Effects of reflex stimulus intensity and stimulus onset asynchrony on prepulse inhibition and perceived intensity of the blink-eliciting stimulus

Prepulse inhibition of the blink reflex is widely applied to investigate information processing deficits in schizophrenia and other psychiatric patient groups. The present experiment investigated the hypothesis that prepulse inhibition reflects a transient process that protects preattentive processing of the prepulse. Participants were presented with pairs of blinkeliciting noises, some preceded by a prepulse at a variable stimulus onset asynchrony (SOA), and were asked to rate the intensity of the second noise relative to the first. Inhibition of blink amplitude was greater for a 110-dB (A) noise than for a 95-dB(A) noise with a 120-ms SOA, whereas there was no difference with a 30-ms SOA. The perceived intensity was also lower for the 110-dB(A) noise than for the 95-dB(A) noise with the 120-ms SOA, but not with the 30-ms SOA. The parallel results support a relationship between prepulse inhibition of response amplitude and perceived intensity. However, the prepulse did not reduce intensity ratings relative to control trials in some conditions, suggesting that prepulse inhibition is not always associated with an attenuation of the perceived impact of the blink-eliciting stimulus.

Relative contribution of expectancy and immediate arousal to the facilitatory effect of an auditory accessory stimulus

An auditory stimulus speeds up a digital response to a subsequent visual stimulus. This facilitatory effect has been related to the expectancy and the immediate arousal that would be caused by the accessory stimulus. The present study examined the relative contribution of these two influences. In a first and a third experiment a simple reaction time task was used. In a second and fourth experiment a go/no-go reaction time task was used. In each of these experiments, the accessory stimulus preceded the target stimulus by 200 ms for one group of male and female volunteers (G Fix). For another group of similar volunteers (G Var) the accessory stimulus preceded the target stimulus by 200 ms in 25% of the trials, by 1000 ms in 25% of the trials and was not followed by the target stimulus in 50% of the trials (Experiments 1a and 1b) or preceded the target stimulus by 200 ms in 6% of the trials and by 1000 ms in 94% of the trials (Experiments 2a and 2b). There was a facilitatory effect of the accessory stimulus for G Fix in the four experiments. There was also a facilitatory effect of the accessory stimulus at the 200-ms stimulus onset asynchrony for G Var in Experiments 1a and 1b but not in Experiments 2a and 2b. The facilitatory effects observed were larger in the go/no-go task than in the simple task. Taken together, these results suggest that expectancy is much more important than immediate arousal for the improvement of performance caused by an accessory stimulus.

Wideband inhibition modulates the effect of onset asynchrony as a grouping cue

Onset asynchrony is arguably the most powerful grouping cue for the separation of temporally overlapping sounds (see Bregman 1990). A component that begins only 30–50 ms before the others makes a greatly reduced contribution to the timbre of a complex tone, or to the phonetic quality of a vowel (e.g. Darwin 1984). This effect of onset asynchrony does not necessarily imply a cognitive grouping process; instead it may result from peripheral adaptation in the response to the leading component in the few tens of milliseconds before the other components begin (e.g., Westerman and Smith 1984). However, two findings suggest that the effect of onset asynchrony cannot be explained entirely by peripheral adaptation. First, though the effect is smaller, the contribution of a component to the phonetic quality of a short-duration vowel is reduced when it ends after the other components (Darwin and Sutherland 1984; Roberts and Moore 1991).

Contralateral influences of wideband inhibition on the effect of onset asynchrony as a cue for auditory grouping

Onset asynchrony is an important cue for segregating sound mixtures. A harmonic of a vowel that begins before the other components contributes less to vowel quality. This asynchrony effect can be partly reversed by accompanying the leading portion of the harmonic with an octave-higher captor tone. The original interpretation was that the captor and leading portion formed a perceptual group, but it has recently been shown that the captor effect depends on neither a common onset time nor harmonic relations with the leading portion. Instead, it has been proposed that the captor effect depends on wideband inhibition in the central auditory system. Physiological evidence suggests that such inhibition occurs both within and across ears. Experiment 1 compared the efficacy of a pure-tone captor presented in the same or opposite ear to the vowel and leading harmonic. Contralateral presentation was at least as effective as ipsilateral presentation. Experiment 2 used multicomponent captors in a more comprehensive evaluation of harmonic influences on captor efficacy. Three captors with different fundamental frequencies were used, one of which formed a consecutive harmonic series with the leading harmonic. All captors were equally effective, irrespective of the harmonic relationship. These findings support and refine the inhibitory account. © 2007 Acoustical Society of America.

The influence of adaptation and inhibition on the effects of onset asynchrony on auditory grouping

Onset asynchrony is an important cue for auditory scene analysis. For example, a harmonic of a vowel that begins before the other components contributes less to the perceived phonetic quality. This effect was thought primarily to involve high-level grouping processes, because the contribution can be partly restored by accompanying the leading portion of the harmonic (precursor) with a synchronous captor tone an octave higher, and hence too remote to influence adaptation of the auditory-nerve response to that harmonic. However, recent work suggests that this restoration effect arises instead from inhibitory interactions relatively early in central auditory processing. The experiments reported here have reevaluated the role of adaptation in grouping by onset asynchrony and explored further the inhibitory account of the restoration effect. Varying the frequency of the precursor in the range ± 10% relative to the vowel harmonic (Experiment 1), or introducing a silent interval from 0 to 320 ms between the precursor and the vowel (Experiment 2), both produce effects on vowel quality consistent with those predicted from peripheral adaptation or recovery from it. However, there were some listeners for whom even the smallest gap largely eliminated the effect of the precursor. Consistent with the inhibitory account of the restoration effect, a contralateral pure tone whose frequency is close to that of the precursor is highly effective at restoring the contribution of the asynchronous harmonic (Experiment 3). When the frequencies match, lateralization cues arising from binaural fusion of the precursor and contralateral tone may also contribute to this restoration. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Lateral asymmetry of voluntary attention orienting

We recently demonstrated that automatic attention favors the right side of space and, in the present study, we investigated whether voluntary attention also favors this side. Six reaction time experiments were conducted. In each experiment, 12 new 18-25-year-old male right-handed individuals were tested. In Experiments 1, 2, 3 (a, b) and 4 (a, b), tasks with increasing attentional demands were used. In Experiments 1, 2, 3a, and 4a, attention was oriented to one or both sides by means of a central spatially informative visual cue. A left or right side visual target appeared 100, 300, or 500 ms later. Attentional effects were observed in the four experiments. In Experiments 2, 3a and 4a, these effects were greater when the cue indicated the right side than when it indicated the left side (respectively: 16 ± 10 and 44 ± 6 ms, P = 0.015, for stimulus onset asynchrony of 500 ms in Experiment 2; 38 ± 10 and 70 ± 7 ms, P = 0.011, for Experiment 3a, and 23 ± 11 and 61 ± 10 ms, P = 0.009, for Experiment 4a). In Experiments 3b and 4b, the central cue pointed to both sides and was said to be non-relevant for task performance. In these experiments right and left reaction times did not differ. The most conservative interpretation of the present findings is that voluntary attention orienting favors the right side of space, particularly when a difficult task has to be performed.

Associative priming in color naming: Interference and facilitation

In Experiment 1, color-naming interference for target stimuli following associated primes was greater in a group making a lexical decision to the prime than in a group reading the prime silently. High-frequency targets were responded to more quickly than low-frequency targets. In Experiment 2, with subjects naming the prime, there was evidence of associative interference when the prime and the target were grouped temporally but not when the intertrial interval was comparable with the prime-target interval. Associative primes presented at a short (120-msec) prime-target stimulus onset asynchrony facilitated color naming in Experiment 3. Taken together, the results suggest that the effect of faster processing of the base word in a color-naming task is facilitatory and that color-naming priming interference arises when associative prime processing increases conflict between word and color responses by enhancing phonological or articulatory activation of the base word.

Grammatical priming of visual word recognition in fourth-grade children

Previous work examining context effects in children has been limited to semantic context. The current research examined the effects of grammatical priming of word-naming in fourth-grade children. In Experiment 1, children named both inflected and uninflected noun and verb target words faster when they were preceded by grammatically constraining primes than when they were preceded by neutral primes. Experiment 1 used a long stimulus onset asynchrony (SOA) interval of 750 msec. Experiment 2 replicated the grammatical priming effect at two SOA intervals (400 msec and 700 msec), suggesting that the grammatical priming effect does not reflect the operation of any gross strategic effects directly attributable to the long SOA interval employed in Experiment 1. Grammatical context appears to facilitate target word naming by constraining target word class. Further work is required to elucidate the loci of this effect.

Semantic priming in Alzheimer's dementia: Evidence for dissociation of automatic and attentional processes

The nature of the semantic memory deficit in dementia of the Alzheimer's type (DAT) was investigated in a semantic priming task which was designed to assess both automatic and attention-induced priming effects. Ten DAT patients and 10 age-matched control subjects completed a word naming semantic priming task in which both relatedness proportion (RP) and stimulus-onset asynchrony (SOA) were varied. A clear dissociation between automatic and attentional priming effects in both groups was demonstrated; however, the DAT subjects pattern of priming deviated significantly from that of the normal controls. The DAT patients failed to produce any priming under conditions which encouraged automatic semantic processing and produced facilitation only when the RP was high. In addition, the DAT group produced hyperpriming, with significantly larger facilitation effects than the control group. These results suggest an impairment of automatic spreading activation in DAT and have implications for theories of semantic memory impairment in DAT as well as models of normal priming. (C) 2001 Academic Press.

Lateral asymmetry of voluntary attention orienting

We recently demonstrated that automatic attention favors the right side of space and, in the present study, we investigated whether voluntary attention also favors this side. Six reaction time experiments were conducted. In each experiment, 12 new 18-25-year-old male right-handed individuals were tested. In Experiments 1, 2, 3 (a, b) and 4 (a, b), tasks with increasing attentional demands were used. In Experiments 1, 2, 3a, and 4a, attention was oriented to one or both sides by means of a central spatially informative visual cue. A left or right side visual target appeared 100, 300, or 500 ms later. Attentional effects were observed in the four experiments. In Experiments 2, 3a and 4a, these effects were greater when the cue indicated the right side than when it indicated the left side (respectively: 16 ± 10 and 44 ± 6 ms, P = 0.015, for stimulus onset asynchrony of 500 ms in Experiment 2; 38 ± 10 and 70 ± 7 ms, P = 0.011, for Experiment 3a, and 23 ± 11 and 61 ± 10 ms, P = 0.009, for Experiment 4a). In Experiments 3b and 4b, the central cue pointed to both sides and was said to be non-relevant for task performance. In these experiments right and left reaction times did not differ. The most conservative interpretation of the present findings is that voluntary attention orienting favors the right side of space, particularly when a difficult task has to be performed.

Which factors are important for crossmodal attentional effect?

Some results in the literature suggest that crossmodal attention is very sensitive to the features of the experimental protocol. The current work examined the possible contribution of the asynchrony between the onset of the cue and the target (SOA) and the kind of task performed by the observer to the manifestation of crossmodal attentional effect. In a first experiment, a target (Gabor patch), whose spatial frequency had to be discriminated, was presented 133 or 159 ms after an auditory cue, in a close location on the same side or in a distant location on the opposite side. The crossmodal attentional effect was observed only for the 159 ms SOA. In a second experiment, the SOA was again 133 ms, but the location of the target had to be discriminated, instead of its spatial frequency. A crossmodal attentional effect was observed. The results of these two experiments indicate that crossmodal attentional effect depends on the SOA and the task. It takes longer to develop when the task requires the discrimination of the spatial frequency of the target than the discrimination of its location.

Electrophysiological and behavioral correlates of stable automatic semantic retrieval in aging

Previous studies have shown both declining and stable semantic-memory abilities during healthy aging. There is consistent evidence that semantic processes involving controlled mechanisms weaken with age. In contrast, results of aging studies on automatic semantic retrieval are often inconsistent, probably due to methodological limitations and differences. The present study therefore examines age-related alterations in automatic semantic retrieval and memory structure with a novel combination of critical methodological factors, i.e., the selection of subjects, a well-designed paradigm, and electrophysiological methods that result in unambiguous signal markers. Healthy young and elderly participants performed lexical decisions on visually presented word/non-word pairs with a stimulus onset asynchrony (SOA) of 150 ms. Behavioral and electrophysiological data were measured, and the N400-LPC complex, an event-related potential component sensitive to lexical-semantic retrieval, was analyzed by power and topographic distribution of electrical brain activity. Both age groups exhibited semantic priming (SP) and concreteness effects in behavioral reaction time and the electrophysiological N400-LPC complex. Importantly, elderly subjects did not differ significantly from the young in their lexical decision and SP performances as well as in the N400-LPC SP effect. The only difference was an age-related delay measured in the N400-LPC microstate. This could be attributed to existing age effects in controlled functions, as further supported by the replicated age difference in word fluency. The present results add new behavioral and neurophysiological evidence to earlier findings, by showing that automatic semantic retrieval remains stable in global signal strength and topographic distribution during healthy aging.

The temporal impulse response function in infantile nystagmus.

Despite rapid to-and-fro motion of the retinal image that results from their incessant involuntary eye movements, persons with infantile nystagmus (IN) rarely report the perception of motion smear. We performed two experiments to determine if the reduction of perceived motion smear in persons with IN is associated with an increase in the speed of the temporal impulse response. In Experiment 1, increment thresholds were determined for pairs of successively presented flashes of a long horizontal line, presented on a 65-cd/m2 background field. The stimulus-onset asynchrony (SOA) between the first and second flash varied from 5.9 to 234 ms. In experiment 2, temporal contrast sensitivity functions were determined for a 3-cpd horizontal square-wave grating that underwent counterphase flicker at temporal frequencies between 1 and 40 Hz. Data were obtained for 2 subjects with predominantly pendular IN and 8 normal observers in Experiment 1 and for 3 subjects with IN and 4 normal observers in Experiment 2. Temporal impulse response functions (TIRFs) were estimated as the impulse response of a linear second-order system that provided the best fit to the increment threshold data in Experiment 1 and to the temporal contrast sensitivity functions in Experiment 2. Estimated TIRFs of the subjects with pendular IN have natural temporal frequencies that are significantly faster than those of normal observers (ca. 13 vs. 9 Hz), indicating an accelerated temporal response to visual stimuli. This increase in response speed is too small to account by itself for the virtual absence of perceived motion smear in subjects with IN, and additional neural mechanisms are considered.

Does Age Matter? Semantic Memory in Healthy Young and Elderly Adults

Background: Semantic memory processes have been well described in literature. However, the available findings are mostly based on relatively young subjects and concrete word material (e.g. tree). Comparatively little information exists about semantic memory for abstract words (e.g. mind) and possible age related changes in semantic retrieval. In this respect, we developed a paradigm that is useful to investigate the implicit (i.e. attentionindependent) access to concrete and abstract semantic memory. These processes were then compared between young and elderly healthy subjects. Methods: A well established tool for investigating semantic memory processes is the semantic priming paradigm, which consists both of semantically unrelated and related word pairs. In our behavioral task these noun-noun word pairs were further divided into concrete, abstract and matched pronounceable non-word conditions. With this premise, the young and elderly participants performed a lexical decision task: they were asked to press a choice of two buttons as an indication for whether the word pair contained a non-word or not. In order to minimize controlled (i.e. attention-dependent) retrieval strategies, a short stimulus onset asynchrony (SOA) of 150ms was set. Reaction time (RT) changes and accuracy to related and unrelated words (priming effect) in the abstract vs. concrete condition (concreteness effect) were the dependent variables of interest. Results and Discussion: Statistical analysis confirmed both a significant priming effect (i.e. shorter RTs in semantically related compared to unrelated words) and a concreteness effect (i.e. RT decrease for concrete compared to abstract words) in the young and elderly subjects. There was no age difference in accuracy. The only age effect was a commonly known general slowing in RT over all conditions. In conclusion, age is not a critical factor in the implicit access to abstract and concrete semantic memory.

Processing of English words with fine acoustic contrasts and simple tones: A mismatch negativity study

The purpose of this study was to compare the robustness of the event-related potential (ERP) response, called the mismatch negativity (MMN), when elicited by simple tone stimuli (differing in frequency, duration, or intensity) and speech stimuli (CV nonword contrast /de:/ vs. /ge:/ and CV word contrast /deI/ vs. /geI/). The study was conducted using 30 young adult subjects (Groups A and B; n = 15 each). The speech stimuli were presented to Group A at a stimulus onset asynchrony (SOA) of 610 msec and to Group B at an SOA of 900 msec. The tone stimuli were presented to both groups at an SOA of 610 msec. MMN responses were elicited by the simple tone stimuli (66.7%-96.7% of subjects with MMN "present," or significantly different from zero, p < 0.05) but not the speech stimuli (10% subjects with MMN present for nonwords, 10% for words). The length of the SOA (610 msec or 900 msec) had no effect on the ability to obtain consistent MMN responses to the speech stimuli. The results indicated a lack of robust MMN elicited by speech stimuli with fine acoustic contrasts under carefully controlled methodological conditions. The implications of these results are discussed in relation to conflicting reports in the literature of speech-elicited MMNs, and the importance of appropriate methodological design in MMN studies investigating speech processing in normal and pathological populations.