Human brain activity related to speed discrimination tasks

This study examined the ionic mechanism of ibutilide, a class III antiarrhythmic in clinical use, on freshly isolated human atrial cells. Cells had resting potentials of -71.4 +/- 2.4 mV, action potentials with overshoot of 36.8 +/- 1.8 mV, duration of 265 +/- 89 msec at 90% repolarization and slow repolarization (n = 16). Ibutilide, at 10(-7) M, markedly increased action potential duration. Four types of outward currents were detected: Ito, Iso, a delayed rectifier and IK1. Ibutilide had no inhibitory effect on these outward currents at 10(-7) M (n = 28). In K(+)-free solutions and -40 mV holding potential, mean peak inward current at 20 mV was -1478 +/- 103 pA (n = 12). Ibutilide increased this current to -2347 +/- 75 pA at 10(-7) M, with half maximal effect (Kd) of 0.1 to 0.9 nM between -10 and +40 mV (n = 21). At similar concentrations, the drug increased APD, with Kd of 0.7 and 0.23 nM at 70 and 90% repolarization, respectively (n = 8). Ibutilide shifted the mid-point of the steady-state inactivation curve from -21 to -12.2 mV (n = 6), and reduced current decline during repetitive depolarization (n = 5). The drug induced inward current was carried by Na+o through a nifedipine inhibited inward channel because Na+o removal eliminated the effect, and nifedipine abolished the inward current and the drug induced APD prolongation. We propose that a Na+ current through the L-type Ca++ channel mediates ibutilide's potent clinical class III antiarrhythmic action.     

Human abilities revealed through auditory tests.

Used established findings from studies of visual, musical, and speech perception abilities to guide the construction of auditory ability tests. 44 measures based on these tests were obtained from a sample of 241 adult males (mean age 25.64 yrs). Correlation and factorial analyses were used to indicate structural interrelationships and relationships with education, musical experience, general intelligence, and age. The results indicate separate capacities for Auditory Verbal Comprehension, Auditory Immediate Memory, Temporal Tracking, Auditory Cognition of Relationships, Discrimination Among Sound Patterns, Speech Perception Under Distraction/Distortion, and Maintaining and Judging Rhythm. (61 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes of auditory word discrimination induced by inversion of the visual field.

Examined auditory discrimination in normal hospital staff members during induced visual conflict. Discrimination of words accompanied by background noise was measured at 6 speech-signal-noise intensity levels during preexperimental (normal vision), experimental (inverted vision), and postexperimental (normal vision) periods. A control condition (no inverted vision) served as a check for the possible effects of practice or fatigue. Significant losses of word discrimination occurred only in the inverted vision condition. Discrimination losses occurred at all intensity levels in which speech was accompanied by noise, prior to walking in the inverted vision condition, following a walking period, and after removal of inversion eyepieces. Results are attributed to a process of visually induced conflict in which Ss were unable to decenter the altered contents of vision. Affinities between reports of induced alterations of experience and pathological alterations of experience are discussed. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generalized auditory same-different discrimination by pigeons.

Three pigeons were trained in a successive same/different (S/D) procedure using compound auditory stimuli (pitch/timbre combinations). Using a go/no-go procedure, pigeons successfully learned to discriminate between sequences of either all same (AAAA...or BBBB...) or all different (ABCD...) sequences consisting of 12 sounds. Both pitch and timbre were subsequently established as controlling dimensions. Transfer tests with novel stimuli revealed a generalized basis for the discrimination (novel pitch/timbre combinations, novel pitches, novel instruments, and complex natural & man-made sounds). These results indicate for the first time that pigeons can learn generalized same/different discriminations in a nondominant modality. When combined with earlier visual results, they support a qualitative similarity among birds and primates in their capacity to judge this type of fundamental stimulus relation across different modalities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human auditory evoked potentials during speech-voice activity]

Pectinesterase (PE), from commercial orange peels or ammonium sulfate fractionation (50-80% saturation) of pea pods, was detected on polyacrylamide gels after native acidic polyacrylamide gel electrophoresis (PAGE) or sodium dodecyl sulfate (SDS)-PAGE by using the synthetic substrate beta-naphthyl acetate (beta-NA). The release of beta-naphthol (at 322 nm) from beta-NA was proportional to PE activity. The PE activity bands on polyacrylamide gels after native acidic PAGE or SDS-PAGE were stained with a combination of tetrazotized o-dianisidine and beta-NA. This fast and sensitive method can be used for enzyme purification and characterization.     

Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials

Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.     

Relationship between auditory intensity discrimination in noise and olivocochlear efferent system activity in humans

The intravenous (i.v.) steroid anesthetic, eltanolone, compares favorably to propofol with respect to its induction characteristics. This double-blind investigation was designed to compare the induction and recovery profile of eltanolone (versus propofol) when it was used for both induction and maintenance of ambulatory anesthesia. Eighty-three consenting ASA physical status I-III outpatients undergoing minor gynecologic or urologic procedures lasting 10-40 min were randomly assigned to one of three anesthetic treatment groups. All patients received midazolam, 2 mg i.v., and fentanyl, 50 micrograms i.v., before induction of anesthesia. The control group (Group 1) was induced with propofol, 2.4 mg/kg i.v. (18-60 yr or ASA physical status I or II) or 1.6 mg/kg i.v. (61-80 yr and/or ASA physical status III), followed by intermittent bolus doses of 0.6 mg/kg i.v. in combination with N2O 67% for maintenance of anesthesia. In Group 2, anesthesia was induced with eltanolone, 0.75 mg/kg i.v., (18-60 yr and/or ASA physical status I or II) or 0.5 mg/kg i.v. (61-80 yr and/or ASA physical status III), and maintained with intermittent bolus injections of 0.2 mg/kg i.v. and N2O 67%. Group 3 received eltanolone, 1.0 mg/kg i.v. (18-60 yr and/or ASA physical status I or II), or 0.75 mg/kg i.v. (61-80 yr and/or ASA physical status III), followed by intermittent bolus injections of 0.2 mg/kg i.v. and N2O 67%. In addition to recording the induction and recovery times and side effects, psychomotor testing was performed before and at 30-min intervals after anesthesia. Induction times (57 +/- 23, 67 +/- 26, and 61 +/- 22s, respectively) were similar in all three groups. Although eltanolone produced no pain on injection (versus 52% in the propofol group), 10% of the eltanolone-treated patients (versus none in the propofol group) developed transient cutaneous (rash-like) reactions. The total dose of study medication used during the anesthetic period was 9.2 +/- 3.7 mg.kg-1.h-1 in the propofol group compared with 3.3 +/- 1.4 mg.kg-1.h-1 and 3.3 +/- 1.9 mg.kg-1.h-1 in Groups 2 and 3, respectively. Early recovery times were significantly shorter after propofol anesthesia. However, times to ambulation, micturition, and being judged "fit for discharge," as well as recovery of cognitive function, were similar in all three groups. Although ethanolone seems to be a safe and effective i.v. anesthetic, these data suggest that it is unlikely to replace propofol in the ambulatory setting. Implications: Eltanolone is an investigational steroid anesthetic that causes less pain on injection and less cardiovascular depression than propofol (the most widely used intravenous anesthetic in the outpatient setting). Unfortunately, emergence from anesthesia after ambulatory surgery is slower with eltanolone compared with propofol. Therefore, it is unlikely that eltanolone will replace propofol for outpatient anesthesia.     

Differential glycosylation of auditory and vestibular hair bundle proteins revealed by peanut agglutinin

Up to four morphologically distinct types of cross-link are found between the stereocilia in the hair bundles of avian hair cells. These links are involved in mechanotransduction, force transmission across the bundle, and maintenance of hair bundle structure. They appear to be specialisations of the cell coat, but very little is known about their molecular composition. Chick inner ear tissues were therefore screened with a number of different lectins to find markers for specialisations of the hair bundle surface. One lectin, peanut agglutinin (PNA), which recognises the dissacharide Gal beta 1-3GalNAc, was found to be a fairly selective marker for vestibular hair bundles, but it does not stain the stereocilia of auditory hair cells. The staining patterns observed with PNA in the vestibular system closely resemble those seen with a monoclonal antibody (mab) directed against a 275 kD component of the hair cell's apical surface known as the hair-cell antigen (HCA). However, unlike PNA, the mab recognises both vestibular and auditory hair cells. A detailed comparison of the fluorescence staining patterns observed with PNA and the anti-HCA mab indicates that binding sites for both ligands spatially codistribute on the surface of vestibular hair cells. The lectin and the anti-HCA mab binding sites are both sensitive to trypsin treatment, and, with sections of the vestibular system, PNA pretreatment blocks subsequent anti-HCA mab staining. Immunoelectron microscopy of vestibular hair bundles shows that PNA and the anti-HCA mab both label a type of cross-link known as the shaft connector. This link type is present on both auditory and vestibular hair bundles but reacts with PNA only in the vestibular system. The lectin jacalin, which has greater specificity for Gal beta 1-3GalNAc than does PNA, also only labels vestibular and not auditory hair bundles. Although terminal sialic acid residues can block both PNA and jacalin binding, neuraminidase treatment does not unmask cryptic binding sites for these lectins on auditory hair cells but does reveal PNA and jacalin staining at a number of other locations in the inner ear. The results obtained with the lectins PNA and jacalin indicate that either the HCA or other components of the shaft links are differentially glycosylated in the vestibular and auditory epithelia of the bird. The functional significance for such a difference in glycosylation remains to be determined, but auditory and vestibular hair cells operate over different frequency ranges, and variations in glycosylation might confer different micromechanical properties on the hair bundles in these two systems.     

Receptive field plasticity in the auditory cortex during frequency discrimination training: Selective retuning independent of task difficulty.

Classical conditioning is known to induce frequency-specific receptive field (RF) plasticity in the auditory cortex (ACx). This study determined the effects of discrimination training on RFs at 2 levels of task difficulty. Single unit and cluster discharges were recorded in the ACx of adult guinea pigs trained in a tone-shock frequency discrimination paradigm (30 intermixed trials each of positive CS [CS+]-shock and negative CS [CS–] alone) with behavioral performance indexed by the cardiac deceleration CR. After training in an easy task in which Ss developed discriminative CRs, they were trained in a difficult task (reduced frequency distance between CS+ and CS–) in which they failed to discriminate. However, frequency-specific RF plasticity developed at both levels of task difficulty. Responses to the frequency of the CS+ were increased, whereas responses to other frequencies, including the CS– and the prepotent best frequency (BF) were reduced. In many cases, tuning was shifted such that the frequency of the CS+ became the new BF. The effects were present or stronger after a 1-hr retention interval. The role of RF plasticity in the ACx is discussed for behavioral performance and information storage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional specialization in auditory cortex: responses to frequency-modulated stimuli in the cat's posterior auditory field

The mammalian auditory cortex contains multiple fields but their functional role is poorly understood. Here we examine the responses of single neurons in the posterior auditory field (P) of barbiturate- and ketamine-anesthetized cats to frequency-modulated (FM) sweeps. FM sweeps traversed the excitatory response area of the neuron under study, and FM direction and the linear rate of change of frequency (RCF) were varied systematically. In some neurons, sweeps of different sound pressure levels (SPLs) also were tested. The response magnitude (number of spikes corrected for spontaneous activity) of nearly all field P neurons varied with RCF. RCF response functions displayed a variety of shapes, but most functions were of low-pass characteristic or peaked at rather low RCFs (<100 kHz/s). Neurons with strong responses to high RCFs (high-pass or nonselective RCF response function characteristics) all displayed spike count-SPL functions to tone burst onsets that were monotonic or weakly nonmonotonic. RCF response functions and best RCFs often changed with SPL. For most neurons, FM directional sensitivity, quantified by a directional sensitivity (DS) index, also varied with RCF and SPL, but the mean and width of the distribution of DS indices across all neurons was independent of RCF. Analysis of response timing revealed that the phasic response of a neuron is triggered when the instantaneous frequency of the sweep reaches a particular value, the effective Fi. For a given neuron, values of effective Fi were independent of RCF, but depended on FM direction and SPL and were associated closely with the boundaries of the neuron's frequency versus amplitude response area. The standard deviation (SD) of the latency of the first spike of the response decreased with RCF. When SD was expressed relative to the rate of change of stimulus frequency, the resulting index of frequency jitter increased with RCF and did so rather uniformly in all neurons and largely independent of SPL. These properties suggest that many FM parameters are represented by, and may be encoded in, orderly temporal patterns across different neurons in addition to the strength of responses. When compared with neurons in primary and anterior auditory fields, field P neurons respond better to relatively slow FMs. Together with previous studies of responses to modulations of amplitude, such as tone onsets, our findings suggest more generally that field P may be best suited for processing signals that vary relatively slowly over time.     

Ethanol consumption by rats is inversely related to hepatic alcohol dehydrogenase activity

Under normal circumstances the rate of hepatic ethanol oxidation and the rate at which ethanol is removed from the blood are dependent on the hepatic activity of alcohol dehydrogenase. It is possible that ethanol metabolism, and thus hepatic alcohol dehydrogenase, could influence ethanol consumption. In this study 11 adult female Wistar rats were provided with 20% ethanol as their sole drinking fluid and ethanol consumption was measured. After a further period of drinking tap water, the hepatic alcohol dehydrogenase activity was determined. A significant inverse relationship was found between the ethanol consumption by the rats and the hepatic activity of alcohol dehydrogenase (P < 0.05). This enzyme could therefore play a role in determining the amount of alcohol an animal will consume.     

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)     

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.     

Neuronal responses across cortical field A1 in plasticity induced by peripheral auditory organ damage

The adult auditory cortex is capable of a plastic reorganization of its tonotopic map after damage to restricted parts of the cochlear sensory epithelium. We examine the precise conditions of cochlear damage required to demonstrate such plasticity in the primary auditory cortex (A1) of the cat and the changes observed in neuronal responses in the A1 which has reorganized in plasticity of the tonotopic map. From these data we attempt to predict the conditions required for similar plasticity to occur in humans after cochlear damage.     

Poor children learning to read do not have trouble with auditory discrimination but do have trouble with phoneme recognition.

The present study confirms the hypothesis, derived from the research of M. A. Wallach and L. Wallach (1976) and L. Wallach and M. A. Wallach (1976), on teaching disadvantaged children to read, that the troubles poor children frequently have with sounds stem not from deficiencies in auditory discrimination but from inadequate skill in phonemic analysis. Almost all of 76 disadvantaged and 70 middle-class kindergarten-age Ss could readily hear phoneme differences in words, as indicated by their ability to respond differentially to words that differed only in single phonemes, which were similar. On the other hand, almost all of the disadvantaged Ss, but almost none of the middle-class Ss, did very poorly on tasks involving phonemic analysis of words (e.g., indicating whether given sounded phonemes occurred in various spoken words). (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition and aging: Similarities between younger and older adults as revealed by the processing of unattended auditory information.

The ability to selectively attend to an auditory stimulus appears to decline with age and may result from losses in the ability to inhibit the processing of irrelevant stimuli (i.e., the inhibitory deficit hypothesis; L. Hasher & R. T. Zacks, 1988). It is also possible that declines in the ability to selectively attend are a result of age-related hearing losses. Three experiments examined whether older and younger adults differed in their ability to inhibit the processing of distracting stimuli when the listening situation was adjusted to correct for individual differences in hearing. In all 3 experiments, younger and older adults were equally affected by irrelevant stimuli, unattended stimuli, or both. The implications for auditory attention research and for possible differences between auditory and visual processing are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

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 fear conditioning is related to dopaminergic and serotonergic biological markers.

Biological markers for acquisition and extinction of fear conditioning were studied in 40 individuals selected for displaying either good or poor acquisiton of fear conditioning, as estimated by the skin conductance response. Participants with a short serotonin transporter (5-HTT) promoter allele or low monoamine oxidase activity in platelets (trbc-MAO) displayed better acquisition than those with only long alleles or high trbc-MAO, whereas participants with a long dopamine D4 receptor (D4DR) exon III allele showed delayed extinction compared with those with only short alleles. The findings, that D4DR exon III and 5-HTT promotor genotypes and trbc-MAO activity are related to human fear conditioning, a basic form of associative learning, are consistent with animal studies suggesting a genetic contribution to fear conditioning. The authors suggest that in humans these genetic mechanisms are partly dopaminergic and serotonergic in origin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)