Human cortico-hippocampal activity related to auditory discrimination revealed by neuromagnetic field

We carried out multi-dipole estimation and pursued spatio-temporal brain activity on a time scale of several milliseconds during an auditory discrimination task using a whole-cortex type SQUID system. Neuronal activities were estimated in the medial (hippocampus, parahippocampal gyrus, etc.) and lateral temporal cortices (superior and middle temporal gyri, etc.), the dorsolateral prefrontal cortex (middle and inferior frontal gyri, etc.) and the parietal cortex (supramarginal gyrus, etc.) in the 280-400 ms latency range. The activity in the posterior hippocampal region was the most prominent and long-lasting in parallel with the activities in the other regions. Therefore, the posterior hippocampal region is a central structure engaged in auditory discrimination. The whole-cortex neuromagnetic measurements provided the possibility of imaging the time-varying activities of the human cortico-hippocampal neural networks.     

Regional brain activity during tasks devoted to the central executive of working memory

Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish precisely the functions of the CE from the storage function of the slave systems. The aim of the present study was to isolate brain areas that subserve manipulation of information by the CE when the influence of storage function was removed. A PET activation study was performed with four cognitive tasks, crossing conditions of temporary storage and manipulation of information. The manipulation of information induced an activation in the right (BA 10/46) and left (BA 9/6) middle frontal gyrus and in the left parietal area (BA7). The interaction between the storage and manipulation conditions did not reveal any significant changes in activation. These results are in agreement with the hypothesis that CE functions are distributed between anterior and posterior brain areas, but could also reflect a simultaneous involvement of controlled (frontal) and automatic (parietal) attentional systems. In the other hand, the absence of interaction between the storage and manipulation conditions demonstrates that the CE is not necessarily related to the presence of a memory load.     

Inhibition of return in discrimination tasks.

Although inhibition of return is known to affect a wide range of detection tasks, it has not been found consistently in discrimination tasks. To examine this issue, 5 experiments were conducted in which participants discriminated between a visual target and a distractor. The responses were not inhibited if, before the onset of stimuli, attention had been overtly oriented (i.e., an eye movement was made) to the future target location and the stimulus at that location was the same symbol as the upcoming target. However, if attention was covertly oriented (i.e., no eye movement was made) to the future location of the target, or if the stimulus at the earlier attended location was a symbol different from the target, responses to the target were inhibited. Overall, the findings provide insights into the relation between movements of attention and discrimination judgments and support the notion that inhibition of return is an attentional phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypnotic susceptibility as related to gestalt closure tasks.

Studied the relationship of gestalt closure tasks to hypnotizability (Harvard Group Scale of Hypnotic Susceptibility and Stanford Hypnotic Susceptibility Scale) as a test of the hypothesis that the more highly hypnotizable do better on a task of holistic visuospatial functioning than those less responsive to hypnosis. Several other cognitive tasks were included. Four studies were conducted with 125 male and 106 female high school and college students. In Study I, high hypnotizables scored significantly higher than low hypnotizables on the gestalt closure tasks, but there were no significant correlations between hypnotizability and the other cognitive tasks. In Studies II and III, females showed significant correlations between hypnotic susceptibility and gestalt closure scores. In Study IV, a significant correlation between hypnotic susceptibility and gestalt closure was found for males. Results are consistent with studies of different types of cognitive functioning (hemispheric preference, creativity, attentional distribution, imaginative involvement, and absorption), all indicating differences in cognitive abilities associated with high hypnotizability. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural dynamics of motion processing and speed discrimination

A neural network model of visual motion perception and speed discrimination is presented. The model shows how a distributed population code of speed tuning, that realizes a size-speed correlation, can be derived from the simplest mechanisms whereby activations of multiple spatially short-range filters of different size are transformed into speed-turned cell responses. These mechanisms use transient cell responses to moving stimuli, output thresholds that covary with filter size, and competition. These mechanisms are proposed to occur in the V1-->MT cortical processing stream. The model reproduces empirically derived speed discrimination curves and simulates data showing how visual speed perception and discrimination can be affected by stimulus contrast, duration, dot density and spatial frequency. Model motion mechanisms are analogous to mechanisms that have been used to model 3-D form and figure-ground perception. The model forms the front end of a larger motion processing system that has been used to simulate how global motion capture occurs, and how spatial attention is drawn to moving forms. It provides a computational foundation for an emerging neural theory of 3-D form and motion perception.     

Performance of psychopaths on cognitive tasks related to frontal lobe function.

On the basis of their performance on several cognitive tasks, including the Wisconsin Card Sorting Test (WCST), the Necker Cube, and a sequential matching memory task (SMMT), E. E. Gorenstein (see record 1983-01261-001) concluded that psychopaths have specific deficits in cognitive processes associated with frontal-lobe functioning. However, it is argued that his diagnostic procedures were inadequate and his results confounded by group differences in age, education, general ability, and substance abuse. In the present study, the WCST, Necker Cube, and SMMT were administered to 46 male prison inmates divided into low-, medium-, and high-psychopathy groups on the basis of a 22-item checklist developed by the present author (see record 1982-02477-001). ANOVAs and ANCOVAs (with age, education, IQ, and substance use as covariates) failed to detect any group differences in task performance. Similar results were obtained when diagnoses were based on the Socialization scale of the California Psychological Inventory and the DSM-III criteria for antisocial personality disorder and when multiple criteria were used. Some general problems associated with attempts to explain psychopathy in terms of brain damage or dysfunction are discussed. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human brain activity during spontaneously reversing perception of ambiguous figures

Looking at ambiguous figures results in rivalry with spontaneous alternation between two percepts. Using event-related functional magnetic resonance imaging, we localized transient human brain activity changes during perceptual reversals. Activation occurred in ventral occipital and intraparietal higher-order visual areas, deactivation in primary visual cortex and the pulvinar. Thus, without any physical stimulus changes, salient perceptual flips briefly engage widely separated specialized cortical areas, but are also associated with intermittent activity breakdown in structures putatively maintaining perceptual stability. Together, the dynamics of integrative perceptual experience are reflected in rapid spatially differentiated activity modulation within a cooperative set of neural structures.     

Is speed of processing information related to intelligence and achievement?

Speed of processing information, measured by mean response time and slope of response times for tasks of varying levels of complexity, was correlated with intelligence (measured by the Lorge-Thorndike Intelligence Test, which emphasizes power rather than speed) and with achievement (measured by Stanford Achievement Test scores in reading and mathematics). Three tasks (sentence–picture comparison, pictorial similarities and differences, and matrix analysis) were individually administered to 94 6th graders, 51 males and 43 females. Reliability of mean response time was greater than that of slope and correlated significantly with IQ (–.6) and with achievement (–.4–.5). Correlations with achievement dropped to near zero with IQ partialled out. Speed of processing information was found to generalize across experimental tasks and to reliably indicate intellectual ability. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Withdrawing attention at little or no cost: detection and discrimination tasks

At the request of the Dutch government, a group of researchers looked into the experiences of gay men and lesbians in organized, nonprofessional sports. The principal finding was that gay men and lesbians do not experience much discrimination. This circumstance results from the invisibility and silencing of homosexuality in athletics, both by sports organizations and by gay men and lesbians themselves. But in those sports where lesbians have become open about their sexuality, especially in soccer, they do encounter a high level of discrimination. Gay men, on the other hand, have not become visible in any sport. Several suggestions are offered on how to open up sports for lesbians and gay men.     

Human visual evoked responses are related to heart rate.

Attempted to determine the relation between changes in heart rate (HR) and averaged evoked potentials. 16 male undergraduates with variable HRs received 50 flashes of light during fast heart beats, 50 during slow heart beats, and 50 during midrange HR level. Evoked responses were recorded from the scalp overlying the right and left occipital lobes. HR, respiration, eye movements, and cephalic blood flow were also recorded. Results indicate that spontaneous changes in HR were related to changes in visual evoked responses and that this relation differed for the cerebral hemispheres. Cephalic pulse amplitude was largest following slow heart beats and smallest following fast heart beats, which suggests that changes in HR are related to changes in cerebrovascular as well as electrocortical activity. Results are discussed in terms of formulations derived from behavioral studies regarding the relation between cardiovascular activity and attentional processes. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is reading ability related to activation dumping speed? Evidence from immediate repetition priming

In parallel processing models, residual activity constitutes noise that must be dumped, and fast dumping is associated with efficient processing. Subjects performed a continuous lexical decision task with repetitions (Experiments 1 and 2). Efficient readers (who had high comprehension and vocabulary scores) showed smaller repetition priming than did inefficient readers, but mostly at Lag 0 (equivalent to 3-sec stimulus onset asynchrony [SOA]). Experiment 3 manipulated the empty inter-repetition interval. It was found that reading ability was negatively related to repetition priming mostly when the SOA was 3 sec, but less so when it was 2 or 4 sec. Experiment 4 failed to find similar reading ability differences when the task was continuous recognition. The findings are interpreted as showing that efficient readers managed to dump residual activity related to subsemantic information in less than 3 sec, whereas inefficient readers required 3-4 sec.     

Gastric oxyntic cell structure as related to secretory activity

The oxyntic, or parietal cell has two characteristic membrane systems. The mammalian intracellular canaliculi are specialized networks of narrow channels lined with numerous microvilli. The other common to all oxyntic cells is the tubulovesicles, a system of tubules and vesicles. The tubulovesicular compartment is drastically depleted during maximal gastric acid secretion and this is coincident with an increase in the cell surface membrane area. A plausible explanation of this process is the fusion and transfer of tubulovesicular membranes to the plasma membrane. However, for many years there was no convincing evidence of the connections between these two membrane systems. How the tubulovesicular membranes transform into plasma membrane without demonstrable connections has been an enigma to electron microscopists. Recent ultra-high resolution scanning electron microscopic observation on the rat oxyntic cell treated with aldehyde-osmium-aldehyde method revealed that in the resting stage, the tubulovesicles were isolated spherical vesicles. But after tetragastrin stimulation, they were interconnected by slender connecting tubules forming a tubulovesicular network. Then this network was fused to the intracellular canaliculus at relatively few points. These connections between the tubulovesicles and luminal surface membrane was also demonstrated in the frog oxynticopeptic cells. In this review, these membrane transformations as well as changes of the H+/K(+)-ATPase, the lectin binding glycocalyx and the cytoskeleton during secretion will be illustrated and discussed.     

Dissociation of brain ERP topographies for tonal and phonetic oddball tasks

ERP topographies for 30 scalp electrodes were examined in 26 healthy right-handed volunteers during oddball tasks (20% targets) using binaurally presented consonant-vowel syllables or complex tones. Response hand was counterbalanced across participants. Both window averages and a principal components analysis (PCA) with Varimax rotation revealed task-related (tonal/phonetic) hemispheric asymmetries for N2, early P3, and particularly for N2-P3 amplitude. In the tonal task, N2 was maximal over right lateral-temporal regions, and early P3 over right medial-parietal regions. For the phonetic task, N2 was maximal over the left lateral-parietal regions, and late P3/N3 over left medial-parietal regions. A response-related frontal negativity (N3) interacted with task-related asymmetries in an unbalanced fashion. The distinct, asymmetric N2 and P3 topographies for tonal and phonetic tasks presumably reflect differential involvement of cortical structures in pitch (right frontotemporal) and phoneme (left parietotemporal) discrimination.     

Sex differences in brain regions activated by grammatical and reading tasks

Do the brains of men and women show similar patterns of functional organization for language, or are men more strongly lateralized? We used PET to measure cerebral blood flow (CBF) as men and women read real and nonce verbs, and produced past tense forms. While the overall patterns of reaction time, error, and brain activation were similar, there were also significant sex-related differences in CBF patterns. During the past tense generation tasks, men showed left-lateralized activation while women recruited bilateral perisylvian cortex, confirming differences in functional laterality. During all tasks, women showed higher activation in occipital and/or cerebellar regions, suggesting differences in basic reading strategies. We conclude that sex differences in functional cortical organization exist in the absence of significant behavioral differences.     

Individual differences in response to novelty, amphetamine-induced activity and drug discrimination in rats

Individual group, and ethnic differences in behavior have been an object of long, continuing, and contentious interest, both in the sciences and in popular culture. For well over 2,000 years, psychological traits, particularly those described as 'intelligence', have generally been considered the major factors in fitness in humans. After reviewing contemporary scientific thinking on intelligence, the psychometric methods used for the construction of psychological tests are presented and examined in the context of natural selection and metric characters. There are essential differences between the disciplines of genetics and of psychology such that the concepts of the two are more divergent than might superficially appear to be the case. The analysis leads to the conclusion that standard psychometric methodology cannot yield tests appropriate for measurement of evolutionary fitness characters.     

Human discrimination of the implicit orientation of simple symmetrical patterns

A hydraulic calcium phosphate cement made of beta-tricalcium phosphate [beta-Ca3(PO4)2], monocalcium phosphate monohydrate [Ca(H2PO4)2-H2O], and water was used as a delivery system for the antibiotic gentamicin sulfate (GS). GS, added as powder or as aqueous solution, was very beneficial to the physicochemical properties of the cement. The setting time increased from 2 to 4.5 min with 3% (w/w) GS and then slowly decreased to 3.75 min with 16% (w/w) GS. The tensile strength increased from 0.4 to 1.6 MPa with 16% (w/w) GS. These effects were attributed to the presence of sulfate ions in GS. The release of GS from the cement was measured in a pH 7.4 phosphate-buffered saline solution at 37 degrees C by USP paddle method. Factors such as cement porosity, GS content and presence of sulfate ions or polymeric additives were investigated. The amount of GS released was roughly proportional to the square root of time up to approximately 50% release. Afterwards, the release rate markedly slowed down to zero. In all but two cement formulations, the total dose of GS was released within 7 days, indicating that no irreversible binding occurred between the cement paste and the antibiotic. When small amounts of hydroxypropylcellulose or poly(acrylic acid) were added to the cement, the maximum fraction released was a few percent lower than the total GS dose, suggesting some binding between the polymer and GS. The GS release rate was strongly influenced by the presence of sulfate ions in the cement paste and by the cement porosity. The higher the sulfate ion content of the cement paste, the lowe the GS release rate. This influence was attributed to the finer cement micro-structure induced by the presence of sulfate ions. Furthermore, when the initial cement porosity was increased from 38 to 69%, the release rate almost tripled (0.16 to 0.45 h-1/2). Finally, the biological activity of GS in the cement was maintained, as measured by assaying the release medium.     

Changes in serum dopamine beta hydroxylase activity related to coma

Dopamine Beta Hydroxylase (DBH) activity was determined in 24 deeply comatose patients enrolled in the Collaborative Study of Cerebral Survival. All patients had been without cerebral responsiveness or spontaneous respirations for at least 15 minutes. Patients were examined, EEGs performed and blood for DBH drawn within 24 hours of the cerebral insult. DBH activity was lower in the deeply comatose patients than in a group of 51 age matched normal individuals. It is postulated that destruction or inactivation of the central nervous system (CNS) and particularly of the cerebrum may result in lowered serum DBH activity through decreased activation of sympathetic nerve terminals.     

Human brain metabolic response to caffeine and the effects of tolerance

OBJECTIVE: Since there is limited information concerning caffeine's metabolic effects on the human brain, the authors applied a rapid proton echo-planar spectroscopic imaging technique to dynamically measure regional brain metabolic responses to caffeine ingestion. They specifically measured changes in brain lactate due to the combined effects of caffeine's stimulation of glycolysis and reduction of cerebral blood flow. METHOD: Nine heavy caffeine users and nine caffeine-intolerant individuals, who had previously discontinued or substantially curtailed use of caffeinated products because of associated anxiety and discomforting physiological arousal, were studied at baseline and then during 1 hour following ingestion of caffeine citrate (10 mg/kg). To assess state-trait contributions and the effects of caffeine tolerance, five of the caffeine users were restudied after a 1- to 2-month caffeine holiday. RESULTS: The caffeine-intolerant individuals, but not the regular caffeine users, experienced substantial psychological and physiological distress in response to caffeine ingestion. Significant increases in global and regionally specific brain lactate were observed only among the caffeine-intolerant subjects. Reexposure of the regular caffeine users to caffeine after a caffeine holiday resulted in little or no adverse clinical reaction but significant rises in brain lactate which were of a magnitude similar to that observed for the caffeine-intolerant group. CONCLUSIONS: These results provide direct evidence for the loss of caffeine tolerance in the human brain subsequent to caffeine discontinuation and suggest mechanisms for the phenomenon of caffeine intolerance other than its metabolic effects on elevating brain lactate.