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Planum temporale boundaries in dating


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After Planum temporale boundaries in dating loss, the deprived cortex can reorganize to process information from the remaining modalities, a phenomenon known as cross-modal reorganization. In blind people this cross-modal processing supports compensatory behavioural enhancements in the nondeprived modalities. Deaf people also show some compensatory visual enhancements, but a direct relationship between these abilities and cross-modally reorganized auditory cortex has only been established in an animal model, the congenitally deaf cat, and not in humans.

We tested for a correlation between this measure and visual motion detection thresholds, a visual function where deaf people show enhancements as compared to hearing. We found that the cortical thickness of a region in the right hemisphere planum temporale, typically an auditory region, was greater in deaf individuals with better visual "Planum temporale boundaries in dating" detection thresholds.

This same region has previously been implicated in functional imaging studies as important for functional reorganization. When an individual is deprived of a sensory modality, the other senses can compensate for the loss with behavioural enhancements. This effect has been demonstrated in both deaf and blind humans, as well as in animal models of sensory deprivation for a review, see [ 12 ]. Generally, the sensory enhancements that occur after deprivation are attributed to the extra processing power that is afforded by the recruitment of the deprived sensory cortex, which is thought to reorganize to support the enhancement.

Support for this relationship between enhanced sensory behaviour and cross-modal processing comes from human research on blindness, where enhanced performance on various tasks correlates with task-related activity [ 3 — 7 ], and cortical thickness [ 8 ] of visual regions in the occipital cortex.

While the evidence for this relationship is convincing, no research to date has established a direct connection between cross-modal plasticity and enhanced sensory behaviour in deaf people.

In deaf people, research on enhanced sensory behaviour and cross-modal plasticity has progressed mostly independently.

However, the specificity of the...

In terms of sensory compensation, much research has focused on the role of vision. While some behavioural enhancements have been attributed to changes in visual attention for a review, see [ 11 ]others appear to be due to changes to basic sensory processing.

These include enhancements to motion detection [ 12 ], discrimination of the angle of motion direction [ 13 ], a larger field of view [ 1415 ], and faster reaction times to visual stimuli [ 16 — 18 ], with a possible bias for peripheral visual fields [ 1920 ] but see [ 1718 ]. Some of these behavioural enhancements may be supported by changes to both the peripheral and early cortical components of the visual system.

For example, visual field area in deaf people correlates with neural rim area on the retina, denotative of increased retinal ganglion cells, and changes to the retinal neural fiber layer distribution [ 15 ]. Additionally, reaction times for target detection correlate with early Planum temporale boundaries in dating potentials in the visual cortex [ 17 ]. However, none of these behavioural enhancements have been directly associated with plasticity in the auditory cortex.

In early-deaf people, this activity consistently occurs in the right hemisphere planum temporale and adjoining superior temporal gyrus [ 21 — 27 ]. The left planum temporale [ 2526 ] and primary auditory cortex [ 2122 ] also show activity in response to motion versus static stimuli, although these regions are not activated in every study [ 232627 ].

While these studies clearly demonstrate the responsivity of the deprived sensory cortex to the nondeprived stimuli, they do not assess its association with enhanced sensory performance, as has been done in the human blind population with correlation and regression analyses e.

Testing the relationship between the auditory cortex and vision is necessary to demonstrate that cross-modal reorganization in deaf people supports enhanced visual abilities [ 28 ]. In the current study, we hypothesized that compensatory visual enhancements in deaf people are supported by plasticity in auditory cortex.

Based on parallel research questions in the blind [ 8 ], we reasoned that if a cortical region supports sensory enhancement in the deaf, then its cortical thickness will vary in relation to behavioural performance. Although much previous research Planum temporale boundaries in dating examined anatomical changes in the deaf brain, results have concentrated on changes that are associated with sensory "Planum temporale boundaries in dating" [ 29 — 37 ] rather than compensatory plasticity.

In auditory regions, these changes include decreased white matter volume [ 30333438 ] and white matter integrity, as measured by diffusion-weighted MRI [ 29 — 3135 ]. In contrast, grey matter volume in auditory regions appears to be preserved after deafness [ 33 — 38 ].

Few studies have examined cortical thickness, and no changes have been documented between deaf and hearing adults in auditory regions with this measure [ 35 ]. Given the lack of evidence for atrophy of grey matter after deafness, we expected that cortical thickness might capture compensatory plasticity, rather than disuse-related atrophy.

To test our hypothesis, we used visual motion detection thresholds as a gauge for enhanced visual abilities, based on evidence for improved performance in the deaf as compared to hearing on this task Planum temporale boundaries in dating 12 ].

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