Effects of aging on behavioral assessment performance: implications for clinically relevant models of neurological disease

Laboratory investigation

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Despite the role of aging in development of neurological and neurodegenerative diseases, the effects of age are often disregarded in experimental design of preclinical studies. Functional assessment increases the clinical relevance of animal models of neurological disease and adds value beyond traditional histological measures. However, the relationship between age and functional impairment has not been systematically assessed through a battery of functional tests.


In this study, various sensorimotor and behavioral tests were used to evaluate effects of aging on functional performance in naive animals. Sensorimotor measures included locomotor activity; Rotarod, inclined plane, and grip-strength testing; and modified Neurological Severity Score. The Morris water maze was used to examine differences in learning and memory, and the elevated plus maze and forced swim test were used to assess anxiety-like and depressive-like behaviors, respectively.


Older Sprague-Dawley rats (18–20 months) were found to perform significantly worse on the inclined plane tests, and they exhibited alterations in elevated-plus maze and forced swim test compared with young adult rats (3–4 months). Specifically, older rats exhibited reduced exploration of open arms in elevated plus maze and higher immobility time in forced swim test. Spatial acquisition and reference memory were diminished in older rats compared with those in young adult rats.


This study demonstrates clear differences between naive young adult and older animals, which may have implications in functional assessment for preclinical models of neurological disease.

Abbreviation used in this paper:mNSS = modified Neurological Severity Score.

Article Information

Address correspondence to: Charles L. Rosen, M.D., Ph.D., West Virginia University, One Medical Center Drive, PO Box 9183 Health Sciences Center, Morgantown, West Virginia 26506-9183. email: crosen@hsc.wvu.edu.

Please include this information when citing this paper: published online June 29, 2012; DOI: 10.3171/2012.5.JNS112224.

© AANS, except where prohibited by US copyright law.



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    The effect of age on sensorimotor assessment with the grip strength test (A), inclined plane test (B), and total locomotor activity (C). The grip strength and inclined plane tests were significantly different between young adult and older animals (p < 0.05), with older animals exhibiting stronger grip force and young adult animals performing better on the inclined plane. No difference in total locomotor activity was measured. Error bars indicate SEM. Statistical significance was determined using an unpaired t-test. *p < 0.05, **p < 0.01, and ***p < 0.0001.

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    Fixed-speed (left) and accelerating (right) Rotarod test in young adult (light gray bars) and older animals (dark gray bars). The fixed-speed test included trials at 12, 16, 20, 24, 28, 32, 36, and 40 rpm. The accelerating test was conducted over 5 minutes while reaching a maximum speed of 50 rpm. No statistically significant difference was seen between young adult and older animals on either variation of Rotarod testing. Error bars indicate SEM.

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    Reduced performance on the balance beam subtest (part of mNSS) in older animals. Older animals (dark gray bar) were comparable to young adult animals (light gray bar) in all mNSS subtests except for balance beam in which young animals excelled in contrast to older animals. Error bars indicate SEM. Statistical significance was determined using an unpaired t-test. *p < 0.05.

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    Effect of age on behavior using the elevated plus maze assessment. Older animals (dark gray bars) spent less time in the open arms (A) and made fewer entries into the open arms (B), but the groups did not differ in terms of average speed in the open arms (C). In the closed arms, young animals (light gray bars) explored more readily than the older animals, resulting in a higher average speed within the closed arms (D). Error bars indicate SEM. Statistical significance was determined using an unpaired t-test. *p < 0.05 and **p < 0.01.

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    Effect of age on total immobility time, immobile episodes, distance traveled, and speed in the forced swim test. Older animals (dark gray bars) spent more time immobile (A) and had a greater number of immobile episodes (B), but they traveled a similar distance (C) at a similar speed (D). There was no statistically significant difference in latency to first immobile episode (E). Error bars indicate SEM. Statistical significance was determined using an unpaired t-test. *p < 0.05.

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    The role of age in spatial acquisition determined using the Morris water maze. Older animals (dark gray bars) exhibited increased latency (left) and distance to platform (right) when compared with young animals (light gray bars) at later time points, despite being nearly identical when first exposed to the maze. Error bars indicate SEM. Statistical significance was determined using 2-way ANOVA with Bonferroni post hoc test. *p < 0.05, **p < 0.01, and ***p < 0.001.

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    Reduction in reference memory in older animals as measured in the Morris water maze probe test. Older animals made fewer entries (A), spent less time (B), and traveled a shorter distance (C) in the counter zone than the young animals. The proximity average (D) was lower among young animals, indicating greater reference memory ability. Error bars indicate SEM. Statistical significance was determined using an unpaired t-test. *p < 0.05, **p < 0.01, and ***p < 0.0001.



Badan IBuchhold BHamm AGratz MWalker LCPlatt D: Accelerated glial reactivity to stroke in aged rats correlates with reduced functional recovery. J Cereb Blood Flow Metab 23:8458542003


Cenci MAWhishaw IQSchallert T: Animal models of neurological deficits: how relevant is the rat?. Nat Rev Neurosci 3:5745792002


Daviglus MLPlassman BLPirzada ABell CCBowen PEBurke JR: Risk factors and preventive interventions for Alzheimer disease: state of the science. Arch Neurol 68:118511902011


Fisher MFeuerstein GHowells DWHurn PDKent TASavitz SI: Update of the stroke therapy academic industry roundtable preclinical recommendations. Stroke 40:224422502009


Hamm RJJenkins LWLyeth BGWhite-Gbadebo DMHayes RL: The effect of age on outcome following traumatic brain injury in rats. J Neurosurg 75:9169211991


Hamm RJWhite-Gbadebo DMLyeth BGJenkins LWHayes RL: The effect of age on motor and cognitive deficits after traumatic brain injury in rats. Neurosurgery 31:107210781992


Hunter AJMackay KBRogers DC: To what extent have functional studies of ischaemia in animals been useful in the assessment of potential neuroprotective agents?. Trends Pharmacol Sci 19:59661998


Maurissen JPMarable BRAndrus AKStebbins KE: Factors affecting grip strength testing. Neurotoxicol Teratol 25:5435532003


Mehan NDStrauss KI: Combined age- and trauma-related proteomic changes in rat neocortex: a basis for brain vulnerability. Neurobiol Aging [epub ahead of print]2011


Monville CTorres EMDunnett SB: Comparison of incremental and accelerating protocols of the rotarod test for the assessment of motor deficits in the 6-OHDA model. J Neurosci Methods 158:2192232006


Pan WDing YYu YOhtaki HNakamachi TKastin AJ: Stroke upregulates TNFalpha transport across the blood-brain barrier. Exp Neurol 198:2222332006


Pitsikas NCarli MFidecka SAlgeri S: Effect of life-long hypocaloric diet on age-related changes in motor and cognitive behavior in a rat population. Neurobiol Aging 11:4174231990


Popa-Wagner ABuga AMKokaia Z: Perturbed cellular response to brain injury during aging. Ageing Res Rev 10:71792011


Popa-Wagner ACrăiţoiu SBuga AM: Central nervous system aging and regeneration after injuries. A systematic approach. Rom J Morphol Embryol 50:1551672009


Porsolt RDAnton GBlavet NJalfre M: Behavioural despair in rats: a new model sensitive to antidepressant treatments. Eur J Pharmacol 47:3793911978


Porsolt RDBrossard GHautbois CRoux S: Rodent models of depression: forced swimming and tail suspension behavioral despair tests in rats and mice. Curr Protoc Neurosci 14:8.10A.18.10A.102001


Rivlin ASTator CH: Objective clinical assessment of motor function after experimental spinal cord injury in the rat. J Neurosurg 47:5775811977


Rosen CLDinapoli VANagamine TCrocco T: Influence of age on stroke outcome following transient focal ischemia. J Neurosurg 103:6876942005


Sacco RL: Risk factors, outcomes, and stroke subtypes for ischemic stroke. Neurology 49:5 Suppl 4S39S441997


Schaechter JD: Motor rehabilitation and brain plasticity after hemiparetic stroke. Prog Neurobiol 73:61722004


Stroke Therapy Academic Industry Roundtable: Recommendations for standards regarding preclinical neuroprotective and restorative drug development. Stroke 30:275227581999


Vollmer DGTorner JCJane JASadovnic BCharlebois DEisenberg HM: Age and outcome following traumatic coma: why do older patients fare worse?. J Neurosurg 75:Suppl 1S37S491991


Walf AAFrye CA: The use of the elevated plus maze as an assay of anxiety-related behavior in rodents. Nat Protoc 2:3223282007


Watanabe TOkuda YNonoguchi NZhao MZKajimoto YFurutama D: Postischemic intraventricular administration of FGF-2 expressing adenoviral vectors improves neurologic outcome and reduces infarct volume after transient focal cerebral ischemia in rats. J Cereb Blood Flow Metab 24:120512132004


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