Automatic and Controlled Attentional Processes in Amnestic Mild Cognitive Impairment: The Use of a Mini-Verbal Test

doi:10.4236/psych.2012.35053

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Psychology

2012. Vol.3, No.5, 379-383

Published Online May 2012 in SciRes (http://www.SciRP.org/journal/psych) http://dx.doi.org/10.4236/psych.2012.35053

Automatic and Controlled Attentional Processes in Amnestic

Mild Cognitive Impairment: The Use of a Mini-Verbal Test

Jonas Jardim de Paula1, Danielle de Souza Costa1, Edgar Nunes de Moraes2,

Rodrigo Nicolato3, Manuel Sedó4, Leandro Fernandes Malloy-Diniz1,3

1Neuropsychological Investigations Laboratory, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

2Internal Medicine Department, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

3Mental Health Department, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

4Mini-Verbal Tests, Boston, US

Email: [email protected]

Received December 19th, 2011; revised January 20th, 2012; accepted February 23rd, 2012

Recent finding suggests that in Amnestic Mild Cognitive Impairment (MCI) executive functions deficits

may be a frequent clinical finding. Automatic and Controlled attentional processes are related to the allo-

cation of cognitive resources in different stimuli, being important to executive functioning. The present

study aims at assessing the hypothesis of executive dysfunction deficits in MCI patients. Method: forty

five MCI patients and forty five normal aging controls (NC) were assessed with the Five Digits Test (5D),

a Mini-Verbal test version of the Stroop Test. Group comparisons were performed by t tests and the

non-parametric Mann-Whitney test. Results: comparisons indicates significant differences between NC

and MCI in efficiency measures of controlled attentional processes, with moderate effect sizes, but not in

automatic attentional processes or processing speed. Conclusion: the present work shows a selective pat-

tern of impairment in MCI, indicating specific deficits in executive functioning with spared processing

speed.

Keywords: Executive Functions; Selective Attention; Five Digit Test; MCI; Attentional Process

Introduction

Mild Cognitive Impairment (MCI) is an intermediate clinical

condition between normal aging and dementia (Petersen et al.,

2001). MCI patients show deficits in specific cognitive func-

tions, do not fill the criteria for dementia diagnosis and have

none or mild impairment in daily life activities. The impairment

may occur in only one cognitive domain (Amnestic or Non-

Amnestic MCI) or multiple domains (Multiple Domain Amnes-

tic MCI or Multiple Domain Non-Amnestic MCI) (Petersen &

Negash, 2008). Some neuropathological markers (Apostolova

et al., 2006) and cognitive-behavioral patterns are being inves-

tigated as possible predictors for MCI to be converted into de-

mentia (Palmer et al., 2010). One possible cognitive profile

which may play a role in this conversion is the executive func-

tions impairment (Balota et al., 2010).

Executive functions are a group of cognitive processes in-

volving abstraction, inhibition, fluency, set shifting, problem

solving and self-regulation. One of the most consensual defini-

tions of this construct is the one proposed by Lezak, Howieson

and Loring (2005): “capacities that enable a person to engage

successfully in independent, purposive, self-serving behavior”.

In a developmental perspective the executive functions show an

inverted “U” shaped curve (Zelazo, Craik, & Booth, 2004),

associated with the maturation of cortico-subcortical connec-

tions of the Prefrontal Cortex, Basal Ganglia, Thalamus and

Cerebellum (Fuster, 2009). The executive changes across the

lifespan seem to be mediated by a significant slowness in proc-

essing speed and a reduced working memory capacity

(Salthouse & Meinz, 1995). Education is an important factor

for executive performance. Lin and Col. (2007) suggest that the

decline of some components of executive functions such as

attention allocation, planning, and initiation are more related to

the aging process whereas educational level is more prone to

explain the decline of initiation, switching, ﬂexibility, and

online updating. Recent research indicated that even in Amnes-

tic MCI (MCI) patients might show executive functions im-

pairment. Kramer and Col. (2007) found significant differences

between MCI and normal aging controls in neuropsychological

tests of executive functioning, like the Stroop Color-Word Test,

the Wisconsing Card Sorting Test, Verbal Fluency and Draw-

ing Fluency. The similar results were shown by Traykov and

Col. (2007) using the Stroop Color Word Test and the Modified

Card Test, but not the Trail Making. These findings indicate

that different aspects of executive functioning may be impaired

in MCI, like cognitive shifting, fluency, planning abilities and

selective attention. Executive impairment may be a frequent

finding in these patients and might play a role in the conversion

into dementia.

Usually the assessment of executive functions is carried out

with classic neuropsychological tests such as the Stroop

Color-Word Test (Stroop, 1935) and the Trail Making Test

(Reiten, 1955). These measures are adequate for the detection

of executive dysfunction in subjects with dementia and MCI

(Fisher et al., 1990; Koss et al., 1984; Kramer et al., 2007).

Nonetheless, these tasks are greatly influenced by formal edu-

cation and reading abilities (Johnson, Flicker & Lichtenberg,

2006; Lucas et al., 2005). An alternative in these situations is

the Mini-Verbal Tests (MVT) which try to be as independent as

possible from school learning and culturally-acquired routines

J. J. DE PAULA ET AL.

of the subjects. In the MVT the verbal content is limited to a

few well-known familiar concepts, shown to the subject as

series of visual images. MVT tasks are ideal for the assessment

of cognitive functions of bilingual, illiterate or very low edu-

cated people, since their results are less biased by other inter-

venient factors (Sedó, 2004).

An important feature of the executive functioning is the se-

lective allocation of attentional resources to specific environ-

mental stimuli. The human attentional system may be divided

into three major components: an alerting/vigilance network

involved in the regulation of arousal and alert tonus; a posterior

attentional network involved in spatial orientation and percep-

tion of sensory stimuli; and an anterior/executive network in-

volved in the detection of events, conscious attentional proc-

essing and executive control of behavior (Lang, 2002). The

posterior network is related to automatic attentional process,

conducting intuitive allocation of attentional resources in spa-

tial information and is also related to the posterior parietal lobe

and its connections with the thalamus and the brainstem,

(Cohen et al., 1998) while the anterior network is related to

controlled attentional process which involves conscious alloca-

tion of rescources, inhibition and a greater involvement of ex-

ecutive control, being associated with the anterior cingulate

cortex and its connections with the prefrontal cortex and the

thalamus (Cohen et al., 1998). Performance in neuropsy-

chological assessment of this process indicates that controlled

attentional process demands more cognitive resources, which

may be seen in the increase of time needed to perform the tasks

(a measure of speed) and higher error rate (a measure of effi-

ciency) (Lucas et al., 2005).

The Five Digit Test (5D), proposed by Sedó (2004) is a

MVT adaptation of the Stroop Color-Word Test. For the test

execution the subject must know only the first five numbers (1 -

5) and their corresponding symbols, which are always shown in

the canonical display. The test measures the continuous verbal

performance at different levels of the attentional network, since

it involves an automatic process (reading numbers and counting

figures) and a controlled process where subjects must inhibit an

automatized routine of processing in favor of a secondary

non-intuitive one (saying the number of digits instead of read-

ing the digit).

The present work aims at assessing the performance of MCI

patients in the 5D task and compare the automatic and con-

trolled processes of selective attention speed and efficiency in

these participants. The tested hypothesis is that MCI patients

show greater impairment in the controlled process than in the

automatic process when compared to normal aging controls

(NC).

Method

Participants

Forty five patients diagnosed with MCI (23 men and 22

women) and forty five NC (21 men and 24 women) were as-

sessed for this study. The NC group was composed by patients'

relatives or community older adults recruited by local an-

nouncements, while the MCI patients were invited after clinical

evaluation in a clinical center specialized in gerontology. The

inclusion criteria for the NC group were total score on the Bra-

zilian version of the Mini-Mental State Exam above the pro-

posed cutoff for education (Brucki et al., 2003), total score on

the fifteen item version of the Yeasavage Geriatric Depression

Scale (Brazilian version) below the cutoff score for depression

(Paradella, Lourenço & Veras, 2005) and no functional im-

pairment assessed by the Lawton-Brody (Lawton & Brody,

1969) and Katz (Katz, Downs, Cash & Grotz, 1970) daily life

activities indexes. The MCI group was diagnosed by a multid-

isciplinary assessment conducted by at least one gerontologist

and one clinical neuropsychologist based on the Petersens and

col. criteria for MCI (2001). Also a semi-structured interview

based on the DSM-IV was conducted by the researchers for

screening other neuropsychiatric conditions. All participants

were assessed in accordance with the Declaration of Helsinki,

and the Research Ethics Committee of the Universidade Federal

de Minas Gerais (334/06) gave written consent and approval.

Participants’ data is shown in Table 1.

Procedure

The cognitive screening was conducted by the use of the

Mini-Mental State Exam and the Clock Drawing Test. Selective

attention was assessed with the 5D, a MVT test divided into

four successive parts: 1) decoding, 2) retrieving, 3) inhibiting

and 4) shifting, which involve, respectively: reading, Counting,

choosing, and switching a series of stimuli (Figure 1). Each

part of the test is preceded by a training containing 10 items;

after the instructions, the subject has four trials to correctly

respond to the items. If the subject is unable to perform the

training items, the test is interrupted. The items are shown in

pages of 50 items (10 rows of five items) and each of them is

surrounded by a rectangular frame. Previous studies attested its

validity and potential for clinical use (Lang, 2002; Sedó, 2004).

Figure 1.

The five digits test.

380

J. J. DE PAULA ET AL.

In the decoding part of the test, the subject is shown a series

of 50 boxes that require automatic reading of the items inside

each box, which are groups of one to five congruous digits (one

1, two 2 s, three 3 s…) that must be read. In the second part,

Retrieving, the subject is shown a series of 50 boxes where one

to five stars must be counted. In the third part—the inhibition

part—digits are shown in incongruous forms (one 4, two 3 s,

five 1 s…) and the person is asked to say the number of digits,

demanding a controlled process of inhibition. In the fourth part

of the test an additional difficulty is shown to the subject:

he/she has to switch from counting to reading in 20% of the

items of the page (the items marked by a much darker frame),

resulting in a series of congruent and incongruent items that

demand a more intense controlled process of inhibition and

“shifting”.

The four parts of the 5D measure the “speed” of information

processing (time in seconds) and the “efficiency” of their re-

sponses (number of errors). Considering the processes involved

the test can be divided in automatic attentional processes (De-

coding/Retrieving) and controlled attentional processes (Inhib-

iting/Shifting). An interference score was computed as recom-

mended by the test author (Sedó, 2004) subtracting the reading

time of the inhibiting and shifting components, creating two

new variables: executive-inhibiting and executive-shifting.

Statistical Analysis

Data distribution was assessed by the Kolmogorov-Smirnnov

test. Continuous variables with parametric distribution were

compared by independent samples t tests and effect sizes were

estimated by Cohen’s d. Non parametric data were compared

by the Mann-Whitney U Test and effect sizes estimated by the r

statistic (Z/√N). The frequency of gender in the two samples

was compared by a chi-square test. Significance levels were

established at 0.05.

Results

Comparisons between the MCI group and the NC on the 5D

are shown on Table 1. No differences in age and education

were found between the two groups (p > 0.05). No significant

differences on gender frequency were found (p > 0.05). Besides

screening tests, only measures of efficiency in controlled atten-

tional components differed significantly (p < 0.001), with mod-

erate effect sizes. The group differences considering Automatic

and Attentional Processes in terms of “speed” and “efficiency”

are exposed in Figure 2.

Discussion

This study evaluated the performance of MCI patients in a

MVT version of the Stroop Color-Word Task considering the

automatic and the controlled processes of selective attention.

As expected, controlled attentional process demands more cog-

nitive resources, which is illustrated by the slower times of

execution and loss of efficiency when the two conditions were

compared. This phenomenon however was more prone in MCI

patients when efficiency was considered, but no differences

were found between this group and healthy older adults when

speed was compared. These findings suggest that MCI patients

show a “fast but inaccurate” pattern of performance commonly

found in clinical conditions where executive functions are often

impaired (Kogan, 1971).

These findings are complementary to other studies that sug-

gest that even in MCI executive functions may be impaired. In

the 5D test Moderate Effect Sizes were found when efficiency

Table 1.

Participants description and group comparisons.

NC MCI

Mean (SD) Median Mean (SD)Median

t/U p d/r

Age (Years)1 73.97 (6.59) 75.00 73.87 (6.59)74.00 0.06 0.953 -

Education (Years)1 4.30 (2.26) 4.00 4.70 (3.01) 4.00 –0.58 0.563 -

Mini-Mental State Exam1 26.70 (2.35) 27.00 23.99 (1.89)24.00 4.915 0.001 1.27

Clock Drawing Test2 3.89 (1.46) 4.20 2.46 (1.47) 2.38 213.50 0.001 –0.530

Decoding (Time)1 33.03 (15.58) 27.00 40.43 (12.97)41.00 –1.19 0.239 -

Decoding (Errors)2 0.03 (0.18) 0.00 0.10 (0.40) 0.00 434.50 0.544 -

Retrieving (Time)1 37.90 (14.71) 34.00 41.57 (13.97) 41.00 –0.990 0.326 -

Retrieving (Errors)2 0.23 (0.77) 0.00 0.20 (0.61) 0.00 448.50 0.966 -

Inhibiting (Time)1 63.63 (20.40) 61.00 73.97 (38.39) 65.00 –1.30 0.200 -

Inhibiting (Errors)2 1.80 (1.67) 1.00 5.37 (5.05) 5.00 238.00 0.001 –0.473

Shifting (Time)1 92.40 (23.73) 90.00 104.80 (37.05)99.28 –154 0.129 -

Shifting (Errors)2 4.07 (3.33) 3.50 9.98 (6.91) 7.00 205.50 0.001 –0.538

Executive Inhibition1 29.30 (21.86) 26.00 33.80 (30.83)27.00 –0.65 0.517 -

Executive Shifting1 57.77 (20.44) 57.00 65.54 (32.36)54.28 –1.11 0.271 -

1Parametric Distribution, independent samples t tests and Cohen’s d used; 2Non-Parametric Distribution, Mann-Whitney U Test and r used; NC: Normal

Conrols; MCI: Amnestic Mild Cognitive Impairment.

J. J. DE PAULA ET AL.

Figure 2.

Relationship between Speed, Efficiency, Group and Attentional Process. MCI: Amnestic Mild Cognitive Impairment, CI: Confidence

Interval 95%.

in controlled attentional process of these patients was compared

to efficiency in the control group, indicating deficits in inhibi-

tion and cognitive shifting. However no differences were found

in the time required to complete the tasks, suggesting no proc-

essing speed impairments in this population. Even in the “pur-

est” executive indexes of interference (executive-inhibition and

executive-shifting) related to speed of performance no differ-

ence was found. As pointed by Salthouse and Meinz (1995)

even the interference scores of stroop-like tasks are largely

influenced by processing speed and may not reflect executive

impairment. The dissociation of performance between the speed

and efficiency components of controlled attentional process has

an important meaning for clinical practice and must be consid-

ered in the perspective shown above, where a maintenance of

speed and lack of accuracy may indicate a more specific im-

pairment of executive functioning.

In terms of anatomical correlates the controlled attentional

process is associated with the anterior attentional network, con-

sisted of the anterior cingulate cortex and its connections to the

thalamus and the prefrontal cortex. Some authors like Nagata et

al. (2009) argue that executive impairments in controlled atten-

tional tasks might be secondary to histopathological changes in

medial temporal lobe regions, a common feature of Alz-

heimer’s Disease Dementia and MCI (Apostolova et al., 2006).

The disruption of neuronal networks associated with these re-

gions may secondarily affect other cognitive functions. The

proximity and density of neuronal connections between these

regions and the anterior cingulated cortex may be a risk factor

for controlled attentional process impairment in these patients.

Balota and Col. (2010) report that the errors on incongruent

trials were the best predictor of those who convert, differently

from those who do not, to Alzheimer disease dementia over a

14-year period. The results of the current study, aligned with

other findings, suggest that the association of medial temporal

lobe atrophy, controlled attentional process and MCI conver-

sion to dementia should be better investigated by other re-

searches.

The use of MVT tasks in low educated subjects proves it is

useful for clinical and research purposes. Other 5D studies in-

dicate good construct and criterion validity for patients of dif-

ferent ages and educational-cultural backgrounds (Sedó & De-

Cristoforo, 2001; Hsieh & Tori, 2007) and the 5D Test seems

ideal for the population assessed in this study. Drawbacks in

instruments like the chromatic (Lezak, Howieson, & Loring,

2005) and linguistic (Cox et al., 1997) properties of traditional

neuropsychological tests like the Stroop Color-word Test have

limited their uses in contexts where difficulties with color per-

ception, reading problems, and language disorders are present.

This is just the recurrent profile of the elderly in Brazil, where

illiteracy reaches 26% (IBGE, 2009). MVT tests in these con-

texts appear to be an appropriate choice for the assessment of

processing speed and executive functions.

The present study has important limitations. First, although it

is well characterized, the sample size is small, limiting the gen-

eralization of the findings. Also, as no other measures of execu-

tive functioning were used in the assessment of these patients

for the research, it is difficult to argue about the construct

specificity of the efficiency impairment as an indicator of a

more generalized executive dysfunction. However, the present

finding indicates a more specific pattern of executive impair-

ment in MCI patients where efficiency may be selectively im-

paired despite speed preservation. The 5D also shows good

evidences of clinical validity for the studied population.

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