Successive Stimulus Presentations Research Articles

A Treatment Evaluation of Successive and Simultaneous Visual Stimulus Presentation During Tact Training with Children with Autism

A Treatment Evaluation of Successive and Simultaneous Visual Stimulus Presentation During Tact Training with Children with Autism

Performance of working memory of musicians and non-musicians in tests with letters, digits, and geometrical shapes

Background. Recent researches points out that musical training might have a positive influence on human cognitive domain and working memory improvements are thought to mediate this influence. However, there is some discrepancy among results of researches dealing with working memory testing of musicians and non-musicians. Materials and Methods. The participants were the students who for 10–15 years had been engaged in regular musical practice (musicians) and their peers who had no previous musical experience (non-musicians). A computerized working memory test for letters, digits and shapes with successive presentation of stimuli was applied in the current study. Results. Musicians and non-musicians did not differ in the overall number of mistakes and latency of responses made in all subtests for letters, digits and shapes. The left hand made significantly more mistakes than the right one in both groups, but this regularity was more typical of non-musicians. The right hand responded faster than the left one while doing all subtests in both groups, but such a motor asymmetry was more evident for nonmusicians. Musicians mostly did not demonstrate an increase in latency of responses with task complexity growing from set to set of stimuli, while non-musicians did. Conclusions. The efficiency of working memory test performance did not differ among musicians and non-musicians. Musicians have tighter interhemispheric cooperation during the memory test and that was indicated by a lesser motor asymmetry. Musicians have almost equal latency of responses regardless of task complexity, while non-musicians require more time for responding to stimuli during growing task complexity, probably because of using different search patterns in working memory or tighter interhemispheric cooperation.

Temporal Modulations of Contact Force during Haptic Surface Exploration.

Individuals constantly modulate their exploratory movements and adapt their internal hypotheses to incoming sensory information to achieve a thorough and realistic percept. Perception depends on the exploratory movements as well as influencing them. While this seems to be common sense, scientifically we know very little about the temporal dynamics during haptic exploration. To address this, we investigated the exploratory force modulations of two groups of healthy young adults during the exploration of grated surfaces with differing detection difficulty during successive (n = 20) and random stimulus presentation (n = 20). Results showed that exploratory force depended on stimulus properties and increased with increasing detection difficulty. Both experiments yielded the same direction of results with slightly smaller effects in the random stimulus presentation group. Across exploration time average fingertip force also increased. The biggest increase occurred systematically at the beginning (within the first 40 percent) of exploration time per stimulus indicating that most critical information is received during the initial contact phase and is directly transformed into the exploration procedure and force application. Furthermore, video-analyses and comparisons to our high temporal resolution data revealed strong dynamic changes in pressure application during test stimulus exploration with differences in the force dynamics and exploration strategies of simple and difficult stimuli.

Effects of Successive and Simultaneous Stimulus Presentations on Absolute and Relational Stimulus Control in Adult Humans

Human participants can readily learn to demonstrate absolute or relational stimulus control, but little is known about human’s tendencies toward one form of control or another in situations that allow either form of control to be expressed. To examine these tendencies, we combined elements of the procedures used to study peak shift and stimulus transposition. In Experiment 1, half of the 40 participants received successive discrimination training and the other half received simultaneous discrimination training with line-length stimuli. All participants then received both a generalization test and a transposition test. Absolute stimulus control predominated except under the combination of simultaneous discrimination training and a transposition test. In Experiment 2, 40 additional participants were trained with 2 pairs of training stimuli instead of 1 in what was otherwise an identical procedure. The results suggested a shift toward relational control. A novel form of relational control was observed in some participants (chiefly those who received successive discrimination training) that involved selective stimulus transposition. Specifically, participants selected the stimulus that matched the relation of S+ to S-, but only when both test lines were similar to the S + s.

Analyzing the Stimulus Control Acquisition in Simple Discrimination Tasks through Eye Movement

In order to investigate whether simultaneous or successive presentation of stimuli is related to the duration of eye fixation (i.e., the time spent gazing a specific stimulus), this study described the eye movements of young adults in simultaneous and successive simple discrimination tasks. Using 12 landscape scenes as visual stimuli, three participants were exposed to a simple discrimination training with simultaneously presented stimuli (Si Procedure) and then to a second simple discrimination training with successively presented stimuli (Su Procedure). Another three participants were exposed to the Procedure in the opposite order. In both cases, the learning criterion was that at least 90% of the responses should be correct in one block. Eye movements were recorded during the whole experiment. Participants achieved the learning criteria in both procedures. Beyond that, eye fixation time in the Su Procedure was higher than in the Si Procedure, regardless of the training sequence. Taken together with previous results in different experiments, our findings suggest that the duration of eye fixation plays a central role in the establishment of different stimulus control topographies.

Age-related declines in hemispheric asymmetry as revealed in the binaural interaction component

The binaural interaction component (BIC) is a physiological index of binaural processing. The BIC is defined as the brain activity resulting from binaural (diotic or dichotic) stimulus presentation minus the brain activity summed across successive monaural stimulus presentations. Smaller binaural-induced activity relative to summed monaural activity is thought to reflect neural inhibition in the central auditory pathway. Since aging is commonly associated with reduced inhibitory processes, we evaluate the hypothesis that the BIC is reduced with increasing age. Furthermore, older listeners typically have reduced hemispheric asymmetry relative to younger listeners, interpreted in terms of compensation or recruitment of neural resources and considered an indication of age-related neural plasticity. Binaural stimuli designed to elicit a lateralized percept generate maximum neural activity in the hemisphere opposite the lateralized position. In this investigation, we evaluated the hypothesis that the BIC resulting from stimuli lateralized to one side (due to interaural time differences) results in less hemispheric asymmetry in older than younger listeners with normal hearing. Behavioral data were obtained to assess the acuity of binaural processing. Data support the interpretation that aging is marked by reduced central auditory inhibition, reduced temporal processing, and broader distribution of activity across hemispheres compared to young adults.

Cognitive Set Reconfiguration Signaled by Macaque Posterior Parietal Neurons

When faced with problems, we can flexibly change our ways of thinking or our point of view. Our cognitive flexibility arises from this ability of shifting cognitive sets. To elucidate how this dynamic process is implemented in the primate brain, single-unit activity was recorded from the posterior parietal cortex (PPC) of two monkeys performing analogs of the Wisconsin Card Sorting Test, which is most commonly used to test cognitive flexibility in humans. We successfully trained the monkeys to promptly perform set shifting, mostly within a single trial, and found shift-related activity: PPC neurons were transiently activated when the monkeys shifted from one cognitive set to another, but not when they shifted in the opposite direction. This shift-related activity emerged about 4 s before the actual behavioral responses, and it well predicted whether the cognitive set would be successfully shifted. These results provide insights into single-unit level mechanisms of cognitive flexibility.

How fast small things become large: Dynamic change in judgment

Judgments are context bound. Moreover, in most situations, context is changing; hence judgments often reflect a dynamic adaptation to these changes. This study is on working memory load as a factor that potentially moderates speed of adaptation to new context. Two specific stimulus formats used in generalization tests, simultaneous vs successive presentation, were intended to reflect substantial differences in memory load. Conditions that place a higher memory load on the respondent (successive presentation) should show slower changing effects than do conditions that entail a lower memory load (simultaneous presentation). Sixty participants were trained in two stimulus two forced‐choice visual discriminations of size. Later generalization tests included more extreme visual stimuli. The stimulus that was seen as neither “small” nor “large” (50% ratings each) changed in the direction of the central stimuli within the stimulus series, with both successive and simultaneous stimulus presentation (adaptation). Multilevel regression analyses showed that change increased gradually in successive stimulus presentation, whereas change was immediate in simultaneous presentation. A significant three‐way interaction indicated that generalization was faster with simultaneous presentation of generalization test stimuli than with successive presentation. The results showed that the speed of Point of Subjective Indifference (PSI) shift depends on the mental representation of experience that is strongly related to working memory. The study therefore makes a contribution to the understanding the speed of behavioural change during transition, e.g., the transition from school to work. On a macro‐level, model application may assist rapid learning and behavioural adaptation, for instance when individuals change from one cultural context to another.

The neurochemical basis of human cortical auditory processing: combining proton magnetic resonance spectroscopy and magnetoencephalography

BackgroundA combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate the electrophysiology of rapid auditory processing and the neurochemistry of the auditory cortex in 15 healthy adults. To assess rapid auditory processing in the left auditory cortex, the amplitude and decrement of the N1m peak, the major component of the late auditory evoked response, were measured during rapidly successive presentation of acoustic stimuli. We tested the hypothesis that: (i) the amplitude of the N1m response and (ii) its decrement during rapid stimulation are associated with the cortical neurochemistry as determined by proton magnetic resonance spectroscopy.ResultsOur results demonstrated a significant association between the concentrations of N-acetylaspartate, a marker of neuronal integrity, and the amplitudes of individual N1m responses. In addition, the concentrations of choline-containing compounds, representing the functional integrity of membranes, were significantly associated with N1m amplitudes. No significant association was found between the concentrations of the glutamate/glutamine pool and the amplitudes of the first N1m. No significant associations were seen between the decrement of the N1m (the relative amplitude of the second N1m peak) and the concentrations of N-acetylaspartate, choline-containing compounds, or the glutamate/glutamine pool. However, there was a trend for higher glutamate/glutamine concentrations in individuals with higher relative N1m amplitude.ConclusionThese results suggest that neuronal and membrane functions are important for rapid auditory processing. This investigation provides a first link between the electrophysiology, as recorded by magnetoencephalography, and the neurochemistry, as assessed by proton magnetic resonance spectroscopy, of the auditory cortex.

Performing hand actions assists the visual discrimination of similar hand postures

Recent theoretical work has suggested that internal predictive signals are used for motor control and coordination. The predictive signal – proposed to be the output of a forward model – would be a sensory representation of action. Hence, these sensory representations could potentially influence other sensory processes. We report here how performance of hand actions assisted the visual discrimination of target hand postures presented at random times within an on-going series of hand images. Reaction times to discriminate the targets were significantly shorter when the displayed images were both sequential and congruent with the action being performed. Hence, the planning or execution of action appears to allow better prediction of a displayed series of congruent images. In further control experiments, we show that the motor–visual priming effect is unlikely to be due to differential attentional demands and it is specific to a first person perspective display; it is short lasting, being lost if a 500 ms delay is introduced between successive stimulus presentations. The data are interpreted as evidence supporting the hypothesis that forward models in the motor system provide action-specific sensory predictions that are available to cognitive processes.

The effect of temporal delay and spatial differences on cross-modal object recognition.

In a series of experiments, we investigated the matching of objects across visual and haptic modalities across different time delays and spatial dimensions. In all of the experiments, we used simple L-shaped figures as stimuli that varied in either the x or the y dimension or in both dimensions. In Experiment 1, we found that cross-modal matching performance decreased as a function of the time delay between the presentation of the objects. We found no difference in performance between the visual-haptic (VH) and haptic-visual (HV) conditions. Cross-modal performance was better when objects differed in both the x and y dimensions rather than in one dimension alone. In Experiment 2, we investigated the relative contribution of each modality to performance across different interstimulus delays. We found no differential effect of delay between the HH and VV conditions, although general performance was better for the VV condition than for the HH condition. Again, responses to xy changes were better than changes in the x or y dimensions alone. Finally, in Experiment 3, we examined performance in a matching task with simultaneous and successive presentation conditions. We failed to find any difference between simultaneous and successive presentation conditions. Our findings suggest that the short-term retention of object representations is similar in both the visual and haptic modalities. Moreover, these results suggest that recognition is best within a temporal window that includes simultaneous or rapidly successive presentation of stimuli across the modalities and is also best when objects are more discriminable from each other.

Symmetry training in pigeons can produce functional equivalences.

Functional stimulus equivalence has been demonstrated using a transfer of training design with matching-to-sample training in which two sample stimuli are associated with the same comparison stimulus (A-B, C-B; many-to-one matching). Equivalence is shown by training a new association (A-D) and demonstrating the presence of an emergent relation (C-D). In the present experiment, we show that symmetry training, in which a bidirectional association is trained between two stimuli (A-B, B-A, using successive stimulus presentations followed by reinforcement), can also produce functional equivalence using a transfer of training design (i.e., train B-C, test A-C). The results suggest that training pigeons in the substitutability of two stimuli may be sufficient to produce functional stimulus equivalence between them. The results also have implications for the development of an emergent transitive relation, because training on A-B and B-C relations results in the emergence of an untrained A-C relation, if B-A training also is provided.

A multichannel PC tachistoscope with high resolution and fast display change capability.

The number of channels that PC tachistoscopes can have has increased recently (Bokhorst, 1995; Myors, 1998); however, neither the quality of display nor speed of image switching has been improved. This article shows the capability of VESA's VBE 3.0 standard (1998) for increasing the number of channels of high-quality images. And the refresh rate can be set to the fastest cathode ray tube (CRT) scanning rate the monitor can tolerate in order to reduce the timing delay of changing display. A PCTSCOPE library was written in C to provide these capabilities, which is compatible with conventional DOS real mode. The PC tachistoscope can have numbers of channels with various resolutions and colors and different refresh rates. For example, 25 images with the resolution of 640 x 480 pixels and 256 colors can be loaded to video memory, and vertical refresh rate can be set to 180 Hz. It takes less than 6 msec to change the display among 25 channels in synchronizing with the start of the video scanning frame. In this library, the number of channels, the resolution of the images, and the speed of changing display all are improved. The multichannel PC tachistoscope with this technique is especially suitable for research requiring high-quality images and rapid successive presentation of stimuli.

Multiple perceptual distortions and their modulation in leftsided visual neglect

There is an ongoing debate concerning the perception and neural representation of space in neglect. Four experiments are here reported designed to further investigate the nature of perceptual distortions and their modifiability in patients with neglect. In Experiment 1 it was found that neglect patients, in contrast to left- or right-hemisphere lesioned control patients and normal subjects, show similar distortions of perceived visual space when judging the extension of horizontal distances ( space distortion) as compared to the horizontal size of objects ( size distortion). Similar deficits were present in most neglect patients in a newly developed space bisection task. These results attest that neglect patients have perceptual distortions related to within-object (size) and between-object (distance) spatial processing in their horizontal plane. Objects were oversized by 33% and distances by 19% horizontally in neglect patients, whereas all control groups showed nearly veridical spatial coding (deviations<5%). In Experiment 2 the modifiability of these distortions was tested by the use of slow visual background motion. Leftward, coherent background motion transiently restored normal horizontal size and distance coding in neglect patients, whereas rightward motion aggravated the deficit significantly in the distance task, but not in the size task. None of the other subject groups showed any influence of background motion on spatial judgments. Experiment 3 evaluated possible effects of simultaneous vs successive stimulus presentation in perceptual distortions, thus modulating attentional factors. Neglect patients performed significantly better — although not normal — with a successive presentation of the spatial stimuli (2 s, 10 s delay) as compared to the simultaneous condition in the size judgment task, but not in the distance task. In contrast, this manipulation had no effects in any of the control groups. Experiment 4 reports more detailed results of subject J.S., a neglect patient with a right mediotemporal lesion, who showed a marked horizontal size distortion, but normal horizontal distance judgments. Despite some fluctuation in J.S.’s size judgments he showed a significant overestimation of horizontal object size by +22% to +40% across several test blocks and testing sessions. Thus, performance fluctuations due to attentional or other reasons cannot fully account for J.S.’s dissociation in size vs distance judgments. He thus shows that the visual coding of horizontal spatial extension within an object can be dissociated from that of the spatial extension between objects along the horizontal plane. Finally, performance in the three spatial tasks (used in Experiment 1) was found to correlate significantly with three typical tests of spatial neglect (line bisection, cancellation, copying, r=0.42–0.77), thereby indicating a significant relationship to the neglect syndrome. Together, the results of the four experiments are interpreted in support of multiple spatial–perceptual distortions in visual neglect, which are influenced by visual motion and attention. Perceptual distortions relating to objects and space between objects are present in most neglect patients, but may dissociate, as in case J.S. It is argued that these might reflect the existence of several, partially overlapping and diverging neural maps for the representation of different spatial attributes in the horizontal plane. Furthermore, it is hypothesized that these perceptual distortions constitute an important element of the spatial–perceptual deficits encountered in the syndrome, contribute to its severity, but are not the key deficit of the disorder.

Response-independent habituation of the orienting response in the preweanling rat

The effect of pattern of stimulus presentation on habituation of the cardiac component of the orienting response to an auditory stimulus was investigated in four experiments. The duration of stimulus presentation was held constant, but some animals were given six 10-sec stimulus presentations and others were given a single 60-sec stimulus. During the first 10 sec of the auditory stimulus, heart rate (HR) decreased approximately 40 beats per minute (bpm) in both groups, but during subsequent 10-sec epochs, the changes in HR were markedly different in the two groups. For those animals given a single 60-sec stimulus, the cardiac orienting response did not habituate; that is, HR either continued to decrease or remained approximately 40 bpm below baseline. In contrast, those animals given six 10-sec stimulus presentations showed smaller decreases in HR with each successive stimulus presentation, and after approximately four presentations, no detectable change in HR was observed. Despite these dramatic differences in habituation of the cardiac component of the orienting response, neither group oriented to the auditory stimulus when it was presented again following a short retention interval. Moreover, with increasing retention intervals, both groups showed the same forgetting function (reappearance of the orienting response). The implications of these findings for theories of the orienting response as well as theories of habituation are discussed.

Conditional discrimination learning by pigeons: The role of simultaneous versus successive stimulus presentations.

Conditional discrimination learning by pigeons: The role of simultaneous versus successive stimulus presentations.

Event-related potential correlates of impaired attention in schizophrenic children

Electrophysiological correlates of focused attention were studied in 13 schizophrenic and 19 age- and gender-matched children. Subjects performed a version of the Continuous Performance Task (CPT) in which a target was designated as any digit from 0 through 9 occurring on two successive stimulus presentations. Signal digits were surrounded by distractor digits which varied in position, value, and number. Event-related potentials (ERPs) elicited by each stimulus of a target pair were recorded from midline and homologous parietal, temporal, and occipital electrode placements. Schizophrenic children made significantly more errors of omission and commission than normal children. The amplitude and time course of the intertrial CNV was the same for both groups. There was a circumscribed amplitude asymmetry, left smaller than right, for the P1/N1 and P2 measures which was greater in normal than in schizophrenic children. The P3 component was significantly larger to the second stimulus of the target pair than to the first for both groups and larger for the normal than the schizophrenic children to both stimuli.

Conditional discrimination learning by pigeons: The role of simultaneous versus successive stimulus presentations.

Conditional discrimination learning by pigeons: The role of simultaneous versus successive stimulus presentations.

Attempts to demonstrate magnetic discrimination by homing pigeons in flight

Eight homing pigeons, trained to fly between two elevated feeders within a flight tunnel, were tested for their ability to discriminate between two magnetic field stimuli and two acoustic stimuli, using a unitary discrete-trials procedure with successive presentation of stimuli. Magnetic stimuli consisted of the ambient magnetic field and a reduced magnetic field in which the vertical component of the field was reduced to 50% of its ambient value. Acoustic stimuli consisted of an ambient white noise and the white noise plus a tone. Stimuli were paired with food reward and either a time penalty (Experiment 1) or electric shock (Experiment 2). Although subjects could discriminate sounds with our procedures, none of the subjects demonstrated discrimination of magnetic fields. The failure of pigeons to discriminate magnetic stimuli is discussed as a consequence of either the failure to provide conditions sufficient for such discrimination or the absence of a magnetic sense in these animals.

Differential effects of phenylbutazone and local anesthetics on nociception in the equine

The effects of procaine, mepivacaine and phenylbutzone on pain perception in the equine were studied using two behavioral assays of nociception; the thermal evoked hoof withdrawal reflex and skin twitch reflex. Pain perception threshold was measured as the latency from onset of thermal stimuli to reflex withdrawal of the forelimb or contraction of the cutaneous musculature. Procaine 2% and mepuvacaine 2% prolonged the hoof withdrawal reflex latency when administered locally by producing a block of the palmar and metacarpal nerves. Significant analgesia lasted 90 min and 210 min for procaine and mepivacaine, respectively. Phenylbutzaone (7.3 mg/kg) failed to alter pain thresholds measured over a 36 h post-treatment period. However, pain thresholds rose over time with successive trials. These data suggest that in the equine (1) phenylbutazone does not alter normal cutaneous pain perception, and (2) successive presentation of painful stimuli increases nociceptive thresholds.