Behavioral flexibility: A review, a model, and some exploratory tests.

This paper aimed to explore and clarify the concept of behavioral flexibility. A selective literature review explored how the concept of behavioral flexibility has been used in ways that range from acknowledging the fact that animals' behavior is not always bounded by instinctual constraints, to describing the variation between species in their capacity for innovative foraging, a capacity that has repeatedly been linked to having a brain larger than would be predicted from body size. This wide range of usages of a single term has led to some conceptual confusion. We sought to find a more precise meaning for behavioral flexibility by representing it within a simple formal model of problem solving. The key to our model is to distinguish between an animal's state of knowledge about the world and its observable behavior, using a construct of response strength to represent that underlying knowledge. We modelled behavioral flexibility as a parameter in the function that transforms response strengths into observable response probabilities. We tested this model in simulations based on some recent experimental work on animal problem solving. Initial results showed that parametric manipulation can mimic some of the behavioral effects that have been attributed to flexibility.

Serial reversal learning in gray squirrels: Learning efficiency as a function of learning and change of tactics.

Learning allows individuals to adapt their behaviors flexibly to a changing environment. When the same change recurs repeatedly, acquiring relevant tactics may increase learning efficiency. We examined this relationship, along with the effects of proactive interference and other interference information, in a serial spatial reversal task with 5 gray squirrels (Sciurus carolinensis). Squirrels completed an acquisition and 11 reversal phases with a poke box in which 2 of 4 possible reward locations were baited diagonally in a square array. In this situation, an efficient tactic is to locate the diagonally related locations consecutively (integrative search tactic) instead of searching rewards in a clockwise or counterclockwise direction (sequential search tactic). All squirrels formed a learning set, acquiring successive reversals in fewer trials. Although 4 squirrels gradually employed more integrative tactics in locating the rewards both within and between phases, sequential tactics were used in the first trial of each phase. This suggests the integrative tactic did not depend on an association between the rewarded locations but was learned as a spatial pattern and/or by use of extra-apparatus cues to locate individual rewards. Generalized estimating equation models showed that learning efficiency increased with experience and tactic change. Although tactic change partially mediated the effect of learning on learning efficiency, learning remained an independent contribution to improved efficiency. Squirrels that used more integrative tactics made fewer total errors than squirrels that used less integrative tactics, suggesting that learning a task-relevant tactic using spatial cues can provide direct benefits in maximizing rewards and minimizing time costs.

Can leisure activities slow dementia progression in nursing home residents? A cluster-randomized controlled trial.

BACKGROUND: To examine the effects of complex cognitive (mahjong) and physical (Tai Chi) activities on dementia severity in nursing home residents with dementia. METHODS: Cluster-randomized open-label controlled design. 110 residents were randomized by nursing home into three conditions: mahjong, Tai Chi, and simple handicrafts (control). Activities were conducted three times a week for 12 weeks. Clinical Dementia Rating (CDR) was taken at 0 (baseline), 3 (post-treatment), 6, and 9 months. The outcome measure was CDR sum-of-box, which is a composite measure of both cognitive and functional deterioration in dementia. RESULTS: Intent-to-treat analyses were performed using multilevel regression models. Apolipoprotein E ε4 allele and education were included as covariates. Neither treatments had effects on the cognitive and functional components of the CDR, but mahjong had a significant interaction with time on the CDR sum-of-box total, suggesting a slower rate of global deterioration in the mahjong group as compared with the control group. CONCLUSIONS: Mahjong led to a gradual improvement in global functioning and a slightly slower rate of dementia progression over time. The effect was generalized and was not specific to cognition or daily functioning.

Mental and physical activities delay cognitive decline in older persons with dementia.

OBJECTIVES: To examine the effects of cognitive stimulation (mahjong) and physical exercise (tai chi [TC]) on cognitive performance in persons with dementia. DESIGN: Cluster-randomized open-label controlled design. SETTING: Nursing homes. PARTICIPANTS: One hundred ten residents, most of whom were cholinesterase-inhibitor naive. Inclusion criteria were Mini-Mental State Examination (MMSE) = 10-24 and suffering from at least very mild dementia (Clinical Dementia Rating ≥ 0.5). Exclusion criteria were being bedbound, audio/visual impairment, regular activity participation before study, or contraindications for physical or group activities. INTERVENTIONS: Homes were randomized into three conditions (mahjong, TC, and simple handicrafts [control]). Activities were conducted three times weekly for 12 weeks. MEASUREMENTS: Primary outcome was MMSE. Secondary outcomes were immediate/delayed recall, categorical fluency, and digit span. Various biological risk factors, including apolipoprotein E ε4 allele, were included as covariates. Measures were collected at 0 (baseline), 3 (posttreatment), 6, and 9 months. RESULTS: Intent-to-treat analyses were performed using mixed-effects regression. Mahjong's effect varied by time for MMSE, delayed recall, and forward digit span. TC had similar effects but not for delayed recall. The typical pattern was that control participants deteriorated while mahjong and TC participants maintained their abilities over time, leading to enlarged treatment effects as time progressed. By 9 months, mahjong and TC differed from control by 4.5 points (95% confidence interval: 2.0-6.9; d = 0.48) and 3.7 points (95% confidence interval: 1.4-6.0; d = 0.40), respectively, on MMSE. No treatment effects were observed for immediate recall and backward digit span. CONCLUSIONS: Mahjong and TC can preserve functioning or delay decline in certain cognitive domains, even in those with significant cognitive impairment.

Leisure activities alleviate depressive symptoms in nursing home residents with very mild or mild dementia.

OBJECTIVES: : To examine whether leisure activities can alleviate depressive symptoms among nursing home residents with very mild to mild dementia. METHODS: : A cluster-randomized open-label controlled design. Thirty-six residents with at least moderate depressive symptoms were randomized by home into three conditions-mahjong (a.k.a. mah-jongg), tai chi, and handicrafts (placebo). Activities were conducted three times weekly for 12 weeks. Outcome measure was Geriatric Depression Scale (GDS) administered at baseline, posttreatment, and at 6 months. RESULTS: : Repeated-measures analysis of variance showed a group by time interaction on the GDS. Unlike control and tai chi participants whose scores remained relatively unchanged, the mahjong group reported a drop of 3.25 points (95% confidence interval: 1.00-5.50) on the GDS at posttreatment but gained back 2.83 points (95% confidence interval: 1.95-5.47) at 6 months. Activity discontinuation might be the reason for depression to return to baseline. CONCLUSIONS: : Mahjong can lower depressive symptoms in those with mild dementia, but activity maintenance may be essential for long-term effects.

Under-recognition of dementia in long-term care homes in Hong Kong.

OBJECTIVE: To examine the extent to which dementia in nursing homes is recognized by staff. METHODS: About 189 residents with very mild to moderate dementia (Clinical Dementia Rating, CDR ≥ 0.5) and Mini-Mental State Examination (MMSE) = 10-24 were recruited from 12 nursing homes in Hong Kong. A senior staff in each home provided information on whether the participant was known to have dementia, and if so, the exact diagnosis. Logistic regression was conducted to predict identification by age, gender, whether for-profit or non-profit home, length of stay, MMSE, CDR, activities of daily living, and use of cholinesterase inhibitors and antipsychotic medications. RESULTS: It was observed that 42.3% of the sample had mild dementia and 14.8% had moderate dementia. Although identification rates increased with increasing severity of cognitive impairment, only 30.0% of those with mild dementia and 64.3% of those with moderate dementia were known to have dementia by the homes. Identification rates did not differ between for-profit homes and non-profit homes which had regular MMSE screening. Logistic regression analysis showed that only MMSE (OR = 0.85, 95% CI = 0.76-0.95, p = 0.005) and CDR = 2 (as compared with CDR = 0.5; OR = 4.78, 95% CI = 1.23-18.65, p = 0.024) were significantly associated with dementia recognition. No other factors were related to dementia recognition. CONCLUSIONS: Despite a high prevalence of dementia in long-term care facilities, recognition of dementia as a medical condition in residents by staff was suboptimal, and MMSE screening in some homes did not seem to increase awareness significantly.