Location and frequency cues in auditory selective attention

The roles of frequency and location cues in auditory selective attention were investigated in a series of experiments in which target tones were distinguished from distractors by frequency, location, or the conjunction of frequency and location features. When frequency separations in high-rate tone sequences were greater than 1 octave, participants were fastest at identifying targets defined by frequency and were sometimes faster at identifying conjunction than location targets. Frequency salience diminished as filtering demands were reduced: At long interstimulus intervals (> 2.0 s), performance was superior in location conditions. The results suggest that frequency may play a role in auditory selective attention tasks analogous to the role of spatial position in visual attention.     

Effects of rhyme and spelling patterns on auditory word ERPs depend on selective attention to phonology

ERP responses to spoken words are sensitive to both rhyming effects and effects of associated spelling patterns. Are such effects automatically elicited by spoken words or dependent on selectively attending to phonology? To address this question, ERP responses to spoken word pairs were investigated under two equally demanding listening tasks that directed selective attention either to sub-syllabic phonology (i.e., rhyme judgments) or to melodies embedded within the words. ERPs elicited when participants selectively attended to phonology demonstrated a rhyming effect that was concurrent with online stimulus encoding and an orthographic effect that emerged later. ERP responses to the same stimuli presented under melodic focus, however, showed no evidence of sensitivity to rhyme or spelling patterns. Results reveal limitations to the automaticity of such ERP effects, suggesting that rhyme effects may depend, at least to some degree, on allocation of attention to phonology, which may in turn activate task-incidental orthographic information.     

Perceptual hysteresis in the judgment of auditory pitch shift

Perceptual hysteresis can be defined as the enduring influence of the recent past on current perception. Here, hysteresis was investigated in a basic auditory task: pitch comparisons between successive tones. On each trial, listeners were presented with pairs of tones and asked to report the direction of subjective pitch shift, as either “up” or “down.” All tones were complexes known as Shepard tones (Shepard, 1964), which comprise several frequency components at octave multiples of a base frequency. The results showed that perceptual judgments were determined both by stimulus-related factors (the interval ratio between the base frequencies within a pair) and by recent context (the intervals in the two previous trials). When tones were presented in ordered sequences, for which the frequency interval between tones was varied in a progressive manner, strong hysteresis was found. In particular, ambiguous stimuli that led to equal probabilities of “up” and “down” responses within a randomized context were almost fully determined within an ordered context. Moreover, hysteresis did not act on the direction of the reported pitch shift, but rather on the perceptual representation of each tone. Thus, hysteresis could be observed within sequences in which listeners varied between “up” and “down” responses, enabling us to largely rule out confounds related to response bias. The strength of the perceptual hysteresis observed suggests that the ongoing context may have a substantial influence on fundamental aspects of auditory perception, such as how we perceive the changes in pitch between successive sounds.     

Cognitive impairments associated with formal thought disorder in people with schizophrenia

Formal thought disorder (FTD), or disorganized speech, is one of the central signs of schizophrenia. Despite extensive research, the cognitive processes associated with FTD are still unclear. However, the authors' review of FTD theories and research indicates that considerable progress has been made in identifying possible cognitive impairments associated with FTD. Specifically, FTD is strongly associated with impaired executive functioning and with impaired processing of semantic information. Their review indicates that previous research has not yet supported an association between FTD and either an increase in spreading activation or an impairment within the language production system.     

Perceptual organization of complex auditory sequences: effect of number of simultaneous subsequences and frequency separation

Previous findings on streaming are generalized to sequences composed of more than 2 subsequences. A new paradigm identified whether listeners perceive complex sequences as a single unit (integrative listening) or segregate them into 2 (or more) perceptual units (stream segregation). Listeners heard 2 complex sequences, each composed of 1, 2, 3, or 4 subsequences. Their task was to detect a temporal irregularity within 1 subsequence. In Experiment 1, the smallest frequency separation under which listeners were able to focus on 1 subsequence was unaffected by the number of co-occurring subsequences; nonfocused sounds were not perceptually organized into streams. In Experiment 2, detection improved progressively, not abruptly, as the frequency separation between subsequences increased from 0.25 to 6 auditory filters. The authors propose a model of perceptual organization of complex auditory sequences.     

Perceptual load influences auditory space perception in the ventriloquist aftereffect

A period of exposure to trains of simultaneous but spatially offset auditory and visual stimuli can induce a temporary shift in the perception of sound location. This phenomenon, known as the ‘ventriloquist aftereffect’, reflects a realignment of auditory and visual spatial representations such that they approach perceptual alignment despite their physical spatial discordance. Such dynamic changes to sensory representations are likely to underlie the brain’s ability to accommodate inter-sensory discordance produced by sensory errors (particularly in sound localization) and variability in sensory transduction. It is currently unknown, however, whether these plastic changes induced by adaptation to spatially disparate inputs occurs automatically or whether they are dependent on selectively attending to the visual or auditory stimuli. Here, we demonstrate that robust auditory spatial aftereffects can be induced even in the presence of a competing visual stimulus. Importantly, we found that when attention is directed to the competing stimuli, the pattern of aftereffects is altered. These results indicate that attention can modulate the ventriloquist aftereffect.     

Verbal communication impairments and cognitive control components in people with schizophrenia

Schizophrenia involves multiple communication impairments, including (a) disorganized speech, or formal thought disorder (FTD); and (b) decreased speech output, or poverty of speech. Both FTD and poverty of speech have been hypothesized to be associated with deficits in executive functioning or cognitive control. The current study examined whether FTD and poverty of speech were differentially associated with two distinct aspects of cognitive control, working memory and controlled retrieval. Compared with control participants (n = 30), people with schizophrenia (n = 47) exhibited poorer performance on both working memory and controlled retrieval tasks. However, only FTD (and not poverty of speech) was associated with poor working memory. In contrast, only poverty of speech (and not FTD) had a significant zero-order association with poor controlled retrieval. At the same time, working memory and controlled retrieval interacted to predict FTD, with the highest amount of FTD associated with both poor working memory and poor controlled retrieval. In contrast, psychometric control tasks were not associated with FTD or poverty of speech. This research suggests that FTD and poverty of speech are differentially associated with deficits in distinct aspects of cognitive control.     

Perceptual organization in schizophrenia: the processing of symmetrical configurations

The hypothesis that the perceptual organization dysfunction of patients with poor premorbid schizophrenia is due to a deficit in global visual sensory store processing was tested by assessing their ability to process symmetrical configurations that develop early and have strong prepotent structures. Two same-different judgment tasks in which performance varies as a function of the symmetrical organization and task demands were administered to participants with good and poor premorbid schizophrenia, those with mood disorders, and normal controls. Like the other groups, poor premorbid schizophrenics' latency and error response patterns closely paralled the a priori model of adequate processing. The results support their competence in perceptually processing symmetrical configurations and disconfirm the hypothesis that their input deficiencies represent a general deficiency in all forms of perceptual organization. The implications for specifying their early input dysfunction are discussed.     

Perceptual hysteresis as a marker of perceptual inflexibility in schizophrenia

People with schizophrenia are known to exhibit difficulties in the updating of their current belief states even in the light of disconfirmatory evidence. In the present study we tested the hypothesis that people with schizophrenia could also manifest perceptual inflexibility, or difficulties in the updating of their current sensory states. The presence of perceptual inflexibility might contribute both to the patients’ altered perception of reality and the formation of some delusions as well as to their social cognition deficits. Here, we addressed this issue with a protocol of auditory hysteresis, a direct measure of sensory persistence, on a population of stabilized antipsychotic-treated schizophrenia patients and a sample of control subjects. Trials consisted of emotional signals (i.e., screams) and neutral signals (i.e., spectrally-rotated versions of the emotional stimuli) progressively emerging from white noise – Ascending Sequences – or progressively fading away in white noise – Descending Sequences. Results showed that patients presented significantly stronger hysteresis effects than control subjects, as evidenced by a higher rate of perceptual reports in Descending Sequences. The present study thus provides direct evidence of perceptual inflexibility in schizophrenia.     

Using ERPs to explore the impact of affective distraction on working memory stages in schizophrenia

Research on individuals with schizophrenia (SCZ) shows a variety of emotional and cognitive deficits. We examined the hypothesis that ineffective emotional interference control may impact working memory (WM) performance by disrupting information encoding, maintenance, or retrieval in SCZ. Twenty-eight SCZ and 28 matched healthy controls (HC) performed the visual and verbal delayed-matching-to-sample task (DMST) with trials preceded by negative and nonemotional visual distractors. Event-Related Potentials associated with affective stimuli processing (Late Positive Potential-LPP) and WM-encoding (target-P3), maintenance (Negative Slow Wave-NSW), and retrieval (probe-P3) were analyzed. Patients showed overall worse DMST accuracy than HC. Emotional distraction negatively impacted accuracy during the verbal DMST in both groups combined. Both groups also displayed similar LPP modulation during the presentation of emotional distractors. HC showed enhanced NSW after presentation of a negative distraction, whereas this did not occur in SCZ. Comparable effects of emotional distraction were found for WM-encoding and retrieval in both groups. While emotional and neutral stimuli differentially impacted WM-maintenance on the neural level in HC, we did not observe this effect in SCZ, even though both groups showed similar behavioral and neurophysiological reactions to affective stimuli. Deficits in inhibitory mechanisms in SCZ may be responsible for this effect and may have particular relevance for WM-maintenance difficulties.     

Heterogeneity of auditory verbal working memory in schizophrenia

The heterogeneity of schizophrenia remains an obstacle for understanding its pathophysiology. Studies using a tone discrimination screening test to classify patients have found evidence for 2 subgroups having either a specific deficit in verbal working memory (WM) or deficits in both verbal and nonverbal memory. This study aimed to (a) replicate in larger samples differences between these subgroups in auditory verbal WM; (b) evaluate their performance on tests of explicit memory and sustained attention; (c) determine the relation of verbal WM deficits to auditory hallucinations and other symptoms; and (d) examine medication effects. The verbal WM and tone discrimination performance did not differ between medicated (n = 45) and unmedicated (n = 38) patients. Patients with schizophrenia who passed the tone screening test (discriminators; n = 60) were compared with those who did not (nondiscriminators; n = 23) and healthy controls (n = 47). The discriminator subgroup showed poorer verbal WM than did controls and a deficit in verbal but not visual memory on the Wechsler Memory Scale-Revised (Wechsler, 1987), whereas the nondiscriminator subgroup showed overall poorer performance on both verbal and nonverbal tests and a marked deficit in sustained attention. Verbal WM deficits in discriminators were correlated with auditory hallucinations but not with negative symptoms. The results are consistent with a verbal memory deficit in a subgroup of schizophrenia having intact auditory perception, which may stem from dysfunction of language-related cortical regions, and a more generalized cognitive deficit in a subgroup having auditory perceptual and attentional dysfunction.     

Self-consciousness impairments in schizophrenia with and without first rank symptoms using the moving rubber hand illusion

IntroductionThe moving rubber hand illusion allows the evaluation both the sense of body ownership and agency using visuo-motor stimulations.MethodsWe used the moving rubber hand illusion in anatomic congruence with explicit measures to compare active asynchronous and passive synchronous movements in patients diagnosed with schizophrenia with first rank symptoms (FRS) (n = 31) versus without FRS (n = 25).ResultsPatients with FRS are characterized by a lack of agency in active asynchronous condition. The two groups had no sense of ownership in synchronous passive condition. Using a multivariate regression model, we found an association between agency and body ownership measures in the active asynchronous condition in two groups (OR: 1.825, p < 0.001). In the passive condition, this association was only present in the group with first rank symptoms (OR: 2.04, p < 0.001).ConclusionTemporal proximity and sensorimotor information are essential in the understanding of self-consciousness disorders in schizophrenia.     

Effects of location, frequency region, and time course of selective attention on auditory scene analysis

Often, the sound arriving at the ears is a mixture from many different sources, but only 1 is of interest. To assist with selection, the auditory system structures the incoming input into streams, each of which ideally corresponds to a single source. Some authors have argued that this process of streaming is automatic and invariant, but recent evidence suggests it is affected by attention. In Experiments 1 and 2, it is shown that the effect of attention is not a general suppression of streaming on an unattended side of the ascending auditory pathway or in unattended frequency regions. Experiments 3 and 4 investigate the effect on streaming of physical gaps in the sequence and of brief switches in attention away from a sequence. The results demonstrate that after even short gaps or brief switches in attention, streaming is reset. The implications are discussed, and a hierarchical decomposition model is proposed.     

选择性注意对听觉内隐学习的影响

内隐学习被认为是人类无意识、无目的获得复杂规则的自动化过程。已有研究表明, 在人工语法学习范式下, 视觉内隐学习的发生需要选择性注意。为了考察选择性注意对内隐学习的影响是否具有通道特异性, 本研究以90名大学生为被试, 以人工语法为学习任务, 采用双耳分听技术, 在听觉通道同时呈现具有不同规则的字母序列和数字序列, 考查被试在听觉刺激下对注意序列和未注意序列构成规则的习得情况。结果发现：只有选择注意的序列规则被习得, 未选择注意的序列规则未能被习得。研究表明：在人工语法学习范式下, 只有选择注意的刺激维度能够发生内隐学习。选择性注意对内隐学习的影响具有跨通道的适用性, 不仅适用于视觉刺激, 也同样适用于听觉刺激。     

Perceptual depth synthesis in the visual system as revealed by selective adaptation

Selective adaptations was used to determine the degree of interactions between channels processing relative depth from stereopsis, motion parallax, and texture. Monocular adaptations with motion parallax or binocular stationary adaptation caused test surfaces, viewed either stationary binocularly or monocularly with motion parallax, to appear to slant in the opposite direction compared with the slant initially adapted to. Monocular adaptations on frontoparallel surfaces covered with a pattern of texture gradients caused a subsequently viewed test surface, viewed either monocularly with motion parallax or stationary binocularly, to appear to slant in the opposite direction as the slant indicated by the texture in the adaptation condition. No aftereffect emerged in the monocular stationary test condition. A mechanism of independent channels for relative depth perception is dismissed in favor of a view of an asymmetrical interactive processing of different information sources. The results suggest asymmetrical inhibitory interactions among habituating slant detector units receiving inputs from static disparity, dynamic disparity, and texture gradients.     

Neuropsychological impairments in the syndromes of schizophrenia: a comparison between different dimensional models

This study investigates the associations between the different symptom dimensions of schizophrenia and neuropsychological performances. Globally, the results replicate previously described associations. The "negative" dimension correlates with impaired sustained attention and working memory, thus suggestive of dorsolateral frontal cortex dysfunction. "Disorganization" correlates with the ability to inhibit proactive interference. thus with ventromedial frontal dysfunction. The results also add support to the view that the "psychotic" dimension described in three-dimension models includes in fact two distinct dimensions, (1) "hallucinations," here associated to episodic memory measures, and (2) "delusions", here associated to visuospatial attention, thus suggestive of mediotemporal and posterior neocortical dysfunction, respectively.     

ERP study of pre-attentive auditory processing in treatment-refractory schizophrenia

Event-related potential (ERP) studies have demonstrated impaired auditory sensory processing in patients with schizophrenia, as reflected in abnormal mismatch negativity (MMN). We sought to extend this finding by evaluating MMN in 13 treatment-refractory patients with schizophrenia, and 14 age- and gender-matched healthy controls. Subjects responded to infrequent visual stimulation while ignoring binaurally presented auditory tones. The amplitude and topographical pattern of the MMN were analyzed. The control group presented the expected reduction in the amplitude of the MMN from frontal to central and parietal locations. In comparison, the MMN amplitude was not reduced in the treatment-refractory patients, and was largest at the central-posterior electrode location. In addition, patients displayed larger negativities at left frontal, and left- and right-temporal electrode locations than the control subjects. These findings are consistent with pre-attentive abnormalities in treatment-refractory patients with schizophrenia.     

Neuropsychological impairments in schizophrenia: Integration of performance-based and brain imaging findings

Until recently, the dominant view was that schizophrenia patients have limited, if any, neuropsychological impairments, and those that are observed are only secondary to the florid symptoms of the disorder. This view has dramatically changed. This review integrates recent evidence demonstrating the severity and profile of neuropsychological impairments in schizophrenia. We present quantitative evaluation of the literature demonstrating that the most severe impairments are apparent in episodic memory and executive control processes, evident on a background of a generalized cognitive deficit. The neuropsychological impairments potentially represent genetic liability to the disorder, as similar, yet milder, impairments are evident in schizophrenia patients even before the onset of psychotic symptoms, as well as in the nonpsychotic relatives of schizophrenia patients. Corresponding cognitive neuroimaging literature on executive functions, episodic memory, and working memory in schizophrenia documenting abnormalities in frontal and medial temporal lobes is summarized, and current models integrating neuropsychological and neuroimaging data are discussed.