Fragile X

Question 1

What is fragile X sndrome

Answer 1

• genetic disorder
• known etiology
• isn’t quite a developmental disorder but is a common cause of intellectual disability
• affects 1/4000 males (Turner 1996)
• 1/5000 to 8000 females (Crawford 2001)
• had distinctive physical, intellectual behavioural and emotional features

Question 2

physical characteristics of Fragile X

Answer 2

• may or may not be present and more common in males
• broad forehead, elongated face, large prominent ears, crossed eyes
• indentation of chest, mitral valve prolapse, low muscle tone, flat fleet
• seizures in about 10%

Question 3

behavioural weaknesses of fragile X

Answer 3

• social anxiety
• hyperarousal to sensory stimuli
• distractability
• irritability
• high activitly level
• repetitive motor behaviour
• difficulty coping with change or unpredictable events
• language problems
• clearly similar to ASD

Question 4

behavioural strengths in fragile X

Answer 4

• imitation
• visual learning
• long term memory
• sensitive to others emotions
• good sense of humor

Question 5

what causes fragile x sydrome

Answer 5

• Fragile X has narrowing at the end of some of the X chromosomes (males have XY females have XX)
• FMR-1 gene located at fragile site, produces FMRP protein which is required for brain development & function
• the triplet CGG is repeated in the FMR-1 gene, and if number of repeats is too large then gene becomes faulty
• short 6-50 times, most people medium 50-200 times, FMR-1 still works, no fragile X, 200 times or more then faulty gene and no longer producing FMRP protein
• the consequences of this differ for men and women

Question 6

discuss consequences of FMR-1 mutation in males and females

Answer 6

• all men with mutation will have fragile x
• women with mutation on only one X are carriers - as one copy of the X is switched in in each cell then half cells will have faulty gene switched on. They’ll produce less protein but at least some will be produced
• its usually passed on by mother carriers, daughters qill be carriers with some symptoms, sons will have full fragile x sundrome`

Question 7

discuss executive functio impairemnts in fragule x v generally

Answer 7

• attention
• inhibition
• the profile of these difficulties is distict from other developmental disorders

Question 8

discuss attentional profile of fragile x syndrome

Answer 8

• Munir 2000
• boys with FXS, boys with downs syndrome, and controls
• battery of attention ad EF tasks
• e.g. selective attention, divided attention, sustained attention
• selective attention was worse in FXS than down suyndrome
• divided attention was same
• sustained attention was same for FXS, downs and poor performance of typical developing age matches, other tasks performed worse tha controls
• FXS was worse in EF correct inhibitions task than DS, but DS better than FXS in same-opposite EF task

Question 9

discuss the executive functions of FXS

Answer 9

• wilding 2002
• further analysed munir 2000s work
• types of errors made differed between control groups and suyndromeg groups
• FXS and DS pattern similar but FXS more impaired
• probable difficulties in inhibiting previously successful response

Question 10

discuss working memory in FXS

Answer 10

• munir 2000 part b
• same gorups as before: so boys with FXS dows control groups
• working memory tasks: phonological loop: tests on nonword repetition, forward digit span
• visuospatial sketchpad: spatial memory task
• central executive: backward digit span, story retelling task

Question 11

discuss inhibition in fragile x

Answer 11

• cornish 2004
• proposed a primary deficit in behavioural inhibition leading to:
• difficulties attending to and processing complex sequential information (tendency to repeat processes rather than switch)
• tangential and perseverative language
• pattern of difficulties is not consistent with the idea of impaired and intact modalities

Question 12

summarise the cognitive aspects of fragile x

Answer 12

• abnormalities in attention and ex funct
• but some areas impaired more than others
• may be the result of problems with behavioural inhibition
• this would explain some of hte unusual behavioural features

Question 13

what studies are needed into fragile x

Answer 13

• more longitudinal studies to assess cognitive performance over time and find developmental trajectories

Question 14

discuss link between fragile x and ASD

Answer 14

• obv some of the symptoms overlap
• 1/4 males with FXS meet criteria for ASD - Bailey 1998
• FXS is the single most common genetic ‘cause’ of ASD
• but some argue that FXS jus t causes the same behavioural features of ASD for different reasons: e.g. social difficulties due to hyperarousal and anxiety rather than a failure in theory of mind
• Grant 2007 found no diff between FXS and FXS with ASD and false beleif tasks: they were both ewually as bad. suggests task difficulty may relate to working memory issues rather than lack of theory of mind
• Dalton 2008, FXS and also ASD (separate) performed worse on identifying emotions of faces
• Hoeft 2011, brain volumes for ASD and FXS were sometimes on opposite extrmemes (a lot more, a lot less) relative to control groups e.g. orbitofrontal cortex, amygdala. does suggesrt same symptoms for different reasons