Metabolic control and auditory information processing at altered glucose levels in insulin-dependent diabetes

Previous work with a visual reaction time (RT) paradigm showed rate of mental processing to be slowed during a state of brain energy depletion (i.e., hypoglycemia). The present study employed an analog auditory RT paradigm to determine if modality differences in processing information might occur in response to glucose alteration. A balanced crossover design was used in which men with insulin-dependent diabetes completed RT tasks of increasing complexity at each of the following glucose levels: hypoglycemia (60 mg/dL), normoglycemia/control (110 mg/dL), and hyperglycemia (300 mg/dL). Results revealed two performance groups. A convergent group displayed slower RT responding during hypoglycemia, consistent with the visual RT pattern of results. A divergent group displayed better responding on one RT measure during hypoglycemia, and generally poorer responding on all RT measures during the other glucose conditions. Subjects in the divergent group maintained more stringent metabolic control and tended to have experienced more episodes of hypoglycemic unconsciousness. The present results provide the first evidence that more stringent metabolic control may be related to generally slower rates of processing auditory information. Possible explanations for these findings include hypotheses of immutable structual derangement, state-dependent performance effects, and a U-shaped response curve.     

Working memory and attention in pediatric brain tumor patients treated with and without radiation therapy

Children are at risk for cognitive difficulties following the diagnosis and treatment of a brain tumor. Longitudinal studies have consistently demonstrated declines on measures of intellectual functioning, and recently it has been proposed that specific neurocognitive processes underlie these changes, including working memory, processing speed, and attention. However, a fine-grained examination of the affected neurocognitive processes is required to inform intervention efforts. Radiation therapy (RT) impacts white matter integrity, likely affecting those cognitive processes supported by distributed neural networks. This study examined working memory and attention in children during the early delayed stages of recovery following surgical resection and RT. The participants included 27 children diagnosed with pediatric brain tumor, treated with (n = 12) or without (n = 15) RT, who completed experimental and standardized measures of working memory and attention (n-back and digit span tasks). Children treated with radiation performed less well than those who did not receive radiation on the n-back measure, though performance at the 0-back level was considerably poorer than would be expected for both groups, perhaps suggesting difficulties with more basic processes such as vigilance. Along these lines, marginal differences were noted on digit span forward. The findings are discussed with respect to models of attention and working memory, and the interplay between the two.     

The inability to ignore auditory distractors as a function of visual task perceptual load

Using a response competition paradigm, we investigated the ability to ignore target response-compatible, target response-incompatible, and neutral visual and auditory distractors presented during a visual search task. The perceptual load model of attention (e.g., Lavie & Tsal, 1994) states that task-relevant processing load determines irrelevant distractor processing in such a way that increasing processing load prevents distractor processing. In three experiments, participants searched sets of one (easy search) or six (hard search) similar items. In Experiment 1, visual distractors influenced reaction time (RT) and accuracy only for easy searches, following the perceptual load model. Surprisingly, auditory distractors yielded larger distractor compatibility effects (median RT for incompatible trials minus median RT for compatible trials) for hard searches than for easy searches. In Experiments 2 and 3, during hard searches, consistent RT benefits with response-compatible and RT costs with response-incompatible auditory distractors occurred only for hard searches. We suggest that auditory distractors are processed regardless of visual perceptual load but that the ability to inhibit cross-modal influence from auditory distractors is reduced under high visual load.     

Allocation of cognitive processing capacity during human autonomic classical conditioning

In each of two experiments, allocation of cognitive processing capacity was measured in college-student subjects during autonomic discrimination classical conditioning. A 7.0-sec delay paradigm was used to establish classically conditioned responses to a reinforced visual conditioned stimulus (CS+). Electrodermal responses were the primary measures of autonomic classical conditioning. Allocation of processing capacity was measured by monitoring performance on a secondary reaction-time (RT) task. The auditory secondary-task RT signal was presented before, and 300, 500, 3500, 6500, and 7500 msec following CS onset. The RT signal was also presented following properly and improperly cued shock unconditioned stimuli (UCSs). Significant discrimination classical conditioning was obtained in both experiments. Comparison with control subjects who did not receive the RT signals indicated that the presence of the RT signals did not interfere with the development of classical conditioning. Four principal findings were obtained with the secondary-task RT measure. First, RTs to signals presented during CS+ were consistently slower than RTs to signals presented during CS-. This finding indicates that greater capacity allocation occurred during CS+ than CS- and is consistent with recent cognitive interpretations of classical conditioning. Second, the largest capacity allocation (i.e., slowing of RTs) occurred 300 msec following CS+ onset. This finding is consistent with the notion that subjects are actively processing the signal properties of the CS+ at 300 msec following CS+ onset. Third, presentation of the UCS when improperly cued (following CS-) significantly increased capacity allocation, whereas presentation of the same UCS when properly cued (following CS+) did not affect capacity allocation. These findings indicate that subjects were actively prepared for the UCS following CS+ but not following CS- and that a surprising UCS elicits greater capacity allocation than does an expected UCS. Fourth, large electrodermal responders to the CSs exhibited patterns of capacity allocation during the CSs, particularly during the CS+, different from those of small electrodermal responders. In particular, they exhibited significantly longer RTs at 300 msec after CS+ onset than did the small responders, followed by a shortening of RT at 500 msec relative to the small responders. This finding suggests that large electrodermal responders devote greater processing capacity to significant environmental stimuli than do small responders and that their processing may begin and be completed more rapidly. All in all, the data indicate the complexity of the cognitive processes that occur during human classical conditioning and the usefulness of the secondary-task technique in integrating conditioning theories and psychophysiology with cognitive psychology.     

In-situ X-ray diffraction during tensile deformation of ultrafine-grained copper using synchrotron radiation

At the synchrotron facility, Super Photon Ring – 8 GeV, in-situ X-ray diffraction during tensile deformation was conducted on ultrafine-grained Cu with a grain size of about 300 nm fabricated by equal-channel angular pressing. The diffraction profile was observed with the time resolution of about 1 s using multiple MYTHEN detectors, and the diffraction angle and the full-width at half-maximum of some Bragg peaks were determined using the pseudo-Voigt function. From the analysis of Bragg peaks, it was found out that there are microscopically three regions; elastic, plastic and transition regions. The 0.2% proof stress obtained from the stress–strain curve locates within the microscopic transition region. Microstrain was evaluated using the Williamson–Hall method and the dislocation density was also obtained from the microstrain. The dislocation density starts increasing before 0.2% proof stress, which is associated with dislocation bow-out and emission from grain boundaries. The Taylor relationship seems to be still satisfied after 0.2% proof stress.     

Performance-based and parent ratings of attention in children treated for a brain tumor: The significance of radiation therapy and tumor location on outcome

Children are at increased risk for cognitive difficulties following the diagnosis and treatment of a brain tumor. Radiation therapy (RT) and tumor location are commonly-cited predictors of neurocognitive functioning. Disruptions to foundational neurocognitive processes such as attention, working memory, and processing speed underlie declines on measures of general intellectual functioning. While several studies have examined visual sustained attention in pediatric brain tumor patients, auditory sustained attention has yet to be examined. This study employs a longitudinal design to examine performance-based and parent ratings of attention in children undergoing surgical resection of a brain tumor (n = 29) and treated with (n = 11) or without (n = 18) RT at 6.79 months post-surgery (baseline) and then again at 30.56 months post-surgery (follow-up). The measures include an auditory continuous performance test (CPT) and parent ratings of attention and hyperactivity on a behavior rating scale. Ultimately, children treated with and without RT performed similarly on performance-based and parent ratings of attention. However, the performance on the auditory CPT differed according to tumor location, with children with infratentorial tumors committing more inattention and inhibitory control errors compared to children with supratentorial tumors. Parent ratings did not differ according to tumor location, and parent ratings and auditory sustained attention performance are not significantly correlated. The findings are interpreted in the context of neurocognitive and brain development.     

The Development of Global and Local Processing: A Comparison of Children to Adults

In light of the adult model of a hemispheric asymmetry of global and local processing, we compared children (M _age = 8.4 years) to adults in a global-local reaction time (RT) paradigm. Hierarchical designs (large shapes made of small shapes) were presented randomly to each visual field, and participants were instructed to identify either the global or the local level in each of two blocks. We obtained evidence of a global-local processing asymmetry, with stronger effects for children than for adults. In both children and adults, responses were faster and more accurate for global identification in the right hemisphere and for local identification in the left hemisphere. Similarly, a significant asymmetry of global and local interference was obtained in children but not in adults. Interference reflects the RT cost of conflicting information at the nonattended level. For example, local interference indicates the degree to which inconsistency at the local level slows global identification. Stronger evidence for lateralized processing in children is discussed within the framework of increasing interhemispheric transfer. That is, as interhemispheric transfer increases, cost of presentation to the nonpreferred hemisphere (e.g., local identification in the right hemisphere) is reduced.     

Syntactic structure modifies attention during speech perception and recognition

The present paper demonstrates the interaction of syntactic structure and speech perception with a response task which minimizes the effects of memory: reaction time (RT) to clicks during sentences. (1) In 12-word unfamiliar sentences each with two clauses, RT is relatively slow overall to clicks located at the end of the first clause but decreases as a function of clause length. Clicks at the beginning of the second clause are not affected by length of the preceding clause. (2) In familiar sentences, RT is relatively fast to clicks located at the end of a clause while RT to clicks at the beginning of clauses is relatively unaffected by familiarity. (3) RT is not fastest overall to clicks located between clauses either in novel or familiar sentences. (4) As in previous studies, the subject's subsequent judegment of the location of the click tone are towards the clause break. (5) We could find no systematic interaction between RT and subjective click location. Findings (1) to (3) are consistent with the view that perceptual processing alternates between attending to all external stimuli and developing an internal representation of the stimuli. Finding (3) is in conflict with an “information channel” view of immediate attention to speech, which would predict high sensory attention to non-speech stimuli between clauses. However, findings (4) and (5) indicate that the channel view of perception may be correct for that perceptual processing which occurs after the immediate organization of the speech stimulus into major segments.     

The influence of prosodic structure on the resolution of temporary syntactic closure ambiguities

This paper investigates the influence of prosodic structure on the process of sentence comprehension, with a specific focus on the relative contributions of syntactic and prosodic information to the resolution of temporary syntactic closure ambiguities. We argue that prosodic structure provides an initial memory representation for spoken sentences, and that information from this prosodic representation is available to inform syntactic parsing decisions. This view makes three predictions for the processing of temporary syntactic ambiguity: 1. When prosodic and syntactic boundaries coincide, syntactic processing should be facilitated. 2. When prosodic boundaries are placed at misleading points in syntactic structure, syntactic processing should show interference effects. 3. The processing difficulties that have been reliably demonstrated in reading experiments for syntactically complex sentences should disappear when those sentences are presented with a felicitous prosodic structure in listening experiments. These predictions were confirmed by series of experiments measuring end-of-sentence comprehension time and cross-modal naming time for sentences with temporary syntactic closure ambiguities. Sentences with coinciding or conflicting prosodic and syntactic boundaries were compared to a prosodic baseline condition.This research was supported in part by NIMH grant R29 MH51768 to the first author and NIMH grant T32 MH19729 to the Northeastern University Psychology Department.     

On the dissociation between reaction time and response duration as a function of lexical and sublexical reading: An examination of phonetic decoding and computational models

Neurobiological models of reading account for two ways in which orthography is converted to phonology: (1) familiar words, particularly those with exceptional spelling-sound mappings (e.g., shoe) access their whole-word lexical representations in the ventral visual stream, and (2) orthographically unfamiliar words, particularly those with regular spelling-sound mappings (i.e., pseudohomophones [PHs], which are orthographically novel but sound like real words; e.g., shue) are phonetically decoded via sublexical processing in the dorsal visual stream. The present study used a naming task in order to compare naming reaction time (RT) and response duration (RD) of exception and regular words to their PH counterparts. We replicated our earlier findings with words, and extended them to PH phonetic decoding by showing a similar effect on RT and RD of matched PHs. Given that the shorter RDs for exception words can be attributed to the benefit of whole-word processing in the orthographic word system, and the longer RTs for exception words to the conflict with phonetic decoding, our PH results demonstrate that phonetic decoding also involves top-down feedback from phonological lexical representations (e.g., activated by shue) to the orthographic representations of the corresponding correct word (e.g., shoe). Two computational models were tested for their ability to account for these effects: the DRC and the CDP+. The CDP+ fared best as it was capable of simulating both the regularity and stimulus type effect on RT for both word and PH identification, although not their over-additive interaction. Our results demonstrate that both lexical reading and phonetic decoding elicit a regularity dissociation between RT and RD that provides important constraints to all models of reading, and that phonetic decoding results in top-down feedback that bolsters the orthographic lexical reading process.     

The role of syllables in word recognition among beginning Finnish readers: Evidence from eye movements during reading

The eye movements of Finnish first and second graders were monitored as they read sentences where polysyllabic words were either hyphenated at syllable boundaries, alternatingly coloured (every second syllable black, every second red) or had no explicit syllable boundary cues (e.g., ta-lo vs. talo vs. talo = “house”). The results showed that hyphenation at syllable boundaries slows down reading of first and second graders even though syllabification by hyphens is very common in Finnish reading instruction, as all first-grade textbooks include hyphens at syllable boundaries. When hyphens were positioned within a syllable (t-alo vs. ta-lo), beginning readers were even more disrupted. Alternate colouring did not affect reading speed, no matter whether colours signalled syllable structure or not. The results show that beginning Finnish readers prefer to process polysyllabic words via syllables rather than letter by letter. At the same time they imply that hyphenation encourages sequential syllable processing, which slows down the reading of children, who are already capable of parallel syllable processing or recognising words directly via the whole-word route.     

The effect of visual search efficiency on response preparation: neurophysiological evidence for discrete flow

Most models assume that response time (RT) comprises the time required for successive processing stages, but they disagree about whether information is transmitted continuously or discretely between stages. We tested these alternative hypotheses by measuring when movement-related activity began in the frontal eye field (FEF) of macaque monkeys performing visual search. Previous work showed that RT was longer when visual neurons in FEF took longer to select the target, a finding consistent with prolonged perceptual processing during less efficient search. We now report that the buildup of saccadic movement-related activity in FEF is delayed in inefficient visual search. Variability in the delay of movement-related activity accounted for the difference in RT between search conditions and for the variability of RT within conditions. These findings provide neurophysiological support for the hypothesis that information is transmitted discretely between perceptual and response stages of processing during visual search.     

The space of an object: object attention alters the spatial gradient in the surround

Although object-based attention enhances perceptual processing of information appearing within the boundaries of a selected object, little is known about the consequences for information in the object's surround. The authors show that distance from an attended object's center of mass determines reaction time (RT) to targets in the surround. Of 2 targets in the surround, both equidistant from a cue, the target closer to the center of mass was detected faster. Moreover, RT was shown to be a linear function of distance from the center of mass of a fixed, attended object, and changes to the shape of the object and its center of mass predictably altered RT. Object-based attention leads to a pattern of facilitation in the surround that may contribute to the organization of visual scenes.     

Processing speed in children treated for brain tumors: effects of radiation therapy and age

The current study examined processing speed in children two years post-treatment for brain tumors (BT) with radiation therapy (RT) compared to those treated with without RT. Participants included 59 children (4–17 years) with BT assessed as part of the Brain Radiation Investigative Study Consortium (BRISC). Processing speed was assessed at two time points: Time1 (3–9 months post-surgery) for 26 children who received whole brain or focal RT (RT group) and 33 treated without RT (no-RT group), and again two years later (Time2) for 42 participants (17 RT, 25 no-RT). Linear mixed effects (LME) regression analyses examined differences in cognitive and motor speed between groups and across visits, with age at Time1 (age1) treated as a moderating variable, and sex and primary tumor size as covariates. No effects for treatment group or visit were found for motor speed (Pegboard) or mean reaction time (Attention Network Task). On the Wechsler Processing Speed Index (PSI), the no-RT group performed better than the RT group, with a group-by-age interaction such that across visits, the difference between the no-RT and RT groups was larger among children who were older at initial treatment (≥10 years) than among those who were younger (<10 years). Cumulative brain injury earlier in life (tumor, surgery, plus RT) may result in greater impact on more complex tasks of cognitive efficiency. Children receiving RT showed reduced processing speed over time, with a larger group difference among those who were over 10 years at treatment.     

Grain orientation effects on delamination during fatigue of a sensitized Al–Mg alloy

Fatigue crack growth experiments were conducted in humid air (RH~45%) at 25 °C on 29-mm-thick plate samples of an aluminium–magnesium (Al–Mg) 5083-H131 alloy in the long transverse (LT) direction. Samples were tested in both the as-received condition and after sensitization at 175 °C for 100 h. Delamination along some grain boundaries was observed in the short transverse plane after fatigue testing of the sensitized material, depending upon the level of ΔK and K_max. Orientation microscopy using electron backscattering diffraction and chemical analyses using transmission electron microscopy and energy dispersive spectroscopy of grain boundaries revealed that Mg segregation and the orientation of grains had key roles in the observed grain boundary delamination of the sensitized material.     

Detrimental effect of cellular precipitation on the creep strength of Inconel740H

Cellular precipitation (also known as discontinuous precipitation) has been observed at the grain boundaries of a newly developed nickel-based Inconel740H alloy designed for use at 700?°C in advanced ultrasupercritical coal-fired power plants. By means of element mapping and selected area diffraction, the cellular precipitates were identified as Cr-rich M₂₃C₆ carbides. The onset of cellular precipitation was found to follow a pucker mechanism in Inconel740H. The cellular precipitates at the grain boundaries, even at low volume fractions, were severely detrimental to the creep strength at 750?°C. The creep rupture life of Inconel740H containing cellular precipitates at grain boundaries was only one-tenth of that for the alloy without cellular precipitates. The reason for the drastically decreased creep rupture life is attributed to the poor resistance of cellular precipitates to crack propagation during creep.     

Psychometric and information processing properties of selected response time models

This paper discusses the compatibility of some response time (RT) models with psychometric and with information processing approaches to response times. First, three psychometrically desirable properties of probabilistic models for binary data, related to the principle of specific objectivity, are adapted to the domain of RT models. One of these is the separability of item and subject parameters, and another is double monotonicity. Next, the compatibility of these psychometric properties with one very popular information processing approach, the serial-additive model, is discussed. Finally, five RT models are analyzed with respect to their compatibility with the psychometric properties, with serial-additive processing and with some alternative types of processing. It is concluded that (a) current psychometric models each satisfy one or more of the psychometric properties, but are not (easily) compatible with serial-additive processing, (b) at least one serial-additive processing model satisfies separability of item and subject parameters, and (c) RT models will more easily satisfy double monotonicity than the other two psychometric properties.     

The Effect of Mental Practice on Performance in a Sequential Reaction Time Task

The effect of mental practice on performance in a dot-location RT task was investigated. Participants (N = 40) were required either to mentally practice, physically practice, or do no practice on an RT task in which the signals appeared in a repeating sequence. Correct mental practice, as opposed to incorrect mental practice and no practice, was predicted to have a positive (enhancing) effect on performance of the RT task. Despite previous evidence that mental rehearsal does enhance performance in many perceptual-motor tasks, neither correct nor incorrect mental rehearsal affected subsequent sequence learning; that is, no mental practice effect was observed. That surprising result is discussed in terms of motivational, psychoneuromuscular, separate memory systems, and transfer-appropriate processing explanations of mental practice.     

Effect of memory set-size upon event related potentials for concrete and abstract kanji stimuli.

Event related potentials (ERP) and reaction times (RT) were recorded during the performance of memory-retrieval tasks using the Japanese kanji characters. P300 latency and RT increased as the memory set-size increased. The slope differences between RT and P300 latency were larger for stimuli when concrete kanji were used than when abstract kanji were used. This suggests that, in memory search, the 20 subjects were likely to employ direct lexical access when processing concrete kanji and likely to use phonetic coding when processing abstract kanji.     

Motor preparation of manual aiming at a visual target manipulated in size, luminance contrast, and location

We conducted two experiments to investigate whether the motor preparation of manual aiming to a visual target is affected by either the physical characteristics (size or luminance contrast) or spatial characteristics (location) of the target. Reaction time (RT) of both finger lifting (ie stimulus-detection time) and manual aiming (ie movement-triggering time) to the onset of the target was measured. The difference of RT (DRT) between two tasks (ie the difference of task complexity) was examined to clarify the temporal characteristics of manual aiming per se during visuomotor integration. Results show classical characteristics: RT decreased as either the target size or luminance contrast increased. Furthermore, the task-complexity and target-location factors significantly interacted with each other, where the aiming RT was longer than the finger-lifting RT and the effects of target location on RT differed for each task. However, the task factor did not interact with either the size or luminance-contrast factor, implying that the motor preparation of manual aiming is associated with the spatial characteristics rather than the physical characteristics of the target. Inspection of DRT revealed that the time needed for motor preparation for an ipsilateral target was significantly shorter than that for a contralateral target. This was the case both for the left and for the right hand. Foveal targets required longer processing time, implying a disadvantageous function of motor preparation for the gazed target. The left-hand superiority for the target appearing in the left visual field was also observed. Such lateralised effect and left-hand advantage to the left visual field in manual aiming suggest that visuospatial information processing is activated during the preparation of aiming action, with faster processing in the right hemisphere.