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At least 595 records · Page 33Linked to original sources
PubMed2003

Intra-prefrontal 8-OH-DPAT and M100907 improve visuospatial attention and decrease impulsivity on the five-choice serial reaction time task in rats.

RATIONALE: The central serotonergic systems are a major target for drugs used to treat neuropsychiatric disorders such as depression and schizophrenia in which disruption of frontal cortex function has been implicated. However, it is not known precisely how serotonin (5-HT) modulates the medial prefrontal cortex (mPFC) to affect cognitive function and behaviour. OBJECTIVE: To investigate the roles of 5-HT(1A) and 5-HT(2A) receptors in mPFC on performance of the five-choice serial reaction time task (5CSRT), which assesses visuospatial attention, impulsivity and motivational processes. METHODS: Following training on the 5CSRT, rats were implanted with bilateral guide cannulae aimed at the mPFC. Rats received intra-mPFC infusions of either 8-OH-DPAT (10, 30 and 100 ng) or M100907 (30, 100 and 300 ng) according to a Latin square design. RESULTS: Both 8-OH-DPAT and M100907 selectively enhanced accuracy of target detection. When the stimulus duration was shortened, infusions of 8-OH-DPAT continued to improve accuracy, whereas M100907 decreased premature responding and omissions, thus partly dissociating the effects of these two compounds. Similar effects were obtained following systemic administration of M100907 and 8-OH-DPAT. The effects of 8-OH-DPAT were blocked by the 5-HT(1A) antagonist WAY 100635, at a dose that itself had no significant effects on behaviour. CONCLUSIONS: These results indicate that modulation of 5-HT function within the mPFC via distinct receptors can enhance performance on the 5CSRT. These findings suggest a mechanism by which serotonergic agents improve cognitive function, which may be relevant to their therapeutic benefit in the treatment of neuropsychiatric disorders.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2002

A novel, direct spatio-temporal approach for analyzing fMRI experiments.

We introduce a novel approach to couple temporal similarity with spatial neighborhood information. This is achieved by concatenating the K nearest, spatially contiguous neighbors of a pixel time-course (TC) of T time-instances. This produces a new TC of (K+1)T time instances. Depending on how "nearest" is defined, we have various options. Strictly spatial nearness means augmenting a given TC by its K nearest neighbors in some canonical spatial order. A more powerful and flexible option is to order the TCs to be concatenated according to their temporal similarity to the central voxel TC. For this study, we have chosen Pearson's cross-correlation coefficient as the measure of similarity. For more than a single neighbor, two concatenation options are possible. The direct ordering option requires that the TCs to be concatenated be spatially contiguous to the central pixel. The more flexible indirect option merely demands that one of a chain of temporally similar TCs be spatially connected to the central pixel. We also apply the temporal similarity criterion to the more conventional spatial (median) filtering, and show that it gives superior result to a strict spatial filtering. The method is tested and verified on a null fMRI dataset onto which we superposed two types of "activations" with known temporal behavior and spatial location. It is also applied to a real dataset containing visual activation. We also propose a strategy, based on the flexibility of the method, to determine a consensus, "core" set of activations.

Brain↗
PubMed2003

Choosing a safe place to cross the road: the relationship between attention and identification of safe and dangerous road-crossing sites.

BACKGROUND: Safe pedestrian behaviour relies on cognitive skills, including the ability to focus attention on the traffic environment and ignore irrelevant stimuli. An important pedestrian skill that young children find difficult is the ability to find a safe place to cross the road. The aim of this study was to examine the relationship between attention and children's ability to identify safe and dangerous road-crossing sites. METHODS: Participants were 95 children (aged 6.5 years, 8.6 years and 10.4 years) and 33 adults. Ability to identify safe and dangerous road-crossing sites was assessed using computer presentations of five safe and five dangerous sites. Attention was assessed using the Stroop test for resistance to interference. Correlations were calculated between Stroop test measures and pedestrian task measures (accuracy and speed of identifying safe and dangerous road-crossing sites) for each age group separately. RESULTS: The ability to identify safe and dangerous road-crossing sites and the ability to resist interference increased with age. Significant correlations were observed between identification of safe and dangerous road-crossing sites and performance on the Stroop test for children but not for adults. DISCUSSION: The results indicated that attention is required for identifying road-crossing sites quickly and accurately, especially for younger children. Road safety training programmes for children may need to take into account the development of children's attention.

Accident Prevention↗
PubMed2000

Individual differences in road crossing ability in young children and adults.

Young children are more at risk of traffic pedestrian accidents than adults. Previous experiments have failed to show large differences between adults and children in crossing behaviour. The reasons for this are not clear, but it could be that some children are more at risk than others, because of individual differences. These differences have been difficult to investigate in the past. This paper examines a double video technique developed to solve the problems. Two groups of participants, children and adults (mean age 7 years 2 months and 20 years 6 months respectively), were presented with the video and asked to indicate by pressing a button when they would choose to cross the road. Variables measured included the total number of crossings made and the percentage of those that were safe, number of missed opportunities and unsafe gaps chosen, the mean starting delay and gap size chosen, and the correlation between the delay and the gap chosen for each individual. Results showed that, although there were large and significant differences between adults and children on total crossings, percentage safe crossings, mean starting delay and gap size chosen, the structure of the road crossing behaviour was very similar. Children make decisions in the same way as adults, but are less good at it. There were large individual differences, suggesting that some children were more at risk than others, with possible factors being impulsivity and fine motor coordination. It is suggested that the video technique may, with some refinements, make a useful tool to screen children at risk and to use in remedial training.

Adult↗
PubMed1992

Choice with delayed and probabilistic reinforcers: effects of variability, time between trials, and conditioned reinforcers.

In a discrete-trials procedure with pigeons, a response on a green key led to a 4-s delay (during which green houselights were lit) and then a reinforcer might or might not be delivered. A response on a red key led to a delay of adjustable duration (during which red houselights were lit) and then a certain reinforcer. The delay was adjusted so as to estimate an indifference point--a duration for which the two alternatives were equally preferred. Once the green key was chosen, a subject had to continue to respond on the green key until a reinforcer was delivered. Each response on the green key, plus the 4-s delay that followed every response, was called one "link" of the green-key schedule. Subjects showed much greater preference for the green key when the number of links before reinforcement was variable (averaging four) than when it was fixed (always exactly four). These findings are consistent with the view that probabilistic reinforcers are analogous to reinforcers delivered after variable delays. When successive links were separated by 4-s or 8-s "interlink intervals" with white houselights, preference for the probabilistic alternative decreased somewhat for 2 subjects but was unaffected for the other 2 subjects. When the interlink intervals had the same green houselights that were present during the 4-s delays, preference for the green key decreased substantially for all subjects. These results provided mixed support for the view that preference for a probabilistic reinforcer is inversely related to the duration of conditioned reinforcers that precede the delivery of food.

Animals↗
PubMed2000

A study of orientation in a zero gravity environment by means of virtual reality simulation.

When the International Space Station (ISS) is completed and starts its operation, crew members will be stationed for three months or more in orbit aboard the ISS. As they stay longer in the space environment, "habitability" for them will become most important in the design of the interior space. One of the problems about habitability in a zero gravity (0 G) environment is disorientation. Crew members have difficulty in discriminating between "up" and "down" and more serious disorientations may cause space motion sickness. Crew members rely on visual perception to orient themselves because they can't use their sense of equilibrium in a 0 G environment. Although color and the direction of equipment of Space Shuttles or modules has been considered, no systematic study has been conducted on interior space. This study intended to clarify how people acquire visual information and recognize their orientation in a 0 G environment by an experiment in which a subject wears a head-mounted display (HMD) and enters a virtual weightless state represented by computer graphics (CG). Visual information of a room and the degree-of-freedom of motion were varied to examine the influence of the conditions on such a simple task as movement through several connected modules, and the performance and the behavior of each subject were investigated.

Humans↗
PubMed1999

Anxiety and increased 5-HT1A receptor response in NCAM null mutant mice.

Mice deficient in the neural cell adhesion molecule (NCAM) show behavioral abnormalities as adults, including altered exploratory behavior, deficits in spatial learning, and increased intermale aggression. Here, we report increased anxiety-like behavior of homozygous (NCAM-/-) and heterozygous (NCAM/-) mutant mice in a light/dark avoidance test, independent of genetic background and gender. Anxiety-like behavior was reduced in both NCAM+/+ and NCAM-/- mice by systemic administration of the benzodiazepine agonist diazepam and the 5-HT1A receptor agonists buspirone and 8-OH-DPAT. However, NCAM-/- mice showed anxiolytic-like effects at lower doses of buspirone and 8-OH-DPAT than NCAM+/+ mice. Such increased response to 5-HT1A receptor stimulation suggests a functional change in the serotonergic system of NCAM-/- mice, likely involved in the control of anxiety and aggression. However, 5-HT1A receptor binding and tissue content of serotonin and its metabolite 5-hydroxyindolacetic acid were found unaltered in every brain area of NCAM-/- mice investigated, indicating that expression of 5-HT1A receptors as well as synthesis and release of serotonin are largely unchanged in NCAM-/- mice. We hypothesize a critical involvement of endogenous NCAM in serotonergic transmission via 5-HT1A receptors and inwardly rectifying K+ channels as the respective effector systems.

8-Hydroxy-2-(di-n-propylamino)tetralin↗