Auditory selective attention in blind subjects: An ERP study

Auditory event-related potentials (ERPs) were recorded in early blind subjects and sighted controls when they attended to stimuli delivered to a designated ear under dichotic conditions. The scalp distribution of the processing negativity (PN), the endogenous negativity elicited by attended stimuli, was in the blind posterior to that in the sighted. This suggests that posterior brain areas normally involved in vision participate in auditory selective attention in the early blind. Furthermore, occasional higher-frequency tones in the to-be-ignored ear elicited a negativity (presumably the mismatch negativity; MMN) that had a posterior scalp distribution in the blind as compared to controls. This suggests that the posterior brain areas of the blind also participate in processing of auditory stimulus changes occurring outside the focus of attention.

Experimental Brain Research, 1995

Previous event-related potential (ERP) studies have suggested a possible participation of the visual cortex of the blind in auditory processing. In the present study, somatosensory and auditory ERPs of blind and sighted subjects were recorded when subjects were instructed to attend to stimuli of one modality and to ignore those of the other. Both modalities were stimulated with frequent ("standard") and infrequent ("deviant") stimuli, which differed from one another in their spatial locus of origin. In the sighted, deviant stimuli of the attended modality elicited N2 type of deflections (auditory N2b and somatosensory N250) over the lateral scalp areas. In contrast, in the blind, these ERP components were centroposteriorly distributed, suggesting an involvement of posterior brain areas in auditory and somatosensory stimulus discrimination. In addition, the mismatch negativity, elicited by deviant auditory stimuli even when the somatosensory stimuli were attended, was larger in the blind than in the sighted. This appears to indicate enhanced automatic processing of auditory stimulus changes in the blind. Thus, the present data suggest several compensatory changes in both auditory and somatosensory modalities after the onset of early visual deprivation.

2017

Neural plasticity, the ability of neural tissue to adapt to a number of environments, is considered a defining characteristic of the brain. However, plasticity is poorly understood at the systems level. The exact limits of neural plasticity, which areas can adapt and what functions they can perform, have not been well described in the literature. The study of deaf individuals represents a unique window into this phenomenon. Areas of the brain that are considered part of auditory cortex in a hearing person are still present in deaf individuals. Which functions these areas of cortex can perform in a deaf person, and which they cannot, may help us to understand the limits of plasticity in these tissues. Chapter 1 reviews the literature on neurological and behavioral changes in the deaf as it pertains to visual processing. Chapter 2 describes an optical imaging study, which used a peripheral visual attention task and fast optical imaging to examine changes in the auditory cortex of deaf individuals. Chapter 3 describes event-related potential (ERP) data on changes in an auditory ERP and attention-related components. Finally, Chapter 4 reviews the findings described above and proposes future directions for this research.

Physiological Research

The purpose was to test parameters of visual evoked potentials (VEPs) and of event-related potentials (ERPs) in deaf subjects to verify visual and cognitive CNS functions in a handicapped group of the population. Three types of visual stimuli (with dominating parvocellular or magnocellular system activation or with cognitive tasks) were used in the study. Six deaf persons (4 women, 2 men, mean age 17 years) and 6 persons with normal hearing (sex- and age-matched) were included in this pilot study. In all types of stimulation, latencies and amplitudes of main VEPs and ERPs components were evaluated. No significant latency differences were found. However, significantly reduced amplitudes were found in the occipital area for responses to motion and cognitive stimuli which might be interpreted as a part of functional reorganization of the extrastriate and cognitive cortical areas of deaf subjects.

Neurophysiology, 2019

In this study, systemic neurophysiological and neuropsychological mechanisms providing processing of visual information in subjects suffering from auditory deprivation were examined. In 30 men (21 to 25 year old) with complete congenital deafness and 30 control normally hearing men of the same age (groups D and C, respectively), cortical visual evoked potentials (VEPs, photostimulation of the right and left eyes by LED flashes, recording from the O1 and O2 loci) and neurodynamic characteristics of processing of visual information within the go/nogo/go paradigm were analyzed. Under conditions of the respective tests, all indices that characterize processing of simple visual information in deaf subjects (including number of processed stimuli, minimum exposure of the signal, and number of errors) were significantly worse than in the control group. It was also found that median values of the latency of the early VEP components (P1, N1, and P2) in group D were significantly smaller than the respective values in group C. At the same time, median latencies of the late VEP waves (N2 and P3) in deaf subjects were significantly greater than the analogous C-group values. Median values of the peak-to-peak amplitudes of all, with no exceptions, VEP components in group D were significantly (two times or even more) smaller than those in control subjects. Patterns of correlations between the indices of visual information processing and time/amplitude parameters of visual VEPs in the examined groups noticeably differed from each other. Thus, specific brain mechanisms responsible for processing of visual information in persons with auditory deprivation and with normal hearing demonstrate significant dissimilarity; central mechanisms of the visual system in deaf subjects undergo considerable cross-modality modifications.

PLoS ONE, 2011

Individuals with profound deafness rely critically on vision to interact with their environment. Improvement of visual performance as a consequence of auditory deprivation is assumed to result from cross-modal changes occurring in late stages of visual processing. Here we measured reaction times and event-related potentials (ERPs) in profoundly deaf adults and hearing controls during a speeded visual detection task, to assess to what extent the enhanced reactivity of deaf individuals could reflect plastic changes in the early cortical processing of the stimulus. We found that deaf subjects were faster than hearing controls at detecting the visual targets, regardless of their location in the visual field (peripheral or perifoveal). This behavioural facilitation was associated with ERP changes starting from the first detectable response in the striate cortex (C1 component) at about 80 ms after stimulus onset, and in the P1 complex (100-150 ms). In addition, we found that P1 peak amplitudes predicted the response times in deaf subjects, whereas in hearing individuals visual reactivity and ERP amplitudes correlated only at later stages of processing. These findings show that long-term auditory deprivation can profoundly alter visual processing from the earliest cortical stages. Furthermore, our results provide the first evidence of a co-variation between modified brain activity (cortical plasticity) and behavioural enhancement in this sensorydeprived population.

Behavioural Brain Research, 2009

2020

There is a general impression that visually blind individuals show an exceptionally better perception of other sensory modalities such as hearing, touch and smell sensations. In this study, we intended to compare the mid-latency auditory evoked potential response (MLAEP) or Middle latency Response (MLR) to get an idea of the activity pattern of auditory thalamus and cortex between 30 visually handicapped subjects and 30 normal sighted subjects. The results showed a decrease in many of the MLR wave latencies, but highly significant for the wave Pa (P value <0.002). This fact can be reflected as an evidence of existence of crossmodal neuroplasticity. We also inferred that there are significant gender differences with latencies shorter in males than females (P value <0.02) in the blind subjects group which could be attributed to their rehabilitation training.

PLoS ONE, 2012

The phenomenon of blindsight has been largely studied and refers to residual abilities of blind patients without an acknowledged visual awareness. Similarly, ''deaf hearing'' might represent a further example of dissociation between detection and perception of sounds. Here we report the rare case of a patient with a persistent and complete cortical deafness caused by damage to the bilateral temporo-parietal lobes who occasionally showed unexpected reactions to environmental sounds despite she denied hearing. We applied for the first time electrophysiological techniques to better understand auditory processing and perceptual awareness of the patient. While auditory brainstem responses were within normal limits, no middle-and long-latency waveforms could be identified. However, event-related potentials showed conflicting results. While the Mismatch Negativity could not be evoked, robust P3-like waveforms were surprisingly found in the latency range of 600-700 ms. The generation of P3-like potentials, despite extensive destruction of the auditory cortex, might imply the integrity of independent circuits necessary to process auditory stimuli even in the absence of consciousness of sound. Our results support the reverse hierarchy theory that asserts that the higher levels of the hierarchy are immediately available for perception, while low-level information requires more specific conditions. The accurate characterization in terms of anatomy and neurophysiology of the auditory lesions might facilitate understanding of the neural substrates involved in deaf-hearing.

Nature, 1999

Despite reports of improved auditory discrimination capabilities in blind humans and visually deprived animals, there is no general agreement as to the nature or pervasiveness of such compensatory sensory enhancements. Neuroimaging studies have pointed out differences in cerebral organization between blind and sighted humans, but the relationship between these altered cortical activation patterns and auditory sensory acuity remains unclear. Here we compare behavioural and electrophysiological indices of spatial tuning within central and peripheral auditory space in congenitally blind and normally sighted but blindfolded adults to test the hypothesis (raised by earlier studies of the effects of auditory deprivation on visual processing) that the effects of visual deprivation might be more pronounced for processing peripheral sounds. We find that blind participants displayed localization abilities that were superior to those of sighted controls, but only when attending to sounds in pe...