ArticlePDF Available

Reactivity to Visual Signals in Neurofibromatosis Type 1: Is Everything OK?

Authors:

Abstract and Figures

Objective: Deficits in multiple aspects of attention are a hallmark of the cognitive impairments found with neurofibromatosis type I (NF1). Given, however, that some attention components are hierarchically organized, it is possible that sustained attention, flexibility, and resistance to interference deficits observed in NF1 may be because of weakened lower order attention components. This study investigated the state of these low-level components in NF1. Method: Twenty participants with NF1 (ages 7-13) and 20 matched controls participated in a visual task. They were required to locate a target as quickly and as accurately as possible and to ignore a potential distractor that could appear either before, at the same time, or after the target. Response times (RTs) were collected, and indices of alerting (i.e., reactivity to warning signals), distraction, and interruption (i.e., reactivity to signals appearing during attentive processing) were computed. Results: The amplitude of the indices differed between the groups, F(2, 76) = 3.1, p < .05. No difference was found with alerting (p > .85) or distraction (p > .84), but the interruption index was higher in the NF1 group than the controls (p < .043). Conclusions: Elementary components on which more complex attention processes are based are not all ok in NF1. It is suggested that overreactivity to and longer inspection of visual signals occurring outside the current focus of attention characterizes NF1 and that this might be partially responsible for focus of attention instability and lower interference resistance in NF1.
Content may be subject to copyright.
Reactivity to Visual Signals in Neurofibromatosis Type 1:
Is Everything OK?
George A. Michael
Université de Lyon Sophie Garcia
Centre Hospitalier Lucien Hussel Vienne, France
Vania Herbillon and Laurence Lion-François
Hôpital Femme Mère Enfant Lyon, France
Objective: Deficits in multiple aspects of attention are a hallmark of the cognitive impairments found
with neurofibromatosis type I (NF1). Given, however, that some attention components are hierarchically
organized, it is possible that sustained attention, flexibility, and resistance to interference deficits
observed in NF1 may be because of weakened lower order attention components. This study investigated
the state of these low-level components in NF1. Method: Twenty participants with NF1 (ages 7–13) and
20 matched controls participated in a visual task. They were required to locate a target as quickly and as
accurately as possible and to ignore a potential distractor that could appear either before, at the same time,
or after the target. Response times (RTs) were collected, and indices of alerting (i.e., reactivity to warning
signals), distraction, and interruption (i.e., reactivity to signals appearing during attentive processing)
were computed. Results: The amplitude of the indices differed between the groups, F(2, 76) 3.1, p
.05. No difference was found with alerting (p.85) or distraction (p.84), but the interruption index
was higher in the NF1 group than the controls (p.043). Conclusions: Elementary components on
which more complex attention processes are based are not all ok in NF1. It is suggested that overreac-
tivity to and longer inspection of visual signals occurring outside the current focus of attention
characterizes NF1 and that this might be partially responsible for focus of attention instability and lower
interference resistance in NF1.
Keywords: neurofibromatosis type I, NF1, visual attention, alerting, distraction, interruption
Neurofibromatosis type I (NF1) is an autosomal dominant con-
dition with a prevalence rate of approximately 1:3000 to 1:4000
(Acosta, Gioia, & Silva, 2006;Friedman, 1999;NINDS, 2007).
Children and adolescents with NF1 demonstrate learning difficul-
ties and poor academic performance, which would appear to stem
from deficits displayed in a wide range of cognitive skills, includ-
ing visual–spatial abilities, language, reading and writing, and
executive functioning (Acosta et al., 2006;Gilboa et al., 2011;
Isenberg, Templer, Gao, Titus, & Gutman, 2013;North, Hyman, &
Barton, 2002). Approximately 33%–50% of children with NF1
demonstrate multiple attention deficits (North et al., 2002;Rosser
& Packer, 2003), a hallmark of cognitive impairments (Templer,
Titus, & Gutmann, 2013). These include deficits in sustained
attention, selective attention, divided attention, task switching, and
response inhibition (Hyman, Arthur, & North, 2006;Hyman,
Shores, & North, 2005;Isenberg et al., 2013;Templer et al., 2013),
especially when tasks require a high degree of cognitive control
(Huijbregts, Swaab, & de Sonneville, 2010;Rowbotham, Pit-ten
Cate, Sonuga-Barke, & Huijbregts, 2009). These deficits are found
across sensory modalities (Isenberg et al., 2013) and are likely the
source of inattentive and impulsive behaviors in natural environ-
ments (Gilboa et al., 2011).
However, attention functions are not completely independent
from one other. Given that some components are hierarchically
organized, it is possible that some attention problems may be
because of deficits at the more elementary level of information
processing. For instance, Sturm, Willmes, Orgass, and Hartje
(1997,Sturm et al., 2004) showed that both attention orienting and
executive functioning in neurologically impaired patients could
benefit from exclusively training a lower level attention compo-
nent, the ability to prepare to process and react to high-priority
signals. Thus, this phasic alerting represents the lowest level of the
hierarchy, which is a prerequisite for higher functions, such as
orienting and executive functioning. This also lends support to the
This article was published Online First November 25, 2013.
George A. Michael, Laboratoire d’Étude des Mécanismes Cognitifs,
Université de Lyon (EA 3082), Université Lyon 2, Lyon, France; Sophie
Garcia, Service de Neurologie, Centre Hospitalier Lucien Hussel, Vienne,
France; Vania Herbillon, Epilepsie, sommeil et explorations fonctionnelles
neuropédiatriques, Hôpital Femme Mère Enfant, Lyon, France; Laurence
Lion-François, Service de Neurologie pédiatrique, Hôpital Femme Mère
Enfant, Lyon, France.
We thank Givors Primary School, France. This work was supported by
the LabEx CORTEX (ANR-11-LABX-0042) of Université de Lyon, within
the program “Investissements d=Avenir” (ANR-11-IDEX-0007) operated
by the French National Research Agency (ANR).
Correspondence concerning this article should be addressed to George
A. Michael, Université de Lyon, Université Lumière – Lyon 2, Laboratoire
d=Etude des Mécanismes Cognitifs, Département de Psychologie Cognitive
& Neuropsychologie, 5, Avenue Pierre Mendès-France, 69676 Bron Ce-
dex, France. E-mail: George.Michael@univ-lyon2.fr
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
Neuropsychology © 2013 American Psychological Association
2014, Vol. 28, No. 3, 423–428 0894-4105/14/$12.00 DOI: 10.1037/neu0000046
423
idea that, at least in part, the brain structures subserving attention
are hierarchically arranged (Mesulam, 1999;Petersen & Posner,
2012;Posner & Petersen, 1990). Therefore, one might ask whether
some of the attention deficits described in NF1 stem from disrup-
tions in even more elementary components. The cross-modal na-
ture of attention deficits in NF1 is a sign they are not secondary to
difficulties with perceptual processing of particular types of stim-
uli (Isenberg et al., 2013). It is still possible, however, that prob-
lems with attention and executive functioning may be secondary to
weakened elementary attention components on which selective
attention and executive functioning rely. For instance, selective
attention, cognitive flexibility, and response inhibition could de-
pend on the capacity to interrupt ongoing activities to orient
attention toward potentially relevant environmental signals (Mi-
chael, Boucart, Degreef, & Godefroy, 2001a;Michael, Garcia,
Bussy, François-Lion, & Guibaud, 2009).
Having advance knowledge of a forthcoming target results in
recruiting attention to process that target without being distracted
by irrelevant stimuli (LaBerge, Auclair, & Siéroff, 2000). When
the target appears, attention is oriented toward its location, en-
gaged on it, and maintained on it while it is processed (Posner &
Petersen, 1990). If a task-irrelevant event occurs at the same time
as the appearance of the target, then it produces interference that
should be resolved quickly because of knowledge about the target.
If such an event occurs after the processing of the target has begun,
the presence and location of this event are coded (Posner, Inhoff,
Friedrich, & Cohen, 1987) by specific and early components that
generate excitatory impulses. If these impulses signal that the
event is sufficiently salient (Koch & Ullman, 1985), then reactions
are produced, such as a brief (i.e., phasic) alerting state and
subsequent interruption of the ongoing processing (Posner et al.,
1987) to allow for a brief exploration of the salient event (Michael
et al., 2001a;). Thus, efficient attentional control is not based only
on processes such as selection, inhibition, and higher executive
functioning. At the earliest level, there are components such as the
coding and localizing of sensory signals, which are purely percep-
tual components. They are followed by the establishment of the
salience of these signals and then the reactivity to these signals, the
existence of which is corroborated mostly through the performance
of brain injured patients (Michael et al., 2001a,2009;Michael &
Desmedt, 2004). This study therefore sets out to assess some of
these elementary components in NF1, on the basis of a simple
visual attention task that has been previously described (Michael et
al., 2009). The extreme ease with which this task can be carried out
suggests that it relies less on complex cognitive demands. It
assesses (a) reactivity to stimuli following a warning signal (i.e.,
phasic alerting), (b) reactivity to distractors occurring at the same
time as the target signals (i.e., distractions), and (c) reactivity to
distractors occurring sometime after the target (i.e., interruptions
of ongoing activities).
Method
The method was identical to the one already described in Mi-
chael et al. (2009).
Subjects
The control group consisted of 20 healthy children (10 boys and
10 girls) aged 7–13 (Mage 9.7 1.8). The patient group
consisted of 20 children with NF1 (14 boys and 6 girls) also aged
7–13 (Mage 9.2 1.9). The NF1 group had a mean IQ
performance score of 91 13.4 and a mean verbal IQ score of
97 13.7 (the IQ was measured with the Wechsler Intelligence
Scale for Children—Third Ed.; Wechsler, 1991). Their mean score
on the short form of the Conners’ Parent Rating Scale (CPRS-
short) was 14 6 (cutoff score 15). Anatomical MRIs were
available for 18 cases. In 22% of cases the MRI revealed no
T2-weighted hyperintensities (T2H), whereas in the other cases,
such T2H were present in the cerebellum, thalamus, and basal
ganglia. All of the NF1 participants met the diagnostic criteria
defined by the National Institutes of Health Consensus Conference
(1988) and took part in this study before receiving medication. The
participants overall all had normal or corrected-to-normal vision,
and their parents had provided their written informed consent for
them to take part in the study. Ethical approval for the study was
granted by the CCPRB ethics committee of the Léon Bérard
Centre Régional de Lutte Contre le Cancer, Lyons, France.
Stimuli
The stimuli were 10 computerized black-and-white pictures
taken from Living English Structure for Schools (Stannard Allen,
1971), all portraying characters in various humorous situations.
The target was a white chicken, and the distractor a black cat, each
occupying an angular space of 5° 5.7° at a viewing distance of
30 cm. To minimize perceptual confusion, different colors were
used for the target and distractor. All of the stimuli were displayed
within a virtual rectangle subtending an angular space of 27.7°
13.9°. The rectangle was centered on the fixation point. The
stimuli were displayed against the white background of a Dell
Latitude computer with a Pentium 200MHz processor.
Procedure
At the start of each trial a humorous scene was displayed for
1,500 ms, after which the chicken (i.e., the target) was added to the
left or right of the scene. Four conditions were tested: (a) the
distractor-absent condition, where the distractor (i.e., the cat) was
not present; (b) the 300-ms distractor-present condition, where
the cat appeared 300 ms before the chicken; (c) the 0 ms distractor-
present condition, where the cat and chicken appeared simultane-
ously; and (d) the 300-ms distractor-present condition, where the
cat appeared 300 ms after the chicken. The distractor was always
positioned opposite the target (i.e., when the chicken was on the
left, the cat was on the right, and vice versa). Even though the
distractor may also act as a cue when presented before the target,
the term “distractor” is used throughout for convenience sake. The
display remained on the screen until a response was given, with the
next trial commencing 1,000 ms after the response. The four
conditions were presented in completely random order, and it was
not possible to predict where the target would be in each trial.
Subjects were asked to locate the target (left or right) as quickly
and as accurately as possible by hitting two predefined response
keys with the index finger of their right and left hand, respectively.
Response times (RTs) and errors were recorded by the computer
from when the target appeared. No feedback was given about each
trial. Each subject completed a session of 40 trials (10 trials per
condition). The test was preceded by a 10-trial training session.
The procedure is described in Figure 1.
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
424 MICHAEL, GARCIA, HERBILLON, AND LION-FRANÇOIS
Indices and Statistical Analyses
Median RTs were subjected to a mixed analysis of variance
(ANOVA), with the tested condition (absent-distractor, distractor
at 300 ms, 0 ms, and 300 ms) as within-subjects factor and group
(controls vs. NF1) as between-groups factor. Median RTs were
also used to extract three attention indices, each assessing different
components: (a) The alerting component was computed by sub-
tracting RTs recorded in the 300-ms condition from RTs in the
distractor-absent condition (Michael et al., 2009). Phasic alerting
refers to greater readiness to respond to external stimuli soon after
a warning signal (Posner, 1978). In the 300-ms condition, the
sudden prior appearance of the cat serves as a warning signal that
the target is imminent, helps orient attention in time, and speeds up
processing of the target once it is there. The inverse spatial
relationship between the target and distractor also provides infor-
mation about the location of the future target, making processing
even faster. (b) The difference between the 0-ms and 300-ms
conditions denoted distraction (Michael et al., 2009). The overall
screen luminance in these two conditions is the same, but simul-
Figure 1. Trial events forming part of the experiment reported in this article. The stimuli shown are not actual
size. A humorous scene was displayed for 1,500 ms in the center of a computer screen. A target (white chicken)
was then added to the scene, and subjects were asked to locate it (to the right or left of the scene) by hitting two
predefined response keys. In some trials, the target was presented on its own, but in others it was accompanied
by a distractor to ignore (black cat). The target-to-distractor time interval varied systematically: The distractor
was displayed either before or after the target or even at the same time. The conditions tested were intermixed.
All of the stimuli were black and white. Response times were recorded from when the target first appeared. From
Living English Structure for Schools (p. 88), by W. S. Allen, 1971, Essex, UK: Pearson Longman. Copyright,
1971, by Pearson Longman. Adapted with permission.
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
425
VISUAL ATTENTION IN NF1
taneous presentation of the target and distractor in the 0-ms con-
dition creates interference that slows RTs. Conversely, the prior
appearance of the distractor acts as a cue that speeds up RTs
because the position of the distractor interferes less with that of the
target (c). The brief interruption of ongoing activities, computed
by subtracting RTs recorded in the 300-ms condition from those
recorded in the 300-ms condition (Michael et al., 2009)is
defined as the brief inspection of signals appearing during target
processing (Michael et al., 2001a). In the 300-ms condition, the
distractor appears 300 ms after the target, that is, after target
processing is presumed to have begun. The interference effects
generated by the distractor at these late stages can be attributed to
the inspection of changes during ongoing activities. The indices
were subjected to a mixed ANOVA, with index (alerting, distrac-
tion, interruption) as within-subjects factor and group (controls vs.
NF1) as between-groups factor.
Results
Median RTs
The main effect of group was significant, F(1, 38) 10.7, p
.002,
2
.86. The NF1 group (705 ms) was slower than the
control group (554 ms). The main effect of condition was also
significant, F(3, 114) 18, p.0001,
2
.13, as was the
Group Condition interaction, F(3, 114) 2.9, p.04,
2
.01, which was investigated with post hoc (Newman–Keuls) com-
parisons. Regarding the controls’ performance, their RTs were
faster in the 300-ms condition (478 ms) than in any of the other
conditions (absent, 577 ms, p.002; 0 ms, 571 ms, p.001; 300
ms, 590 ms, p.001), but no other difference was found. The
pattern of results for the NF1 group was slightly different. Whereas
their RTs were faster in the 300-ms condition (621 ms) than in
the other conditions (absent, 697 ms, p.007; 0 ms, 708 ms, p
.006; 300 ms, 792 ms, p.0001), they were also slower in the
300-ms condition than in the absent-distractor (p.002) and the
0-ms conditions (p.003). The results are shown in Figure 2A.
The mean error percentage was not analyzed in detail because it
was below 3% (controls, 0.88 1.7; NF1, 2.5 6.6) and many
cells contained 0 values.
Attention Indices
The main effect of group did not reach significance, F(1, 38)
0.1, p.72,
2
.05. However, the main effect of index was
significant, F(2, 76) 4.5, p.015,
2
.63, because of higher
values for interruption (141 ms) than both alerting (87 ms, p
.027) and distraction (89 ms, p.013). No difference was found
between alerting and interruption (p.92). The Group Index
interaction reached significance, F(2, 76) 3.1, p.05,
2
.32.
Newman–Keuls post hoc comparisons showed that, for the con-
trols, the values of the indices were similar (alerting, 99 ms;
distraction, 92 ms; interruption, 111 ms; all ps.66). For the NF1
group, interruption lasted longer (171 ms) than both alerting (76
ms, p.018) and distraction (86 ms, p.036), with no difference
found between alerting and distraction (p.70). Finally, compar-
isons between the NF1 group and controls in respect of each index
revealed no difference as regards alerting (p.85) and distraction
(p.84), but the interruption index was higher in the NF1 group
(p.043). The results are shown in Figure 2B.
The suggestion based on these results is that the NF1 group
reacts more strongly to visual signals appearing during attentive
processing of a target and, consequently, interrupts such process-
ing for longer. Thus, there is evidence of dissociable components
in NF1. This dissociation supposes decreased internal homogene-
ity through these basic components. And, indeed, Cronbach’s
Figure 2. Performance of controls (black symbols) and NF1 participants (white symbols) in a psychophysical
task which required them to locate (left-right) a target and ignore a distractor. Error bars represent 1 SEM.A:
Mean mdn response times (in ms) for locating the target in the absence of the distractor and when the distractor
appeared before, at the same time as, or after the target. B: Mean attention indices (in ms). C: Regression analysis
showing the difference between the NF1 and control participants in the linear link between distraction and
interruption.
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
426 MICHAEL, GARCIA, HERBILLON, AND LION-FRANÇOIS
alpha coefficient was lower in NF1 (.55) than in controls (.83), and
the difference between them was significant (Fisher ztest 1.69,
p.046; Kim & Feldt, 2008). It is interesting that the dissociation
found between distraction and interruption lends support to the
idea that although both these conditions involve distractor process-
ing, they are based on different components (Michael et al., 2001a,
2009;Michael, Kleitz, Sellal, Hirsch, & Marescaux, 2001b). We
investigated the link between these two components further by
subjecting the distraction and interruption indices to a regression
analysis. Interruption predicted distraction in how the controls
performed (␤⫽.74, p.0045) but not the NF1 group (␤⫽.09;
p.43). The effect of group on regression slopes was significant,
F(1, 36) 6.62, p.015, suggesting distraction and interruption
are indeed dissociable because how they relate to each other differs
between the two groups. The results are shown in Figure 2C.
Discussion
We assessed some elementary attention components in NF1 by
measuring reactivity to task-irrelevant visual signals occurring at
varying temporal intervals from a target (Michael et al., 2001a,
2009). Apart from our finding of generally slower RTs by partic-
ipants with NF1, which are a hallmark of slowed information
processing overall (Huijbregts & de Sonneville, 2011;Rowbotham
et al., 2009), this study detected disturbed interruption of target
processing because of the appearance of a distractor. The results
suggest that some elementary components of attention can be
selectively disturbed without affecting the others and lead us to
believe that dysfunctions of more complex attentional processes
reported in NF1 may be because of such elementary disturbances.
Evidence for these conclusions stem from the longer raw RTs
recorded when the distractor occurred 300 ms after the target but
also from the increment in the interruption index. Sensory signals
entering the visual field may attract attention even if processing of
task-relevant information is in progress. Interruption reveals the
workings of a mechanism that is actively searching for important
changes occurring outside the current focus of attention. It in-
volves detecting and inspecting scene changes that might require
changes in attitude and is essential for adaptive and coherent
behavior (Michael et al., 2001a,2009). There may be major
consequences for attentive behavior if this component is disrupted.
For instance, reduced reactivity to sensory signals can mean what
happens in the surroundings of a target is ignored, a behavior
found in patients with lesions of the posterior thalamus (Michael et
al., 2001a) and cerebellum (Michael et al., 2009). Conversely,
heightened reactivity, such as those reported after damage to the
frontal lobe (Michael, Garcia, Fernandez, Sellal, & Boucart, 2006;
Michael et al., 2001b) and found in the performance of the NF1
participants in this study, could disrupt one’s ability to focus
attention and, in addition, create a weakened resistance to inter-
ference that could make it difficult to focus continuously on a
primary task. These are problems with which NF1 participants are
frequently characterized (e.g., Gilboa et al., 2011;North et al.,
2002;Templer, 2013).
From a theoretical point of view, there is strong evidence that
distraction and interruption of ongoing processing are independent
functions (Michael et al., 2009). However, there is also evidence
that they may be implemented within the same neural network
involving the reticular formation, thalamus, cerebellum, and right
ventral frontal cortex (Michael et al., 2001b). One interpretation is
that distinct parts of the same network support these distinct
components of attention. This study offers some supporting evi-
dence for this. The strong regression coefficient observed between
these distinct parts and components in the control participants
lends support to the idea that they are linked. In the NF1 group, the
dissociation between the normal distraction and disturbed inter-
ruption, as well as their weakened interrelation, suggest they are
independent of each other.
One limit of our study is that it does not directly rule out the
possibility that the performance of the NF1 participants reflects
just a delay in the development of the elementary attention com-
ponents under investigation. It was previously demonstrated that
these components assessed with our paradigm do not exhibit any
developmental pattern, at least not beyond age 8 years (Michael et
al., 2009). Consequently, the difference in the performance pattern
found in the NF1 group compared to the control group cannot be
attributed to delayed development. Another limit is that this study
does not reveal whether the heightened reactivity found in NF1 is
because of weakened focusing on the target or as a result of
increased salience of signals occurring in the surroundings of the
target, which are two distinct components (Michael & Desmedt,
2004;Theeuwes, 1991) that precede reactivity to sensory signals
(Michael et al., 2001a;Posner et al., 1987). Cognitive and com-
putational models (e.g., Koch & Ullman, 1985) assume that dif-
ferences between elementary visual features serve to determine the
degree at which an item of the visual field is salient compared with
the others and the degree at which visual attention should be
directed toward it. Heightened salience—which is an even more
elementary process than the ones assessed here—can account for
the results of our study. Future research on NF1 should be able to
better characterize such elementary components of attention that
condition interruption of ongoing activities, as well as the way and
the degree at which competing salient yet task-irrelevant events
produce interruptions.
Overall, not all elementary components on which attentive pro-
cessing is built are normal in participants with NF1. We found
overreactivity to, and longer inspection of, visual signals occurring
outside the current focus of attention. This may be partially re-
sponsible for difficulties in focusing attention and weakened re-
sistance to interference in controlled tasks but also for inattentive
and impulsive behavior in natural environments (Payne et al.,
2011).
References
Acosta, M. T., Gioia, G. A., & Silva, A. J. (2006). Neurofibromatosis type
1: New insights into neurocognitive issues. Current Neurology and
Neuroscience Reports, 6, 136–143. doi:10.1007/s11910-996-0036-5
Friedman, J. M. (1999). Epidemiology of neurofibromatosis type 1. Amer-
ican Journal of Medical Genetics, 89, 1–6. doi:10.1002/(SICI)1096-
8628(19990326)89:11::AID-AJMG33.0.CO;2-8
Gilboa, Y., Rosenblum, S., Fattal-Valevski, A., Toledano-Alhadef, H.,
Rizzo, A., & Josman, N. (2011). Using a virtual classroom environment
to describe the attention deficits profile of children with neurofibroma-
tosis type 1. Research in Developmental Disabilities, 32, 2608–2613.
doi:10.1016/j.ridd.2011.06.014
Huijbregts, S. C. J., & de Sonneville, L. (2011). Does cognitive impairment
explain behavioral and social problems of children with neurofibroma-
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
427
VISUAL ATTENTION IN NF1
tosis type 1? Behavior Genetics, 41, 430436. doi:10.1007/s10519-010-
9430-5
Huijbregts, S., Swaab, H., & de Sonneville, L. (2010). Cognitive and motor
control in neurofibromatosis type I: Influence of maturation and hyper-
activity-inattention. Developmental Neuropsychology, 35, 737–751. doi:
10.1080/87565641.2010.508670
Hyman, S. L., Arthur, E., & North, K. N. (2006). Learning disabilities in
children with neurofibromatosis type 1: Subtypes, cognitive profile, and
attention-deficit-hyperactivity disorder. Developmental Medicine &
Child Neurology, 48, 973–977. doi:10.1017/S0012162206002131
Hyman, S. L., Shores, A., & North, K. N. (2005). The nature and frequency
of cognitive deficits in children with neurofibromatosis type 1. Neurol-
ogy, 65, 1037–1044. doi:10.1212/01.wnl.0000179303.72345.ce
Isenberg, J. C., Templer, A., Gao, F., Titus, J., & Gutman, D. (2013).
Attention skills in children with neurofibromatosis type I. Journal of
Child Neurology, 28, 45–49. doi:10.1177/0883073812439435
Kim, S., & Feldt, L. (2008). A comparison of tests for equality of two or
more independent alpha coefficients. Journal of Educational Measure-
ment, 45, 179–193. doi:10.1111/j.1745-3984.2008.00059.x
Koch, C., & Ullman, S. (1985). Shifts in selective visual attention: To-
wards the underlying neural circuitry. Human Neurobiology, 4, 219
227.
LaBerge, D., Auclair, L., & Siéroff, E. (2000). Preparatory attention:
Experiment and theory. Consciousness and Cognition, 9, 396434.
doi:10.1006/ccog.1999.0429
Mesulam, M. M. (1999). Spatial attention and neglect: Parietal, frontal and
cingulate contributions to the mental representation and attentional tar-
geting of salient extrapersonal events. Philosophical Transactions of the
Royal Society of London B Biological Sciences, 354, 1325–1346. doi:
10.1098/rstb.1999.0482
Michael, G. A., Boucart, M., Degreef, J.-F., & Godefroy, O. (2001a). The
thalamus interrupts top-down attentional control for permitting explor-
atory shiftings to sensory signals. NeuroReport, 12, 2041–2048. doi:
10.1097/00001756-200107030-00050
Michael, G. A., & Desmedt, S. (2004). The human pulvinar and attentional
processing of visual distractors. Neuroscience Letters, 362, 176–181.
doi:10.1016/j.neulet.2004.01.062
Michael, G. A., Garcia, S., Bussy, G., François-Lion, L., & Guibaud, L.
(2009). Reactivity to visual signals and the cerebellar vermis: Evidence
from a rare case with Rhombencephalosynapsis. Behavioral Neurosci-
ence, 123, 86–96. doi:10.1037/a0013726
Michael, G. A., Garcia, S., Fernandez, D., Sellal, F., & Boucart, M. (2006).
The ventral premotor cortex (vPM) and resistance to interference. Be-
havioral Neuroscience, 120, 447–462. doi:10.1037/0735-7044.120.2
.447
Michael, G. A., Kleitz, C., Sellal, F., Hirsch, E., & Marescaux, C. (2001b).
Controlling attentional priority by preventing changes in oculomotor
programs: A job for the premotor cortex? Neuropsychologia, 39, 1112–
1120. doi:10.1016/S0028-3932(01)00029-X
National Institute of Neurological Disorders and Stroke. (2007). Neurofi-
bromatosis fact sheet (NIH Publication No. 06-2126). Bethesda, MD:
National Institutes of Health.
National Institutes of Health Consensus Development Conference State-
ment: Neurofibromatosis. (1988). Archives of Neurology, 45, 575–578.
North, K., Hyman, S. L., & Barton, B. (2002). Cognitive deficits in
neurofibromatosis 1. Journal of Child Neurology, 17, 605–612. doi:
10.1177/088307380201700811
Payne, J. M., Hyman, S. L., Shores, E. A., & North, K. N. (2011).
Assessment of executive function and attention in children with neuro-
fibromatosis type 1: Relationships between cognitive measures and real
world behavior. Child Neuropsychology, 17, 313–329. doi:10.1080/
09297049.2010.542746
Petersen, S. E., & Posner, M. I. (2012). The attention system of the human
brain: 20 years after. Annual Review of Neuroscience, 35, 73–89. doi:
10.1146/annurev-neuro-062111-150525
Posner, M. I. (1978). Chronometric explorations of mind. Hillsdale, NJ:
Erlbaum.
Posner, M. I., Inhoff, A., Friedrich, F. J., & Cohen, A. (1987). Isolating
attentional systems: A cognitive-anatomical analysis. Psychobiology,
15, 107–121.
Posner, M. I., & Petersen, S. E. (1990). The attention system of the human
brain. Annual Review of Neuroscience, 13, 25–42. doi:10.1146/annurev
.ne.13.030190.000325
Rosser, T. L., & Packer, R. J. (2003). Neurocognitive dysfunction in
children with neurofibromatosis type 1. Current Neurology and Neuro-
science Reports, 3, 129–136. doi:10.1007/s11910-003-0064-3
Rowbotham, I., Pit-ten Cate, I. M., Sonuga-Barke, E. J. S., & Huijbregts,
S. C. J. (2009). Cognitive control in adolescents with neurofibromatosis
type 1. Neuropsychology, 23, 5060. doi:10.1037/a0013927
Stannard Allen, W. (1971). Living English structure for schools. Istanbul,
Turkey: Longman.
Sturm, W., Longoni, F., Weis, S., Specht, K., Herzog, H., Vohn, R.,...
Willmes, K. (2004). Functional reorganisation in patients with right
hemisphere stroke after training of alertness: A longitudinal PET and
fMRI study in eight cases. Neuropsychologia, 42, 434450. doi:
10.1016/j.neuropsychologia.2003.09.001
Sturm, W., Willmes, K., Orgass, B., & Hartje, W. (1997). Do specific
attention deficits need specific training? Neuropsychological Rehabili-
tation, 7, 81–103. doi:10.1080/713755526
Templer, A. K., Titus, J., & Gutmann, D. (2013). A neuropsychological
perspective on attention problems in neurofibromatosis type 1. Journal
of Attention Disorders, 17, 489496. doi:10.1177/1087054711433422
Theeuwes, J. (1991). Cross-dimensional perceptual selectivity. Perception
& Psychophysics, 50, 184–193. doi:10.3758/BF03212219
Wechsler, D. (1991). The Wechsler intelligence scale for children—third
edition. San Antonio, TX: The Psychological Corporation.
Received April 23, 2013
Revision received October 8, 2013
Accepted October 10, 2013
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
428 MICHAEL, GARCIA, HERBILLON, AND LION-FRANÇOIS
... Although attention is the most frequently affected ability in children with NF1 (Lehtonen et al., 2013), our findings did not provide evidence for the presence of attention deficits in adults with NF1. The absence of a difference in performance in the alertness and sustained attention tasks in adults with NF1 is in contrast to previous studies in children with NF1 (Isenberg et al., 2013;Michael et al., 2014;Payne et al., 2019;Torres Nupan et al., 2017). In two NF1 studies, the same measure of alertness showed diminished alertness in children with NF1 compared to controls (Huijbregts et al., 2011;Rowbotham et al., 2009). ...
... Furthermore, sustained attention was affected in 63% of children with NF1 (Hyman et al., 2005). The first reason for the lack of attention differences between adults with NF1 and controls could be due to developmental changes from childhood to adulthood (Descheemaeker et al., 2013;Michael et al., 2014). The delay in the development of attention components (Stuss, 1992) could reflect the attention deficits mainly seen in children with NF1 (Michael et al., 2014). ...
... The first reason for the lack of attention differences between adults with NF1 and controls could be due to developmental changes from childhood to adulthood (Descheemaeker et al., 2013;Michael et al., 2014). The delay in the development of attention components (Stuss, 1992) could reflect the attention deficits mainly seen in children with NF1 (Michael et al., 2014). It would be interesting to take the maturation process into consideration in future prospective longitudinal studies. ...
Article
Full-text available
Objective Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that is associated with cognitive disabilities, including attention and motor learning problems. These disabilities have been extensively studied in children with NF1 but limited studies have been performed in adults. Method Attention, motor learning and intellectual performance were studied with neuropsychological tasks in 32 adults with NF1 and 32 controls. Results The NF1 and control group performed similarly on attention and motor learning tasks, although controls had shorter reaction times than adults with NF1 during the motor learning task (t[60] = −2.20, p = .03). Measures of attention or motor learning were not significantly associated with reduced intellectual performance in NF1. Conclusion In contrast to many studies in children with NF1, our findings did not provide evidence for presence of attention or motor learning problems in adults with NF1 in neuropsychological tasks. Our observations may be of clinical importance to determine treatment focus in adults with NF1.
... In the present study, infants with NF1 showed faster reaction times than typically developing infants; Fig. 2 shows that this is strongest at the 5-month timepoint. Shorter xation durations during viewing of static arrays (indicating faster shifting between array elements) at 6 months have been previously related to later attention and cognitive di culties (Papageorgiou et (2014) found that older children with NF1 showed over reactivity and longer inspection of visual signals that were presented outside the current focus of attention; faster reaction times to a peripheral stimulus in the present cohort may potentially capture similar processes (Michael et al., 2014). Interestingly, one previous study reported that higher GABA levels were related to faster reaction times in a behavioural go/no go task in NF1 (Ribiero et al., 2015) and a second study reported associations between higher GABA and faster RTs in a visuospatial working memory task ; testing the degree to which our infant ndings re ect alterations in cortical inhibition is an important future step. ...
Preprint
Full-text available
Background Neurofibromatosis Type 1 is a genetic condition diagnosed in infancy that substantially increases the likelihood of a child experiencing cognitive and developmental difficulties, including Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD). One of the most characteristic cognitive differences observed in children with NF1 is in visuospatial processing, but whether this contributes to broader difficulties with cognitive and learning skills is unclear. To address this question requires longitudinal prospective studies from infancy, where the relation between visuospatial difficulties and cognitive development can be mapped over time. Methods We report data from 28 infants with NF1 tested longitudinally at 5, 10 and 14 months compared to cohorts of 29 typical likelihood infants (with no history of NF1 or ASD and/or ADHD), and 123 infants with a family history of ASD and/or ADHD. We used an eyetracking battery to measure visual spatial attention. Results Infants with NF1 demonstrated intact social orienting, but slower development of endogenous visual foraging. This slower development presented as prolonged engagement with a salient stimulus in a static display relative to typically developing infants. In terms of exogenous attention shifting, NF1 infants showed faster saccadic reaction times than typical likelihood infants. However, the NF1 group demonstrated a slower developmental improvement from 5 to 14 months of age. Individual differences in foraging and saccade times were concurrently related to visual reception abilities within the full infant cohort (NF1, typical likelihood and those with a family history of ASD/ADHD). Conclusions Our results provide preliminary evidence that alterations in saccadic reaction time and visual foraging may contribute to learning difficulties in infants with NF1; social orienting and engagement develop typically in these infants.
... Lower performances have been consistently found on the Judgement Orientation Line test [25], a standardized test of visuospatial perception measuring the ability to match the angle and orientation of lines in space [26]. Deficits in the perceptual analysis of shapes and their spatial features [27], impairments in visual learning [28,29] and abnormal reactivity to visual signals [30] have also been evidenced using various cognitive tasks. Moreover, children with NF1 exhibit reduced visuomotor integration [31] and a high prevalence of motor problems [32]. ...
Article
Full-text available
Background Neurofibromatosis type 1 (NF1) is a genetic disorder often associated with cognitive dysfunctions, including a high occurrence of deficits in visuoperceptual skills. The neural underpinnings of these visuoperceptual deficits are not fully understood. We used steady-state visual evoked potentials (SSVEPs) to investigate possible alterations in the synchronization of neural activity in the occipital cortex of children with NF1. Methods SSVEPs were measured using electroencephalography and compared between children with NF1 ( n = 28) and neurotypical controls ( n = 28) aged between 4 and 13 years old. SSVEPs were recorded during visual stimulation with coloured icons flickering at three different frequencies (6 Hz, 10 Hz, and 15 Hz) and analyzed in terms of signal-to-noise ratios. A mixed design ANCOVA was performed to compare SSVEP responses between groups at the three stimulation frequencies. Pearson’s correlations with levels of intellectual functioning as well as with symptoms of ADHD, ASD and emotional/behavioral problems were performed. The impact of psychostimulant medication on the SSVEP responses was analyzed in a subset of the NF1 group ( n = 8) with paired t-tests. Results We observed reduced signal-to-noise ratios of the SSVEP responses in children with NF1. The SSVEP responses were negatively correlated with symptoms of inattention and with symptoms of emotional/behavioral problems in the NF1 group. The SSVEP response generated by the lowest stimulation frequency (i.e., 6 Hz) was rescued with the intake of psychostimulant medication. Conclusions Impaired processing of rhythmic visual stimulation was evidenced in children with NF1 through measures of SSVEP responses. Those responses seem to be more reduced in children with NF1 who exhibit more symptoms of inattention and emotional/behavioral problems in their daily life. SSVEPs are potentially sensitive electrophysiological markers that could be included in future studies investigating the impact of medication on brain activity and cognitive functioning in children with NF1.
... Cependant, rester attentif n'est pas chose aisée. L'humain est doté de systèmes qui interrompent les activités en réponse à des sollicitations externes pour les traiter (Michael et al., 2001(Michael et al., , 2014(Michael et al., , 2015. Ainsi, prêter attention à des bruits, des mouvements, des scènes est un comportement naturel dans le sens où la prise en compte des changements de l'environnement immédiat permet une meilleure appréhension de la situation afin de réagir de façon appropriée et d'adapter son comportement en conséquence (Couffe & Michael, 2017 ;Michael & Couffe, 2018). ...
Article
Acquérir et intégrer de nouvelles connaissances et de nouvelles stratégies de résolution de problèmes sont autant d’activités qui ont besoin de l’attention. Celle-ci permettrait de se centrer ponctuellement ou longuement sur les informations importantes et de diminuer l’impact de bruits et voix de fond dans une classe. Cependant, rester attentif n’est pas chose aisée puisque l’attention fluctue naturellement de manière irrégulière et non prévisible. Cet article essaye de résumer les liens entre attention, apprentissages et compréhension à la fois chez l’enfant et chez l’adulte, d’aborder le rôle de l’environnement physique de la classe et le rôle de l’enseignant dans le recentrage et le maintien de l’attention. Enfin, quelques techniques existantes permettant de diminuer les effets délétères de l’inattention sont discutées.
... Individuals are affected in different domains of attention, impulsivity, hyperactivity and executive functioning, and to different degrees [46,49]. Visual attention seems consistently impaired in NF1 patients [50,51] and would lead to instability in focusing attention and lower resistance to interference in controlled tasks but also to inattentive and impulsive behaviour in natural environments. ...
Article
Full-text available
Introduction. Cognitive and behavioural problems associated with Neurofibromatosis type 1 (NF1) are common sources of distress and the reasons behind seeking help. Here we describe patients with NF1 or NF1-like phenotypes referred to a Tier 3 Child and Adolescent Psychiatry Department and highlight the benefits of a multidisciplinary assessment. Methods: Prospective data were gathered from NF1 patients aged 7-15 years, referred by the NF1 Referral Centre due to additional difficulties either in management or diagnosis. For the selected cases, we performed a psychiatric assessment, a tailored neuropsychological evaluation based on clinical demands and history, broad speech and motor skills evaluations if there were concerns regarding language, motor abilities and/or learning difficulties and autism specific evaluations, if clinically relevant. No exclusion criteria were applied. Results: Complex NF1 cases represented only 5% of the patients (11/224). Assessments revealed the complexity of NF1 phenotype and a variety of problems including learning difficulties, emotional problems and autism spectrum disorders. Specific evaluations of language, motor, attentional and neurovisual domains were essential to guide tailored intervention strategies. Conclusions: In terms of clinical implications, the heterogeneity of NF1 phenotypical manifestations needs to be considered when developing assessment and remediation approaches for children with complex NF1.
... Children with NF1 have been shown to have serious defects in visual-spatial learning ability. In addition, children with NF1 have a slow response to visual signals, long RT and weak resistance to interference, resulting in unstable attention [21]. This finding suggests that NF1 patients face obstacles throughout the processing of visual information. ...
Article
Full-text available
Cognitive dysfunction accompanied by neurofibromatosis type 1 is one of the significant characteristics of this neurocutaneous disorder and has a serious impact on patients' quality of life. Although studies on cognitive function in children with neurofibromatosis type 1 have revealed that attentional impairment is a key deficit in these patients, few studies have examined their neuropsychological profile, especially whether the attentional function is also abnormal and specific in adult patients with neurofibromatosis type 1. In this study, we used the revised attention network test to examine the function of three attentional networks-alerting, orienting and executive control-in 20 adult patients with neurofibromatosis type 1 in comparison to 20 normal controls. Adult patients with neurofibromatosis type 1 showed significant greater conflict effect for the executive control network, but no significant differences were found for alerting and orienting network relative to normal controls. These results provide evidence that there is an attentional deficit which is specifically associated with the executive control network in adult patients with neurofibromatosis type 1.
... 21,22 These findings are consistent with the high rate of omission errors in the presence of visual distractors in our children/adolescents with NF1. In a related study, Michael et al. 23 asked patients with NF1 to locate a target as quickly and as accurately as possible while ignoring any potential distractor that could appear before, simultaneously with, or after the target. They found that during attentive processing, patients with NF1 tended to overreact to or overinspect vi-sual signals occurring outside the focus of attention. ...
Article
Full-text available
Background and purpose: The objective of this study was to determine if the MOXO visual- and vocal-distractors-based continuous performance test distinguishes patients with attention deficit hyperactivity disorder (ADHD) and neurofibromatosis type 1 (NF1) from those without NF1. Methods: Thirty-five patients (16 males; mean age 9.91 years) attending a multidisciplinary NF1 clinic completed the MOXO test. The findings were compared to 532 healthy age-matched standardized control subjects (285 males) without ADHD. Results: The overall performance in the MOXO text was significantly worse in the NF1 group than in controls (p<0.01), but no group-specific pattern was identified. Impulsivity and hyperactivity were significantly more prominent in males than females (p<0.01). Compared to controls, the NF1 group exhibited significantly more failures to respond to target stimuli in the presence of visual distractors. Conclusions: MOXO scores are abnormal in patients with NF1, but the test cannot differentiate between NF1 with ADHD characteristics and ADHD. The test highlights sex differences in ADHD characteristics in NF1. Overreactivity to visual distractors may form part of the attention deficit in NF1.
Article
Full-text available
This systematic review aimed to examine the possible implication of visual-perceptual, visuo-attentional and oculomotor processing in the reading deficits frequently experienced by children with Neurofibromatosis type 1 (NF1), as previously shown in dyslexia. Using PRISMA methodological guidelines, we examined 49 studies; most of these reported visual-processing deficits in this population, raising the importance of directly studying the visuo-perceptual and visuo-attentional processes and eye-movement control involved in the learning-to-read process in NF1. The discussion provides a reflection for a better understanding of how visual-processing skills interact with reading deficits in NF1, as well as new avenues for their screening and care.
Preprint
Full-text available
Background: Neurofibromatosis type 1 (NF1) is a genetic disorder often associated with cognitive dysfunctions, including a high occurrence of deficits in visuoperceptual skills. The neural underpinnings of these visuoperceptual deficits are not fully understood. We used steady-state visual evoked potentials (SSVEPs) to investigate possible alterations in the synchronization of neural activity in the occipital cortex of children with NF1. Methods: SSVEPs were measured using electroencephalography and compared between children with NF1 (n = 28) and neurotypical controls (n=28) aged between 4 and 13 years old. SSVEPs were recorded during visual stimulation with coloured icons flickering at three different frequencies (6Hz, 10Hz and 15 Hz) and analyzed in terms of signal-to-noise ratios. A mixed design ANCOVA was performed to compare SSVEP responses between groups at the three stimulation frequencies. Pearson’s correlations with levels of intellectual functioning as well as with symptoms of ADHD, ASD and emotional/behavioural problems were performed. The impact of psychostimulant medication on the SSVEP responses was analyzed in a subset of the NF1 group (n=8) with paired t-tests. Results: We observed reduced signal-to-noise ratios of the SSVEP responses in children with NF1. The SSVEP responses were negatively correlated with symptoms of inattention and with symptoms of emotional/behavioural problems in the NF1 group. The SSVEP response generated by the lowest stimulation frequency (i.e., 6Hz) was rescued with the intake of psychostimulant medication. Conclusions: Impaired processing of rhythmic visual stimulation was evidenced in children with NF1 through measures of SSVEP responses. Those responses seem to be more reduced in children with NF1 who exhibit more symptoms of inattention and emotional/behavioral problems in their daily life. SSVEPs are potentially sensitive electrophysiological markers that could be included in future studies investigating the impact of medication on brain activity and cognitive functioning in children with NF1.
Article
Full-text available
The efficacy of game-like computerised adaptive training programmes for intensity aspects of attention (alertness and vigilance) and selectivity aspects of attention (selective and divided attention) was studied in patients with left or right focal brain damage of vascular aetiology. Each patient received consecutive training in the two most impaired of the four attention domains. Control tests were performed by means of a standardised computerised attention test battery comprising tests for the four attention functions. Assessment was carried out at the beginning and after each of two training periods of 14 one-hour sessions each. There were significant specific training effects for both intensity aspects (alertness and vigilance), and also for response time in the selective attention and error rate in the divided attention task. For selectivity aspects of attention, reaction time also improved after training of basic attention domains. The application of inferential single case procedures revealed not only a high degree of specific training effects in individual cases but also a substantial number of deteriorations in performance after non-specific training of basic attention problems by tasks requiring selectivity of attention. The results are discussed in the light of a hierarchical organisation of attention functions.
Article
Full-text available
Notes that research suggests that a neural network that includes parts of the posterior parietal lobe and midbrain is involved in covert shifts of visual attention. The present study investigated whether this system is an isolated visual attentional module or part of a more general attentional system. The dual-task technique was used to determine whether covert visual orienting can take place while a person's attention is engaged in a language processing task. Nine patients with unilateral parietal lesions resulting from stroke and 16 19–35 and 60–75 yr old controls participated in Exp I, and 22 young normal Ss served in Exp II. Results provide evidence of interference between the 2 tasks, which suggests some common operations. However, results also indicate that whatever is common to the 2 tasks does not have the same anatomical location as that of visual-spatial attention. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Full-text available
Here, we update our 1990 Annual Review of Neuroscience article, "The Attention System of the Human Brain." The framework presented in the original article has helped to integrate behavioral, systems, cellular, and molecular approaches to common problems in attention research. Our framework has been both elaborated and expanded in subsequent years. Research on orienting and executive functions has supported the addition of new networks of brain regions. Developmental studies have shown important changes in control systems between infancy and childhood. In some cases, evidence has supported the role of specific genetic variations, often in conjunction with experience, that account for some of the individual differences in the efficiency of attentional networks. The findings have led to increased understanding of aspects of pathology and to some new interventions.
Article
The Japanese Neurocutaneous Syndrome Research Group (JNCSRG) conducted a nationwide survey of neurofibromatosis 1 (NF1) patients in Japan. Three thousand one hundred and seventy seven NF1 patients were reported and their clinical information of age at diagnosis, manifestations, course, life and welfare were evaluated. The number affected was estimated to be 40,000 in the Japanese population of 120,000,000. Although malignant neoplasm (neurofibrosarcoma (29.2%) and brain tumor (11.0%)) were usually the cause of patient death, cardiovascular rupture and bleeding from peripheral blood vessels were other causes (9.7%). Affliction in nearly 50% of patients was presumed to occur as a result of new mutation. Many patients required medical care as well as financial support. Our JNCSRG epidemiological survey generated much needed nationwide information on NF1 patients, and may provide a basis for future research and patient management.
Article
Correction for ‘Spatial attention and neglect: parietal, frontal and cingulate contributions to the mental representation and attentional targeting of salient extrapersonal events’ by M.-M. Mesulam (Phil. Trans. R. Soc. Lond. B 354 , 1325–1346. (doi: [10.1098/rstb.1999.0482][1])). In the legend to figure 3 (p. 1332), the words left and right were mistakenly transposed. [1]: /lookup/doi/10.1098/rstb.1999.0482
Article
Cognitive deficits and academic learning difficulties are the most common neurologic "complication" of neurofibromatosis 1 in childhood and can be responsible for significant lifetime morbidity. There is a slight increase in the frequency of mental retardation (Wechsler Full-Scale IQ < 70) in children with neurofibromatosis 1, but the mean Full-Scale IQ for the patient group is within 1 SD of the population mean. Academic difficulties are common, as are specific deficits in visuospatial ability, executive function, expressive and receptive language, and attentional skills. Behavioral and psychosocial problems have a major impact on quality of life, although there are few objective studies in this area. Current research is focusing on the pathogenesis of the disorder. Clinical studies have identified possible radiologic and pathologic markers for cognitive deficits in neurofibromatosis 1, which can now be explored in animal models. (J Child Neurol 2002;17:605-612).
Article
Describes a unified experimental approach to the study of the mind based on experiments in the time course of human information processing. New studies on the role of intensity in information processing, on vigilance, and on orienting and detecting are presented. A historical introduction to mental chronometry together with an integration of performance and physiological techniques for its study are provided. (15 p ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Article
This article extends the Bonett (2003a) approach to testing the equality of alpha coefficients from two independent samples to the case ofm≥2independent samples. The extended Fisher-Bonett test and its competitor, the Hakstian-Whalen (1976) test, are illustrated with numerical examples of both hypothesis testing and power calculation. Computer simulations are used to compare the performance of the two tests and theFeldt (1969)test (for m=2) in terms of power and Type I error control. It is shown that the Fisher-Bonett test is just as effective as its competitors in controlling Type I error, is comparable to them in power, and is equally robust against heterogeneity of error variance.