The use of latent trajectory models in psychopathology research.
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Despite the recent surge in the development of powerful modeling strategies to test questions about individual differences in stability and change over time, these methods are not currently widely used in psychopathology research. In an attempt to further the dissemination of these new methods, the authors present a pedagogical introduction to the structural equation modeling based latent trajectory model, or LTM. They review several different types of LTMs, discuss matching an optimal LTM to a given question of interest, and highlight several issues that might be particularly salient for research in psychopathology. The authors augment each section with a review of published applications of these methods in psychopathology-related research to demonstrate the implementation and interpretation of LTMs in practice. (+info)
Dynamical analysis reveals individuality of locomotion in goldfish.
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Goldfish swimming was analysed quantitatively to determine if it exhibits distinctive individual spatio-temporal patterns. Due to the inherent variability in fish locomotion, this hypothesis was tested using five nonlinear measures, complemented by mean velocity. A library was constructed of 75 trajectories, each of 5 min duration, acquired from five fish swimming in a constant and relatively homogeneous environment. Three nonlinear measures, the 'characteristic fractal dimension' and 'Richardson dimension', both quantifying the degree to which a trajectory departs from a straight line, and 'relative dispersion', characterizing the variance as a function of the duration, have coefficients of variation less than 7%, in contrast to mean velocity (30%). A discriminant analysis, or classification system, based on all six measures revealed that trajectories are indeed highly individualistic, with the probability that any two trajectories generated from different fish are equivalent being less than 1%. That is, the combination of these measures allows a given trajectory to be assigned to its source with a high degree of confidence. The Richardson dimension and the 'Hurst exponent', which quantifies persistence, were the most effective measures. (+info)
Perception-related modulations of local field potential power and coherence in primary visual cortex of awake monkey during binocular rivalry.
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Cortical synchronization at gamma-frequencies (35-90 Hz) has been proposed to define the connectedness among the local parts of a perceived visual object. This hypothesis is still under debate. We tested it under conditions of binocular rivalry (BR), where a monkey perceived alternations among conflicting gratings presented singly to each eye at orthogonal orientations. We made multi-channel microelectrode recordings of multi-unit activity (MUA) and local field potentials (LFP) from striate cortex (V1) during BR while the monkey indicated his perception by pushing a lever. We analyzed spectral power and coherence of MUA and LFP over 4-90 Hz. As in previous work, coherence of gamma-signals in most pairs of recording locations strongly depended on grating orientation when stimuli were presented congruently in both eyes. With incongruent (rivalrous) stimulation LFP power was often consistently modulated in consonance with the perceptual state. This was not visible in MUA. These perception-related modulations of LFP occurred at low and medium frequencies (< 30 Hz), but not at gamma-frequencies. Perception-related modulations of LFP coherence were also restricted to the low-medium range. In conclusion, our results do not support the expectation that gamma-synchronization in V1 is related to the perceptual state during BR, but instead suggest a perception-related role of synchrony at low and medium frequencies. (+info)
Olfactory discrimination ability of human subjects for enantiomers with an isopropenyl group at the chiral center.
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The ability of 20 human subjects to distinguish between nine enantiomeric odor pairs sharing an isopropenyl group at the chiral center was tested in a forced-choice triangular test procedure. I found (i). that as a group, the subjects were only able to significantly discriminate the optical isomers of limonene, carvone, dihydrocarvone, dihydrocarveol and dihydrocarvyl acetate, whereas they failed to distinguish between the (+)- and (-)-forms of perillaalcohol, perillaaldehyde, isopulegol and limonene oxide; (ii). marked interindividual differences in discrimination performance, ranging from subjects who were able to significantly discriminate between eight of the nine odor pairs to subjects who failed to do so with six of the nine tasks; and (iii). that with none of the nine odor pairs the antipodes were reported to differ significantly in subjective intensity when presented at equal concentrations. Additional tests of the chemesthetic potency and threshold measurements of the optical isomers of dihydrocarvone, dihydrocarveol, and dihydrocarvyl acetate suggest that the discriminability of these three enantiomeric odor pairs is indeed due to differences in odor quality. Analysis of structure-activity relationships suggest that the combined presence of (i). an isopropenyl group at the chiral center; (ii). a methyl group at the para-position; and/or (iii). an oxygen-containing group at the meta-position allows for the discrimination of enantiomeric odor pairs. (+info)
Volatile release from liquids: a comparison of in vivo APCI-MS, in-mouth headspace trapping and in vitro mouth model data.
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In-mouth volatile release from flavoured water was followed using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) or using a hand-held, computer-controlled device based on sequential trapping of flavours on Tenax traps. The present results verify recent in vitro data obtained with a sophisticated, fully computerized mouth model apparatus and confirm its validity for the simulation of in-mouth dynamic volatile release. In-nose APCI-MS measurements showed considerable person-to-person variability in non-trained individuals during drinking due to subconscious control of muscles during swallowing and subsequent breathing. Data showed a 'swallow breath' volume reaching the nasal cavity from the throat, not from the mouth cavity. Flavour enriched air from the mouth was shown to be transported to the nose (via exhalation) immediately after the swallowing event, but the dynamic process of volatile equilibration between residuals of the swallowed liquid and the exhaled air predominantly determined volatile in-nose concentration. Owing to its dynamic character, the process of volatile equilibration and release in the throat upon exhalation should be similar to the in-mouth process studied in the present work. A full mechanical simulation of retronasal volatile transport, however, will remain difficult. (+info)
Individual differences in anterior cingulate/paracingulate morphology are related to executive functions in healthy males.
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The neuropsychological correlates of inter-individual variations in cortical folding are poorly understood. Anterior cingulate (AC) cortex is one region characterized by considerable variability, particularly with respect to the paracingulate sulcus (PCS), which is present in only 30-60% of individuals and more commonly found in the left cerebral hemisphere. To investigate whether inter-individual differences in this PCS asymmetry are related to cognitive performance, we classified 30 healthy right-handed males as displaying either a leftward, rightward or symmetric pattern of folding based on the incidence and extent of the PCS in each hemisphere, and compared their performance on tasks engaging executive cognitive processes associated with frontal lobe function. We found that the more common leftward PCS asymmetry was associated with better performance across verbal and non-verbal executive tasks, but that PCS variability had no effect on tasks less dependent on executive functions. These results suggest that the leftward pattern of folding is associated with a non-specific performance advantage on cognitively demanding executive function tasks, possibly due to differences in functional interactions between AC/paracingulate cortex and connected frontal regions. It therefore appears that normal variations in brain morphology are associated with individual differences in cognitive abilities. (+info)
Individual differences in error processing: a review and reanalysis of three event-related fMRI studies using the GO/NOGO task.
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Three previous studies using the GO/NOGO task were examined to characterize the pattern of functional activation seen during error-related processing. The large sample size (n = 44) also allowed investigation of the influence of individual differences in age, sex, self-reported absentmindedness and reaction speed on the level of activation. Errors were seen to activate a network of regions including the anterior cingulate cortex (ACC), pre-supplementary motor area (pre-SMA), bilateral insula, thalamus and right inferior parietal lobule. Split-half comparisons performed for each of the individual difference variables indicated greater ACC and pre-SMA activation for older subjects while slower responders showed greater activation in the parietal, lateral PFC, insula and ACC regions. Whereas males and females demonstrated equivalent levels of activation in both the ACC and insula, self-reported absentmindedness related to reduced activation in these regions. Our review of the current imaging literature on error-related activation indicates that, despite the use of a variety of other cognitive paradigms, the network of regions identified here is consistent with these previous studies, suggesting that these regions are critical to a 'general' error-related response. Furthermore, this response is, in part, influenced by individual differences in both demographic characteristics and behavioural performance. (+info)
A voxel-based morphometric study to determine individual differences in gray matter density associated with age and cognitive change over time.
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Voxel-based morphometry (VBM) was used to examine the relation between age and gray matter density cross-sectionally and to study the association between gray matter density and longitudinal decline in performance on cognitive tests in healthy, non-demented elderly individuals. Participants were neuropsychologically tested at baseline and again after 3 years. Thirty-seven subjects (mean age 72.5 years) who showed a decline in cognitive test performance at follow-up were compared with 38 individually matched control subjects (mean age 71.8 years) whose performance did not change over time. Magnetic resonance imaging scans were acquired at follow-up and individual differences in regional gray matter density were examined with VBM. The largest age effects were found in various regions in the prefrontal cortex, the (medial) temporal lobes and the striate cortex. Longitudinal cognitive decline was associated with decreased gray matter density in prefrontal areas, the (medial) temporal lobes and the posterior parietal cortex. These findings suggest that prefrontal and temporal cortical regions are of particular relevance both in aging and age-related cognitive decline in healthy elderly individuals. (+info)