Long-term episodic memory deficits in
Alzheimer's dise
ase (AD)
are well ch
ar
acterised but, until recently, short-term memory (STM) function h
as
attr
acted f
ar less
attention. We employed
a recently-developed, del
ayed reproduction t
ask which requires p
articip
ants to reproduce precisely the remembered loc
ation of items they h
ad seen only seconds previously. This p
ar
adigm provides not only
a continuous me
asure of loc
aliz
ation error in memory, but
also
an index of
relational binding by determining the frequency with which
an object is mispl
aced to the loc
ation of one of the other items held in memory. Such
binding errors in STM h
ave previously been found on this t
ask to be sensitive to medi
al tempor
al lobe (MTL) d
am
age in foc
al lesion c
ases. Twenty individu
als with p
athologic
al mut
ations in presenilin 1 or
amyloid precursor protein genes for f
amili
al Alzheimer's dise
ase (FAD) were tested together with 62 he
althy controls. P
articip
ants were
assessed using the del
ayed reproduction memory t
ask,
a st
and
ard neuropsychologic
al b
attery
and structur
al MRI.
abspara0015">Overall, FAD mutation carriers were worse than controls for object identity as well as in gross localization memory performance. Moreover, they showed greater misbinding of object identity and location than healthy controls. Thus they would often mislocalize a correctly-identified item to the location of one of the other items held in memory. Significantly, asymptomatic gene carriers – who performed similarly to healthy controls on standard neuropsychological tests – had a specific impairment in object-location binding, despite intact memory for object identity and location. Consistent with the hypothesis that the hippocampus is critically involved in relational binding regardless of memory duration, decreased hippocampal volume across FAD participants was significantly associated with deficits in object-location binding but not with recall precision for object identity or localization. Object-location binding may therefore provide a sensitive cognitive biomarker for MTL dysfunction in a range of diseases including AD.