Cellular and molecular mechanisms underlying learning and memory impairments produced by cannabinoids.
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Why does smoking marijuana impair learning and memory? Behavioral studies suggest that a disruption of normal hippocampal function contributes to these deficits. In vitro experiments find that cannabinoid receptor activation reduces neurotransmitter release below the levels required to trigger long-term changes in synaptic strength in the hippocampus. Cannabinoids reduce glutamate release through a G-protein-mediated inhibition of the calcium channels responsible for neurotransmitter release from hippocampal neurons. These mechanisms likely play a role in the learning and memory impairments produced by cannabinoids and by endogenous cannabinoid receptor ligands. (+info)
Adult learning deficits after neonatal exposure to D-methamphetamine: selective effects on spatial navigation and memory.
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The effects of neonatal d-methamphetamine (MA) treatment on cued and spatial learning and memory were investigated. MA was administered to neonatal rats on postnatal days 11-20. All groups received four subcutaneous injections per day. Group MA40-4 received 40 mg. kg(-1). d(-1) of MA in four divided doses (10 mg/kg per injection). Group MA40-2 received 40 mg. kg(-1). d(-1) of MA in two divided (20 mg/kg/injection) and saline for the other two injections per day. Controls received saline for four injections per day. As adults, both MA groups showed no differences in swimming ability in a straight swimming channel. The MA40-4 group showed no differences in cued learning, but was impaired in hidden platform learning in the Morris water maze on acquisition. They also showed reduced memory performance on probe trials. Similar trends were seen on reversal learning and reversal probe trials. Reduced platform-size learning trials caused spatial learning impairments to re-emerge in the MA40-4 group. The MA40-2 group showed no differences in straight channel swimming, but was slower at finding the visible platform during cued learning. They were also impaired during acquisition and memory trials in the Morris hidden platform maze. They showed a similar trend on reversal learning and memory trials, but were not different during reduced platform-size learning trials. When the MA40-2 group's performance on hidden platform learning and memory trials was adjusted for cued trial performance, the spatial learning deficits remained. Deficits of spatial learning and memory are a selective effect of neonatal methamphetamine treatment irrespective of other learning and performance variables. (+info)
FRAXA and FRAXE: the results of a five year survey.
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We report the results of a five year survey of FRAXA and FRAXE mutations among boys aged 5 to 18 with special educational needs (SEN) related to learning disability. We tested their mothers using the X chromosome not transmitted to the son as a control chromosome, and the X chromosome inherited by the son to provide information on stability of transmission. We tested 3738 boys and 2968 mothers and found 20 FRAXA and one FRAXE full mutations among the boys and none among the mothers. This gives an estimated prevalence of full mutations in males of 1 in 5530 for FRAXA and 1 in 23 423 for FRAXE. We found an excess of intermediate and premutation alleles for both FRAXA and FRAXE. For FRAXA this was significant at the 0.001 level but the excess for FRAXE was significant only at the 0.03 level. We conclude that the excess of intermediate and premutation sized alleles for FRAXA may well be a contributing factor to the boys' mental impairment, while that for FRAXE may be a chance finding. We studied approximately 3000 transmissions from mother to son and found five instabilities of FRAXA in the common or intermediate range and three instabilities of FRAXE in the intermediate range. Thus instabilities in trinucleotide repeat size for FRAXA and FRAXE are rare, especially among alleles in the common size range. (+info)
Do learning disability services need epilepsy specialist nurses?
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Epilepsy is known to cause higher rates of morbidity and mortality than in the general population. It is estimated that one third of people with a learning disability also have epilepsy, and that their epilepsy is generally more difficult to control. Given these two statements and with the trend to place the majority of people with learning disabilities in small community homes rather than large medical institutions, it follows that there is a need for up-to-date information and education for individuals and carers in a variety of settings to ensure best care and quality of life is achieved. Is there a need for specialist epilepsy nurses to work in this field? (+info)
Effects of high-probability requests on the latency to initiate academic tasks.
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The purpose of this study was to evaluate the effectiveness of a high-probability request sequence on the latency to and duration of compliance to a request for completion of an independent math assignment. The participant was an elementary-school student with learning disabilities who exhibited noncompliance during math instruction. The results showed that high-probability requests were effective in reducing the latency to compliance but only minimally affected duration of engagement. (+info)
The social development of children with severe learning difficulties: a case study of an inclusive education initiative between two primary schools in Oxfordshire, UK.
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This case study of primary age children in two linked Oxfordshire schools investigated the contribution of staff attitudes and practices to inequalities in education, and contrasted the socialisation of children with similar learning difficulties in different educational placements. Participant observation of a group of children and carers in a special school suggested areas of more rigorous inquiry. Structured observations compared this group with a matched sample of children with similar learning difficulties in a mainstream setting. Staff on both sites were invited to comment on findings arising from analysed data in order to identify attitudes and policies which might account for the observed differences in practice. The study was engendered by experience of differences arising from educational placement. The theoretical stance arose through reviewing previous work, predominantly the debate on inclusive education, and the wider issues of human rights and equal opportunities embedded in the social development of people with disabilities. The theoretical framework underpinning this study is established in some depth. The project was designed to investigate issues of the wider social perspective, by conducting a micro-study of one model of educational inclusion whose outcomes have direct relevance to those issues. (+info)
Volume of focal brain lesions and hippocampal formation in relation to memory function after closed head injury in children.
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OBJECTIVES: (1) A study of verbal learning and memory in children who had sustained a closed head injury (CHI) at least 3 months earlier. (2) To relate memory function to focal brain lesion and hippocampal formation volumes using morphometric analysis of MRI. METHODS: A group of 245 children who had been admitted to hospital for CHI graded by the Glasgow coma scale (GCS), including 161 patients with severe and 84 with mild CHI completed the California verbal learning test (CVLT) and underwent MRI which was analysed for focal brain lesion volume independently of memory test data. Brain MRI with 1.5 mm coronal slices obtained in subsets of 25 patients with severe and 25 patients with mild CHI were analysed for hippocampal formation volume. Interoperator reliability in morphometry was satisfactory. RESULTS: Severity of CHI and age at study significantly affected memory performance. Regression analysis showed that bifrontal, left frontal, and right frontal lesion volumes incremented prediction of various learning and memory indices after entering the GCS score and age into the model. Extrafrontal lesion volume did not contribute to predicting memory performance. CONCLUSIONS: Prefrontal lesions contribute to residual impairment of learning and memory after severe CHI in children. Although effects of CHI on hippocampal formation volume might be difficult to demonstrate in non-fatal paediatric CHI, further investigation using functional brain imaging could potentially demonstrate hippocampal dysfunction. (+info)
Reliability and validity of the CANDID--a needs assessment instrument for adults with learning disabilities and mental health problems.
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BACKGROUND: People with learning disabilities and mental health problems have complex needs. Care should be provided according to need. AIM: To develop a standardised needs-assessment instrument for adults with learning disabilities and mental health problems. METHOD: The Camberwell Assessment of Need for Adults with Developmental and Intellectual Disabilities (CANDID) was developed by modifying the Camberwell Assessment of Need (CAN). Concurrent validity was tested using the Global Assessment of Functioning (GAF) and the Disability Assessment Schedule (DAS). Test-retest and interrater reliability were investigated using 40 adults with learning disabilities and mental health problems. RESULTS: CANDID scores were significantly correlated with both DAS (P < 0.05) and GAF scores (P < 0.01). Correlation coefficients for interrater reliability were 0.93 (user), 0.90 (career), and 0.97 (staff ratings); for test-retest reliability they were 0.71, 0.69 and 0.86 respectively. Mean interview duration was less than 30 minutes. CONCLUSIONS: The CANDID is a brief, valid and reliable needs assessment instrument for adults with learning disabilities and mental health problems. (+info)