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Short Communication
The Effects of Nicotine and Sucrose on Spatial Memory
and Attention
C.B. HARTE* and R.B. KANAREK
Department of Psychology, Tufts University, Medford, MA 02155, USA
(Received 15 December 2003; Revised 6 February 2004; In final form 4 March 2004)
Both nicotine and sucrose can enhance performance on
cognitive tasks. However, little is known about whether
nicotine and sucrose could act jointly to augment mental
performance. To investigate if there is an interaction
between nicotine and sucrose on cognitive behavior,
performance on a continuous performance task (CPT)
and a spatial memory task was examined in 14 healthy
smokers after they had drunk 8 oz of either a sucrose- or
aspartame-containing beverage, and then chewed a piece
of gum containing either 2 mg nicotine or no nicotine. To
assess changes in mood as a function of nicotine and
sucrose intake, the profile of mood states (POMS) test
was administered three times during each test session.
Participants made significantly more correct responses
and significantly fewer incorrect responses on the CPT
when they received nicotine than when they received the
placebo gum. Closer analysis of the data revealed that
there was an interaction between sucrose consumption
and nicotine intake. Nicotine increased hits and
decreased misses when participants were given the
sucrose-containing beverage, but not when they
were given the aspartame-containing beverage. Neither
nicotine nor sucrose affected spatial memory or mood
across experimental sessions. However, when data were
analyzed for just the first session, participants who drank
the sucrose-containing beverage performed significantly
better on the spatial memory task than those who
drank the aspartame-containing beverage. No gender
differences in the effects of nicotine or sucrose on
cognitive performance were detected. The results
provide support that both nicotine and sucrose have
positive effects on cognitive behavior, and that under
some conditions the two variables have additive effects
on performance.
Keywords: Attention; Memory; Nicotine; Sucrose
The growing concerns about the health problems
related to cigarette smoking have generated much
research investigating the underlining causes of
the habit. It is widely accepted that nicotine is
primarily responsible for the addictive properties of
tobacco. Nicotine, like other drugs of abuse, leads to
addiction by acting on the brain’s reward systems.
Nicotine, however, has other properties that may
contribute to its abuse potential. Some individuals
may smoke, at least in part, as a result of nicotine’s
positive effects on cognitive behavior (Levin, 1992).
Nicotine can improve short-term memory (Krebs
et al., 1994; Phillips and Fox, 1998), working memory
(Pineda et al., 1998) and memory reaction time
(Sherwood et al., 1991; Warburton et al., 2001).
Improvements in memory after nicotine ingestion
typically are attributed to the drug’s ability to
enhance attention or increase arousal (Rusted and
Eaton-Williams, 1991; Mancuso et al., 2001).
Despite abundant data substantiating nicotine’s
positive effects on cognition, it remains unclear
whether performance is augmented following drug
administration as a result of nicotine per se, or due to
drug’s actions in relieving withdrawal symptoms
(Warburton et al., 1986; Rusted and Eaton-Williams,
1991; Sherwood et al., 1991; 1992). In support of the
latter possibility, Mumenthaler et al. (1998) found that
nicotine improves performance more consistently if
participants are in a nicotine withdrawal state than if
they have recently consumed the drug. To determine
ISSN 1028-415X print/ISSN 1476-8305 online q2004 Taylor & Francis Ltd
DOI: 10.1080/10284150410001704543
*Corresponding author. Address: Psychology Research Laboratory, Mailman Research Center, McLean Hospital, 115 Mill Street,
Belmont, MA 02478-9106, USA. Tel.: þ1-617-855-3630. Fax: þ1-617-855-2778. E-mail: charte@mclean.org
Nutritional Neuroscience,Volume 7 Number 2 (April 2004), pp. 121–125
if nicotine itself has cognitive enhancing effects,
participants have been tested at their preferred
nicotine levels (Phillips and Fox, 1998). This pro-
cedure eliminates nicotine deprivation effects, but
does not control for variability in nicotine intake
across participants. Moreover, when nicotine is
administered during the testing session, participants
already have nicotine in their bloodstream, making it
difficult to isolate effects due to experimental
administration of nicotine from varying baseline
levels. Even if the nicotine content of a cigarette is
carefully controlled, nicotine ingestion via smoking
may be problematic because of differences in the way
in which individuals inhale (Levin, 1992). To help
resolve this issue, other methods of presenting
nicotine, such as nicotine gum or a nicotine patch
with an appropriate placebo condition are useful.
Sugar intake can also enhance cognitive proces-
sing. Consumption of a glucose-containing beverage
improves performance on a variety of cognitive tasks
(Benton et al., 1994; Su
¨nram-Lea et al., 2001).
Similarly, intake of sucrose-containing foods
enhances skills on tasks of mental behavior in
children and young adults (Kanarek and Swinney,
1990; Busch et al., 2002).
The present study investigated whether nicotine
and sucrose, individually or in combination, affected
attention, spatial memory, and/or mood in smokers.
Nicotine was administered in gum form to ensure
greater control over the dose participants ingested,
and participants were asked to refrain from smoking
for only 2 h prior to entering the laboratory to
minimize nicotine withdrawal effects.
Five male and 9 female smokers residing around
the Tufts University campus volunteered to take part
in this study. The participants had been smoking at
least 10 cigarettes per day for a minimum of 1 year
prior to the start of the study (see Table I for details).
At an orientation meeting, participants completed a
health-screening questionnaire and provided written
informed consent. All participants were in good
physical and mental health. Participants were
excluded if they were taking medications with
arousal or sedative effects.
Participants were told the experiment was inves-
tigating cognitive processes in smokers. On each of
the four test sessions, participants were asked to
abstain from eating, drinking (with the exception of
water), and smoking for 2 h prior to arriving at the
laboratory. On the first test day, all participants
competed the Fagerstrom test of nicotine depen-
dence, which is comprised of six questions related to
smoking habits and is graded 0 (not dependent on
nicotine) to 10 (very dependent on nicotine)
(Fagerstrom and Schneider, 1989; Heatherton et al.,
1991). Participants also answered four questions
assessing their use of smoking for weight manage-
ment. Each question was scored on a 7-point Likert
scale, and the sum of the four questions used to
obtain an overall score ranging from 4 (minimal use
of smoking for weight maintenance) to 28 (high use
of smoking for weight maintenance) (Table I).
At the beginning of each session, participants com-
pleted the profile of mood states (POMS) question-
naire, which consists of 65 mood state adjectives each
measured on a 5-point Likert scale (McNair et al.,
1971). The scores are used to calculate a total mood
score as well as six subscale scores designed to assess
levels of confusion, fatigue, vigor, anger, depression
and tension. After completing the POMS, participants
drank either 8 oz of Country Time
w
pink lemonade
(70 calories, 17 g sugar) or 8 oz of a “placebo”
aspartame-containing beverage, Crystal Light
w
pink lemonade (5 calories, 0 g sugar). The two
beverages were rated as being virtually indistinguish-
able in taste during pilot testing.
Ten minutes after participants finished
the beverage, they completed a second POMS
questionnaire. Participants then were given either a
piece of nicotine gum (CVS
w
Nicotine Polarilex
Gum USP, 2 mg) or a piece of placebo gum (Trident
Advantage
w
sugarless gum) and chewed the gum for
the remainder of the experiment. The two pieces
of gum were similar in appearance, taste and
consistency, and were flavored with mint. A third
POMS questionnaire was completed 12 min later.
Immediately following the POMS, attention was
assessed using a continuous performance task (CPT).
Letters were presented randomly one letter at a time
on a computer screen, and participants were told to
respond to the appropriate target. There were two
TABLE I Participant characteristics (males, n¼5; females, n¼9)
Variable Mean Range SD
Age
Male 19.00 18–20 0.71
Female 19.33 18–21 1.22
Male þFemale 19.21 18–21 1.10
FTND*
Male 4.60 3–7 2.80
Female 2.22 0–5 1.56
Male þFemale 3.07 0– 7 1.94
SWMT
†
Male 5.60 4–7 1.52
Female 7.67 4 – 17 4.80
Male þFemale 6.93 4– 17 3.99
Years smoking
Male 3.50 2–8 2.55
Female 3.94 1–7 2.04
Male þFemale 3.79 1– 8 2.15
Cigarettes/day
Male 13.60 11– 15 1.95
Female 14.22 10–23 5.26
Male þFemale 14.00 10–23 4.28
SD, standard deviation; FTND, Fagerstrom test of nicotine dependence;
SWMT, smoking for weight management test.
*
Maximum possible score ¼
10:
†
Maximum possible score ¼28:
C.B. HARTE AND R.B. KANAREK122
CPT conditions: an XB target (correct hit: an “X”
followed by a “B”) and a PR target (correct hit: a “P”
followed by an “R”). Each letter was presented for
100 milliseconds with an inter-stimulus interval of
1 s. The CPTwas calibrated to produce correct targets
25% of the time, and was administered for 15 min.
Because there were two target conditions (XB, PR),
participants underwent each condition twice in an
ABAB or BABA format.
To assess spatial memory, following the CPT, a map
with four fictitious “continents” was shown on a
computer screen. Each continent was comprised of
eight “countries” for which fictitious names were
given. All 24 countries were given a name from one
of four categories: flowers, earth metals, bones of
the body, and gems. By pressing the space bar on the
computer, the participant advanced through the
map, viewing one country at a time. Each country
name appeared on the screen for an amount of time
determined by the participant. The complete set of
country names was presented in the same order each
time. The four map categories were counterbalanced
across test sessions. The map presentation termi-
nated once the participant cycled through all 24
countries eight times, or when 7 min had elapsed.
A blank paper copy of the map then was provided,
and participants were asked to fill in as many country
names as possible on the corresponding map.
Each participant participated in all four experi-
mental sessions, with no less than 2 days intervening
between test sessions. The order of the four
conditions was counterbalanced across participants.
At the completion of the experiment, participants
received $50 and were debriefed as to the purpose of
the study.
The protocol met the American Psychological
Association’srequirementsforhumansubject
research, and was approved by the Tufts University
Institutional Review Board.
Data were analyzed using a repeated measures
two-way ANOVA with nicotine and sucrose
conditions as within-subjects variables. CPT data
were analyzed for correct hits, misses, and
false alarms during the first 5 min, second 5 min
and last 5 min of the test as well as for the total
15 min. There were no differences among con-
ditions when data were analyzed separately in
5-min blocks. However, across the 15 min test
session, participants made significantly more correct
hits (Fð1;13Þ¼9:71;p,0:01) (Fig. 1), and less misses
when chewing the nicotine gum than when
chewing the placebo gum (Fð1;13Þ¼4:82;p,0:05)
(Fig. 2). More detailed examination of the data
revealed that nicotine significantly increased hits
(tð13Þ¼2:60;p,0:02), and decreased misses
(tð13Þ¼2:51;p,0:03) when participants were
given the sucrose-containing beverage, but not
when they were given the aspartame-containing
beverage.
Neither nicotine nor sucrose affected recall on the
spatial memory task across experimental sessions.
However, performance significantly improved
across the sessions (Fð3;39Þ¼3:40;p,0:05)
(Table II). As a result of this learning effect, data
were analyzed separately using a between subjects
two-way ANOVA for the first session of the
experiment before learning took place. Although
there were only a small number of participants in
each condition, the analysis indicated that parti-
cipants who drank the sucrose-containing beverage
recalled significantly more countries ð20:7^3:2Þ
than those who drank the aspartame-containing
beverage ð15:9^5:6Þ(Fð1;10Þ¼6:28;p,0:05).
The number of countries recalled did not vary as a
function of nicotine administration.
Mood as measured by the last POMS did not differ
as a function of nicotine or sucrose administration
at any measurement point. No gender differences
FIGURE 1 Mean (^SEM) total correct hits on the CPT task as a function of nicotine and sucrose administration. Bars without common
superscripts are different as determined by a repeated measures two-way ANOVA, p,0:01:
EFFECTS OF NICOTINE AND SUCROSE 123
in the effects of nicotine or sucrose on cognitive
performance were detected.
As in previous studies (Rusted and Eaton-
Williams, 1991; Warburton and Mancuso, 1998;
Mancuso et al., 2001), nicotine improved perform-
ance on an attention task in male and female
smokers. Although these data replicate earlier
results, the positive effects of nicotine on attention
were significant only when participants had drunk
the sucrose-containing beverage, but not when they
had consumed the aspartame-containing drink.
These results suggest that sucrose intake enhanced
the positive effects of nicotine on participants’ ability
to maintain attention on the CPT. These findings are
reminiscent of data from a recent experiment which
demonstrated that sucrose augmented the pain
relieving actions of nicotine in smokers (Kanarek
and Carrington, 2004).
Nicotine had no effect on spatial memory.
A number of variables may have contributed to
the failure to replicate previous experiments in
which nicotine did improve memory (Rusted et al.,
1998; Warburton and Mancuso, 1998; Warburton
et al., 2001). First, results of prior studies indicate that
nicotine is more effective in enhancing memory
when a difficult task is used rather than an easy one
(Rusted and Eaton-Williams, 1991; Rusted et al.,
1998). In the present experiment, the memory task
was relatively easy, with most participants making
few errors. Support for the idea that task difficulty
influences the effects of nicotine on memory also
comes from recent work in which positive effects of
nicotine on memory were observed when the task
was made more difficult by decreasing the total
presentation time of the maps, and the number of
times the participants were allowed to cycle through
the maps before recalling country names (Kanarek
and D’Anci, 2004). Second, the effects of nicotine on
cognitive behavior are more pronounced when
participants are going through drug withdrawal
(Mumenthaler et al., 1998) than when as in the
present experiment, participants are only minimally
nicotine-deprived. Third, although studies have
found positive effects of nicotine on memory using
the same dose and method of drug administration as
in the present experiment (Sherwood et al., 1991;
Phillips and Fox, 1998), most studies have employed
nicotine inhalation as the method of drug admini-
stration (e.g. Krebs et al., 1994; Rusted et al., 1998;
Mancuso et al., 2001; Warburton et al., 2001). It is
possible that a greater dose of the drug is obtained
when nicotine is inhaled than when it is orally
consumed. Finally, a learning effect could have
masked the memory enhancing effects of nicotine in
this study. Future studies could alleviate this
problem by having practice sessions on the map
before the actual test sessions, or using more
participants and a between subject design.
There is a growing body of literature indicating that
sugar intake can have positive effects on cognitive
behavior (e.g. Benton et al.,1994;Su
¨nram-Lea et al.,
2001; Busch et al., 2002). However, in the present study,
sucrose had no effect on memory when examined
across the experiment. As for nicotine, there are a
number of reasons for the discrepancy between our
FIGURE 2 Mean (^SEM) total misses on the CPT task as a function of nicotine and sucrose administration. Bars without common
superscripts are different as determined by a repeated measures two-way ANOVA, p,0:05:
TABLE II Recall scores, including frequency of maximum
number of country names recalled,* for the spatial memory task
for each consecutive testing session
Experimental
session
number Mean Range SD
Frequency of
maximum
recall score
1 17.93 6–24 5.21 1
2 18.86 9–24 4.85 3
3 20.29 11–24 4.60 4
4 21.07 11–24 4.14 7
SD, standard deviation.
*
Maximum possible score ¼24:
C.B. HARTE AND R.B. KANAREK124
findings and those of others. First, as noted above,
the memory task may have been too simple. Second,
the dose of sucrose may have been too small.
The sucrose-containing beverage had 17 g of sucrose,
which is comprised of equal parts of glucose and
fructose. Thus, participants took in 8.5g of glucose.
Results of prior studies, however, suggest that 25 g of
glucose is needed to produce optimum effects on
memory (Benton et al., 1994). Indeed, in more recent
studies using larger amounts of sucrose, the sugar did
have positive effects on spatial memory (Kanarek and
D’Anci, 2004). Additionally, the fact that participants
were only asked to abstain for eating for 2 h could
have limited the effects of the sugar on memory.
Sugars are more effective in enhancing memory
when participants have undergone an overnight fast
than when they have recently consumed a meal
(Benton et al.,1994;Buschet al., 2002). Finally, as for
nicotine, the learning effect across sessions may
have confounded the actions of sucrose on memory.
In support of this possibility, when data were analyzed
for just the first session, participants who consumed
sucrose remembered significantly more countries than
those who did not consume the sugar.
Neither nicotine nor sucrose affect mood in this
experiment. In addition to the variables listed above
which may have influenced these results, Hurt and
colleagues (1998), reported serum levels of nicotine
reach their peak approximately 30 min after partici-
pants begin to chew nicotine gum. In the present
study, participants would have either just been
finishing the CPT or just starting the spatial memory
task when serum nicotine levels were at peak. Thus,
waiting 12 min after gum administration to complete
the third POMS may have been too hasty in order to
accurately detect a mood change.
The results of this study provide support
for the hypothesis that both nicotine and
sucrose have positive effects on cognitive behavior,
and suggest that under some conditions the two
variables may have additive effects on cognitive
performance.
Acknowledgements
This study was supported by grant RO1DAO4132
from the National Institute on Drug Abuse. The
authors thank the subjects who participated in this
study and Deborah L. Levy, Ph.D. for her generous
assistance.
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