PERCEPTION AND COGNITION: INTERACTIONS IN THE AGEING BRAIN EDITED BY : Harriet A. Allen and Katherine L. Roberts PUBLISHED IN : Frontiers in Aging Neuroscience 1 September 2016 | Perception and C ognition: Interactions in the Ageing Brain Frontiers in Aging Neuroscience Frontiers Copyright Statement © Copyright 2007-2016 Frontiers Media SA. All rights reserved. All content included on this site, such as text, graphics, logos, button icons, images, video/audio clips, downloads, data compilations and software, is the property of or is licensed to Frontiers Media SA (“Frontiers”) or its licensees and/or subcontractors. The copyright in the text of individual articles is the property of their respective authors, subject to a license granted to Frontiers. The compilation of articles constituting this e-book, wherever published, as well as the compilation of all other content on this site, is the exclusive property of Frontiers. 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For the full conditions see the Conditions for Authors and the Conditions for Website Use. ISSN 1664-8714 ISBN 978-2-88919-937-2 DOI 10.3389/978-2-88919-937-2 About Frontiers Frontiers is more than just an open-access publisher of scholarly articles: it is a pioneering approach to the world of academia, radically improving the way scholarly research is managed. The grand vision of Frontiers is a world where all people have an equal opportunity to seek, share and generate knowledge. Frontiers provides immediate and permanent online open access to all its publications, but this alone is not enough to realize our grand goals. Frontiers Journal Series The Frontiers Journal Series is a multi-tier and interdisciplinary set of open-access, online journals, promising a paradigm shift from the current review, selection and dissemination processes in academic publishing. 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Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: researchtopics@frontiersin.org 2 September 2016 | Perception and C ognition: Interactions in the Ageing Brain Frontiers in Aging Neuroscience PERCEPTION AND COGNITION: INTERACTIONS IN THE AGEING BRAIN The cover is an image from Scarborough beach, 1956. We are grateful to all the participants who have given up their time to take part in research. Copyright (c) 1956 G Barron. Permission granted to reproduce, intact and without distortion or editing of the image, for personal and educational use only. Topic Editors: Harriet A. Allen, University of Nottingham, UK Katherine L. Roberts, University of Warwick, UK 3 September 2016 | Perception and C ognition: Interactions in the Ageing Brain Frontiers in Aging Neuroscience Healthy ageing can lead to declines in both perceptual and cognitive functions. Impaired per- ception, such as that resulting from hearing loss or reduced visual or tactile resolution, increases demands on ‘higher-level’ cognitive functions to cope or compensate. It is possible, for example, to use focused attention to overcome perceptual limitations. Unfortunately, cognitive functions also decline in old age. This can mean that perceptual impairments are exacerbated by cognitive decline, and vice versa, but also means that interventions aimed at one type of decline can lead to improvements in the other. Just as improved cognition can ameliorate perceptual deficits, improving the stimulus can help offset cognitive deficits. For example, making directions and routes easy to follow can help compensate for declines in navigation abilities. In this Topic, we bring together papers from both auditory and visual researchers that address the interaction between perception and cognition in the ageing brain. Many of the studies demonstrate that a broadening of representations or increased reliance on gist underlie percep- tual and cognitive age-related declines. There is also clear evidence that impaired perception is associated with poor cognition although, encouragingly, it can also be seen that good perception is associated with better cognition. Compensatory cognitive strategies were less successful in improving perception than might be expected. We also present papers which highlight important methodological considerations that are required when studying the older brain. Citation: Allen, H. A., Roberts, K. L., eds. (2016). Perception and Cognition: Interactions in the Ageing Brain. Lausanne: Frontiers Media. doi: 10.3389/978-2-88919-937-2 4 September 2016 | Perception and C ognition: Interactions in the Ageing Brain Frontiers in Aging Neuroscience Table of Contents 06 Editorial: Perception and Cognition: Interactions in the Aging Brain Harriet A. Allen and Katherine L. Roberts 09 Perception and Cognition in the Ageing Brain: A Brief Review of the Short- and Long-Term Links between Perceptual and Cognitive Decline Katherine L. Roberts and Harriet A. Allen Section: Impaired perception and impaired cognition 16 The role of auditory and cognitive factors in understanding speech in noise by normal-hearing older listeners Tim Schoof and Stuart Rosen 30 Cognitive spare capacity in older adults with hearing loss Sushmit Mishra, Stefan Stenfelt, Thomas Lunner, Jerker Rönnberg and Mary Rudner 43 The effect of functional hearing loss and age on long- and short-term visuospatial memory: evidence from the UK biobank resource Jerker Rönnberg, Staffan Hygge, Gitte Keidser and Mary Rudner 56 What’s on TV? Detecting age-related neurodegenerative eye disease using eye movement scanpaths David P. Crabb, Nicholas D. Smith and Haogang Zhu 66 Age-group differences in speech identification despite matched audiometrically normal hearing: contributions from auditory temporal processing and cognition Christian Füllgrabe, Brian C. J. Moore and Michael A. Stone Section: Common Decline 91 The ups and downs of global motion perception: a paradoxical advantage for smaller stimuli in the aging visual system Claire V. Hutchinson, Tim Ledgeway and Harriet A. Allen 99 Preserved fine-tuning of face perception and memory: evidence from the own-race bias in high- and low-performing older adults Jessica Komes, Stefan R. Schweinberger and Holger Wiese 109 Reduced audiovisual recalibration in the elderly Yu Man Chan, Michael J. Pianta and Allison M. McKendrick 118 How does aging affect the types of error made in a visual short-term memory ‘object-recall’ task? Raju P. Sapkota, Ian van der Linde and Shahina Pardhan 127 The sound-induced flash illusion reveals dissociable age-related effects in multisensory integration David P. McGovern, Eugenie Roudaia, John Stapleton, T. Martin McGinnity and Fiona N. Newell 5 September 2016 | Perception and C ognition: Interactions in the Ageing Brain Frontiers in Aging Neuroscience Limited Benefit from Compensatory Cognition 136 A rightward shift in the visuospatial attention vector with healthy aging Christopher S. Y. Benwell, Gregor Thut, Ashley Grant and Monika Harvey 147 The drive-wise project: driving simulator training increases real driving performance in healthy older drivers Gianclaudio Casutt, Nathan Theill, Mike Martin, Martin Keller and Lutz Jäncke 161 Age-related increases in false recognition: the role of perceptual and conceptual similarity Laura M. Pidgeon and Alexa M. Morcom 178 Holistic face perception in young and older adults: effects of feedback and attentional demand Bozana Meinhardt-Injac, Malte Persike and Günter Meinhardt Methodological considerations 191 Spread of activation and deactivation in the brain: does age matter? Brian A. Gordon, Chun-Yu Tse, Gabriele Gratton and Monica Fabiani EDITORIAL published: 08 June 2016 doi: 10.3389/fnagi.2016.00130 Frontiers in Aging Neuroscience | www.frontiersin.org June 2016 | Volume 8 | Article 130 | Edited by: Gemma Casadesus, Kent State University, USA Reviewed by: Matthieu P. Boisgontier, University of Leuven, Belgium *Correspondence: Harriet A. Allen h.a.allen@nottingham.ac.uk Received: 16 February 2016 Accepted: 25 May 2016 Published: 08 June 2016 Citation: Allen HA and Roberts KL (2016) Editorial: Perception and Cognition: Interactions in the Aging Brain. Front. Aging Neurosci. 8:130. doi: 10.3389/fnagi.2016.00130 Editorial: Perception and Cognition: Interactions in the Aging Brain Harriet A. Allen 1 * and Katherine L. Roberts 2 1 School of Psychology, University of Nottingham, Nottingham, UK, 2 Department of Psychology, University of Warwick, Coventry, UK Keywords: aging, perception, cognition, vision, audition The Editorial on the Research Topic Perception and Cognition: Interactions in the Aging Brain Healthy aging can lead to declines in both perceptual and cognitive functions. Many of the studies in this Topic demonstrate such age-related declines, but also identify links between them. Encouragingly, these links suggest that improving perception could benefit cognition. In addition, while compensatory cognitive strategies were mainly unsuccessful in improving perception, cognitive training was effective under certain conditions. COMMON AGE-RELATED DECLINE Cognitive and perceptual change may be linked because they are susceptible to the same age- related factors. In the present Topic, several studies suggest an age-related widening of tuning or a decrease of inhibition between representations. Both Chan et al. and McGovern et al. find that older adults are more likely to judge sound and lights presented asynchronously as synchronous. At the same time, Sapkota et al. find that older adults report more distractor items in a memory test. Pidgeon and Morcom also find that older adults are more susceptible to intrusions from distractor items, particularly if they are conceptually or perceptually similar to the target item. Similarly, Meinhardt-Injac et al. find that the unattended half of a face has a bigger influence on older (compared to younger) adults’ judgments of face identity. These have some conceptual similarity with cognitive researchers’ suggestions of age-related loss of focus, increased distractibility, and increased effects of similarity. For example, increased interference from distractors could be due to increased ambiguity in the way that target items are represented in the brain. In perceptual regions this could present as widening of tuning of receptors (Hua et al., 2006; Yu et al.; Betts et al., 2007). In higher-level areas this could present as less distinct category representations, leading to a higher reliance on “gist.” The results of Hutchinson et al. and Komes et al. might be considered inconsistent with this broadening of tuning account. Hutchinson’s finding of enhanced motion perception in older people could be interpreted as reflecting an age-related narrowing, rather than broadening, of tuning, while Komes’ results indicate that poor memory is not associated with poor perceptual representations. In both cases, further research will help discriminate between a purely perceptual account and explanations that rely on attention and strategy changes. It therefore seems that while widening of tuning and more gist-based processing offer an explanation for a wide range of results, it is not yet a comprehensive explanation for all changes that occur with aging. It is not clear, for example, whether higher cognitive processes can offset the effects of perceptual tuning changes. 6 Allen and Roberts Perception and Cognition in Aging FROM IMPAIRED PERCEPTION TO IMPAIRED COGNITION Poor perception may lead to, or exacerbate, cognitive impairment (see Roberts and Allen for a review). As perceptual input gets harder to discriminate, more cognitive effort, or processes are required to decode the incoming signal. This may lead to worse performance by older adults because, effectively, the task they are performing is harder. Mishra et al. attempt to quantify this loss of cognitive resources through their Cognitive Spare Capacity Test. When perceptual and cognitive deficits co-occur, cognitive skills may appear worse due to knock-on effects of poor perception on cognition. Thus, it might be tempting to ascribe a cognitive cause to what is, in fact, a perceptual deficit. Perceptual deficits can impact on cognition to the extent that a measure of (cognitively controlled) eye movements has potential to be used to diagnose eye disease (Crabb et al.). It is therefore important to fully account for perceptual impairment before concluding that there is a cognitive deficit, as was done in this Topic by Schoof and Rosen and Füllgrabe et al. In these studies, older adults were recruited who, unusually, had normal hearing sensitivity as measured by audiogram. Auditory temporal perception was also evaluated, as it is often impaired in older age and impacts on speech-in-noise perception. Even in these audiometrically-normal adults, the ability to understand speech in noise was predicted by a combination of temporal processing ability and cognitive performance (Füllgrabe et al.). Accounting for perception may therefore need to go beyond perceptual sensitivity to also consider suprathreshold processing (Allen et al., 2010; Füllgrabe et al.). In the longer term, older adults with hearing impairment can show a faster rate of cognitive decline than those without (Lin et al., 2013). While this could be mediated by a separate factor, such as social isolation (Strawbridge et al., 2000), it may be that continual exposure to impoverished perceptual input leads to decrements in cognitive processes. A test of this idea is offered by Rönnberg et al., who discuss whether continued mismatch between perceptual input and long-term memory (LTM) representations could lead to less efficient LTM function. They find that even performance on a visually presented memory task is correlated with hearing loss, suggesting the impact of perceptual loss may be supramodal (Rönnberg et al.). These studies suggest that the constant, and cumulative effort of coping with impaired perception could impact substantially on age-related cognitive decline. COGNITIVE IMPROVEMENTS FROM TRAINING AND PERCEPTUAL INTERVENTIONS In this Research Topic, while there was evidence for compensatory cognitive strategies, in most cases this led to different, rather than equivalent performance to younger adults. For example, reliance on gist led to increased false recognition (Pidgeon and Morcom), and reduced right- hemispheric dominance led to reduced pseudoneglect on a line bisection task (Benwell et al.). Komes et al. found that older adults who had more accurate memory for faces had a more bilateral electroencephalographic response than those with less accurate memory, presumably indicating some sort of cognitive compensatory process, but they still performed worse than younger adults. In contrast, optimizing the perceptual input did, in some cases, lead to unimpaired cognition (e.g., Hutchinson et al.; Schoof and Rosen). This is demonstrated here by Rönnberg et al., who found that the impact of hearing loss on cognition could be mitigated via hearing aids. Although direct comparisons are limited by the difficulty of equating the complexity of perceptual and cognitive tasks, these results certainly put some limits on the extent of possible compensation mechanisms. Older adults did show a benefit from cognitive training, particularly when that training was optimized for their needs. Casutt et al. improved older adults’ on-road driving behavior and cognitive performance through training in a driving simulator. Meinhardt-Injac et al. found that older adults could benefit from feedback on a face-processing task when cognitive demands were low, although they were unable to benefit when cognitive demands were high. METHODOLOGICAL CONSIDERATIONS To clarify the relative contributions of perception and cognition, it may be tempting to use perceptual tests in one modality and cognitive tests in another (e.g., Rönnberg et al.; Schoof and Rosen; Füllgrabe et al.). Sometimes this is deliberate, so that cognitive measures will not be confounded by perceptual difficulties, but sometimes it is simply due to an established cognitive test being in a particular modality. It should be noted, though, that cognitive skills are not necessarily supramodal. Cognitive impairments such as neglect can arise in one modality but not another (e.g., Sinnett et al., 2007). Furthermore, some perceptual features are more critical to one modality than another (e.g., spatial location, Roberts et al., 2006, 2009). It is also important to consider whether outcome measures are optimized to detect age-related effects. Gordon et al. report that functional magnetic resonance imaging measures of the peak and spread of activation are separately informative about older adults’ performance on a cognitive task. During performance on a Sternberg task, some age-related effects were only apparent when looking at measures of spread. Komes et al. also found differences in the distribution of (EEG) activation in older adults with good vs. poor memory. CONCLUSIONS The link between perception and cognition is not well understood. It is possible that perception and cognition are affected by the same, superordinate cause. How much of age-related change can be explained by gradual widening of tuning or categories is a promising and interesting route for further work. This could also help to improve Frontiers in Aging Neuroscience | www.frontiersin.org June 2016 | Volume 8 | Article 130 | 7 Allen and Roberts Perception and Cognition in Aging older adults’ performance on cognitive tasks. For example, where older adults show a broadening of representations or increased reliance on gist, cognitive performance could be improved by providing more distinctive or spatially-separated stimuli (Pidgeon and Morcom; Sapkota et al.). While broadening of tuning appears to have multimodal effects, other interactions between perception and cognition appear to differ between modalities. Impaired perception may put a load on cognition, perhaps eventually leading to capacity loss. It is interesting to note, however, that these studies are predominantly from the auditory domain. It remains to be seen whether this generalizes to visual stimuli. AUTHOR CONTRIBUTIONS All authors listed, have made substantial, direct and intellectual contribution to the work, and approved it for publication. REFERENCES Allen, H. A., Hutchinson, C. V., Ledgway, T., and Gayle, P. (2010). The role of contrast sensitivity in global motion processing deficits in the elderly. J. Vis. 10:15. doi: 10.1167/10.10.15 Betts, L. R., Sekuler, A. B., and Bennet, P. J. (2007). The effects of aging on orientation discrimination. Vision Res. 47, 1769–1780. doi: 10.1016/j.visres.2007.02.016 Hua, T., Li, X., He, L., Zhou, Y., Wang, Y., and Leventhal, A. G. (2006). Functional degradation of visual cortical cells in old cats. Neurobiol. Aging 27, 155–162. doi: 10.1016/j.neurobiolaging.2004.11.012 Lin, F. R., Yaffe, K., Xia, J., Xue, Q.-L., Harris, T. B., Purchase-Helzner, E., et al. (2013). Hearing loss and cognitive decline in older adults. JAMA Intern. Med. 173, 293–299. doi: 10.1001/jamainternmed.2013.1868 Roberts, K. L., Summerfield, A. Q., and Hall, D. A. (2006). Presentation modality influences behavioral measures of alerting, orienting, and executive control. J. Int. Neuropsychol. Soc. 12, 485–492. doi: 10.1017/S1355617706060620 Roberts, K. L., Summerfield, A. Q., and Hall, D. A. (2009). Covert auditory spatial orienting: An evaluation of the spatial relevance hypothesis. J. Exp. Psychol. Hum. Percept. Perform . 35, 1178–1191. doi: 10.1037/a0014249 Sinnett, S., Montserrat, J., Rafal, R., Azanon, E., and Soto- Faraco, S. (2007). A dissociation between visual and auditory hemi-inattention: evidence from temporal order judgements. Neuropsychologia 45, 552–560. doi: 10.1016/j.neuropsychologia.2006. 03.006 Strawbridge, W. J., Wallhagen, M. I., Shema, S. J., and Kaplan, G. A. (2000). Negative consequences of hearing impairment in old age: a longitudinal analysis. Gerontologist 40, 320–326. doi: 10.1016/j.neuropsychologia.2006. 03.006 Conflict of Interest Statement: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Copyright © 2016 Allen and Roberts. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Frontiers in Aging Neuroscience | www.frontiersin.org June 2016 | Volume 8 | Article 130 | 8 MINI REVIEW published: 01 March 2016 doi: 10.3389/fnagi.2016.00039 Perception and Cognition in the Ageing Brain: A Brief Review of the Short- and Long-Term Links between Perceptual and Cognitive Decline Katherine L. Roberts 1 * and Harriet A. Allen 2 1 Department of Psychology, University of Warwick, Coventry, UK, 2 School of Psychology, University of Nottingham, Nottingham, UK Edited by: Gemma Casadesus, Kent State University, USA Reviewed by: Daniel Ortuño-Sahagún, Centro Universitario de Ciencias de la Salud, Mexico Archana Mukhopadhyay, University of Kansas, USA *Correspondence: Katherine L. Roberts k.roberts@warwick.ac.uk Received: 17 September 2015 Accepted: 15 February 2016 Published: 01 March 2016 Citation: Roberts KL and Allen HA (2016) Perception and Cognition in the Ageing Brain: A Brief Review of the Short- and Long-Term Links between Perceptual and Cognitive Decline. Front. Aging Neurosci. 8:39. doi: 10.3389/fnagi.2016.00039 Ageing is associated with declines in both perception and cognition. We review evidence for an interaction between perceptual and cognitive decline in old age. Impoverished perceptual input can increase the cognitive difficulty of tasks, while changes to cognitive strategies can compensate, to some extent, for impaired perception. While there is strong evidence from cross-sectional studies for a link between sensory acuity and cognitive performance in old age, there is not yet compelling evidence from longitudinal studies to suggest that poor perception causes cognitive decline, nor to demonstrate that correcting sensory impairment can improve cognition in the longer term. Most studies have focused on relatively simple measures of sensory (visual and auditory) acuity, but more complex measures of suprathreshold perceptual processes, such as temporal processing, can show a stronger link with cognition. The reviewed evidence underlines the importance of fully accounting for perceptual deficits when investigating cognitive decline in old age. Keywords: perception, cognition, ageing, audition, vision INTRODUCTION It is well known that ageing is associated with declines in both perception and cognition. As we age, there is increased need for perceptual aids such as glasses and hearing aids, and we start to find cognitive tasks such as paying attention and remembering more difficult. It is possible that perception and cognition decline in tandem due to common effects of ageing, but there is also evidence to suggest that declines in perception and cognition impact on each other, both in the short and long term ( Figure 1 ). Here we review evidence that impoverished perceptual input can increase the cognitive difficulty of tasks, while changes to cognitive strategies and processes can compensate, to some extent, for impaired perception. We also review evidence that both visual and auditory perceptual impairments are associated with a faster rate of cognitive decline, and consider whether perceptual aids, such as hearing aids and glasses, can provide protection against cognitive decline. AGE-RELATED DECLINES IN HEARING, VISION AND COGNITION The ability to hear faint sounds in a quiet environment deteriorates with age. Peripheral hearing sensitivity, as measured by the audiogram, is impaired in around a third of 61–70 year olds Frontiers in Aging Neuroscience | www.frontiersin.org March 2016 | Volume 8 | Article 39 | 9 Roberts and Allen Perception, Cognition and Ageing FIGURE 1 | Diagram of the potential links between healthy ageing, auditory and visual perception, and auditory and visual cognition. and almost two thirds of over-70 year olds (Davis, 1989; Cruickshanks et al., 1998; Wilson et al., 1999). Ageing can also affect suprathreshold auditory processing. Sensitivity to temporal fine structure is impaired in older adults, even in those with normal audiometric thresholds (Grose and Mamo, 2010; Füllgrabe, 2013; Füllgrabe et al., 2015), as is sensitivity to changes in the temporal envelope (Füllgrabe et al., 2015). Vision also declines in old age. As with hearing, many of these changes are peripheral, and other changes affect central processing. Hardening of the lens leads to presbyopia, which makes it more difficult to focus on near objects. As well as age- related eye diseases such as cataracts, glaucoma and macular degeneration, healthy ageing is linked to a thickening and yellowing of the lens (Said and Weale, 1959; Ruddock, 1965). Ageing is also associated with changes in color perception (Page and Crognale, 2005), temporal resolution (Wright and Drasdo, 1985; Kim and Mayer, 1994; Culham and Kline, 2002), visual acuity (Spear, 1993), motion perception (Snowden and Kavanagh, 2006; Hutchinson et al., 2012), and a loss of fine detail (high spatial frequency) pattern vision (Elliott, 1987; Pardhan, 2004). Deficits in one sensory modality can sometimes be offset through other senses, e.g., using visual speechreading to support impaired hearing (Dickinson and Taylor, 2011), or increased multisensory integration (Freiherr et al., 2013). This may be limited in older age when both hearing and vision decline, particularly as declines in vision and audition appear to be linked, with higher than expected rates of dual-sensory decline (Dawes et al., 2014). Old age also brings decline in a number of cognitive abilities, including working memory, memory, attention, and executive control (Schaie, 1996; Hedden and Gabrieli, 2004). Cross- sectional and longitudinal studies consistently find that ageing is related to poor performance on tasks involving cognitive control and switching, manipulation of information, visuospatial processing, processing speed and more (for an extensive list of studies, see Hofer et al., 2003). There are a number of proposed explanations for this decline, including generalized slowing (e.g., Salthouse, 1996) and dedifferentiation (e.g., Wilson et al., 2012). In this brief review, we focus on the role of sensory function. A number of cross-sectional, population-based studies have demonstrated a link between (auditory and visual) sensory impairment and poor cognition in old age (Lindenberger and Baltes, 1994; Baltes and Lindenberger, 1997; Lin et al., 2004, 2011; Tay et al., 2006; Moore et al., 2014), that does not simply reflect the visibility or audibility of the task materials (Lindenberger et al., 2001). The association between perception and cognition is also present in younger adults, but is stronger in older adults (Baltes and Lindenberger, 1997). While the evidence for a link between perception and cognition is compelling, it is not universally found. Two studies have found a link between vision and cognition but not hearing and cognition (Anstey et al., 2001; Gussekloo et al., 2005), one study failed to find a link between hearing and cognition (Gennis et al., 1991), and one found no link between visual or auditory function and cognition in a narrow-age cohort sample of 75 year olds (Hofer et al., 2003). The majority of studies that have attempted to link sensory and cognitive decline have used only visual (or auditory) acuity as a proxy for more general perceptual decline (e.g., Anstey et al., 2001; Hofer et al., 2003). If a common factor underlies age-related changes in performance, then we would expect changes to also affect more central, suprathreshold perceptual skills. However, few studies have used more higher order, cortical measures of perception. Humes et al. (2013) used an index of temporal sensory processing and found a clear link to performance on temporal cognitive tasks. Glass (2007) found that visual contrast sensitivity was a better predictor of performance in cognitive tasks with unfamiliar, multiple or complex stimuli than simple stimuli. These results suggest that going beyond simple sensory acuity may reveal a more direct link to cognitive task performance. Various hypotheses have been proposed to account for the link between perception and cognition ( Table 1 ; see Wayne and Johnsrude, 2015 for a recent review of these hypotheses in the Frontiers in Aging Neuroscience | www.frontiersin.org March 2016 | Volume 8 | Article 39 | 10 Roberts and Allen Perception, Cognition and Ageing TABLE 1 | Proposed hypotheses for the link between perceptual and cognitive decline in old age. Hypothesis Description Common cause A third, general factor underlies the decline in both perception and cognition (Lindenberger and Baltes, 1994; Baltes and Lindenberger, 1997). Cognitive load on perception Poor cognition results in poor performance on perceptual tests (Lindenberger and Baltes, 1994). Information degradation Impoverished perceptual input impacts on performance on cognitive tasks (Schneider and Pichora-Fuller, 2000). Sensory deprivation Over time, impoverished perceptual input leads to cognitive decline (Lindenberger and Baltes, 1994). Note that these hypotheses are not mutually exclusive. auditory modality). Here we consider both vision and audition as well as possible effects of compensatory cognition. EFFECTS OF AGEING INFLUENCE BOTH PERCEPTION AND COGNITION (“COMMON CAUSE”) Sensory systems are subject to the same molecular and cellular processes as the rest of the body and as such, any general age- related change will affect both sensory and cognitive mechanisms (e.g., Pathai et al., 2013). Cardiovascular risk factors, for example, are associated with both hearing loss (Shargorodsky et al., 2010) and cognitive decline (Knopman et al., 2001). The link between sensory and cognitive impairment is typically found after adjusting for age, suggesting that it is not simply an effect of general ageing. In a detailed study, Humes et al. (2013) found that the link between age and cognitive function was entirely mediated by sensory function, based on a composite measure of auditory, visual and tactile perception. It therefore seems that while common effects of ageing do affect both perception and cognition, it is likely that perception and cognition directly impact on each other ( Figure 1 ). POOR COGNITION AFFECTS PERFORMANCE ON PERCEPTUAL TASKS (“COGNITIVE LOAD ON PERCEPTION”) Perception and cognition are highly interrelated, such that even measures that might be considered to be entirely sensory, such as the audiogram, have been shown to be influenced by cognition (Zwislocki et al., 1958). More complex perceptual tasks are likely to be more strongly influenced by the participant’s cognitive abilities. While it is important that researchers consider the impact of cognition on their perceptual measures, it seems unlikely that poor cognition drives purely perceptual decline. Schneider and Pichora-Fuller (2000) report empirical evidence of this, based on a study that showed age-related impairment for some perceptual tasks, but not others, despite cognitive demands being held constant across conditions (Pichora-Fuller and Schneider, 1991). In contrast, there is strong evidence that cognition has a compensatory role in adapting to impaired perception (see below and Figure 1 ). A more likely causal link between perception and cognition suggests that impoverished perceptual input impacts on cognitive function, both directly and in the longer term. IMPOVERISHED PERCEPTUAL INPUT DIRECTLY IMPACTS COGNITIVE RESOURCES (“INFORMATION DEGRADATION”) When the perceptual signal is poor, either through degraded stimuli or impaired perception, additional cognitive resources are required to decipher the signal. For example, cognitive load in listening tasks, as measured by the pupil response, is higher for those with hearing loss (Zekveld et al., 2011). This leaves fewer cognitive resources available for performing the cognitive task. A number of studies have demonstrated that recall of target words is impaired if the words are degraded, either through the addition of noise or hearing impairment, even when ensuring that the words can still be identified (e.g., Rabbitt, 1968, 1991; Pichora-Fuller et al., 1995; McCoy et al., 2005; Tun et al., 2009; Ng et al., 2013). This is generally considered to be evidence that the additional effort required to decode degraded stimuli takes up cognitive resources that would otherwise be involved in encoding and rehearsal (Rabbitt, 1968, 1991). Similar effects are found in young and older adults, and it is not yet clear whether ageing confers an additional deficit, over and above that of perceptual loss. Several studies have confounded age and hearing impairment by comparing young, normally-hearing adults with older, hearing-impaired adults (e.g., Pichora-Fuller et al., 1995; Mishra et al., 2014). Verhaegen et al. (2014) found that young and older adults with matched hearing impairment showed similar recall performance on a verbal short-term memory task, which was worse than that found in young adults with normal hearing. On the other hand, the link between working memory capacity and speech- in-noise perception has been shown to be weaker for young adults than normally-hearing older adults (Füllgrabe and Rosen, 2016) who differed in their sensitivity to temporal-fine-structure information (Füllgrabe, 2013). Recently there has been a concerted effort to describe and quantify the loss of cognitive resources when the perceptual input is degraded (Rudner and Lunner, 2014). This includes development of a ‘‘cognitive spare capacity’’ (CSC) test (Mishra et al., 2013), which is a measure of auditory working memory incorporating both storage and executive processing. Using this task under a variety of listening conditions, Mishra et al. (2014) found that older, hearing-impaired adults had similar CSC to young, normally-hearing adults when listening conditions were optimal. This again suggests that task difficulty in old age can relate to sensory, rather than cognitive, impairment. It is worth noting that all of the above evidence comes from auditory studies; the impact of impoverished visual input on visual cognition has been less thoroughly explored. Frontiers in Aging Neuroscience | www.frontiersin.org March 2016 | Volume 8 | Article 39 | 11 Roberts and Allen Perception, Cognition and Ageing Visual sensory quality has been suggested as an explanation for age-related changes in performance of the Stroop task (Ben-David and Schneider, 2009, 2010), providing a sensory explanation for what has previously been considered a change in (cognitive) inhibition. There is also evidence that hearing impairment affects performance on visual tasks. Rönnberg et al. (2014) found that older adults with hearing loss had worse performance on visuospatial short- and long-term memory (LTM) tasks. Similarly, an earlier study found a link between hearing loss and LTM function when the LTM task required motor encoding (Rönnberg et al., 2011). These findings point to more general effects of sensory loss than simply increasing the difficulty of cognitive tasks. Rönnberg et al. (2011) hypothesize that LTM representations are used less by people with hearing loss due to a mismatch between the input signal and the stored signal, and that this disuse leads to a decline in LTM over time. SENSORY IMPAIRMENT LEADS TO COGNITIVE DECLINE (“SENSORY DEPRIVATION”) A handful of longitudinal studies have shown that impaired perception is associated with cognitive decline, providing support for a causal link between perceptual and cognitive decline over time (Lin et al., 2004, 2013; Ghisletta and Lindenberger, 2005). For example, women with impaired (corrected) vision at baseline had a faster rate of cognitive decline over a 4 year period than those without visual impairment (Lin et al., 2004). In addition, Lin et al. (2013) found that poor hearing at baseline was associated with a higher rate of cognitive impairment and a faster rate of cognitive decline over a 6 year period. In contrast, Anstey et al. (2001) found a link between visual, but not auditory, decline and cognition over a 2 year period, and Valentijn et al. (2005) found that although there was a link between perceptual and cognitive decline, there was no convincing evidence that baseline auditory and visual acuity predicted cognitive decline over the following 6 years. The current evidence is therefore mixed, but it is important to note that only the effects of peripheral sensory changes, such as acuity, have been considered. There appears to be a stronger link with cognition when measures of perception go beyond simple sensory acuity (e.g., Humes et al., 2013). Several plausible mechanisms have been proposed to explain how impaired perception could lead to worsening cognition over time (e.g., Lin et al., 2013). One possibility is that poor percep