Cortical reorganisation in the blind (cross-modal) Flashcards
Lessard et al
(1998) - Early blind PS map their auditory environment with better accuracy than controls
Gagnon et al
(2014) - blind PS have reduced taste perception.
- Most likely a results of reduced food variety in congenitally blind PS
Shows how practice of useful senses drives compensatory effects
Elbert et al
(2002) - Tonotopic area of the auditory cortex was enlarged by a factor of 1.8 in blind PS compared to controls
- Latency of the N1m component was sig. decreased
- Reduced latency of auditory evoked potential suggests more efficient processing
Rombaux et al
(2010) - MRI scans to measure the size of the olfactory bulb (OB) in 10 early blind PS compared to controls
- Significant difference (34.3mm3) found between size of OB
- Odor discrimination and free identification tasks in these EB PS yielded higher scores
Veraat et al
(1990) - Visual cortex activity was higher in EB PS compared to blindfolded controls
- lead to the assumption that the visual brain does not lay dormant and unused.
Weeks et al
(2000) - Using PET, Auditory localization tasks activate the visual cortex (V5) of the congenitally blind more than in controls
Cuevas et al
(2011) - Chemosensory ERPs investigated effects of passive odor perception in early blind PS vs controls.
- No difference found in letencies, amplitudes and topographical distribution in the occipital cortex
Renier et al
(2013) - fMRI looked at occipital recruitment of higher level odour tasks in early blind PS.
- Strong activation of occipital cortex found during discrimination and categorisation
Ptito et al
(2005) - investigated neural correlates of tongue stimulation in 6 congenitally blind PS vs blindfolded controls using PET
- Both blind and controls learned (following 7 days training) the letter orientation task to the same degree of accuracy
- After training only, large occipital rCBF increases were seen in blind PS only
- The fact that they were congenitally blind, and no such activity was seen in controls make the results unlikely to be due to mental imagery
Sadato et al
(1996) - Showed that PVC is activated in EB PS performing a braille reading task
this occipital recruitment may have also been driven by lexical processing…
Amedi et al (2003)
(2003) - found V1 activation during verbal-memory task.
- Magnitude of activation highly correlated with blind individuals ability, suggesting a functional role.
Cohen et al
(1997) - TMS to occipital cortex disrupts Braille reading only in blind PS
Therefore occipital recruitment functional
Amedi et al (2001)
(2001) - Tactile presentation of objects caused occipital activation (LOC) in normal PS
Hagen et al
(2002) - Tactile motion activated normal sighted PS’s V5
Zangaladze et al
(1999) - TMS to occipial cortex interferes with processing of tactile orientation tasks in sighted PS
Renier et al
(2013) Some occipital activation of visual brain areas in sighted PS in odour processing task
Pascual-Leone et al
(2008) - blindfolded sighted PS for 5 days and compared Braille accuracy as well as fMRI to sighted controls.
- On day 5, occipital activation found in blindfolded subjects only
- Functionally relevant: blindfolded PS better at Braille + TMS to occipital region disrupted performance in blindfolded PS only
- Occipital activations dissapeared 1 day after removing blindfold
The speed at which occipital recuitment was gained (and then lost) suggests that cross-modal plasticity is mediated by an unmasking of latent connections from non-visual modalities to the visual cortex.
- In sighted individuals, these connections are weaker and more transient due to visual information dominating the visual cortex.
- In blind PS (or indeed, blindfolded PS), the absence of visual inputs allows for an enhancement of cross-modal cortico-cortical connections
Edelman (Neural Darwinism)
(1993) - In the lack of a sensory modality (as in congenital blindness) the target structures are taken over by the afferent inputs from other senses.
Saenz
(2008)
found V5 activation during auditory motion in recovered blind PS
Held et al
(2011)
recovered-blind PS could not match tactile-visual objects within 48h of recovery
- However, following 5 days they could - suggests reweighting of crossmodal connection
