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Table 1 Chronological list of studies examining working memory in people with AN

From: A debate on working memory and cognitive control: can we learn about the treatment of substance use disorders from the neural correlates of anorexia nervosa?

Author
(chronological) and reported WM effect in AN
Participants Type of WM task Brain imaging Main findings ED symptoms and WM findings
Israel et al. (2015) [20]
BETTER
Female adults with ED:
ED-R (n = 19)
ED-BP
(n = 27)
Limitation: no control group, although the authors’ highlight that this is a pilot study.
N-back task with variable cognitive load (arithmetic) and stress (positive and negative feedback) fMRI (1.5 T) ED-R performed consistently better than the ED-BP group on all N-back versions. Further, the ED-R group had increased right DLPFC and premotor cortex activation during the 2-back vs. 0-back task in comparison to ED-BP. ED-BP had weaker WM activation than ED-R. Binge ED symptoms are associated with worse WM performance whereas restricting ED symptoms are associated with better WM performance. Right posterior prefrontal cortex activation is weaker during WM in those with binge ED. Age, BMI, Education influenced these findings, whereas anti-depressant medication and chronicity of illness did not.
Weider et al. (2015) [28]
WORSE
Female adults with ED:
AN (n = 40)
BN (n = 39)
HC (n = 40)
Working Memory Index (WAIS-III Manual): Paced Auditory Serial Addition Test (PASAT) 3, PASAT 2, WAIS-III (Letter Number Sequencing,
Digit Span), WMS-R (Spatial Span)
None The AN group had lower WM scores than both BN and HC. Lowest lifetime BMI and depressive symptoms explained the worse WM performance in the BN group but not the AN group.
Lao-Kaim et al. (2014) [31]
NO DIFFERENCE
Female adults with ED:
AN (n = 31)
HC (n = 31)
N-back task (0, 1, 2 and 3 back). The authors’ specifically examine verbal WM, incorporating the phonological loop, the phonological store, sub-vocal rehearsal and the central executive. fMRI (1.5 T) No significant difference in WM task performance.
All groups showed increased activation in
the bilateral IPL, bilateral middle and superior frontal
gyri extending into the DLPFC, left precuneus
and right insula. The AN group additionally showed positive trends in the left middle temporal gyrus,
right precuneus and left IFG.
Duration of illness may be associated with lower WM accuracy in the AN group. However, anxiety and depression scores were not shown to influence WM ability in AN.
Kothari et al. (2013) [26]
BETTER
Male and female 10 yr old children of mothers with ED (n = 6192) The counting span task - a
computer-based task that simultaneously assesses the
processing and storage components of WM.
None. Increased WM capacity in children with mothers of AN compared to those whose mothers did not have a history of AN (e.g. those with BN or non-ED mothers). Higher maternal education level and child IQ level may mediate the effect of better WM scores.
Brooks et al. (2012) [24]
BETTER
Female adults:
R-AN (n = 13)
HC (n = 20)
The N-back task (1-back and 2-back), presented on a computer screen, with additional subliminal images of food, neutral and aversive scenes None Females with R-AN were significantly better at the N-back task (fewer total errors), compared to HC. However, their superior performance on the N-back task was compromised only when subliminal images of food were presented. This suggests that subcortical (e.g. non-conscious) processing of food stimuli interfered with WM capacity. Higher levels of anxiety correlated with number of errors during the WM task in those with R-AN.
Pruis et al. (2012) [25]
NO DIFFERENCE
Female adults:
Recovered AN (n = 15)
HC (n = 16)
Memoranda arrow was shown, followed by a distracting image of a body (negative, neutral, positive or scrambled), and then another arrow. Participants were instructed to indicate whether the second arrow presentation was in the same orientation as the first. fMRI (3 T) HC and recovered AN wormen did not differ on the WM task overall. Additionally, body images that were rated as negative were more disruptive to WM processes in both groups, but presentation of other distracting body images had no effect on WM. Amygdala and fusiform
activation were greater in women who
had recovered from AN than in controls
when viewing images of bodies during
the WM task. There were no group differences in DLPFC
activity. However, there was more suppression
of medial prefrontal cortex activity in women who had recovered from AN in comparison to controls when negatively rated images were presented
during the working memory task.
More years recovered may have had an influence on negative ratings of bodies and activation levels in the amygdala.
Nikendei et al. (2011) [30]
NO DIFFERENCE
Female adults:
R-AN (n = 34)
BP-AN (n = 19)
WS-AN (n = 16)
HC (n = 30)
Wechsler Memory Scale Revised (WMS-R) – Digit span backwards. None. Currently ill and weight-restored
AN patients did not differ significantly from healthy controls with respect to WM. However, there was impaired mmediate and delayed verbal recall performance in acute AN patients that was found irrespective of
AN subtype, and that persisted in weight-restored AN patients.
ED symptoms or comorbidities did not correlate with WM performance.
Hatch et al. (2010) [23]
BETTER
Female adolescents
AN (n = 37)
HC (n = 45)
IntegNeuro-computerized
Battery using the N-back continuous performance test of sustained attention.
None. During underweight status, AN patients had superior WM capacity in comparison to HC. ED symptoms or comorbidities did not correlate with WM performance.
Dickson et al. (2008) [22]
BETTER
Female adults:
R-AN(n = 24)
HC (n = 24)
The N-back task (1-back and 2-back), presented on a computer screen, with additional subliminal and supraliminal images of food, neutral and aversive scenes None. Participants with AN had superior WM performance compared to the HC during the subliminal condition, but were more distracted than HC by the supraliminal condition. Duration of illness correlated positively with number of errors made by the AN group.
Fowler et al. (2006) [29]
NO DIFFERENCE
Female adults:
AN (n = 25)
HC (n = 25)
Cambridge Neuropsychological Test Automated Battery (CANTAB). Spatial WM is a test of spatial working memory
and strategy performance to find
individually hidden ‘blue tokens’
without returning to a box where
one has previously been found
None. No impairments were observed in spatial WM. ED symptoms or comorbidities did not correlate with WM performance.
Seed et al. (2002) [27]
WORSE
Female adults:
AN (n = 20)
HC (n = 20)
Spatial WM as part of a test battery. A picture of a house is presented for 5 s. The house has
nine windows, four of which are lit. A series of 36
presentations of the same house in which just one window
is lit follows, and the participant has to respond ‘Yes’ if
the window was one of the four lit in the original
presentation, or ‘No’ if it was not. Cortisol measures were also taken.
None. WM performance was impaired in females with AN compared to HC, but cortisol levels did not differ between groups. ED symptoms or comorbidities did not correlate with WM performance.
  1. WM working memory, AN anorexia nervosa, BN bulimia nervosa, ED-R eating disorder restricting type, ED-BP eating disorder binge-purge type, BMI Body Mass Index, IQ Intelligence Quotient, fMRI functional magnetic resonance imaging, DLPFC dorsolateral prefrontal cortex, IPL inferior parietal lobe, IFG inferior frontal gyrus, R-AN restricting anorexia nervosa, BP-AN binge-purge restricting anorexia nervosa; 5 studies reported BETTER WM performance in AN compared to HC; 2 studies reported WORSE WM peformance and 4 studies reported NO DIFFERENCE. 3 studies to date have examined neural function in relation to WM performance in those with AN