Classification of frequencies into ranges by songbirds and humans.

We trained songbirds and humans in go/no-go discriminations among 27 tones. In the compact discrimination, S?+?s formed a contiguous middle range (3080–4040 Hz), and S?–?s formed contiguous lower (2000–2960 Hz) and upper (4160–5120 Hz) ranges. In the distributed discrimination, S?+?s were spread across all 3 ranges. Songbirds acquired the compact discrimination more quickly and with higher accuracy than humans. Songbirds acquired the distributed discrimination only after much extended training; humans did not acquire the distributed discrimination. Compact groups (birds and humans) accurately classified test tones spaced 60 Hz from the training tones, but the distributed groups did not. A single reversal in discrimination between tones on the boundary between the lower S– and middle S+ ranges did not propagate to all the tones in either range. A neural network model provided an account of the classification of tones in songbirds and humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of human eye blink by brief acoustic stimulus.

A corneal air puff (S2) which elicited eye blinks in 10 undergraduates either appeared alone (control) or was preceded by a brief acoustic stimulus (S1) at a variety of temporal intervals (50-2,020 msec). Amplitude of the eye-blink response to S2 was depressed by S1 at short intervals as compared with control trials; peak inhibition appeared at about 70 msec of S1-S2 separation and declined at longer intervals. An intense S1 was more effective than a weak S1 at short intervals. Inhibition was independent of prior experience with S1 and S2 and of overt responding to S1, and no systematic change in inhibition occurred during testing. The temporal course of inhibition was the same as that previously obtained with the acoustic-startle reflex in rats and the nictitating membrane reflex to circumorbital shock in rabbits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Augmentation of the rat's acoustic startle reflex by nonreflexogenic stimuli.

The size of the rat's acoustic startle reflex was augmented by brief acoustic clicks (which did not themselves elicit startle) presented several milliseconds before the reflex-eliciting stimulus (RS). The same clicks presented after the RS gave relatively weak augmentation that was present in the 1st, but not the 2nd, testing session. Brief footshocks set to 75% of each animal's flinch threshold augmented startle when presented both before and after the RS in both testing sessions. Augmentation by a leading footshock increased with shock intensity and also with the intensity of the RS. Augmentation by a trailing footshock increased with shock intensity and also with the intensity of the RS. Reflex size is not fixed at the time of reflex elicitation but can be augmented by a later nonreflexogenic stimulus. Reflex augmentation may be caused by the 2nd member of a stimulus pair discharging elements of the reflex pathway that were partially activated by the 1st. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gamma-range activity evoked by coherent visual stimuli in humans

We tested the hypothesis of a role of gamma-range synchronized oscillatory activity in visual feature binding by recording evoked potentials from 12 subjects to three stimuli: two coherent ones (a Kanizsa triangle and a real triangle) and a non-coherent one (a Kanizsa triangle in which the inducing disks had been rotated so that no triangle could be perceived). The evoked potentials were analysed by convoluting the signal for each subject and each stimulation type by Gabor wavelets centred from 28 up to 46 Hz, providing a continuous measure of frequency-specific power over time. A first peak of activity was found around 38 Hz and 100 ms with a maximum at electrode Cz in each experimental condition. A second peak of activity occurred around 30 Hz and 230 ms, with a maximum at O1 in response to the real triangle and a maximum at Cz in the case of the illusory triangle. At 100 ms we did not find any variations of the gamma-band component of the evoked potential with stimulation type, but the power of the 30 Hz component of the evoked potential between 210 and 290 ms differed from noise only in the case of a coherent triangle, no matter whether real or illusory. We thus found a 30 Hz component whose power correlates with stimulus coherency, which supports the hypothesis of a functional role of high-frequency synchronization in feature binding.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the identification of repeatedly presented brief visual stimuli.

Discusses 2 hypotheses concerning the explanation of increasing perceptual performance with temporal repetition of tachistoscopically-presented visual stimuli. R. N. Haber's conception in terms of increasing phenomenal clarity is criticized, primarily for the confounding influence of the "stimulus error." An alternative explanation in terms of the perceptual independence of successive inputs is presented. The assumption of independence is built into a model that combines aspects of C. W. Eriksen's "clearest form" approach with Bayesian decision theory. 4 items of support for independence are presented. Eriksen found (a) no effect of interstimulus interval on accuracy; and (b) no difference in accuracy whether a form was preceded by the same or a different form, or by a flash. Previous studies by the present authors found (a) lack of influence of the locus on an inconsistent stimulus in a sequence, and (b) quite accurate Bayesian predictions of multiple observation performance in 3 experiments using equal prior probabilities of the stimulus states. (39 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in the selection and use of features for classifying visual stimuli

Two experiments were performed to investigate the classification of pot-like outlines by human judges. In experiment 1, seventy-two pot-like shapes, drawn by using all possible combinations of values of four pot ratios, were classified by twenty subjects and by a computer program. The shapes varied only in quantitative features and possessed no all-or-none characteristics. In experiment 2,256 shapes traced from drawings of existing pots were classified by fifteen judges. The pots varied in both quantitative and all-or-none features. The results showed that there were differences between judges in the weightings they assigned to different features, and the judges themselves could be classified according to the weightings they gave the features. There were even differences in the way different judges used all-or-none features for classifying. Possible mechanisms are suggested for the basis of these differences.     

Hunger selectively modulates corticolimbic activation to food stimuli in humans.

Functional magnetic resonance imaging (fMRI) was used to determine whether visual responses to food in the human amygdala and related corticolimbic structures would be selectively altered by changes in states of hunger. Participants (19–44 yr olds) viewed images of motivationally relevant (food) and motivationally irrelevant (tool) objects while undergoing FMRI in alternately hungry and satiated conditions. Food-related visual stimuli elicited greater responses in the amygdala, parahippocampal gyrus, and anterior fusiform gyrus when participants were in a hungry state relative to a satiated state. The state-dependent activation of these brain structures did not generalize to the motivationally irrelevant objects. These results support the hypothesis that the amygdala and associated inferotemporal regions are involved in the integration of subjective interoceptive states with relevant sensory cues processed along the ventral visual stream. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masking of electrical by acoustic stimuli: behavioral evidence for tonotopic organization

When pure-tone acoustic masking stimuli of various frequencies were presented simultaneously with electrical stimuli applied to cochlear nucleus, only those maskers within a limited frequency range interfered with the detection of the electrical stimuli. The form of the masking functions obtained suggest that the electrical stimulus directly activated only a small population of neurons which were functioning in a tonotopic fashion.     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): II. Vocal signals.

Operant conditioning and multidimensional scaling procedures were used to study auditory perception of complex sounds in the budgerigar. In a same–different discrimination task, budgerigars learned to discriminate among natural vocal signals. Multidimensional scaling procedures were used to arrange these complex acoustic stimuli in a two-dimensional space reflecting perceptual organization. Results show that budgerigars group vocal stimuli according to functional and acoustical categories. Studies with only contact calls show that birds also make within-category discriminations. The acoustic cues in contact calls most salient to budgerigars appear to be quite complex. There is a suggestion that the sex of the signaler may also be encoded in these calls. The results from budgerigars were compared with the results from humans tested on some of the same sets of complex sounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): I. Pure tones.

A new combination of operant conditioning and psychophysical scaling procedures was used to study auditory perception in a small bird. In a same–different discrimination task, budgerigars learned to discriminate among pure tones that varied along one or more acoustic dimensions. Response latencies were used to generate a matrix of interstimulus similarities. Multidimensional scaling procedures were used to arrange these acoustic stimuli in a multidimensional space that supposedly reflects the bird's perceptual organization. For tones that varied in intensity, duration and frequency simultaneously, budgerigars were much more sensitive to frequency changes. From a set of tones that varied only in intensity, it was possible to calculate the growth of loudness with intensity for the budgerigar. For tones that varied only in frequency, budgerigars showed evidence of an "acoustic fovea" for frequency change in the spectral region of 2–4 kHz. Budgerigars and humans also differed in their perceptual grouping of tone sequences that rise, fall, or remain constant in pitch. Surprisingly, budgerigars were much less responsive to pitch contour than were humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): III. Contact calls.

We trained budgerigars by operant conditioning to discriminate among a set of contact calls in a same–different task and analyzed response latencies from this task by using multidimensional-scaling (MDS) and cluster-analysis procedures. Humans listened to the same calls and indicated the similarity between pairs of calls by a direct rating procedure. An MDS program ({sindscal}) was used to arrange these complex acoustic stimuli in multidimensional space reflecting perceptual organization. Multiple regression techniques were used to identify the acoustic characteristics of contact calls that were correlated with the peceptual dimensions obtained from MDS. A number of spectral characteristics (e.g., peak frequency, rate of frequency modulation, and concentration of spectral energy) emerged as important for both budgerigars and humans, but the relative salience of these cues differed for the two species. Additional tests with two groups of budgerigars—cagemates and noncagemates—showed that experience with calls can change the salience of various acoustic characteristics used for perceptual organization and individual recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early potentials evoked by acoustic stimuli: further results (author's transl)

The research work carried out during the last years explains only partially the true nature of the short-latency (less than 50 ms) auditory evoked responses (PEP) in man. Widespread support is given to the hypothesis suggesting a double origin: myogenic and cortical with varying predominance between the two according to the position of the active electrodes and the stimulation parameters. PEP appears to have different characteristics according to the electrode coupling, i.e. inion-lobe, vertex-parietal, and vertex-mastoid. Experiments carried out on normally hearing subjects, on subjects with normal hearing but with marked vestibular signs, and on subjects with severe hearing loss and normal vestibular findings show that the presence of auditory function is one of the essential conditions for the generation of the PEP. Conversely, no influence on PEP is apparent following simultaneous and bilateral inhibition of the steady action potential of the ampullary nerve. Whichever the theoretical origin of the PEP is, it may be concluded that, since the results obtained during the clinical work are still incomplete and controversial, it is not possible to consider the PEP as a true expression of the vestibular function.     

Reflex-inhibiting stimuli and the refractory period of the acoustic startle reflex in the rat.

Previous studies show that if acoustic startle stimuli are presented in pairs, then the reaction to the 2nd stimulus (S2) is reduced, with the size of the refractory decrement determined by the interstimulus interval and the relative intensity of the 1st stimulus (S1). If a neutral stimulus (p) is presented just prior to S1, then the reaction to S1 is similarly inhibited, revealing the phenomenon of prestimulus inhibition. In 2 experiments with male albino Holtzman rats (N = 24) it was found that suppression of the reflex to S2 by S1 was unaffected by prestimulus inhibition of S1 (i.e., reflex amplitudes associated with S2 were identical in pS1-S2 series and S1-S2 series). In contrast, a reduction in the intensity of S1 relative to S2 did reduce the effect of S1 on S2. These data indicate that prestimulus inhibition of the reflex to S1 does not result because the preliminary stimulus attenuates the sensory impact of S1. The inhibitory process may be presumed to have a central locus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of brief and ultrabrief pulse stimuli in unilateral ECT

Exposure of NIH 3T3 cells to 375 mM ethanol at 37 degrees C for 20 min could induce a rapid increase in the protein level and cellular activity of oncogenic proline-directed protein kinase FA/glycogen synthase kinase-3 alpha (PDPK FA/GSK-3 alpha), up to approximately 300% of the control level, in a time- and concentration-dependent manner. The maximal inductive effect on PDPK FA/GSK-3 alpha also occurred within 40 min when cells were treated with only 100 mM ethanol. Similarly, exposure of NIH 3T3 cells to 100 microM cadmium for 2 h could induce a rapid increase in the protein level and cellular activity of PDPK FA/GSK-3 alpha, up to approximately 250% of the control level, in a time- and concentration-dependent manner. The maximal inductive effect on this kinase reached within 3 h when cells were treated with only 50 microM cadmium. The results demonstrate that PDPK FA/GSK-3 alpha may not represent a constitutively active/mitogen-inactivated protein kinase as previously conceived. Taken together with the previous report that PDPK FA/GSK-3 alpha is a heat-inducible protein kinase, the results further demonstrate that PDPK FA/GSK-3 alpha may represent a typical cellular stresses-inducible protein kinase subject to early induction by heat, ethanol and cadmium.     

Temporal integration of acoustic stimulation obtained in reflex inhibition in rats and humans.

Investigated whether inhibition provided by initial stimuli of various durations conforms to established temporal integration functions. Initial stimuli (S1) were noise bursts varying in duration (2, 20, or 200 msec) and intensity (55 or 85 db). Eliciting stimuli (S2) for 6 Holtzman rats were intense tone bursts, which elicited the acoustic startle reflex, and for 9 19–24 yr old humans were electrotactile stimuli to the forehead, which elicited the eye blink. Findings reveal that inhibition was greater with the 85-db S1 stimulus and increased linearly with log increases in duration. Data suggest that the acoustic substrate for reflex inhibition has a long-time constant. There was one exception to this general finding. For 7 human Ss, inhibition declined when the duration of the 85-db S1 was increased from 20 to 200 msec. Postexperimental questioning and video monitoring suggest that this anomaly resulted from a reflex-enhancing arousal process. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention capture by novel stimuli.

In several experiments, observers were given glimpses of 4-word arrays. Accuracy of word localization was tested after each array. Some words, called familiar, appeared many times across the series of arrays; others, called novel, appeared only once. The ratio of novel to familiar words in an array ranged from 0:4 to 4:0. When familiar and novel words were not intermixed (in 0:4 and 4:0 arrays), localization accuracy was higher for familiar words. However, when they were intermixed, especially in 1:3 arrays, accuracy tended to be higher for the novel words. This novel popout effect was the outcome of the suppressed localizability of the familiar words (relative to the 0:4 baseline) and the enhanced localizability of the novel words (relative to the 4:0 baseline). Novel popout may reflect an automatic orientation of attention away from more fluently unfolding regions of the perceptual field (familiar objects) and toward less fluently unfolding regions (novel objects). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans.

Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occurs within minutes of acquisition. However, a limited number of human extinction studies have shown that short interval extinction does not prevent the return of fear. For this reason, we performed an in-depth parametric analysis of human fear extinction using fear-potentiated startle. Using separate single-cue and differential conditioning paradigms, participants were fear conditioned and then underwent extinction either 10 min (Immediate) or 72 hr (Delayed) later. Testing for spontaneous recovery occurred 96 hr after acquisition. In the single cue paradigm, the Immediate and Delayed groups exhibited differences in context, but not fear, conditioning. With differential conditioning, there were no differences in context conditioning and the Immediate group displayed less spontaneous recovery. Thus, the results remain inconclusive regarding spontaneous recovery and the timing of extinction and are discussed in terms of performing translational studies of fear in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response suppression in humans as a function of contingent and non-contingent punishment: Signal properties of stimuli.

Trained an instrumental goal (G) response in 40 undergraduates in 4 groups under intermittent reward (money). When the acquisition criterion was met, reward was withdrawn and different punishment treatments administered. Group C received contingent punishment (electric shock) of the G response whenever it was omitted. Shock occurring on a variable interval schedule provided noncontingent punishment to another group (NC). Contingent and noncontingent punishments were combined and administered to Group C and NC. The 4th group (E) served as a control and received no punishment. This entire study was repeated, and both experiments indicate that the C treatment yielded most suppression, even exceeding that obtained under the C and NC procedure which administered more punishments. Results favor the notion that punishment acts in an analogous, but opposite direction to reward, and that its consequences may be predicted on the basis of the consistency of the information conveyed by a punisher. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing and reaction time.

Because reaction time (RT) tasks are generally repetitive and temporally regular, participants may use timing strategies that affect response speed and accuracy. This hypothesis was tested in 3 serial choice RT experiments in which participants were presented with stimuli that sometimes arrived earlier or later than normal. RTs increased and errors decreased when stimuli came earlier than normal, and RTs decreased and errors increased when stimuli came later than normal. The results were consistent with an elaboration of R. Ratcliff's diffusion model (R. Ratcliff, 1978; R. Ratcliff & J. N. Rouder, 1998; R. Ratcliff, T. Van Zandt, & G. McKoon, 1999), supplemented by a hypothesis developed by D. Laming (1979a, l979b), according to which participants initiate stimulus sampling before the onset of the stimulus at a time governed by an internal timekeeper. The success of this model suggests that timing is used in the service of decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved)