pathology per SE. However, the hearing-impaired show significant better visual performance in motion processing, and in attention demanding circumstances in the periphery. Neurobiologically, one would expect the reorganization of resources from the auditory areas in the hearing impaired to visual processing via cross modal plasticity but this effect is, for some unknown reason, is evident only in higher order visual processing. One such higher order visual processing phenomenon is visual attention and our goal in this study is investigate two modalities namely divided attention using the symbol digit modality test (SDMT) and the central overt attention using the rapid serial visual presentation (RSVP) attentional blink (AB) paradigm.
| Materials and Methods|| |
We recorded the attentional parameters in 30 children with congenital hearing impairment (age: 8.5–11.5 years). These children were randomly selected from 118 hearing impaired students who were screened for visual problems from school for the deaf and hearing-impaired children, Ludhiana Punjab. The age matched controls (n = 30) were selected from a nearby school (Peace Public School, Ludhiana, Punjab). All the procedures that were used to test the subjects were in accordance with the ethical standards of the responsible committee on human experimentation (institutional or regional) and with the Helsinki Declaration of 1975, as revised in 2000. Prior permissions and approval were sought and obtained from the head principal of the hearing-impaired and the normal school. In addition, the teachers of the school were given information briefing the methods used in the study. This was done to help in communication (sign language for the hearing impaired) with the students. The researchers were also well versed with the sign language used in the school.
Informed consent was taken from all students, who participated in the study, including the consent explained to the hearing-impaired children by relevant instructors. Students participants in this study needed to satisfy the following criteria to be included in the study: Best corrected visual acuity of 6/6 and a near visual acuity N6., using the relevant Snellen acuity chart for distance and the standardized reading chart for near. Ocular abnormalities were ruled out using standard anterior and posterior eye examination.
Basic parameters of visual attention were evaluated using two different tests, SDMT and AB. These tests were run on a portable tablet device by using an application (Brain Baseline, Digital Artefacts LLC). The SDMT is a symbol substitution neuropsychological test that examines a subject's divided attention and memory resources. SDMT requires a person to substitute geometric symbols for numbers while scanning a response key. The test measures two parameters; the error rates measuring the divided attention/memory capacity for the task and the speed of processing determines the brain resource allocation for the task. The test involves oculomotor scanning, working memory, motor persistence and visuomotor coordination in order to complete the task at hand. The SDMT, as a neuropsychological tool, has been used in the assessment of many neurological disorders, including Alzheimer's disease, Huntington's disease Parkinson's disease. The second measure of visual attention used in this study is the AB. AB refers to the phenomenon where two objects when presented in rapid intervals (typically between 120 and 250 ms) results in the absence of perception of the second object. The measure is meant to study participant's ability to select multiple items across time, thereby giving an estimate of the “speed” of attentional processing. In this task, participants search a rapidly presented stream of letters, presented one by one at the center of the screen, for specific target letters (RSVP). The test typically presents a letter X followed by a red target letter with a variable time lag between the two letters. The number of trials/presentations is always fixed with the target letter being variable and the error rates determine the size of the AB. The primary outcome measure is the size of the “blink” observed, or how much impact detection of the color target had on the subsequent ability to detect the X when it was present. Both tests were explained and demonstrated to students with hearing impairment by the special educator from the school for the deaf. The results of SDMT and AB were then compared with the age matched controls (subjects with normal hearing).
| Results|| |
We have analyzed the basic parameters of visuospatial attention by using two separate tests. The SDMT and a RSVP based procedure to measure the errors during an AB task. The complete dataset of 60 students (30 hearing impaired with controls of 30 normal hearing) was analyzed using the nonparametric Mann–Whitney U test using a statistical software (Statistical Package for the Social Sciences 21, IBM Inc.,). The data are summarized in [Figure 1]. As shown in [Figure 1]a, the performance of the hearing impaired and the normal hearing school kids did not vary significantly as indicated by the errors (mean ± standard error of the mean [SEM]; hearing impaired: 1.0 ± 0.47 vs. normal controls: 0.48 ± 0.18) committed during the SDMT (Mann–Whitney U test; z = −0.22; n = 30; P = 0.81). This difference may be an indication that the memory capacities of the two groups does not vary.
|Figure 1: Shows the differences in the different facets of visual attention between the hearing impaired children and the normal hearing controls. (a) shows the differences in the error scores of the symbol digit modality test. The difference between the two groups did not reach statistical significance. (b) shows the time (in seconds) taken by the two groups on the symbol digit modality test indicating speed of processing of divided attention. The hearing impaired were significantly slower (P < 0.0001) than the normal controls. (c) shows the error scores in the attentional blink paradigm. The hearing impaired surprisingly made less errors than the normal hearing group|
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However, most interestingly, the speed of processing within the SDMT [Figure 1]b which would indicate a measure of allocation of brain resources for divided attention showed significant differences between the hearing impaired and the normal hearing group (Mann–Whitney U test; z = −5.00; n = 30; P < 0.0001) with the hearing impaired group (mean ± SEM; 355.5 ± 27.2 s) showing slower processing times than the age matched normal controls (209.2 ± 8.2 s). Despite the fact that the hearing impaired were slower and made more (but not statistically significant) errors in the SDMT, the error rates in a standardized AB test based on a RSVP paradigm showed that the hearing impaired made less errors that aged matched controls [Figure 1]c. The hearing impaired made on average 0.09 (±0.02) errors out of a scale of 1 when compared with 0.21 ± 0.03 error rate of the age matched controls. This difference is statistically significant (Mann–Whitney U test; z = −2.17; n = 30; P = 0.03) at the P = 0.05 level but not at the P = 0.01 level.
| Discussion|| |
Our results show that despite showing no statistical differences in the error rates in the SDMT and showing poorer response times in the SDMT, the children amongst the hearing impaired are less prone to making errors in the AB test.
Attention, as a neurobiological phenomenon serves to enhance extra-striate neuronal responses to a stimulus at one spatial location in the visual field and this is often termed as visuospatial attention. More generally, the term attention covers all factors that influence selection mechanisms, whether they are scene driven bottom-up or expectation-driven top-down. The tests used in this study, namely the SDMT and the AB serves to measure the different aspects of visual attention namely, SDMT, which predominantly measures the divided attentional mechanisms within which the errors and time taken in SDMT denotes the memory capacity and the availability of resources for completing the divided attention task in the brain respectively. The RSVP based AB task, on the other hand, is more centrally based and is representative of the bottle neck in the temporal allocation of attentional resources within the brain. Our results indicate that the hearing impaired are more prone to making errors and slower in the SDMT tasks. The SDMT task by design operates on resources that confine to central and peripheral visual representations. Previous reports on visual attention in the hearing impaired and normal hearing adults examined differences in visual perception across different target–flanker spacing conditions and found that deaf adults showed a significantly greater flanker compatibility effect farther out in the periphery than normal hearing adults. The study reports that the hearing impaired made more errors and their response time was slower when compared to normal hearing adults. Our study agrees with this effect although our error rate differences did not reach statistical significance. However, the study reports that the error rates in the near periphery was less in the hearing impaired than normal adults which is in direct contradiction to our results in children which show that hearing impaired children perform poorer in the divided attention SDMT task. Other studies including the seminal Vanderbilt studies pointed to a compensatory role that the visual system plays in individuals with significant hearing impairment. More specifically, these studies show that the visual system appears to play an important role in directing a deaf individual's attention in the near visual periphery. Our discrepancy with the Tharpe et al. study can probably be explained by the fact that effect of distractors in the peripheral visual locations is more detrimental in hearing impaired as compared to normal hearing subjects.
Our results indicate that the hearing-impaired children made less errors in the AB task which was based on the RSVP paradigm. This is direct contradiction with results obtained by Dye and Bavelier who show that the hearing impaired perform poorly in the RSVP task. There are subtle differences in the two RSVP tasks used by them and us with the main difference being the use of letters by us compared to symbols/shapes by them. We have also not classified our children as “game players” as action video games have significant effect on the allocation of attentional resources. We, in our paradigm, only measured the error rates in the AB task, rather than the much more demanding RSVP paradigm used in the Dye Bavelier study. Our hearing-impaired subject, although versed in sign language are not exposed to the American sign language which is also a considerable difference between our subject populations. Moreover, our results are also contradictory to other studies which show that the visual search between hearing impaired and normal humans does not vary.
While active elicitation of attention is an important part of successful communication with young deaf children. Deaf children have been reported to have behavioral problems related to impulsivity and an inability to focus attention. These reports have come from both subjective ratings of teachers and caregivers, as well as from clinical tests of attention skills. For example, mothers have been reported to rate deaf children as having greater distractibility–hyperactivity problems than hearing children using the Parenting Stress Index and Reivich and Rothrock suggested that impulsivity and lack of inhibition accounted for a significant amount of the problem behavior in deaf pupils reported by teachers in their study.
| Conclusions|| |
The goal of this study was to test the different facets of visual attention using the SDMT and Attention blink test. The SDMT, which is an indicator of divided attention indicates that the hearing-impaired children were slower in the task compared to normal hearing children. The more central RSVP based AB task showed that the hearing impaired made less errors compared to the normal controls. We believe that our results are an indication of the profound neural reorganization following sensory deprivation, possibly due to cross-modal plasticity. Our results demonstrate that the spatial distribution of visual attention differ in the deaf population and in normal hearing controls. Development of mature triadic visual attention patterns may be especially important for deaf children, who often need to switch attention between a communication partner and an object to receive visual communication (signs, gestures, or speech reading) about the object.
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Conflicts of interest
There are no conflicts of interest.
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