Cortical reorganisation in the blind (cross-modal)

Question 1

Lessard et al

Answer 1

(1998) - Early blind PS map their auditory environment with better accuracy than controls

Question 2

Gagnon et al

Answer 2

(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

Question 3

Elbert et al

Answer 3

(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

Question 4

Rombaux et al

Answer 4

(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

Question 5

Veraat et al

Answer 5

(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.

Question 6

Weeks et al

Answer 6

(2000) - Using PET, Auditory localization tasks activate the visual cortex (V5) of the congenitally blind more than in controls

Question 7

Cuevas et al

Answer 7

(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

Question 8

Renier et al

Answer 8

(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

Question 9

Ptito et al

Answer 9

(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

Question 10

Sadato et al

Answer 10

(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…

Question 11

Amedi et al (2003)

Answer 11

(2003) - found V1 activation during verbal-memory task.

- Magnitude of activation highly correlated with blind individuals ability, suggesting a functional role.

Question 12

Cohen et al

Answer 12

(1997) - TMS to occipital cortex disrupts Braille reading only in blind PS

Therefore occipital recruitment functional

Question 13

Amedi et al (2001)

Answer 13

(2001) - Tactile presentation of objects caused occipital activation (LOC) in normal PS

Question 14

Hagen et al

Answer 14

(2002) - Tactile motion activated normal sighted PS’s V5

Question 15

Zangaladze et al

Answer 15

(1999) - TMS to occipial cortex interferes with processing of tactile orientation tasks in sighted PS

Question 16

Renier et al

Answer 16

(2013) Some occipital activation of visual brain areas in sighted PS in odour processing task

Question 17

Pascual-Leone et al

Answer 17

(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

Question 18

Edelman (Neural Darwinism)

Answer 18

(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.

Question 19

Saenz

Answer 19

(2008)

found V5 activation during auditory motion in recovered blind PS

Question 20

Held et al

Answer 20

(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