Dietary-free glutamate: implications for research on fear-overconsolidation and PTSD.
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Cerebral Cortex↗
Biomedical subjects
Edward P Chronicle
Publications and source records attributed to Edward P Chronicle.
It looks easy! Heuristics for combinatorial optimization problems.
Human performance on instances of computationally intractable optimization problems, such as the travelling salesperson problem (TSP), can be excellent. We have proposed a boundary-following heuristic to account for this finding. We report three experiments with TSPs where the capacity to employ this heuristic was varied. In Experiment 1, participants free to use the heuristic produced solutions significantly closer to optimal than did those prevented from doing so. Experiments 2 and 3 together replicated this finding in larger problems and demonstrated that a potential confound had no effect. In all three experiments, performance was closely matched by a boundary-following model. The results implicate global rather than purely local processes. Humans may have access to simple, perceptually based, heuristics that are suited to some combinatorial optimization tasks.
Attention↗
Premorbid childhood ocular alignment abnormalities and adult schizophrenia-spectrum disorder.
This study examined the relation between childhood ocular alignment deficits and adult psychiatric outcomes among children at high-risk for schizophrenia and controls. A sample of 265 Danish children was administered a standardized eye exam assessing strabismus and related ocular alignment deficits. All children whose mothers or fathers had a psychiatric diagnosis of schizophrenia comprised the first group (N=90). Children who had at least one parent with a diagnosis other than schizophrenia comprised the first matched control group (N=93). The second control group consisted of children with no parental diagnoses (N=82). In 1992, adult psychiatric outcome data were obtained for 242 of the original subjects. It was found that children who later developed a schizophrenia-spectrum disorder had significantly higher eye exam scale and strabismus scale scores compared to children who developed other non-psychotic psychopathology and children who did not develop a mental illness. The mean rank for children in the high-risk group (offspring of parents with schizophrenia) on the eye scale and the strabismus scale was greater than the mean rank for children in the matched control groups (both offspring of parents with other non-psychotic disorder and no mental illness), although the results failed to reach statistical significance. Results from this study suggest a premorbid relation between ocular deficits and schizophrenia-spectrum disorders in childhood prior to onset of psychopathology in adulthood. Strabismus may serve as a premorbid marker for spectrum disorders and may have implications for the understanding of early aberrant neurological development related to later schizophrenia-spectrum disorders.
Adult↗
Assessing cortical excitability in migraine: reliability of magnetic suppression of perceptual accuracy technique over time.
OBJECTIVES: To examine test-retest reliability of magnetic suppression of perceptual accuracy (MSPA) prior to its use as a marker of cortical excitability in a trial of migraine prophylactic agents. BACKGROUND: MSPA is a relatively novel avenue of research in headache, providing an opportunity to study cortical responsiveness objectively and noninvasively. However, little is known about the reliability of magnetic stimulation protocols such as MSPA in longitudinal research designs. METHODS: We tested 10 healthy headache-free volunteers who had no family history of migraine. In 54 trials, they were briefly presented different three-letter combinations, flashed on a computer screen for 24 ms (target). After a brief interval, each target was followed by a single magnetic pulse through a 90-mm circular coil centered 7 cm above inion in the midline. The interval between target and magnetic pulse was systematically varied. Volunteers were requested to report as many letters as they had possibly identified. After 2 weeks, all volunteers were retested using identical methods. RESULTS: MSPA performance is expressed as a profile of response accuracy (ie, percentage of correctly identified letters) across target-pulse intervals. Profiles were characteristic of normal headache-free subjects at the first test. Analysis of variance revealed no significant difference in profiles between test and retest (F= 2.05; P= .136): the retest profiles are almost coincidental with the test profiles. CONCLUSIONS: MSPA is a safe and objective measure of cortical excitability, which is reliable over time. MSPA, therefore, shows excellent promise as a biological marker of cortical response in trials of migraine prophylactics.
Adult↗
Development and positioning reliability of a TMS coil holder for headache research.
OBJECTIVE: Accurate and reproducible coil positioning is important for headache research using transcranial magnetic stimulation protocols. We aimed to design a transcranial magnetic stimulation coil holder and demonstrate reliability of test-retest coil positioning. METHODS: A coil holder was developed and manufactured according to three principles of stability, durability, and three-dimensional positional accuracy. Reliability of coil positioning was assessed by stimulating over the motor cortex of four neurologically normal subjects and recording finger muscle responses, both at a test phase and a retest phase several hours later. RESULTS: In all four subjects, repositioning of the transcranial magnetic stimulation coil solely on the basis of coil holder coordinates was accurate to within 2 mm. CONCLUSIONS: The coil holder demonstrated good test-retest reliability of coil positioning, and is thus a promising tool for transcranial magnetic stimulation-based headache research, particularly studies of prophylactic drug effect where several laboratory visits with identical coil positioning are necessary.
Equipment Design↗
Cortical inhibition is reduced in chronic and episodic migraine and demonstrates a spectrum of illness.
BACKGROUND: The pathophysiological relationship between episodic migraine and chronic migraine is not fully understood. We aimed to examine transcranial magnetic stimulation (TMS) indices of cortical excitability in patients with episodic migraine (EM) and probable chronic migraine (PCM), and matched controls. METHODS: Cortical excitability was assessed at baseline with two well-established methods: phosphene thresholds (PT) and magnetic suppression of perceptual accuracy (MSPA) profiles. Five EM patients, five PCM patients, and five normal controls participated in the main study. In addition, two patients were reassessed after 30 days of treatment with topiramate. RESULTS: Both PT and MPSA measures were consistent in indicating a continuum of excitability across the three groups: PCM patients had the highest excitability, followed by EM, then controls. In the two treated patients MPSA profiles appeared to normalize at a 100 mg dosage. CONCLUSIONS: Patients with PCM appear to be characterized by very high cortical excitability. This may contribute to their greatly increased attack frequency. TMS-based methods will be important for future research examining the evolution of chronic migraine from episodic migraine over time.
Cerebral Cortex↗
What makes an insight problem? The roles of heuristics, goal conception, and solution recoding in knowledge-lean problems.
Four experiments investigated transformation problems with insight characteristics. In Experiment 1, performance on a version of the 6-coin problem that had a concrete and visualizable solution followed a hill-climbing heuristic. Experiment 2 demonstrated that the difficulty of a version of the problem that potentially required insight for solution stems from the same hill-climbing heuristic, which creates an implicit conceptual block. Experiment 3 confirmed that the difficulty of the potential insight solution is conceptual, not procedural. Experiment 4 demonstrated the same principles of move selection on the 6-coin problem and the 10-coin (triangle) problem. It is argued that hill-climbing heuristics provide a common framework for understanding transformation and insight problem solving. Postsolution receding may account for part of the phenomenology of insight.
Cognition↗
Convex hull or crossing avoidance? Solution heuristics in the traveling salesperson problem.
Untrained adults appear to have access to cognitive processes that allow them to perform well in the Euclidean version of the traveling salesperson problem (E-TSP). They do so despite the famous computational intractability of the problem, which stems from its combinatorial complexity. A current hypothesis is the humans' good performance is based on following a strategy of connecting boundary points in order (the convex hull hypothesis). Recently, an alternative has been proposed, that performance is governed by a strategy of avoiding crossings. We examined the crossing avoidance hypothesis from the perspectives of its capacity to explain existing data, its theoretical adequacy, and its ability to explain the results of three new experiments. In Experiment 1, effects on the solution quality of number of points versus number of interior points were compared. In Experiment 2, the distributions of observed paths were compared with those predicted from the two hypotheses. In Experiment 3, figural effects were varied to induce crossings. The results of the experiments were more consistent with the convex hull than with the crossing avoidance hypothesis. Despite its simplicity and intuitive appeal, crossing avoidance does not provide a complete alternative to the convex hull hypothesis. Further elucidation of human strategies and heuristics for optimization problems such as the E-TSP will aid our understanding of how cognitive processes have adapted to the demands of combinatorial difficulty.
Commerce↗
A ticklish question: does magnetic stimulation of the primary motor cortex give rise to an 'efference copy'?
In order to make accurate predictions about the somatosensory consequences of our own movements, an 'efference copy' of motor output appears to be used (probably in the cerebellum) as a basis for anticipating and canceling incoming information about self-produced movement. One everyday phenomenon that results from these predictive processes is that of being unable to tickle oneself. We examined whether involuntary movements induced by magnetic stimulation of (a) the motor cortex and (b) the bicep muscle, both resulting in standard stimulation of the participant's bare foot, would be perceived as ticklish. In both cases, the stimulus to the foot was rated as ticklish as when the experimenter tickled the participant's foot (using an identical stimulus). We conclude that magnetic stimulation of the motor cortex is unlikely to give rise to an efference copy of motor output.
Adult↗
The role of pictorial convention in haptic picture perception.
An investigation of tactile picture perception is reported. Blindfolded sighted subjects explored either 'line drawings' or 'textured' tactile pictures produced on Zytex swell paper. All pictures were 'two-dimensional', that is they depicted only one object face and so did not represent a third dimension. Both picture sets represented the same objects. Results revealed that the textured pictures, in which solid surfaces of depicted objects were uniformly textured, were recognised more often than tactile line drawings, in which surfaces of objects were simply bounded by lines. There were no significant correlations between imagery ability (visual, cutaneous, or kinaesthetic) and picture recognition success. Texture may be a form of 'uniform connectedness' (Palmer and Rock 1994 Psychonomic Bulletin & Review 1 29-55) or 'common region' (Palmer 1992 Cognitive Psychology 24 436-447), highlighting the global characteristics of stimuli. We argue that textured pictures may encourage the haptic system to take a more globally oriented approach to tactile picture perception, benefiting recognition.
Adolescent↗
Migraine's magnetic attraction.
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Humans↗
Dynamics and constraints in insight problem solving.
This article reports 2 experiments that investigated performance on a novel insight problem, the 8-coin problem. The authors hypothesized that participants would make certain initial moves (strategic moves) that seemed to make progress according to the problem instructions but that nonetheless would guarantee failure to solve the problem. Experiment 1 manipulated the starting state of the problem and showed that overall solution rates were lower when such strategic moves were available. Experiment 2 showed that failure to capitalize on visual hints about the correct first move was also associated with the availability of strategic moves. The results are interpreted in terms of an information-processing framework previously applied to the 9-dot problem. The authors argue that in addition to the operation of inappropriate constraints, a full account of insight problem solving must incorporate a dynamic that steers solution-seeking activity toward the constraints.
Attention↗