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    ABSTRACT: Obtaining the correct balance of nutrients requires that the brain integrates information about the body's nutritional state with sensory information from food to guide feeding behaviour. Learning is a mechanism that allows animals to identify cues associated with nutrients so that they can be located quickly when required. Feedback about nutritional state is essential for nutrient balancing and could influence learning. How specific this feedback is to individual nutrients has not often been examined. Here, we tested how the honeybee's nutritional state influenced the likelihood it would feed on and learn sucrose solutions containing single amino acids. Nutritional state was manipulated by pre-feeding bees with either 1 M sucrose or 1 M sucrose containing 100 mM of isoleucine, proline, phenylalanine, or methionine 24 h prior to olfactory conditioning of the proboscis extension response. We found that bees pre-fed sucrose solution consumed less of solutions containing amino acids and were also less likely to learn to associate amino acid solutions with odours. Unexpectedly, bees pre-fed solutions containing an amino acid were also less likely to learn to associate odours with sucrose the next day. Furthermore, they consumed more of and were more likely to learn when rewarded with an amino acid solution if they were pre-fed isoleucine and proline. Our data indicate that single amino acids at relatively high concentrations inhibit feeding on sucrose solutions containing them, and they can act as appetitive reinforcers during learning. Our data also suggest that select amino acids interact with mechanisms that signal nutritional sufficiency to reduce hunger. Based on these experiments, we predict that nutrient balancing for essential amino acids during learning requires integration of information about several amino acids experienced simultaneously.
    Journal of insect physiology 05/2014;
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    ABSTRACT: Gender-specific rates of unipolar and bipolar disorders are well established for cases with post-pubertal onset. However, there is less certainty about these rates in pre-pubertal children. We undertook a systematic review of community studies that report gender-specific rates for unipolar and bipolar disorders in young children, particularly cases of major depression and mania. Computer databases (Medline, EMBASE, Index to Theses, and PsychInfo) were searched for non-clinical observational studies using recognized diagnostic criteria to identify unipolar and bipolar disorders in children aged ≤12 years. A meta-analysis was undertaken to calculate pooled odds ratios (ORs) for caseness for major depression by gender. The limited data on bipolar disorder were summarized. Analysis of 12 studies (>15,000 children), indicated that the community prevalence of unipolar disorders was higher in boys (1.3%) than in girls (0.8%). Rates of major depression were low (0.61%), but boys were significantly more likely to meet diagnostic criteria than girls (OR = 1.61; 95% confidence interval: 1.11-2.35). Five studies, assessing >5,000 children, identified only one case with a probable diagnosis of mania. This systematic review suggests that boys aged ≤12 years are significantly more likely to experience major depression than girls. However, in younger children, community rates of major depression are low, and it is frequently suggested (but not proven) that most cases are comorbid. The absence of mania suggests either that childhood bipolar phenotypes do not resemble post-pubertal onset cases or that there are problems of case ascertainment.
    Bipolar Disorders 12/2013;
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    Journal of Neurology 11/2013;
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    ABSTRACT: People with psychotic symptoms are reported to have a characteristic reasoning style in which they jump to conclusions. To date, little research has been conducted to investigate if this style changes over time and is associated with improvements or worsening of symptoms. This study considered these questions. Thirty-one service users were recruited from a first-episode service and completed measures of reasoning, psychotic, and non-psychotic symptomatology at two time points over 2 years. Over time, people with psychosis generally became less hasty in their decision-making. Those who became less hasty in their reasoning were less symptomatic. For those who remained very hasty in their reasoning, this was associated with a worsening specifically of the delusional beliefs. This work supports the notion that there is a critical time in the first few years of psychosis during which symptoms and reasoning can change. However, where reasoning style does not change, this may be associated with greater difficulties associated with delusional beliefs. Reasoning biases are common in people with psychosis. The persistence of hasty reasoning may be a marker for poor outcome. Reasoning biases can be addressed by specific treatments. The results are based on a small sample of clinical participants. This study did not consider if treatments for reasoning would have improved outcome of people with psychosis. This study may have benefitted from comparison with a control group of people without psychosis.
    British Journal of Clinical Psychology 11/2013; 52(4):380-393.
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    ABSTRACT: Fast ripples (FRs) are network oscillations, defined variously as having frequencies of > 150 to > 250 Hz, with a controversial mechanism. FRs appear to indicate a propensity of cortical tissue to originate seizures. Here, we demonstrate field oscillations, at up to 400 Hz, in spontaneously epileptic human cortical tissue in vitro, and present a network model that could explain FRs themselves, and their relation to 'ordinary' (slower) ripples. We performed network simulations with model pyramidal neurons, having axons electrically coupled. Ripples (< 250 Hz) were favored when conduction of action potentials, axon to axon, was reliable. Whereas ripple population activity was periodic, firing of individual axons varied in relative phase. A switch from ripples to FRs took place when an ectopic spike occurred in a cell coupled to another cell, itself multiply coupled to others. Propagation could then start in one direction only, a condition suitable for re-entry. The resulting oscillations were > 250 Hz, were sustained or interrupted, and had little jitter in the firing of individual axons. The form of model FR was similar to spontaneously occurring FRs in excised human epileptic tissue. In vitro, FRs were suppressed by a gap junction blocker. Our data suggest that a given network can produce ripples, FRs, or both, via gap junctions, and that FRs are favored by clusters of axonal gap junctions. If axonal gap junctions indeed occur in epileptic tissue, and are mediated by connexin 26 (recently shown to mediate coupling between immature neocortical pyramidal cells), then this prediction is testable.
    European Journal of Neuroscience 10/2013;
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    ABSTRACT: The timing of perceptual events depends on an anatomically and functionally connected network comprising basal ganglia, cerebellum, pre-frontal cortex and supplementary motor area. Recent studies demonstrate the cerebellum to be involved in absolute, duration-based timing, but not in relative timing based on a regular beat. Conversely, functional involvement of the striatum is observed in relative timing, but its role in absolute timing is unclear. This work tests the specific role of the basal ganglia in the perceptual timing of auditory events. It aims to distinguish the hypothesised unified model of time perception (Teki, Grube, & Griffiths, 2012), in which the striatum is a mandatory component for all timing tasks, from a modular system in which they subserve relative timing, with absolute timing processed by the cerebellum. Test groups comprised individuals with Multiple System Atrophy, a disorder in which similar pathology can produce clinical deficits associated with dysfunction of the cerebellum (MSA-C, n=8) or striatum (MSA-P, n=10), and early symptomatic Huntington's disease (HD, n=14). Individuals with chronic autoimmune peripheral neuropathy (n=11) acted as controls. Six adaptive tasks were carried out to assess perceptual thresholds for absolute timing through duration discrimination for sub- and supra-second time intervals, and relative timing through the detection of beat-based regularity and irregularity, detection of a delay within an isochronous sequence, and the discrimination of sequences with metrical structure. All three patient groups exhibited impairments in performance in comparison with the control group for all tasks, and severity of impairment was significantly correlated with disease progression. No differences were demonstrated between MSA-C and MSA-P, and the most severe impairments were observed in those with HD. The data support an obligatory role for the basal ganglia in all tested timing tasks, both absolute and relative, as predicted by the unified model. The results are not compatible with models of a brain timing network based upon independent modules.
    Neuropsychologia 10/2013;
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    ABSTRACT: The relationship between auditory processing and language skills has been debated for decades. Previous findings have been inconsistent, both in typically developing and impaired subjects, including those with dyslexia or specific language impairment. Whether correlations between auditory and language skills are consistent between different populations has hardly been addressed at all. The present work presents an exploratory approach of testing for patterns of correlations in a range of measures of auditory processing. In a recent study, we reported findings from a large cohort of eleven-year olds on a range of auditory measures and the data supported a specific role for the processing of short sequences in pitch and time in typical language development. Here we tested whether a group of individuals with dyslexic traits (DT group; n = 28) from the same year group would show the same pattern of correlations between auditory and language skills as the typically developing group (TD group; n = 173). Regarding the raw scores, the DT group showed a significantly poorer performance on the language but not the auditory measures, including measures of pitch, time and rhythm, and timbre (modulation). In terms of correlations, there was a tendency to decrease in correlations between short-sequence processing and language skills, contrasted by a significant increase in correlation for basic, single-sound processing, in particular in the domain of modulation. The data support the notion that the fundamental relationship between auditory and language skills might differ in atypical compared to typical language development, with the implication that merging data or drawing inference between populations might be problematic. Further examination of the relationship between both basic sound feature analysis and music-like sound analysis and language skills in impaired populations might allow the development of appropriate training strategies. These might include types of musical training to augment language skills via their common bases in sound sequence analysis. This article is part of a Special Issue entitled .
    Hearing research 10/2013;
  • Hearing research 09/2013;
  • BMJ (online) 09/2013; 347:f5270.
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    ABSTRACT: Selective attention to features of interest facilitates object processing in a cluttered and dynamic environment. Previous research found that distinct networks of regions across cortex are activated depending on the attended feature. These networks typically consist of posterior feature-preferring regions and anterior regions involved in attentional processes. In the current study, we investigated the role of white matter connections between the posterior and anterior regions within these networks for attention to features of novel colored dynamic objects. We asked participants to perform a 1-back feature-attention task while we acquired both functional and diffusion-weighted images. Using tract-based spatial statistics and probabilistic tractography, we found that the right superior longitudinal fasciculus (SLF) connected posterior and anterior object-processing regions and that voxels within the SLF correlated with response times on the task. Posterior and anterior regions that were anatomically connected also had increased functional connectivity relative to posterior and anterior regions that were not connected. Our results demonstrate that both functional and structural information has to be taken into account to understand selective attention and object perception.
    Brain Structure and Function 09/2013;
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