Secondary Logo

Journal Logo

Impact of Cochlear Implantation on Cognitive Functions of Older Adults: Pilot Test Results

Jayakody, Dona M. P.*,†; Friedland, Peter L.*,†,‡,§; Nel, Esmeralda||; Martins, Ralph N.¶,#,**; Atlas, Marcus D.*,†,‡; Sohrabi, Hamid R.¶,#

doi: 10.1097/MAO.0000000000001502
HIGHLIGHTS OF THE ACI ALLIANCE 14TH INTERNATIONAL CI CONFERENCE
Free
SDC

Background: A significant relationship between hearing loss and cognitive impairment has been previously reported. Overall, improvement in speech perception in quiet and quality of life has been observed after cochlear implantation. However, the impact of hearing loss treatment using cochlear implantation on cognitive functions is yet to be fully elucidated.

Objective: To investigate the impact of cochlear implantation on cognitive and psychological functions of older adults.

Study Design: Prospective patient-control study.

Participants: A total of 39 participants took part in the study: 23 cochlear implant (CI) candidates (M = 69.04 ± 12.35 yr) and 16 CI recipients (M = 61.75 ± 15.62 yr). All participants completed an assessment of hearing (pure-tone thresholds and speech perception in quiet), and a computerised, nonverbal test battery of cognitive function assessment, as well as a depression, anxiety, and stress scale.

Results: Independent-sample t test scores for the changes between 0 and 12 months revealed that CI recipients performed significantly better on measures of simple reaction time, cognitive flexibility, paired-associate learning, working memory, and strategy use (p < 0.05) compared with implant candidates. Compared with the candidates, recipients also showed significantly lower stress scores (p < 0.05) after 1 year use of a CI.

Conclusion: Our results indicate that even in participants with a long duration, severe to profound hearing loss, cochlear implantation has some impact on improving a number of cognitive functions. This finding warrants future longitudinal investigations with a large sample size to examine if the observed cognitive enhancement benefits are sustainable.

Supplemental Digital Content is available in the text

*Ear Science Institute Australia, Subiaco

Ear Sciences Centre, The University of Western Australia, Crawley

Department of Otolaryngology Head Neck Skull Base Surgery, Sir Charles Gairdner Hospital, Nedlands

§School of Medicine, Notre Dame University, Fremantle

||Department of Biomedical Sciences, Murdoch University, Murdoch

School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA

#Department of Biomedical Sciences, Faculty of Medicine and Health Sciences Macquarie University, Macquarie, NSW

**Cooperative Research Centre for Mental Health, Carlton, VIC, Australia

Address correspondence and reprint requests to Dona M. P. Jayakody, Ph.D., Senior Research Audiologist, Ear Science Institute Australia, 1 Salvado Road, Subiaco, WA 6008, Australia; E-mail: dona.jayakody@earscience.org.au

The authors disclose no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website (http://journals.lww.com/otology-neurotology).

Epidemiological and observational studies have established a significant association between hearing loss and cognitive decline (1). Lin et al. (2) reported a log linear increase in the risk of incident all-cause dementia with the severity of baseline hearing loss (1.27 per 10-dB loss; 95% confidence interval, 1.06–1.50). Hence, those with greater than moderate hearing loss could be at a higher risk of cognitive decline compared with those with mild hearing loss.

Distorted acoustic signal resulting from hearing loss impairs speech perception (3). For a successful speech perception to occur, higher brain centers, from cochlea to auditory cortex and processing by other modalities interact to accomplish functions under a combination of top-down and bottom-up influence (4,5). Hence, speech perception depends on optimal functioning of both auditory and cognitive systems (4,5). Sensory deficits occurring as a result of both age-associated central nervous system neurodegeneration and peripheral hearing loss will result in greater perceptual challenges, which recruit more cognitive resources (5).

For those who suffer from a moderately-severe to profound sensorineural hearing loss, cochlear implantation has been considered one of the viable treatment options (6). Postimplantation, recipients demonstrate excellent speech perception scores in quiet (7,8), significant improvement in quality of life (9), and some benefits in speech perception in noise (10).

Given the strong association between hearing loss and cognitive decline, it is important to measure the cochlear implant (CI) recipients’ performance on cognitive measures to make suitable recommendations for case management.

Standardized cognitive assessments commonly use auditory or visual test stimuli (11). Murphy et al. (12) reported that even a mild-moderate hearing loss can have a significant impact on the outcomes of comprehension and memory measures. Further, how well older adults perform these cognitive assessments are influenced by the severity of their auditory or visual sensory impairment (11).

Current practices use short cognitive assessment tools such as the Mini-Mental State Examination (MMSE) (13) or the Montreal Cognitive Assessment (MoCA) (14) to screen for cognitive impairment. Even though both assessments have been known for their screening reliability, how well these tests may screen mild cognitive impairment in those with a hearing impairment is not elucidated. For example, in addition to the test instructions, 10 of 30 scores on MoCA and 4 of 30 of MMSE test stimuli need to be accurately heard by the participant to attend to the task (11). Not being able to hear or see the test stimuli accurately or entirely could increase the risk of overestimating the patient's degree of cognitive impairment (11,15). Hence, to minimize the risk of over or underestimating the degree of cognitive impairment, recent studies have used nonauditory computerized cognitive test batteries with hearing impaired individuals (16,17).

Given the poor, preimplant speech perception scores exhibited by older implant candidates (8), use of verbally loaded cognitive measures for such patients may disadvantage this cohort. Apparently, hearing loss is not considered a factor that would impair performance on visually presented computerized cognitive test measures (17). Recent studies have used Cambridge Neuropsychological Test Automated Battery (CANTAB) as a valid test measure that can be easily used with hearing impaired (18) and CI recipients (19). Hence, this novel study investigated the impact of cochlear implantation on a number of cognitive functions using a battery of nonverbal cognitive measures (20). These include cognitive flexibility, verbal recognition memory, spatial working memory, executive functions, paired-associate learning, attention, and visual information processing speed.

Back to Top | Article Outline

Study Design

Prospective patient-control study.

Back to Top | Article Outline

Participants

A total of 39 participants took part in the study: 23 cochlear implant candidates (CIC) who have met the criteria for a CI and 16 cochlear implant recipients (CIR). In Australia, CI candidates wait 6 to 12 months to receive their implant through the public, government subsidised system. All the CI candidates of the current study were primarily assessed and considered suitable candidates to receive an implant and therefore, were on the waiting list for 6 to 12 months or more. Demographic details of both the participant groups are reported in Table 1. Details of the implants and speech processors used by the CIR participants are reported in Table 2. All those who were assessed at 12 months were assessed at 6 months as well. The decrease in numbers was partially due to CI candidates receiving an implant after 6 months and therefore had to be excluded from further analysis.

TABLE 1

TABLE 1

TABLE 2

TABLE 2

Ethics approval for this study was obtained from The University of Western Australia Human Research Ethics Committee (RA/4/1/7368). All participants provided informed, signed consent forms before participation in the study.

Back to Top | Article Outline

METHODS

All participants completed a test battery consisting of hearing, speech perception in quiet, and a psychological and a cognitive assessment. CIC completed testing at the baseline, 6 and 12 months while waiting to receive a CI. CIR completed the assessments at the baseline (preop), 6 and 12 months postimplantation.

Back to Top | Article Outline

Hearing Assessment

This was conducted in a soundproof booth by a qualified audiologist. The CIC participants completed a standard unaided pure-tone audiometric (Equinox 2.0 clinical audiometer; Interacoustics A/S, Middelfart, Denmark) and aided free field speech in quiet (consonant–nucleus consonant [CNC] word and phoneme (21) and City University of New York [CUNY] sentence test (22)) assessments with optimized hearing aids at the baseline, 6 and 12 months. Similar to the CIC group, CIR participants also completed unaided pure-tone audiometric assessment and aided free-field speech assessments at the baseline with optimized hearing aids. The CIR participants completed aided free field pure-tone audiometric (Tables 1 and 3) and speech assessments (Table 1—supplementary materials, http://links.lww.com/MAO/A533) with their CI at 6 and 12 months postimplantation.

TABLE 3

TABLE 3

Back to Top | Article Outline

Cognition Assessment

All three participant groups completed a nonverbal cognitive assessment using the CANTAB (20) installed on a computer with an integrated touch screen (Dell, Inspiron One, with Windows 8.1 platform). Before the cognitive assessment, all participants completed a National Adult Reading Test-Revised (23). The National Adult Reading Test-Revised score was used to calculate premorbid IQ. The following cognitive functions were assessed: cognitive flexibility (Attention Switching Task [AST]), delayed matching to sample, episodic memory and new learning skills (Paired-Associate Learning [PAL]), verbal recognition memory-free recall and recognition in immediate and delayed conditions (Verbal Recognition Memory [VRM]), reaction time-simple and complex (Reaction Time [RTI]), and working memory and executive functions (Spatial Working Memory [SWM]).

  1. Motor Screening Task (MOT): A brief introductory exercise was used to familiarize participants with the touch screen interface. MOT identifies difficulties in vision, comprehension, and hand movement of the participant (20). Results of MOT were not analyzed as part of the outcome measures for this study but were used as a screening tool to identify potential difficulties for the participant.
  2. AST: AST is a test of executive functioning and provides a measure of cued attentional set shifting. This activity specifically assesses cognitive flexibility and multitasking capabilities (20). AST is reported to be mediated by prefrontal cortex (24).
  3. DMS: This task assesses participants’ ability to recognize complex visual patterns at different time intervals (20). This test is sensitive to the damages in the medial-temporal lobe (hippocampus) and frontal lobes (25).
  4. PAL: PAL is a recall test of memory in which the participant has to learn the location of specific visual patterns (20). This test is sensitive to temporal and parietal lobe dysfunction (26).
  5. VRM: VRM assesses immediate and delayed memory of verbal information under free recall and forced recognition conditions (20). During this task, the participants were asked to read out loud a list of 12 words that appeared on the computer screen and remember the words at the same time. Then, participants were asked to recall as many words as they could (free recall stage) and to identify the original 12 words from a list containing the original words and distractors (recognition phase). The recall phase of VRM activates areas of the fronto-temporal network,(27) whereas the recognition phase activates the hippocampus (28).
  6. RTI: RTI is a test of attention and measures the speed of response and movement in single and five choice paradigm. During this task, the participants are required to release a home button and touch either a single stimulus or one of five stimuli that appears on the test screen. Outcome measures include reaction time (time taken to release the home button) and movement latencies (time taken to release the home button and to touch the screen) for both simple and five-choice conditions (20).
  7. SWM: It measures the retention and manipulation of visuospatial information in areas such as nonverbal working memory, working visuospatial memory, and strategy use is assessed (20). SWM is sensitive to the functions of prefrontal cortex (29,30).

More details of these tests can be found at http://www.cambridgecognition.com/clinicaltrials/cantabsolutions/tests.

Back to Top | Article Outline

Depression Anxiety Stress Scale-21(DASS-21(31))

The DASS-21 was used to measure the current (past 7 days) severity of a range of symptoms common to depression, stress, and anxiety. The DASS-21 contains 21 questions that are scored on a four-point Likert scale ranging from 0 (never apply to me at all over the last week) to 3 (applied to me very much or almost always over the past week). Scores for Depression, Anxiety, and Stress were separately calculated by summing the scores for the relevant items and the final score for each subcategory was multiplied by two (×2) as per the questionnaire scoring instructions.

Back to Top | Article Outline

Statistical Analysis

Analysis was performed with IBM SPSS Statistics version 22 (IBM Corp, New York, NY). Independent-sample t tests were conducted to determine if the differences in CANTAB test modules scores and DASS-21 questionnaire scores between baseline and 6 months, and between baseline and12 months obtained for were significantly different between the CIC and CIR groups.

At the baseline, partial correlation was performed to investigate the correlation between baseline 4PTA of the implanted or the ear selected for CI surgery, duration of hearing loss and CANTAB and DASS-21 test scores of the CI candidates and recipients. Partial correlation was also performed on a CIR group to investigate the correlation between 4PTA of the implanted ear, aided speech-perception scores and CANTAB and DASS-21 scores 12 months postimplantation. Age, and premorbid IQ scores were controlled during this analysis.

Back to Top | Article Outline

RESULTS

Independent-sample t test results obtained for the changes observed between baseline and 6 months revealed a significant difference between both participant groups for RTI simple reaction time (p = 0.01), SWM between errors (p = 0.02], and SWM between errors four to eight boxes (p = 0.04] tasks (Table 2).

Differences observed between baseline and 12 months revealed a significant difference between the CIR and CIC groups for AST mean latency (p = 0.04), PAL total errors (p = 0.03), RTI simple accuracy score (p = 0.03), SWM between errors (p = 0.03), SWM between errors four to eight boxes (p = 0.05) and SWM strategy (p = 0.02) tasks.

In comparison with the implant candidates, the CIR group showed a significant decline in stress scores between baseline to 12 months (p = 0.02] postimplantation (Table 3, Fig. 1). Over time we have observed a trend in decline in depression, anxiety, and stress scores of the CIR group. However, two CIR participants have gone through life changing events that had negative impact on their mental health which was reflected in their DASS-21 scores (Table 2—supplementary materials, http://links.lww.com/MAO/A534). The CIC group showed a trend in increase in depression, anxiety, and stress scores over time. However, there were no significant changes in anxiety and depression for either group.

FIG. 1

FIG. 1

Back to Top | Article Outline

Correlation Analysis

Partial correlation analysis results revealed that duration of hearing loss positively correlated with baseline AST mean correct latency (r = 0.37, p = 0.02) and baseline SWM between errors (r = 0.36, p = 0.02) scores.

Twelve-months postimplantation, CUNY sentence scores negatively correlated with AST mean correct latency (r = −0.75, p = 0.02) and CNC-words scores negatively correlated with SWM strategy scores (r = −0.74, p = 0.03).

Back to Top | Article Outline

CONCLUSIONS

This study investigated the impact of cochlear implantation on cognitive functions and mental health of postlingually hearing impaired CI recipients. It revealed that 6 months postimplantation, CI recipients showed a significant improvement in spatial working memory and strategy use (SWM) and simple RTI tasks. Twelve months of CI use had a positive impact on cognitive flexibility (AST), PAL, alongside SWM and strategy use and simple RTI tasks consistent with the 6-month findings.

Simple RTI is a measure of attention and processing speed. It measures speed of response and movement in single and five-choice paradigms (20). Processing speed, attention, working memory, and executive functions decline with age (4) and contribute to difficulties in speech understanding in older adults (32). Increase in RTI accuracy scores observed in the CIR group may be attributed to the fact that the improved hearing may have assisted in reducing the cognitive load, and therefore improving information processing speed. RTI is considered the primary cognitive ability underlying more complex cognitive abilities, including executive functioning and working memory (4).

AST is a test of executive functioning and provides a measure of cued attentional set shifting (20). The correlation analysis results of the current study revealed that duration of hearing loss positively correlates with the AST mean latency at the baseline. This suggests that the longer the duration of hearing loss, the greater the time required to rapidly switch attention between auditory objects. These findings are consistent with Shinn–Cunnigham's (33) findings that hearing loss impairs one's ability to switch attention rapidly by increasing the time required to form auditory objects. It is posited that the improvement observed in postimplantation speech perception scores may have facilitated improved attention.

Studies suggest that the PAL is affected by temporal lobe damage in humans (34). Positron emission tomography studies conducted on CI recipients have observed cortical activation in the temporal lobe regardless of the side of the implantation. In addition, a positive correlation has been observed between the degree of cortical activation and speech therapy (35). The results of the current study showed a significant improvement in PAL total errors (p = 0.03). In light of the improved postimplantation speech scores observed in the CIR group (Table 1), we posit that these changes could have helped improve PAL error scores.

The SWM test assesses visuospatial working memory and strategy use (20). It is also sensitive to executive functions (20). SWM is influenced by pathological conditions in the frontal lobe, especially dorsolateral and ventrolateral areas (29). The dorsolateral prefrontal cortex is involved in executive functions, such as the maintenance and manipulation of items in working memory (36). Working memory is defined as a “limited capacity system for temporarily storing and processing the information required to carry out complex cognitive tasks such as comprehension, learning, and reasoning” (Rönnberg et al. (37), p. 2). Preimplantation, the CI recipients of this study had severe-profound hearing loss and performed poorly in speech perception in quiet in optimally aided condition. Existing research suggests a role of working memory in speech understanding (38). CI recipients’ reliance on working memory and strategy use and executive functions to understand speech signal was reflected in reduced SWM error scores and improved strategy use, postimplantation.

A review of existing literature has revealed that to date only a handful of studies have examined the impact of cochlear implantation on cognitive functions of older adults (8,39–41). All of these studies have used cognitive assessments with verbal test materials and some also included cognitive assessments with written and pictorial information. Holden et al. (8) reported that when age, sex, and ethnicity were controlled, duration of severe-profound hearing loss remained significantly correlated with the cognitive standardised data (ρs = −0.206, p = 0.028). Collison et al. (40) failed to find any significant correlation between cognitive and linguistic test scores and word recognition abilities. Even though Heydebrand et al. (41) failed to observe significant improvement in postimplant speech perception scores and general cognitive scores, verbal learning could account for 42% of the variance in 6-month postimplant monosyllabic word scores. Mosnier et al. (42) also reported an improvement in mean scores of all cognitive domains as measured by MMSE, five-word test, clock-drawing test, verbal fluency test, d2 test of attention, and Trail Making Test parts A and B as early as 6 months postimplantation. Our findings are in line with both Heydebrand et al. (41) and Mosnier et al. (42) in that we observed significantly negative correlation between 12 months postimplantation CUNY sentence scores and AST mean correct latency (r = −0.75, p = 0.02) and CNC-words scores and SWM strategy scores (r = −0.74, p = 0.03).

Postimplantation, CI recipients have shown baseline to 12 months postop improvement in mean hearing thresholds (64 dB), mean speech in quiet (68% in CUNY sentences, 32% in CNC-Word, 50% in CNC-Phoneme scores) tasks. These findings are consistent with previous studies that examined the improvement in speech perception in quiet (8,42,43) in older adults. All CI recipients scored between 23.75 dB and 40 dBHL for their postop 4PTA in the implanted ear, suggesting that all CI recipients had access to sound with a well-fitted CI. Cochlear implantation seems to reduce cognitive load by improving speech perception abilities of the implant recipients (42). Further, based on significant decline in stress scores observed in implant recipients compared with the implant candidates, we posit that access to better hearing could have a positive impact on mental health of hearing impaired older adults.

As mentioned above, all the participants in the current study were selected as suitable candidates for cochlear implantation by the established hearing loss and poor aided speech perception criteria (6). Subsequently, a number of these participants received a CI. The CIR group included only those who were implanted at the start of the 12 month data collecting phase. The remainder were not implanted over the 12-month period, and became the CIC group. Any participant who was initially included in the CIC group and was subsequently implanted after several months during the study was excluded. We commenced by assuming that both the groups were comparative and the CIC group were not significantly different to the CIR group in cognitive and psychological measures. During the waiting period, those candidates who had optimized hearing aids continued to use them.

The results of the current study suggest that significantly better results observed in working memory and strategy use, cognitive flexibility and attention, paired associate learning and simple reaction time tasks of CI recipients compared with CI candidates, could reflect lesser cognitive load imposed on working memory and executive functions due to improved postimplantation hearing and speech perception scores.

Back to Top | Article Outline

Limitations

The small sample size in this study is a limitation. Despite this study measuring changes in some cognitive functions, these may require a longer period of time to confirm that these are sustained, and other cognitive functions may need a longer period of time to occur. A longitudinal assessment with a large sample size may provide further information regarding what other cognitive functions are improved/not improved as a function of cochlear implantation.

Back to Top | Article Outline

Acknowledgments

The authors thank Dr Peter Busby and Prof Robert Eikelboom for reviewing the manuscript.

Back to Top | Article Outline

REFERENCES

1. Gurgel RK, Ward PD, Schwartz S, Norton MC, Foster NL, Tschanz JT. Relationship of hearing loss and dementia: A prospective, population-based study. Otol Neurotol 2014; 35:775–781.
2. Lin FR, Metter EJ, O’Brien RJ, Resnick SM, Zonderman AB, Ferrucci L. Hearing loss and incident dementia. Arch Neurol 2011; 68:214–220.
3. Hällgren M. Hearing and Cognition in Speech Comprehension. Methods and Applications. Linköping, Sweden: Linkoping University; 2005.
4. Craik FI. The role of cognition in age-related hearing loss. J Am Acad Audiol 2007; 18:539–547.
5. Pichora-Fuller MK, Singh G. Effects of age on auditory and cognitive processing: Implications for hearing aid fitting and audiologic rehabilitation. Trends Amplif 2006; 10:29.
7. Dillon M, Buss E, Adunka M, et al. Long-term speech perception in elderly cochlear implant users. JAMA Otolaryngol Head Neck Surg 2013; 139:279–283.
8. Holden LK, Finley CC, Firszt JB, et al. Factors affecting open-set word recognition in adults with cochlear implants. Ear Hear 2013; 34:342.
9. de Angelo TCS, Moret ALM, da Costa OA, Nascimento LT, de Freitas Alvarenga K. Quality of life in adult cochlear implant users. CoDAS 2016; 28:106–112.
10. Lenarz M, Sönmez H, Joseph G, Büchner A, Lenarz T. Cochlear implant performance in geriatric patients. Laryngoscope 2012; 122:1361–1365.
11. Dupuis K, Pichora-Fuller MK, Chasteen AL, Marchuk V, Singh G, Smith SL. Effects of hearing and vision impairments on the Montreal Cognitive Assessment. Neuropsychol Dev Cogn B Aging Neuropsychol Cogn 2015; 22:413–437.
12. Murphy DR, Daneman M, Schneider BA. Why do older adults have difficulty following conversations? Psychol Aging 2006; 21:49–61.
13. Folstein MF, Folstein SE, McHugh PR. Mini-mental state. A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975; 12:189–198.
14. Nasreddine ZS, Phillips NA, Bedirian V, et al. The Montreal Cognitive Assessment, MoCA: A brief screening tool for mild cognitive impairment. J Am Geriatr Soc 2005; 53:695–699.
15. Gussekloo J, Oduber C, Westendorp R. Sensory impairment and cognitive functioning in oldest-old subjects: The Leiden 85 + Study. Am J Geriatr Psychiatry 2005; 13:781–786.
16. Bucks RS, Dunlop PD, Taljaard DS, et al. Hearing loss and cognition in the Busselton Baby Boomer cohort: An epidemiological study. Laryngoscope 2016; 126:2367–2375.
17. Dawes P, Emsley R, Cruickshanks KJ, et al. Hearing loss and cognition: The role of hearing aids, social isolation and depression (hearing loss and cognition). PLoS One 2015; 10:e0119616.
18. Wayne RV, Hamilton C, Jones Huyck J, Johnsrude IS. Working memory training and speech in noise comprehension in older adults. Front Aging Neurosci 2016; 8:49.
19. Bansal A. Evaluating The Short-term Effects of Home-based Computerized Multi-domain Cognitive Training in Adult Cochlear Implant Users: A Prospective Randomized Intervention Study. Norway: The Faculty of Medicine, Institute of Health and Society, Department of Community Medicine, University of Oslo; 2014.
20. Cambridge Cognition Ltd. CANTABeclipse Test Administration Guide. England: Cambridge; 2012.
21. Lehiste I, Peterson GE. Linguistic considerations in the study of speech intelligibility. Acoust Soc Am 1959; 31:280–286.
22. Boothroyd A, Hanin L, Hnath T. A sentence test of speech perception: Reliability, set equivalence, and short term learning. Speech and Hearing Science Report RC10 1985.
23. Nelson HE, Willison JR. The Revised National Adult Reading Test-Test Manual. Windsor, UK: NFER-Nelson; 1991.
24. Brass M, Ullsperger M, Knoesche TR, von Cramon DY, Phillips NA. Who comes first? The role of the prefrontal and parietal cortex in cognitive control. J Cogn Neurosci 2005; 17:1367–1375.
25. Sahgal A, Iversen SD. The effects of foveal prestriate and inferotemporal lesions on matching to sample behaviour in monkeys. Neuropsychologia 1978; 16:391–406.
26. Sweeney JA, Kmiec JA, Kupfer DJ. Neuropsychologic impairments in bipolar and unipolar mood disorders on the CANTAB neurocognitive battery. Biol Psychiatry 2000; 48:674–684.
27. Fletcher PC, Henson RNA. Frontal lobes and human memory. Brain 2001; 124:849–881.
28. Henson R. What can functional neuroimaging tell the experimental psychologist? Q J Exp Psychol A 2005; 58:193–233.
29. Owen AM, Evans ACE. Evidence for a two-stage model of spatial working memory processing within the lateral frontal cortex: a positron emission tomography study. Cereb Cortex 1996; 6:31–38.
30. Manes F, Sahakian B, Clark L, et al. Decision-making processes following damage to the prefrontal cortex. Brain 2002; 125:624–639.
31. Lovibond SH, Lovibond PF. Manual for the Depression Anxiety Stress Scales. Sydney: Psychology Foundation; 1995.
32. Humes LE, Dubno JR. Gordon-Salant S, Frisina DR, Popper AN, Fay RR. Factors affecting speech understanding in older adults. The Aging Auditory System: Perceptual Characterization and Neural Bases of Presbycusis. New York, NY: Springer-Verlag; 2010. 211–258.
33. Shinn-Cunningham BG, Best V. Selective attention in normal and impaired hearing. Trends Amplif 2008; 12:283–299.
34. Miller LA, Münoz DG, Finmore M. Hippocampal sclerosis and human memory. Arch Neurol 1993; 50:391–394.
35. Lukaszewicz-Moszynska Z, Lachowska M, Niemczyk K, Lukaszewicz-Moszynska Z, Lachowska M, Niemczyk K. Auditory cortical activation and plasticity after cochlear implantation measured by PET using fluorodeoxyglucose. Funct Neurol 2014; 29:121–125.
36. Miller EK, Cohen JD. An integrative theory of prefrontal cortex function. Annu Rev Neurosci 2001; 24:167–202.
37. Rönnberg J, Lunner T, Zekveld A, et al. The Ease of Language Understanding (ELU) model: Theoretical, empirical, and clinical advances. Front Syst Neurosc 2013; 7:31.
38. Baddeley AD. Working Memory. Oxford: Oxford University Press; 1986.
39. Aplin DY. Psychological assessment of multi-channel cochlear implant patients. J Laryngol Otol 1993; 107:298–304.
40. Collison EA, Munson B, Carney AE. Relations among linguistic and cognitive skills and spoken word recognition in adults with cochlear implants. J Speech Lang Hear Res 2004; 47:496.
41. Heydebrand G, Hale S, Potts L, Gotter B, Skinner M. Cognitive predictors of improvements in adults’ spoken word recognition six months after cochlear implant activation. Audiol Neurotol 2007; 12:254–264.
42. Mosnier I, Bebear JP, Marx M, et al. Improvement of cognitive function after cochlear implantation in elderly patients. JAMA Otolaryngol Head Neck Surg 2015; 141:442–450.
43. Wong YDJ, Moran JM, O’leary JS. Outcomes after cochlear implantation in the very elderly. Otol Neurotol 2016; 37:46–51.
Keywords:

Anxiety; Cochlear implantation; Cognition; Depression; Hearing loss; Stress

Supplemental Digital Content

Back to Top | Article Outline
Copyright © 2017 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company