NoteEarly but not late-blindness leads to enhanced auditory perception
Introduction
Humans have a remarkable capacity to adapt to changes in environmental input, such as those associated with sensory deprivation. In the absence of visual input, blind individuals rely on sensory information from audition and touch to assist their navigation in environments that are generally designed for the sighted. It is not surprising, then, that blind individuals perform better than sighted individuals on attentional and spatial localization tasks (Lessard et al., 1998, Roder et al., 1999). Other research has demonstrated that blind individuals have superior speech perception (Hugdahl et al., 2004, Muchnik et al., 1991, Niemeyer and Starlinger, 1981) and verbal memory abilities (Amedi et al., 2003, Roder and Rosler, 2003). Even short-term visual deprivation of sighted individuals may lead to enhanced sound localization (Lewald, 2007) and pitch discrimination abilities (Gibby, Gibby, & Townsend, 1970).
The timing of blindness onset during development may determine the degree of sensory enhancement in the non-visual modalities (Neville & Bavelier, 2002). In the auditory domain, some studies indicate that early-blind individuals display superior performance compared to late-blind individuals (Gougoux et al., 2004, Voss et al., 2008), while others report these groups have similar abilities (Voss et al., 2004). Previous studies have tended to use different age ranges, with the lower limit for late-onset blindness varying from 5 years (Gougoux et al., 2004) to 18 years (Voss, Gougoux, Lassonde, Zatorre, & Lepore, 2006). With few exceptions (e.g., Kujala, Alho, et al., 1997), neuroimaging evidence suggests that individuals with early- and late-onset blindness show different degrees of cross-modal (occipital) activation during non-visual task processing (Buchel et al., 1998, Burton et al., 2003, Burton et al., 2004, Burton et al., 2002, Fieger et al., 2006). In particular, it has been suggested that 14–16 years represents an important cut-off (Cohen et al., 1999, Sadato et al., 2002). Individuals deprived of any visual input from birth may be most susceptible to changes in brain function induced by blindness. However, previous studies have not compared individuals with no visual experience (congenitally blind) with those becoming blind after visual experience early in life (early-blind).
A number of studies have investigated the ability of blind individuals to discriminate simple auditory stimuli. Early studies reported mixed findings (e.g., Sakurabayashi et al., 1956, Starlinger and Niemeyer, 1981), however, more recent research has supported superior pitch discrimination in blind individuals (Gougoux et al., 2004). None of these studies has attempted to control for differences in musical experience between blind and sighted participants, which is a key variable in auditory research (e.g., Gaab and Schlaug, 2003, Pitt, 1994). Enhanced auditory abilities may be due to greater musical experience, rather than to differences related to vision loss per se. For example, the prevalence of absolute pitch may be higher in blind individuals (Hamilton, Pascual-Leone, & Schlaug, 2004) and blind musicians with absolute pitch may show different brain activation patterns compared to sighted musicians with absolute pitch (Gaab et al., 2006, Ross et al., 2003).
The aim of the present study was to compare auditory perception skills in blind and sighted individuals, while controlling for factors that might influence these abilities. To ascertain whether visual deprivation (rather than practice) is primarily responsible for any observed differences, we systematically matched each blind participant with a sighted control on variables such as musical training and pitch naming ability (absolute pitch). We also directly compared individuals blinded at three phases in development (congenital, early-onset, late-onset) to investigate the developmental time frame for superior non-visual abilities following visual loss.
Section snippets
Participants
This study was approved by the Human Research Ethics Committee at The University of Melbourne. A total of 33 blind and 33 sighted participants took part in the study (N = 66). The blind participants were recruited from community organizations. In all, blindness was caused by peripheral defects. When tested, participants had minimal (or no) light sensitivity, no pattern vision, no significant hearing loss (as assessed by an audiogram) and were free of neurological deficits. All participants were
Results
For all tasks, the primary dependent variable was proportion correct. We applied the standard logit transformation, log(p/(1 − p)), to these proportions to put them on a suitable scale for statistical analysis (Fox, 1997). For each of the three tasks (pitch discrimination, pitch-timbre categorization, and pitch memory) we asked; is there an advantage of the blind over the sighted and if so, does it vary for the three onset groups (congenital, early, and late) and across difficulty levels?
Discussion
Our data support the notion that becoming blind early in life enhances auditory acuity. Blind participants who had functional vision until late childhood (≥14 years) performed no better than their sighted counterparts. This pattern was replicated across tasks and conditions. Our findings are consistent with those of neuroimaging studies which show different patterns of brain activation in early-blind compared to late-blind individuals (Cohen et al., 1999, Sadato et al., 2002).
This is the first
Acknowledgements
This research was supported by The Melbourne Research Grant Scheme 2006. A.G.W. was supported by a National Health and Medical Research Council Clinical Research Training Fellowship (251755). We would like to thank Jason Forte for his helpful comments.
References (47)
- et al.
Improved selective and divided spatial attention in early blind subjects
Brain Research
(2006) - et al.
Functional anatomy of pitch memory—An fMRI study with sparse temporal sampling
Neuroimage
(2003) - et al.
Blind individuals show enhanced perceptual and attentional sensitivity for identification of speech sounds
Cognitive Brain Research
(2004) - et al.
Faster reaction times in the blind than sighted during bimodal divided attention
Acta Psychologica
(1997) More accurate sound localization induced by short-term light deprivation
Neuropsychologia
(2007)- et al.
Human brain plasticity: evidence from sensory deprivation and altered language experience
Progress in Brain Research
(2002) - et al.
Memory for environmental sounds in sighted, congenitally blind and late blind adults: Evidence for cross-modal compensation
International Journal of Psychophysiology
(2003) - et al.
Effects of interstimulus interval on auditory event-related potentials in congenitally blind and normally sighted humans
Neuroscience Letters
(1999) - et al.
Auditory memory in congenitally blind adults: A behavioral-electrophysiological investigation
Cognitive Brain Research
(2001) - et al.
Cortical plasticity in an early blind musician: An fMRl study
Magnetic Resonance Imaging
(2003)
Critical period for cross-modal plasticity in blind humans: A functional MRI study
Neuroimage
Functional characteristics of auditory cortex in the blind
Behavioural Brain Research
Differential occipital responses in early- and late-blind individuals during a sound-source discrimination task
Neuroimage
Early- and late-onset blind individuals show supra-normal auditory abilities in far-space
Current Biology
Early ‘visual’ cortex activation correlates with superior verbal memory performance in the blind
Nature Neuroscience
Enhanced pitch sensitivity in individuals with autism: A signal detection analysis
Journal of Cognitive Neuroscience
Different activation patterns in the visual cortex of late and congenitally blind subjects
Brain
The voice-recognition accuracy of blind listeners
Perception
Dissociating cortical regions activated by semantic and phonological tasks: A fMRI study in blind and sighted people
Journal of Neurophysiology
Cortical activity to vibrotactile stimulation: An fMRI study in blind and sighted individuals
Human Brain Mapping
Adaptive changes in early and late blind: A fMRI study of verb generation to heard nouns
Journal of Neurophysiology
Period of susceptibility for cross-modal plasticity in the blind
Annals of Neurology
Expansion of the tonotopic area in the auditory cortex of the blind
Journal of Neuroscience
Cited by (139)
Brain structural changes in blindness: a systematic review and an anatomical likelihood estimation (ALE) meta-analysis
2023, Neuroscience and Biobehavioral ReviewsEffects of blindness and anosmia on auditory discrimination of temperature and carbonation of liquids
2023, Food Quality and PreferenceDo blind people hear better?
2022, Trends in Cognitive SciencesCitation Excerpt :Improved frequency perception cannot be attributed solely to superior musical abilities, as these findings have been replicated in studies that controlled for musical ability [18,25]. However, the impact of vision during development on frequency processing is less clear because similar superior frequency discrimination was identified in both early- and late-blind subjects [18,27,28]. The simple nature of these tasks may eliminate any biological advantage from improving these skills in the blind.