Positive modulation of cognition and mood in the healthy elderly volunteer following the administration of Centella asiatica ppt

Positive modulation of cognition and mood in the healthy elderlyvolunteer following the administration of Centella asiatica aDepartment of Physiology, Faculty of Medicine, Khon Kaen Univ

Positive modulation of cognition and mood in the healthy elderly

volunteer following the administration of Centella asiatica

aDepartment of Physiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand

bDepartment of Physiology and Biomedical Science Program, Graduate School, Khon Kaen University, Khon Kaen 40002, Thailand

cDepartment of Psychiatry, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand

dDepartment of Otolaryngology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand

eCenter for Research and Development of Herbal Health Product, Faculty of Pharmaceutical Sciences,

Khon Kaen University, Khon Kaen 40002, Thailand

Received 21 February 2007; received in revised form 21 November 2007; accepted 28 November 2007

Available online 4 December 2007

Abstract

Aims of this study: Centella asiatica has a reputation to restore decline cognitive function in traditional medicine and in animal model However, little

evidence regarding the efficacy of Centella asiatica from systematized trials is available Therefore, the present randomized, placebo-controlled, double-blind study investigated the effect of Centella asiatica on cognitive function of healthy elderly volunteer.

Materials and methods: Twenty-eight healthy elderly participants received the plant extract at various doses ranging 250, 500 and 750 mg once

daily for 2 months Cognitive performance was assessed using the computerized test battery and event-related potential whereas mood was assessed using Bond–Lader visual analogue scales prior to the trial and after single, 1 and 2 months after treatment

Results: The results showed that the high dose of the plant extract enhanced working memory and increased N100 component amplitude of

event-related potential Improvements of self-rated mood were also found following the Centella asiatica treatment.

Conclusion: Therefore, the present findings suggest the potential of Centella asiatica to attenuate the age-related decline in cognitive function and

mood disorder in the healthy elderly However, the precise mechanism(s) underlying these effects still require further investigation

© 2008 Elsevier Ireland Ltd All rights reserved

Keywords: Centella asiatica; Cognitive function; Event-related potential; Mood; Elderly

1 Introduction

During aging, a gradual deficit is present with regard to

cog-nitive functions, which normally does not severely disturb the

daily life activities related to the physical, mental, or social

functioning in elderly adults The age-related cognitive decline

has been characterized as a diminution of attentional processes,

episodic and working memory, and processing and

psychomo-tor speed (Nolan and Blass, 1992; Salthouse, 1994; Earles and

Salthouse, 1995; Grady and Craik, 2000; Christensen, 2001)

However, this condition can eventually progress to clinically

∗Corresponding author Tel.: +66 43 348394.

E-mail address:jintanapornw@yahoo.com (J Wattanathorn).

recognizable dementia (Chen et al., 2005; Amieva et al., 2005) Previous studies have demonstrated that age-related impair-ment in working memory is accompanied by the alteration of the event-related potential in respond to the auditory oddball tasks, a most frequent parameters examined in psychophys-iological studies of cognitive aging (Bashore et al., 1989)

It was found that the latencies of P300 and N100 compo-nents increased (Oken and Kaye, 1992; Kugler et al., 1993; Anderer et al., 1996) whereas the amplitudes of these two components were decreased (Coyle et al., 1991; Nordin et al.,

1999)

Recently, numerous studies have suggested that the age-related cognitive decline can be prevented (Solfrizzi et al., 1999) Therefore, a new approach aimed at controlling the decrease in cognitive function was focused Numerous previous studies had

0378-8741/$ – see front matter © 2008 Elsevier Ireland Ltd All rights reserved.

doi: 10.1016/j.jep.2007.11.038

demonstrated that fruits, vegetables and medicinal plants could

prevent the occurrence of the neurochemical and behavioral

changes that occurred in aging (Veerendra Kumar and Gupta,

2002; Joseph et al., 2003; Goyarzu et al., 2004)

Centella asiatica (L) urban, a creeping plant in a family

of Apiaceae, is found almost all over the world including in

China, India and Thailand This plant is claimed to be

bene-fit for managing the central nervous system disorders, skin and

gastrointestinal disorders (Subathra et al., 2005) In addition,

Centella asiatica is also claimed to possess memory enhancing

effect (Veerendra Kumar and Gupta, 2002), anti-inflammatory

(Suguna et al., 1996), wound healing (Suguna et al., 1996),

anti-cancer (Babu et al., 1995) and antioxidant properties (Zainol

et al., 2003) Recently, Centella asiatica products are widely

available in market as cognitive booster However, supported

document with valid biological data is still very limited

There-fore, the current study is carried out to determine the effect of

Centella asiatica on the cognitive function and mood in the

elderly

2 Materials and methods

2.1 Participants

Four male, and twenty-four female healthy elderly volunteers

(mean age 65.05± 3.56 years) were recruited to participate in

this study The Ethical Committee of Faculty of Medicine, Khon

Kaen University, have approved the study, and all subjects gave

written informed consent Prior to participation, each

volun-teer signed an informed consent form and completed a medical

health questionnaire All subjects were also undergone

exten-sive medical evaluation in order to ascertain subject suitability

for entering the double-blind phase of trial Additionally, they

were free of any herbal or prescribed medication that interfered

on the function of nervous system Habitual smokers consuming

more than 10 cigarettes/day were excluded from this study All

participants should abstain from caffeine containing products

throughout each study day and alcohol for a minimum of 12 h

prior to the test session They were divided into four groups:

placebo, CA250, CA500 and CA750 mg/day Each group

con-tained 1 male and no one dropout from the project Moreover,

no significant difference about mean age, education and body

mass index among groups were observed

2.2 Centella asiatica preparation

A standardized extract of Centella asiatica was prepared by

the Center for Research and Development of Herbal Health

Product, Faculty of Pharmaceutical Sciences, Khon Kaen

Uni-versity All Centella asiatica used in this study was obtained

from Tambon Sila, Khon Kaen Province The plant was

authenti-cated and kept as voucher specimen at Faculty of Pharmaceutical

Sciences, Khon Kaen University Standardization and

confor-mity of the extract is assured by strict in-process controls during

manufacture and complete analytical control of the resulting

dry extract A-day capsule contained a specialized aerial part

extract containing total phenolic content equivalent to tannic

acid = 29.9 mg/g In addition, the extract also contained asiati-coside and asiatic acid were presented at concentration of 1.09 and 48.89 mg/g of crude extract, respectively

2.3 Procedures and treatments

This study was a pilot study conducted as 8-week, double-blind, placebo-controlled, randomized trial A random list of numbers was generated by computer After being randomly assigned to various treatment groups Each participant received

one capsule of placebo or Centella asiatica extract at various

doses ranging 250, 500 and 750 mg once daily Placebo and

Centella asiatica capsules had the same colour, texture, size and

smell

All participants were assessed baseline data about cognitive function, mood and quality of life and then they were assessed cognitive performance and mood after the single administration,

1 and 2 months of treatment whereas the quality of life was assessed after 2 months of treatment

The code for study allocation was only broken when the last participant completed the entire follow up Staff involved in the collection of the study’s endpoints was instructed to follow a rigorous protocol and not to discuss any issues related to the use

of medication The review of compliance with medication and side effects was performed independently by the investigators, who were also blinded to group allocation Subjects were asked

to call the study center if they experienced any medical problems during the 60-day study period At the end of the study, they were also asked about adverse events Laboratory tests were drawn at baseline and follow-up visits and compared to see whether any changes suggested adverse events

2.4 Event-related potential measurement

Event-related potential (N100 and P300 amplitude and laten-cies) of all subjects were measured using an “oddball paradigm” (Kennedy et al., 2003) N100 and P300 amplitude and laten-cies were elicited with a standard auditory oddball paradigm Frequent and target tones were presented binaurally through headphones Participants were instructed to listen for and count infrequent target tones (650 Hz, 60 dB, 200 ms), which occurred randomly amongst 82–90 frequent non-target tones (1 kHz, 60 dB, 200 ms) Inter-stimulus intervals varied randomly between 1250 and 3000 ms The latency range in which the N100 and P300 maximum amplitudes and latencies were determined was between 65–135 and 280–375 ms, respectively However, any peaks outside this range were measured manually, with preliminary visual checking of all peaks prior to measurement

2.5 Computerized assessment battery test

The computerized assessment battery test used in this study has been modified from the CDR computerized assessment bat-tery test used in hundreds of European and North American drug trials and sensitive to acute cognitive improvements as well

as impairments with a wide variety of substances (Moss et al., 1998; Wesnes, 2001) Presentation was performed using note-book computers with high-resolution VGA colour monitor and,

with the exception of written word recall tests, all responses

were recorded via two-button (yes/no) response box The entire

selection of tasks took approximately 20 min

Tests were administered in the following order:

Word presentation: Fifteen words, matched for frequency and

concreteness, were presented in sequence on the monitor for the

participant to remember The stimulus duration was 1 s, as was

the inter-stimulus interval

Picture presentation: A series of 20 photographic images was

presented on the monitor at the rate of 1 every 3 s, with a stimulus

duration of 1 s, for the participant to remember

Simple reaction time: The participant was instructed to press

the ‘yes’ response button as quickly as possible every time the

word ‘yes’ was presented on the monitor Fifty stimuli were

presented with an inter-stimulus interval that varied randomly

between 1 and 3.5 s Reaction times were recorded in

millisec-onds

Digit vigilance task: A target digit was randomly selected and

constantly displayed to the right of the monitor screen A series

of digits was presented in the centre of the screen at the rate

of 80 min−1and the participant was required to press the ‘yes’

button as quickly as possible every time the digit in the series

matched the target digit The task lasted 1 min and there were

15 stimulus–target matches Task measures were accuracy (%),

reaction time (milliseconds), and number of false alarms

Choice reaction time: Either the word ‘no’ or the word ‘yes’

was presented on the monitor and the participant was required

to press the corresponding button as quickly as possible There

were 50 trials, of which the stimulus word was chosen randomly

with equal probability, with a randomly varying inter-stimulus

interval of between 1 and 3.5 s Reaction times (millisecond)

and accuracy (%) were recorded

Spatial working memory: A pictorial representation of a

house was presented on the screen with four of its nine windows

lit The participant was instructed to memorize the position of

the illuminated windows In 36 subsequent presentations of the

house, one of the windows was illuminated and the participant

decided whether or not this matched one of the lighted windows

in the original presentation The participant made their response

by pressing the ‘yes’ or ‘no’ response button as quickly as

pos-sible Mean reaction times were measured in milliseconds and

the accuracy of responses to both original and novel (distractor)

stimuli were recorded as percentages that were used to derive a

‘percentage greater than chance performance’ score

Numeric working memory: Five digits were presented

sequentially for the participant to hold in memory This was

followed by a series of 30 probe digits for each of which the

participant decided whether or not it had been in the original series and pressed the ‘yes’ or ‘no’ response button as appropri-ate, as quickly as possible This was repeated two further times with different stimuli and probe digits Mean reaction times were measured in milliseconds and the accuracy of responses to both original and novel (distractor) stimuli were recorded as percent-ages that were used to derive a ‘percentage greater than chance performance ’ score

Delayed word recognition: The original words plus 15

dis-tractor words were presented one at a time in a randomized order For each word, the participant indicated whether or not he or she recognized it as being included in the original list of words by pressing the ‘yes’ or ‘no’ button as appropriate and as quickly

as possible Mean reaction times were measured in milliseconds and the accuracy of responses to both original and novel (dis-tractor) stimuli were recorded as percentages that were used to derive a ‘percentage greater than chance performance’ score

Delayed picture recognition: The original pictures plus 20

distractor pictures were presented one at a time in a randomized order For each picture, participants indicated whether or not it was recognized as being from the original series by pressing the

‘yes’ or ‘no’ button as appropriate and as quickly as possible Mean reaction times were measured in milliseconds and the accuracy of responses to both original and novel (distractor) stimuli were recorded as percentages that were used to derive a

‘percentage greater than chance performance’ score

2.6 Subjective mood measurement

The 16 visual analogue scales of Bond–Lader were combined

as recommended by the authors to form three mood factors:

‘alert’, ‘calm’ and ‘content’

2.7 Statistical analysis

between placebo and various doses of Centella asiatica at

differ-ent time points were made using analysis of variance (ANOVA)

Statistical significance was set at p-value < 0.05.

3 Results

3.1 Characteristics of subjects

The baseline data about characteristic of subjects in all groups were shown inTable 1 No significant difference of all parame-ters among various groups was observed

Table 1

Characteristics of subjects

Baseline data Placebo Centella asiatica 250 Centella asiatica 500 Centella asiatica 750

Age 65.88 ± 5.11 67.25 ± 1.39 62.00 ± 4.34 64.75± 2.71, p = 0.0511

Education year 11.50 ± 6.21 12.25 ± 5.50 10.38 ± 5.80 14.14± 4.91, p = 0.5393

Full scale IQ 102.50 ± 10.61 99.17 ± 16.68 91.40 ± 17.80 99.33± 11.91, p = 0.7605

Blood sugar 93.29 ± 9.32 93.25 ± 6.61 89.75 ± 5.95 96.75± 11.13, p = 0.4500

Blood pressure 120.13 ± 10.26/77.75

± 5.52

121.50 ± 10.89/78.13

± 7.28

123.50 ± 7.76/80.38

± 2.77

124.75± 6.76, p = 0.7465/81.25 ± 4.30, p = 0.4794

Table 2

Mean amplitudes and latencies (S.D.) of event-related potential elicited by oddball paradigm for each group at Fz electrode

Wave Pre-dose baseline Post-dose

P300 latency Placebo 352.25 ± 27.74 339.63 ± 31.52 342.13 ± 25.67 330.63 ± 27.07

CA250 333.38 ± 31.18 337.75 ± 25.39 353.13 ± 36.99 348.50 ± 31.27 CA500 345.00 ± 20.65 336.00 ± 34.90 343.50 ± 28.16 332.88 ± 29.94 CA750 365.00 ± 31.48 337.38 ± 37.89 343.50 ± 35.27 369.88 ± 42.97

F(3,28) = 1.7785, p = 0.1741 F(3,28) = 0.0167, p= 0.9970 F(3,28) = 0.2035, p = 0.8931 F(3,28) = 2.4673, p = 0.0828

P300 amplitude Placebo 574.38 ± 410.53 557.75 ± 538.67 893.75 ± 871.72 1401.00 ± 1325.39

CA250 1595.00 ± 1918.49 1119.38 ± 960.73 801.00 ± 456.01 816.50 ± 527.87 CA500 890.13 ± 1178.20 1187.25 ± 1181.66 715.50 ± 543.00 1456.50 ± 1367.99 CA750 754.25 ± 686.50 863.00 ± 923.14 914.38 ± 823.24 844.63 ± 523.17

F(3,28) = 1.1192, p = 0.3580 F(3,28) = 0.7552, p = 0.5287 F(3,28) = 0.1381, 0.9364 F(3,28) = 0.1381, p = 0.9364

N100 latency Placebo 109.75 ± 29.40 100.69 ± 27.74 93.75 ± 22.63 106.63 ± 2359

CA250 103.56 ± 16.27 108.25 ± 22.71 107.25 ± 17.77 107.56 ± 15.67 CA500 100.56 ± 10.13 98.31 ± 8.09 100.25 ± 16.86 95.38 ± 12.20 CA750 94.56 ± 13.36 102.25 ± 12.26 102.38 ± 13.85 106.75 ± 12.74

F(3,28) = 0.5893, p = 0.6271 F(3,28) = 0.4079, p = 0.7485 F(3,28) = 0.7694, p = 0.5209 F(3,28) = 0.9727, p= 0.4195 N100 amplitude Placebo 3241.25 ± 2752.75 3915.38 ± 3059.96 3621.88 ± 1122.45 3655.88 ± 1903.34

CA250 5408.75 ± 3108.07 4297.50 ± 2017.30 4836.25 ± 1961.17 5005.00 ± 1639.17 CA500 4437.50 ± 2414.69 4515.00 ± 2114.88 3265.00 ± 2340.02 4028.13 ± 1944.52 CA750 4895.39 ± 2422.85 4218.75 ± 1219.84 4151.88 ± 1464.45 6691.25 ± 1542.46**

F(3,28) = 0.9687, p= 0.4213 F(3,28) = 0.1684, p= 0.9168 F(3,28) = 1.1748, p= 0.3370 F(3,28) = 4.7179, p= 0.0087

N100 amplitude **p-value < 0.01 compared with placebo (F(3,28) = 4.7179, p < 0.01) N100 latency of CA750 compared with placebo (F(3,28) = 0.9727, p = 0.4195).

3.2 Event-related potential components (ERP)

The effects of Centella asiatica on ERP components were

and amplitude of both N100 [F(3,28) = 0.9068, p = 0.4503;

F(3,28) = 1.0372, p = 0.3913] and P300 [F(3,28) = 1.7785,

p = 0.1741; F(3,28) = 1.1192, p = 0.3580] showed no significant

difference After 2 months of treatment with Centella asiatica at

dose of 750 mg/day, the subject’s N100 amplitude significantly

increased [F(3,28) = 4.7179, p = 0.0087] whereas no

signifi-cant change in N100 latency was observed [F(3,28) = 0.9727,

p = 0.4198] In addition, there were no significant changes

in either the amplitude or latency of P300 [F(3,28) = 0.9180,

p = 0.4449; F(3,28) = 2.4673, p = 0.0828].

3.3 Cognitive measures

Prior to the determination of Centella asiatica on cognitive

function, baseline data and mean pre-dose raw baseline scores

for all four conditions (placebo, 250, 500 and 750 mg Centella

asiatica) for each individual task scores were subjected to a

one-way ANOVA There were no significant differences on any

measure

Mean pre-dose baseline raw scores and change from

base-line scores for each condition at each post-dose time point on

the individual task outcome measures are represented inTable 3

The results showed that the Centella asiatica extract appeared

to decrease the reaction time while increased the %accuracy

of working memory, which indicated that the plant extract

exerted its influence on both speed and quality of working

mem-ory However, the significant changes in reaction times were

observed only in choice, spatial, numeric and picture reaction times while the significant changes of %accuracy were observed only in spatial, numeric, word and picture recognition due to the high variation of other parameters and limited number of our subjects

3.4 Bond–Lader mood scales

Mean raw scores on the ‘alert’, ‘content’ and ‘calm’ factors obtained from the Bond–Lader visual analogue scales for each condition across each session are displayed inTable 4

3.4.1 Alert factor

It was found that the participants’ subjective ratings score

about alert factor of Centella asiatica treated group at dose

of 750 mg/day showed a significant increase, in compari-son to placebo rating, after 1 and 2 months of treatment

[F(3,28) = 4.0828, p = 0.0016; F(3,28) = 3.7149, p = 0.0229].

3.4.2 Content factor

The present data showed that the rating score about content factor obtained from Bond–Lader visual analogue scale showed

no significant difference between placebo and various groups of

Centella asiatica treatment.

3.4.3 Calm factor

The effect of Centella asiatica extract on clam factor was also determined The results showed that Centella asiatica at

all dosage range used in this study significantly increased the

calm factor after 1 and 2 months of treatment [F(3,28) = 3.3943,

p = 0.0316; F(3,28) = 4.2124, p = 0.0141].

Table 3

Mean pre-dose baseline raw scores and change from baseline scores for each condition at each post-dose time point on the individual task outcome measures Measure Pre-dose baseline score Post-dose

Simple reaction

time (ms)

Placebo 626.09 ± 99.94 620.87 ± 88.74 671.21 ± 141.30 693.47 ± 180.39 CA250 640.46 ± 223.62 637.74 ± 233.15 621.38 ± 249.05 573.87 ± 151.92 CA500 636.61 ± 152.38 592.38 ± 134.25 584.19 ± 139.50 580.01 ± 133.32 CA750 615.47 ± 154.01 641.05 ± 227.45 616.98 ± 142.59 586.17 ± 156.73

F(3,28) = 0.0378, p = 0.9900 F(3,28) = 0.1200, p = 0.9476 F(3,28) = 0.3386, p = 0.7975 F(3,28) = 1.0594, p = 0.3820

Digit vigilance

accuracy (%)

Placebo 40.95 ± 25.94 60.00 ± 26.10 49.05 ± 31.43 64.45 ± 23.35 CA250 58.89 ± 22.08 70.00 ± 19.20 56.67 ± 37.71 67.52 ± 31.61 CA500 50.47 ± 26.35 64.76 ± 34.58 68.57 ± 24.26 66.67 ± 29.81 CA750 54.58 ± 26.42 54.17 ± 30.95 71.43 ± 26.31 68.31 ± 32.61

F(3,24) = 0.6100, p = 0.6150 F(3,24) = 0.3848, p = 0.7649 F(3,25) = 0.8173, p = 0.4965 F(3,25) = 0.0207, p = 0.9958

Digit vigilance

reaction time

(ms)

Placebo 691.21 ± 37.71 684.53 ± 12.28 590.90 ± 190.51 676.01 ± 22.59

CA250 642.43 ± 46.81 678.70 ± 109.13 671.47 ± 75.84 651.12 ± 57.73 CA500 640.38 ± 16.18 762.54 ± 123.85 662.76 ± 45.27 672.85 ± 30.08 CA750 654.24 ± 53.19 654.44 ± 50.38 635.99 ± 38.53 658.75 ± 47.85

F(3,24) = 0.7618, p = 0.5266 F(3,24) = 0.3650, 0.7789 F(3,25) = 0.8499, p = 0.4798 F(3,25) = 0.5326, p = 0.6641

Choice reaction

time (ms)

Placebo 931.22 ± 171.64 883.01 ± 155.60 1012.41 ± 161.47 1031.06 ± 219.37 CA250 967.15 ± 320.46 957.08 ± 338.17 874.25 ± 218.00 834.25 ± 208.19* CA500 922.34 ± 119.26 911.10 ± 185.14 885.27 ± 213.84 798.65 ± 100.20* CA750 842.24 ± 124.81 860.17 ± 109.42 854.42 ± 119.19 838.74 ± 106.04*

F(3,28) = 0.5486, p = 0.6532 F(3,28) = 0.2936, p = 0.8296 F(3,28) = 1.2318, p = 0.3167 F(3,28) = 3.1369, p = 0.0411

Spatial memory

(%accuracy)

Placebo 81.94 ± 14.47 78.45 ± 21.10 78.47 ± 17.36 80.21 ± 17.09 CA250 77.78 ± 16.80 86.81 ± 15.55 88.54 ± 11.35 82.29 ± 20.19 CA500 83.68 ± 24.10 91.67 ± 13.28 84.38 ± 15.99 86.78 ± 10.55 CA750 84.79 ± 24.04 84.37 ± 21.92 90.28 ± 12.69 92.36 ± 16.18

F(3,28) = 0.1839, p = 0.9064 F(3,28) = 0.7194, p = 0.5488 F(3,28) = 1.0419, p = 0.3893 F(3,28) = 0.8645, p = 0.4710

Spatial memory

reaction time

(ms)

Placebo 2385.29 ± 761.48 2020.62 ± 441.03 1866.21 ± 357.60 1822.57 ± 594.97

CA250 2116.33 ± 580.06 1954.26 ± 556.26 1906.65 ± 595.45 1714.48 ± 424.70 CA500 2088.62 ± 847.33 1604.90 ± 339.26 1690.60 ± 404.47 1429.49 ± 220.02 CA750 1590.78 ± 220.39 1506.79 ± 218.17* 1486.29 ± 286.23 1290.17 ± 219.74*

F(3,28) = 2.0860, p = 0.1247 F(3,28) = 3.0928, p = 0.0430 F(3,28) = 1.6188, p = 0.2073 F(3,28) = 3.0860, p = 0.0433

Numeric working

memory

(%accuracy)

Placebo 85.42 ± 11.50 88.33 ± 11.13 88.33 ± 13.92 83.75 ± 15.37

CA250 98.33 ± 3.56* 97.50 ± 3.45* 97.09 ± 4.52 96.67 ± 3.09*

CA500 92.50 ± 10.04 95.00 ± 9.09 90.00 ± 19.19 95.00 ± 7.56*

CA750 96.25 ± 5.17* 97.08 ± 3.75* 97.92 ± 1.72 97.50 ± 3.45*

F(3,28) = 3.7734, p = 0.0216 F(3,28) = 2.4765, p = 0.0820 F(3,28) = 1.2977, p = 0.2947 F(3,28) = 4.1683, p = 0.0147

Numeric working

memory reaction

time (ms)

Placebo 1527.65 ± 154.88 1325.31 ± 160.15 1286.51 ± 203.46 1366.07 ± 237.31

CA250 1429.32 ± 707.37 1329.09 ± 467.90 1205.05 ± 382.51 1209.00 ± 271.95 CA500 1531.55 ± 406.20 1268.84 ± 252.98 1251.14 ± 213.54 1170.19 ± 219.44 CA750 1195.95 ± 165.16 1211.97 ± 196.32 1075.45 ± 173.86 984.49 ± 217.75*

F(3,28) = 1.1061, p = 0.3632 F(3,28) = 0.2814, p = 0.8384 F(3,28) = 1.0344, p = 0.3925 F(3,28) = 3.4838, p = 0.0288

Word recognition

(%accuracy)

Placebo 75.42 ± 13.21 76.25 ± 7.65 79.58 ± 14.41 81.24 ± 9.73 CA250 85.00 ± 11.13 79.58 ± 10.15 76.67 ± 14.47 83.33 ± 9.59 CA500 88.33 ± 10.69 82.08 ± 7.95 88.34 ± 5.91 90.83 ± 6.36*

CA750 86.67 ± 7.97 83.75 ± 5.18 90.00 ± 6.42 90.42 ± 4.15*

F(3,28) = 2.2514, p = 0.1043 F(3,28) = 1.3539, p = 0.2771 F(3,28) = 2.7586, p = 0.0609 F(3,28) = 3.1333, p = 0.0412

Table 3 (Continued )

Measure Pre-dose baseline score Post-dose

Word recognition

reaction time

(ms)

Placebo 2164.17 ± 441.54 1815.69 ± 369.90 1652.98 ± 403.65 1647.23 ± 324.29

CA250 2011.64 ± 619.17 1745.24 ± 546.15 1767.28 ± 389.70 1626.07 ± 627.49 CA500 1953.14 ± 705.49 1582.76 ± 334.46 1459.81 ± 309.07 1439.16 ± 278.40 CA750 1658.19 ± 436.07 1555.17 ± 490.51 1450.09 ± 250.96 1400.85 ± 316.46

F(3,28) = 1.1355, p = 0.3517 F(3,28) = 0.6446, p = 0.5928 F(3,28) = 1.6157, p = 0.2080 F(3,28) = 0.7551, p = 0.5287

Picture recognition

(%accuracy)

Placebo 84.38 ± 10.84 86.88 ± 7.99 93.75 ± 5.18 89.38 ± 5.63 CA250 86.88 ± 7.99 91.25 ± 9.54 88.75 ± 9.54 89.38 ± 11.16 CA500 88.75 ± 9.16 85.00 ± 11.34 88.75 ± 6.94 90.00 ± 3.78 CA750 87.50 ± 5.98 83.13 ± 20.17 92.50 ± 9.64 96.88 ± 3.72*

F(3,28) = 0.3600, p = 0.7823 F(3,28) = 0.5614, p = 0.6449 F(3,28) = 0.8207, p = 0.4934 F(3,28) = 2.3220, p = 0.0967

Picture recognition

reaction time

(ms)

Placebo 2081.19 ± 787.08 1654.23 ± 245.86 1938.81 ± 240.94 1586.45 ± 470.62

CA250 2072.40 ± 480.36 1765.95 ± 409.49 1633.44 ± 282.12*** 1677.62 ± 426.63 CA500 2140.18 ± 958.35 1504.79 ± 321.24 1473.51 ± 209.53*** 1364.52 ± 160.51 CA750 1619.25 ± 285.32 1512.22 ± 290.68 1448.87 ± 198.84*** 1390.04 ± 177.10

F(3,28) = 1.0065, p = 0.4045 F(3,28) = 1.2032, 0.3267 F(3,28) = 7.3583, p = 0.0009 F(3,28) = 1.6066, p = 0.2101

(*) (**) p-value < 0.05 and 0.01 when compared with placebo group, respectively.

4 Discussion

The present study investigated the effect of Centella asiatica

extract on the cognitive performance and mood in the elderly

The results from this study suggest that the ingestion of single

dose of Centella asiatica can modulate only the reaction time of

spatial memory and %accuracy of numeric working memory in

the healthy elderly

Recently, it was found that the numeric working memory

process involved the function of lateral prefrontal cortex (PFC)

(D’Esposito et al., 1999; Smith and Jonides, 1999) whereas the

and Moser, 1998) Previous studies demonstrated that the numeric working memory could be modulated by dopamine,

Goldman-Rakic et al., 2000; Arnsten and Robbins, 2002) and during spatial memory task, both acetylcholine and serotonin in hip-pocampus were simultaneously activated (Stancampiano et al.,

1999) Therefore, the acute effect of Centella asiatica on the

numeric memory and spatial memory might partly occur via the modulation of dopamine and norepinephrine in prefrontal cor-tex together with the modulation of acetylcholine and serotonin

in hippocampus However, the possible underlying

mecha-nisms for acute effect of Centella asiatica on the numeric

Table 4

Mean raw scores on the ‘alert’, ‘content’ and ‘calm’ factors obtained from the Bond–Lader visual analogue scales for each condition across each session

Mood Pre-dose baseline score Post-dose

Alertness Placebo 67.88 ± 7.92 62.00 ± 8.55 62.50 ± 7.96

CA250 64.88 ± 11.78 68.00 ± 7.13 71.88 ± 6.83 CA500 66.13 ± 6.62 69.75 ± 7.96 68.25 ± 10.50 CA750 71.88 ± 5.11 74.63 ± 5.07** 75.88 ± 7.59*

F(3,28) = 1.0976, p = 0.3665 F(3,28) = 4.0825, p = 0.0159 F(3,28) = 3.7149, p = 0.0229

Contentedness Placebo 40.63 ± 6.16 37.75 ± 7.50 38.25 ± 5.85

CA250 39.00 ± 6.72 40.00 ± 3.89 41.88 ± 3.80 CA500 41.25 ± 3.06 40.88 ± 2.75 40.13 ± 4.79 CA750 42.38 ± 3.54 42.63 ± 3.07 42.38 ± 3.50

F(3,28) = 0.6046, p = 0.6175 F(3,28) = 1.4889, p = 0.2390 F(3,28) = 1.3368, p = 0.2824

Calmness Placebo 15.00 ± 2.00 14.25 ± 2.19 13.38 ± 2.07

CA250 15.38 ± 3.25 16.00 ± 2.00 15.88 ± 2.10*

CA500 15.38 ± 1.19 16.13 ± 0.99 15.63 ± 2.56*

CA750 16.25 ± 2.12 16.75 ± 1.04* 17.00 ± 1.51*

F(3,28) = 0.4398, p = 0.7263 F(3,28) = 3.3943, p = 0.0316 F(3,28) = 4.2124, 0.0141

*p < 0.05 compared with placebo, **p < 0.01 compared with placebo.

memory and spatial memory still required further

investiga-tion

The repetitive administration of Centella asiatica further to

2 months showed the significant increase in %accuracy of both

numeric working memory and word recognition In addition,

Centella asiatica also showed significant increase in reaction

time of both numeric working memory and spatial memory

Thus, the present findings suggest that Centella asiatica can

improve both speed and accuracy of working memory Since the

results showed the dissociation of temporal profiles in

%accu-racy of numeric working memory and spatial memory reaction

time, thus, it was reasonable to suggest that the relationship

between the Centella asiatica treatment and working memory

following repetitive administration of this substance might not

be a simple relationship

Interestingly, Centella asiatica also increased the amplitude

of N100 component after 2 months of treatment with high dose

of Centella asiatica whereas no significant changes in N100

latency and P300 latency and amplitude were observed Previous

studies have demonstrated that N100 component is interpreted

as unitary “sensory gain effect” (Wijers et al., 1996; Hillyard et

al., 1998) and related to attention (Wood et al., 2006) especially

the enhanced processing of the attended location including the

spatial properties of the attend stimulus (Mangun et al., 1993)

Recently, it has been reported that this activity involves the

function of temporal lobe (Sabri et al., 2004)

Previous study demonstrated that hippocampus, an important

area in the inner temporal lobe, played a crucial role on working

memory processing both in human and in primate Moreover, the

quality of memory also depended on many factors particularly

efficiency of storage and retrieval processes which in turn

influ-enced by attention process (Cohen and Squire, 1980; Tulving and

Schacter, 1990) In addition, it had been reported that attention

could modify the function of hippocampus (Kentros et al., 2004)

Therefore, the increase in N100 component amplitude in this

study was corresponding to the results which demonstrated the

improve working memory induced by Centella asiatica Based

on these pieces of evidence, we did suggest that the effect of

Centella asiatica to improve working memory might be

associ-ated with the improve attention manifested as the increase N1

amplitude

It is very striking that Centella asiatica improves not only

the cognitive performance but also the mood The high dose of

Centella asiatica could increase calmness and alertness after 1

and 2 months of treatment In addition, the significant increase in

calmness was also observed after Centella asiatica treatment at

medium and high doses for 2 months Our present data

demon-strated the improvement of both alertness and calmness together

with the increase attention, therefore we suggested that the plant

extract might possibly improve positive emotion such as

alert-ness and calmalert-ness, which in turn improve attention and finally

improve working memory However, further study about the

pre-cise relationship among various parameters mentioned above

and possible underlying mechanism are still essential

In conclusion, this study is the first study to demonstrate

the scientific document with many valid biological markers to

support the positive modulation effect of Centella asiatica on

the cognitive function and mood in the healthy elderly However, the precise mechanism(s) underlying these effects still require further investigation

Acknowledgements

This study was supported by Faculty of Medicine, Center for Research and Development of Herbal Health Product and Graduate School, Khon Kaen University Moreover, gratitude was also extends to the Cognitive Drug Research Company who first developed the CDR battery test

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