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PubMedDate not supplied

Orbital prefrontal cortex and guidance of instrumental behavior of rats by visuospatial stimuli predicting reward magnitude.

The orbital prefrontal cortex (OPFC) is part of a circuitry mediating the perception of reward and the initiation of adaptive behavioral responses. We investigated whether the OPFC is involved in guidance of the speed of instrumental behavior by visuospatial stimuli predictive of different reward magnitudes. Unoperated rats, sham-lesioned rats, and rats with bilateral lesions of the OPFC by N-methyl-D-aspartate (NMDA) were trained in a visuospatial discrimination task. The task required a lever press on the illuminated lever of two available to obtain a food reward. Different reward magnitudes were permanently assigned to lever presses to respective sides of the operant chamber; that is, responses to one lever (e.g., the left one) were always rewarded with one pellet and responses to the other lever with five pellets. On each trial, the position of the illuminated lever was pseudorandomly determined in advance. Results revealed that OPFC lesions did not impair acquisition of the task, as the speed of conditioned responses was significantly shorter with expectancy of a high reward magnitude. In addition, during reversal, shift and reshift of lever position-reward magnitude contingencies and under extinction conditions, performance of the OPFC-lesioned and control groups did not differ. It is concluded that the OPFC in rats might not be critical for adapting behavioral responses to changes of stimulus-reward magnitude contingencies signaled by visuospatial cues.

Animals↗
PubMed2004

Dissociable roles of the human somatosensory and superior temporal cortices for processing social face signals.

Faces are multi-dimensional stimuli bearing important social signals, such as gaze direction and emotion expression. To test whether perception of these two facial attributes recruits distinct cortical areas within the right hemisphere, we used single-pulse transcranial magnetic stimulation (TMS) in healthy volunteers while they performed two different tasks on the same face stimuli. In each task, two successive faces were presented with varying eye-gaze directions and emotional expressions, separated by a short interval of random duration. TMS was applied over either the right somatosensory cortex or the right superior lateral temporal cortex, 100 or 200 ms after presentation of the second face stimulus. Participants performed a speeded matching task on the second face during one of two possible conditions, requiring judgements about either gaze direction or emotion expression (same/different as the first face). Our results reveal a significant task-stimulation site interaction, indicating a selective TMS-related interference following stimulations of somatosensory cortex during the emotional expression task. Conversely, TMS of the superior lateral temporal cortex selectively interfered with the gaze direction task. We also found that the interference effect was specific to the stimulus content in each condition, affecting judgements of gaze shifts (not static eye positions) with TMS over the right superior temporal cortex, and judgements of fearful expressions (not happy expressions) with TMS over the right somatosensory cortex. These results provide for the first time a double dissociation in normal subjects during social face recognition, due to transient disruption of non-overlapping brain regions. The present study supports a critical role of the somatosensory and superior lateral temporal regions in the perception of fear expression and gaze shift in seen faces, respectively.

Adult↗
PubMed1987

Perception of front vowels: the role of harmonics in the first formant region.

Vowel matching and identification experiments were carried out to investigate the perceptual contribution of harmonics in the first formant region of synthetic front vowels. In the first experiment, listeners selected the best phonetic match from an F1 continuum, for reference stimuli in which a band of two to five adjacent harmonics of equal intensity replaced the F1 peak; F1 values of best matches were near the frequency of the highest frequency harmonic in the band. Attenuation of the highest harmonic in the band resulted in lower F1 matches. Attenuation of the lowest harmonic had no significant effects, except in the case of a 2-harmonic band, where higher F1 matches were selected. A second experiment investigated the shifts in matched F1 resulting from an intensity increment to either one of a pair of harmonics in the F1 region. These shifts were relatively invariant over different harmonic frequencies and proportional to the fundamental frequency. A third experiment used a vowel identification task to determine phoneme boundaries on an F1 continuum. These boundaries were not substantially altered when the stimuli comprised only the two most prominent harmonics in the F1 region, or these plus either the higher or lower frequency subset of the remaining F1 harmonics. The results are consistent with an estimation procedure for the F1 peak which assigns greatest weight to the two most prominent harmonics in the first formant region.

Female↗
PubMed1988

Detection of complex echoes in noise by an echolocating dolphin.

Dolphins echolocate with short broadband acoustic signals that have good time resolution properties. Received echoes are often complex, with many resolvable highlights or components caused by reflection of the incident signal from external and internal boundaries of a target and from different propagational modes within a target. A series of experiments was performed to investigate how dolphins perceive complex echoes. Echoes were produced by a microprocessor-controlled electronic target simulator that captured each emitted click and retransmitted the signal back to the animal after an appropriate time delay. The use of this "phantom" target allowed for precise control of the number of highlights, the time separation between highlights, and the relative amplitudes of highlights in the simulated echoes. An echolocating dolphin was trained to perform a target detection task in the presence of masking noise using these phantom echoes. The properties of simulated echoes were systematically varied, and corresponding shifts in the dolphin's detection threshold were observed, allowing for inferences of how the dolphin perceived echoes. The dolphin performed like an energy detector with an integration time of approximately 264 microseconds.

Acoustic Stimulation↗
PubMed1999

Impairment of EEG desynchronisation before and during movement and its relation to bradykinesia in Parkinson's disease.

OBJECTIVE: It has been suggested that the basal ganglia act to release cortical elements from idling (alpha) rhythms so that they may become coherent in the gamma range, thereby binding together those distributed activities necessary for the effective selection and execution of a motor act. This hypothesis was tested in 10 patients with idiopathic Parkinson's disease. METHODS: Surface EEG was recorded during self paced squeezing of the hand and elbow flexion performed separately, simultaneously, or sequentially. Recordings were made after overnight withdrawal of medication and, again, 1 hour after levodopa. The medication related improvement in EEG desynchronisation (in the 7.5-12.5 Hz band) over the 1 second before movement and during movement were separately correlated with the improvement in movement time for each electrode site. Correlation coefficients (r) > 0.632 were considered significant (p<0.05). RESULTS: Improvement in premovement desynchronisation correlated with reduction in bradykinesia over the contralateral sensorimotor cortex and supplementary motor area in flexion and squeeze, respectively. However, when both movements were combined either simultaneously or sequentially, this correlation shifted anteriorly, to areas overlying prefrontal cortex. Improvement in EEG desynchronisation during movement only correlated with reduction in bradykinesia in two tasks. Correlation was seen over the supplementary motor area during flexion, and central prefrontal and ipsilateral premotor areas during simultaneous flex and squeeze. CONCLUSIONS: The results are consistent with the idea that the basal ganglia liberate frontal cortex from idling rhythms, and that this effect is focused and specific in so far as it changes with the demands of the task. In particular, the effective selection and execution of more complex tasks is associated with changes over the prefrontal cortex.

Aged↗
PubMed2004

Catechol O-methyltransferase Val158Met polymorphism in schizophrenia: differential effects of Val and Met alleles on cognitive stability and flexibility.

OBJECTIVE: The catechol O-methyltransferase (COMT) Val158Met polymorphism has been associated with cognitive and behavioral phenotypes in schizophrenia. Whether COMT genotype is beneficial may depend on phenotype definition. The authors examined the effects of COMT genotype on a task that distinguishes imitation from reversal learning. They hypothesized that the Val and Met alleles would be associated with deficits in imitation learning and reversal learning, respectively. METHOD: Twenty-six patients with schizophrenia and schizoaffective disorder completed a task requiring alternation between imitation and reversal rules. RESULTS: Met homozygotes showed better acquisition of the imitation rule but greater deficit shifting from imitation to reversal. Val homozygotes had poorer imitation performance and slower reaction times. CONCLUSIONS: The Met allele, by increasing tonic dopamine, may promote cognitive stability but limit cognitive flexibility.

Adult↗
PubMed2006

The human dorsal premotor cortex generates on-line error corrections during sensorimotor adaptation.

A number of different sites in the human brain have been shown to play a role in sensorimotor adaptation. However, the specific role played by each of these structures in the learning process is poorly understood. In the present study, the contribution of the dorsal aspect of the premotor cortex was examined by disrupting activity at this site using transcranial magnetic stimulation (TMS) while subjects wearing prism goggles pointed at visual targets. This manipulation slowed down the rate of adaptation when vision of the hand was available throughout the movement and reduced the presence of on-line trajectory corrections. This was accompanied by a reduced shift in the felt position of the arm. In contrast, TMS did not cause any alteration in the performance of this task when vision of the hand was available only at the end of the movement. Thus, we infer from this pattern of results that the human dorsal premotor cortex contributes to the generation of the visually based on-line error corrections that are responsible for the remapping of arm position sense underlying sensorimotor adaptation.

Adaptation, Physiological↗
PubMed2000

Life in transition: balancing inertial and viscous forces by planktonic copepods.

Copepods (1-10 mm aquatic crustaceans moving at 1-1000 mm s(-1)) live at Reynolds numbers that vary over 5 orders of magnitude, from 10(-2) to 10(3). Hence, they live at the interface between laminar and turbulent regimes and are subject to the physical constraints imposed by both viscous and inertial realms. At large scales, the inertially driven system enforces the dominance of physically derived fluid motion; plankton, advected by currents, adjust their life histories to the changing oceanic environment. At Kolmogorov scales, a careful interplay of evenly matched forces of biology and physics occurs. Copepods conform or deform the local physical environment for their survival, using morphological and behavioral adaptations to shift the balance in their favor. Examples of these balances and transitions are observed when copepods engage in their various survival tasks of feeding, predator avoidance, mating, and signaling. Quantitative analyses of their behavior give measures of such physical properties of their fluid medium as energy dissipation rates, molecular diffusion rates, eddy size, and eddy packaging. Understanding the micromechanics of small-scale biological-physical-chemical interactions gives insight into factors influencing large-scale dynamics of copepod distribution, patchiness, and encounter probabilities in the sea.

Animals↗
PubMed2001

Absolute pitch in infant auditory learning: evidence for developmental reorganization.

To what extent do infants represent the absolute pitches of complex auditory stimuli? Two experiments with 8-month-old infants examined the use of absolute and relative pitch cues in a tone-sequence statistical learning task. The results suggest that, given unsegmented stimuli that do not conform to the rules of musical composition, infants are more likely to track patterns of absolute pitches than of relative pitches. A 3rd experiment tested adults with or without musical training on the same statistical learning tasks used in the infant experiments. Unlike the infants, adult listeners relied primarily on relative pitch cues. These results suggest a shift from an initial focus on absolute pitch to the eventual dominance of relative pitch, which, it is argued, is more useful for both music and speech processing.

Adult↗
PubMed1983

[Changes in the electric organization of the brain in visual search and discrimination processes of different degrees of difficulty].

EEG activity during visual search processes with different degrees of discrimination difficulty was investigated in 13 male subjects. In accordance with the paradigm used by Neisser, 17 corresponding lists of rounded or angular letters were displayed. The task was to select the target letter Z from each list. The discrimination of the letter Z out of the lists of angular letters is the more difficult task. Spectral analysis shows a significant change in alpha-frequency structure during the more difficult search process. There is a shift of the dominant alpha-frequency from 11.5 to 10 Hz with a significant increase and concentration of power in the dominant frequency. This concentration of alpha-power around 10 Hz is more pronounced in the right occipital region than in the left. Concomitantly, there is a significant increase of power in subharmonic theta-frequencies. By consecutive principal analysis of spectral data these results were further differentiated and confirmed. The changes in the alpha- and theta-band during the more difficult search process are the expression of a complex transformation of EEG-frequency structure and patterning which cannot be interpreted by the usual concepts based on the theory of activation. Moreover, they seem to be the neurophysiological correlate of the accommodation (Piaget) of the neurodynamic processes to the altered perceptual conditions and to their effects on the internal matching process.

Adult↗
PubMedDate not supplied

Oedipal grief: mourning or melancholia?

A discussion of "Oedipal Grief" by Robert May, Ph.D. A clinical syndrome seen in late adolescent men, oedipal grief refers to a depressive state sustained by a vengeful conscience and a pattern of self-punitive acting out. The psychopathology of this syndrome is clarified and differentiated sharply from the normal developmental process of grieving the loss of an idealized oedipal father. As a form of developmental melancholia, the repressed ambivalence and weakening of the ego in this syndrome is highlighted. May's reconceptualization of the structural-instinctual model of the superego and ego ideal is then critically reviewed; his tendency to reduce oedipal to preoedipal developmental phenomena is noted. A more developmentally differentiated theoretical model is suggested in terms of the incomplete internalization of the functions of self-control and self-esteem in the type of adolescent personality organization which underlies, and is perpetuated by, the psychopathology in the oedipal grief syndrome. The main task of brief psychotherapy is thus to promote the ego's capacity to tolerate increased inner conflict so that a developmental shift toward greater internalization can take place. The skillful treatment conducted by May is reinterpreted in these terms; and the therapeutic facilitation of adolescent grieving is placed in the context of structural-developmental change.

Child Development↗
PubMedDate not supplied

[The characteristics of the latent periods of movements in cats during the differentiation of tonal and amplitude-modulated signals with changes in the modulation from high frequencies to low].

The latent periods of the forepaw movements of cats were studied in the course of differentiation task performance. Pure tones and amplitude-modulated stimuli had to be differentiated. It was found out that the mean latency of motor responses to pure tones was significantly higher than that of responses to modulated signals. The latencies to the applied stimuli did not differ in the simple task (without differentiation). The latencies were influenced not only by the absolute values of modulation frequency but also by the frequency shift in successive experiments. Lowering modulation frequency decreased the latency. This effect was especially expressed around the values of 205-207 and 33-34 Hz.

Acoustic Stimulation↗
PubMed1998

Breathing patterns and heart rate during simulated occupational upper limb tasks in normal subjects.

BACKGROUND AND PURPOSE: Despite the arms being used extensively in the performance of many occupational tasks, little is known about the pattern of breathing and physiological cost of such work. The purpose of this study was to establish whether a simple change in arm support could alter the workload, pattern of breathing and respiratory muscle recruitment during a low intensity arm task. METHODS: Ten normal subjects performed a simulated work task when sitting, once with the arms supported and once unsupported. Subjects were required, over a five-minute period, to repeatedly pick up a 2 kg object, inspect and hold it for 15 seconds and then pack it in a box. Breathing pattern responses, measured by pneumotachograph and respiratory inductive plethysmography, were minute ventilation (VE), respiratory frequency (Rf), tidal volume (VT) and change in functional residual capacity (FRC). RESULTS: The main findings were that unsupported arm work was more physiologically demanding than supported arm work. During work VE increased as a result of a change in respiratory frequency but not VT which was much more limited when the arms were unsupported. At the completion of activity, when the arms were unloaded, VT initially increased as VE decreased. FRC and VT were reduced during arm work and increased during recovery, mainly as a result of a change in ribcage excursion. CONCLUSIONS: These findings support the theory that during arms activity, intercostal and accessory respiratory muscles act to stabilize the arms and torso, impeding chest wall movement and shifting the respiratory load from these muscles to the diaphragm. This may adversely effect performance of workers who have ventilatory limits to arm work tasks.

Adolescent↗
PubMed2006

Part-time and full-time medical specialists, are there differences in allocation of time?

BACKGROUND: An increasing number of medical specialists prefer to work part-time. This development can be found worldwide. Problems to be faced in the realization of part-time work in medicine include the division of night and weekend shifts, as well as communication between physicians and continuity of care. People tend to think that physicians working part-time are less devoted to their work, implying that full-time physicians complete a greater number of tasks. The central question in this article is whether part-time medical specialists allocate their time differently to their tasks than full-time medical specialists. METHODS: A questionnaire was sent by mail to all internists (N = 817), surgeons (N = 693) and radiologists (N = 621) working in general hospitals in the Netherlands. Questions were asked about the actual situation, such as hours worked and night and weekend shifts. The response was 53% (n = 411) for internists, 52% (n = 359) for surgeons, and 36% (n = 213) for radiologists. Due to non-response on specific questions there were 367 internists, 316 surgeons, and 71 radiologists included in the analyses. Multilevel analyses were used to analyze the data. RESULTS: Part-time medical specialists do not spend proportionally more time on direct patient care. With respect to night and weekend shifts, part-time medical specialists account for proportionally more or an equal share of these shifts. The number of hours worked per FTE is higher for part-time than for full-time medical specialists, although this difference is only significant for surgeons. CONCLUSION: In general, part-time medical specialists do their share of the job. However, we focussed on input only. Besides input, output like the numbers of services provided deserves attention as well. The trend in medicine towards more part-time work has an important consequence: more medical specialists are needed to get the work done. Therefore, a greater number of medical specialists have to be trained. Part-time work is not only a female concern; there are also (international) trends for male medical specialists that show a decline in the number of hours worked. This indicates an overall change in attitudes towards the number of hours medical specialists should work.

Adult↗
PubMed1979

Dynamic phase-shifts between theta generators in the rat hippocampus.

Winson [13] reported on two independent phase-reversed generators in the rat hippocampus. In the present study the synchrony between the two generators was investigated during the sleep-wakefulness cycle and during a behaviour-dependent discriminative learning task. Electrical activities derived from the CA 1 region and dentate gyrus were in phase during slow wave sleep but phase-reversed during the awake state and paradoxical sleep. The degree of phase-reversal was significantly higher during running than during lever pressing. These findings demonstrate that substantial changes occur within the hippocampal circuitry during dynamic shifts of behaviour.

Animals↗
PubMed2005

Carbamazepine induced pitch shift and octave space representation.

Octave-circular pitch perception, the repetition of pitch scale qualities when surpassing the octave interval, has been observed in behavioral data from humans and monkeys, but the underlying anatomy and physiology is still unknown. Here we analyze octave circularity in a concert pianist with absolute pitch, both under medication with the neurotropic drug carbamazepine (CBZ) and without medication. Analysis of 4619 responses in a pitch identification task revealed an internal tone-scale representation, based on the norm-tone scale re A4=440 Hz, with an octave-circular pattern of strongly and weakly represented tones. CBZ caused a global down-shift of pitch (ca. 1 semitone at 500 Hz), but no down-shift of the octave-circular pattern of tone characteristics. This pattern was similar in the six tested octave ranges (32.7-2093 Hz), both under the control and the CBZ condition. Pattern repetition always occurred at octave intervals and did not reflect the stretched octaves of piano tuning. The results indicate that CBZ influences pitch detection peripheral of an octave-circular pitch representation. Thus they support previous evidence for pitch detection in the auditory midbrain and for octave-circular pitch mapping in the auditory thalamus.

Acoustic Stimulation↗
PubMed2000

Shifts in the psychometric function and their implications for models of timing.

This study examined how two models of timing, scalar expectancy theory (SET) and learning to time (LeT), conceptualize the learning process in temporal tasks, and then reports two experiments to test these conceptualizations. Pigeons responded on a two-alternative free-operant psychophysical procedure in which responses on the left key were reinforceable during the first two, but not the last two, quarters of a 60-s trial, and responses on the right key were reinforceable during the last two, but not the first two, quarters of the trial. In Experiment 1 three groups of birds experienced a difference in reinforcement rates between the two keys only at the end segments of the trial (i.e., between the first and fourth quarters), only around the middle segments of the trial (i.e., between the second and third quarters), or in both end and middle segments. In Condition 1 the difference in reinforcement rate favored the left key; in Condition 2 it favored the right key. When the reinforcement rates differed in the end segments of the trial, the psychometric function--the proportion of right responses across the trial--did not shift across conditions; when it occurred around the middle of the trial or in both end and middle segments, the psychometric function shifted across conditions. Experiment 2 showed that the psychometric function shifts even when the overall reinforcement rate for the two keys is equal, provided the rates differ around the middle of the trial. This pattern of shifts of the psychometric function is inconsistent with SET. In contrast, LeT provided a good quantitative fit to the data.

Animals↗