Intracerebral sources of human auditory-evoked potentials

Evoked potentials to brief 1,000-Hz tones presented to either the left or the right ear were recorded from 30 electrodes arrayed over the head. These recordings were submitted to two different forms of source analysis: brain electric source analysis (BESA) and variable-resolution electromagnetic tomography (VARETA). Both analyses showed that the dominant intracerebral sources for the late auditory-evoked potentials (50-300 ms) were in the supratemporal plane and lateral temporal lobe contralateral to the ear of stimulation. The analyses also suggested the possibility of additional sources in the frontal lobes.

Processing of auditory stimuli during visual attention in patients with schizophrenia

BACKGROUND

The aim of this study was to evaluate attentional functioning in patients with schizophrenia with an emphasis on automatic processes using the mismatch negativity (MMN) component of the event-related brain potential.

METHODS

Participants were asked to perform a challenging visual discrimination task and simultaneously ignore auditory stimuli presented in the background. In different blocks of trials, the background was either a sequence of tones that included rare deviant tones differing in pitch or a sequence of tones that alternated regularly in pitch with occasional deviant repetitions. In a second experiment, participants were asked to actively respond to auditory deviant stimuli.

RESULTS

Visual targets generated smaller N1, N2, and P3b deflections in patients than in control subjects, suggesting deficits in controlled attentional processes. Auditory deviant stimuli elicited an MMN that varied in scalp distribution as a function of the deviant-type (pitch vs. pattern). In patients with schizophrenia, impaired auditory discrimination was associated with altered MMN topography and reduced MMN amplitude.

CONCLUSIONS

These findings are consistent with impaired automatic processes in patients with schizophrenia, which may contribute to their difficulties in processing complex auditory sequences. The timing and scalp topography are consistent with impaired auditory pattern analysis in posterior association cortices.

A distributed cortical network for auditory sensory memory in humans

Auditory sensory memory is a critical first stage in auditory perception that permits listeners to integrate incoming acoustic information with stored representations of preceding auditory events. Here, we investigated the neural circuits of sensory memory using behavioral and electrophysiological measures of auditory processing in patients with unilateral brain damage to dorsolateral prefrontal cortex, posterior association cortex, or the hippocampus. We used a neurophysiological marker of an automatic component of sensory memory, the mismatch negativity (MMN), which can be recorded without overt attention. In comparison with control subjects, temporal-parietal patients had impaired auditory discrimination and reduced MMN amplitudes with both effects evident only following stimuli presented in the ear contralateral to the lesioned hemisphere. This suggests that auditory sensory memories are predominantly stored in auditory cortex contralateral to the ear of presentation. Dorsolateral prefrontal damage impaired performance and reduced MMNs elicited by deviant stimuli presented in either ear, implying that dorsolateral prefrontal cortices have a bilateral facilitatory effect on sensory memory storage. Hippocampal lesions did not affect either performance or electrophysiological measures. The results provide evidence of a temporal-prefrontal neocortical network critical for the transient storage of auditory stimuli.

Event-related brain activity associated with auditory pattern processing

One of the basic properties of the auditory system is the ability to analyse complex temporal patterns. Here, we investigated the neural activity associated with auditory pattern processing using event-related brain potentials. Participants were presented with a continuously repeating sequence of four tones with rare changes in either the frequency or timing of one of the tones. Both frequency- and time-deviant sounds generated mismatch negativity (MMN) waves that peaked at midline central electrode sites and inverted in polarity at inferior temporal and occipital sites, consistent with generators in the supratemporal plane. The MMN scalp topography was similar for the frequency- and time-deviant stimuli, suggesting that both spectral and temporal relations among elements of an auditory pattern are encoded in a unified memory trace.

Conjoining auditory and visual features during high-rate serial presentation: processing and conjoining two features can be faster than processing one

The time required to conjoin stimulus features in high-rate serial presentation tasks was estimated in auditory and visual modalities. In the visual experiment, targets were defined by color, orientation, or the conjunction of color and orientation features. Responses were fastest in color conditions, intermediate in orientation conditions, and slowest in conjunction conditions. Estimates of feature conjunction time (FCT) were derived on the basis of a model in which features were processed in parallel and then conjoined, permitting FCTs to be estimated from the difference in reaction times between conjunction and the slowest single-feature condition. Visual FCTs averaged 17 msec, but were negative for certain stimuli and subjects. In the auditory experiment, targets were defined by frequency, location, or the conjunction of frequency and location features. Responses were fastest in frequency conditions, but were faster in conjunction than in location conditions, yielding negative FCTs. The results from both experiments suggest that the processing of stimulus features occurs interactively during early stages of feature conjunction.

A Comparison of Two References for Using Knowledge of Performance in Learning a Motor Task

In the present study, the learning of a task in which the goal of the movement was not isomorphic with a specific movement pattern was examined. The subjects' (N = 48) goal in the task was to be both spatially and temporally accurate in reaching 4 targets with a right arm lever movement. After each acquisition trial, the displacement profile of the movement just produced was provided to all subjects as knowledge of performance (KP). The relative effectiveness of 2 possible references, with which subjects could compare the KP, was examined. One of the references examined was knowledge of results (KR), which was provided by reporting the total absolute timing and amplitude errors from the 4 targets. The other reference examined was a criterion template (CT), Which was defined as the most efficient movement pattern for reaching the 4 targets. In the feedback display, CT was superimposed on the displacement profile of the movement just produced. A factorial design, in which 2 levels of KR (KR, no KR) were crossed with 2 levels of CT (CT, no CT), produced 4 feedback conditions. After 120 acquisition trials with feedback, immediate and delayed retention tests without feedback and a reacquisition test with KR (20 trials per test) were conducted. Acquisition results indicated that KR was a better reference than CT for performing the timing aspect of the movement and for producing the generalized motor program (GMP) associated with the most efficient movement pattern. Delayed retention results showed that KR was also a better reference than CT for learning the most efficient GMP. The calibration strategy undertaken by subjects who were provided with KR during acquisition explains the superiority of the KR reference. The calibration strategy is compared with the pattern-matching activity that was probably undertaken by subjects who had received CT as a reference.

Activation of duration-sensitive auditory cortical fields in humans

The influence of stimulus duration on auditory evoked potentials (AEPs) was examined for tones varying randomly in duration, location, and frequency in an auditory selective attention task. Stimulus duration effects were isolated as duration difference waves by subtracting AEPs to short duration tones from AEPs to longer duration tones of identical location, frequency and rise time. This analysis revealed that AEP components generally increased in amplitude and decreased in latency with increments in signal duration, with evidence of longer temporal integration times for lower frequency tones. Different temporal integration functions were seen for different N1 subcomponents. The results suggest that different auditory cortical areas have different temporal integration times, and that these functions vary as a function of tone frequency.

Attention modulates auditory pattern memory as indexed by event-related brain potentials

The role of selective attention on auditory pattern processing was investigated using the mismatch negativity, an event-related brain potential component associated with sensory memory. Participants responded to changes in an alternating tone pattern in a designated ear while a similar auditory pattern was presented in the opposite ear. Participants were also presented with the same sequences while reading a book (no response required). In all conditions, changes in the pattern elicited a mismatch negativity (MMN) that peaked at 160-220 ms poststimulus. MMN amplitude varied with attention: the amplitude was higher in response to deviant stimuli presented in the attended ear than to the deviant stimuli presented in the unattended ear or during reading. The results show that selective attention modulates auditory pattern memory.

Should Common Optimal Movement Patterns Be Identified as the Criterion to Be Achieved?

Recently, a new paradigm has been proposed for the study of knowledge of performance (Schmidt & Young, 1991). In this paradigm, the experimenters identified an optimal kinematic movement pattern, based on the performance of a best subject, which was imposed on all subjects as the criterion to achieve. This approach, which assumes that this pattern is the best way for all subjects to do the task, was tested in the present experiment. In Experiment 1, a common optimal movement pattern could not be identified by an analysis of scatterplot graphs of the scores plotted as a function of various kinematic vanables or by correlating (within and across subjects [N = 14]) each kinematic variable with the score. In Experiment 2, subjects (N = 12) were retrained in 2 separate sessions, during which they tried to reproduce either a personal best or the best subject's template. Results indicated that scores were similar regardless of the template pattern being used. During training, however, subjects who used their personal template had a lower incidence of zero scores and were more consistent than those who used the template of the best subject. This provided a second line of evidence against the assumption that a common optimal movement pattern exists for this type of task.

Evidence of strategic effects in the modulation of orienting of attention

Two models of visual orienting of attention are frequently described. Voluntary orienting is usually induced by central cues that direct subjects' attention to a given location in the visual space. Automatic orienting is provoked by presentation of peripheral cues. It is shown that automatic orienting induces greater attentional costs and benefits, and is less under a subject's control (Jonides 1981). Furthermore, it is not similarly affected by factors such as signal eccentricity (Umiltà et al. 1991). The present experiment was undertaken to investigate how sensitive automatic orienting produced by peripheral cues is to voluntary modulations of attention. In experiment 1, subjects facing situations daily in which attentional requirements are high, were compared to non-practiced ones. In experiment 2, other groups of practiced subjects facing high or low attentional-demanding situations were tested. In both experiments, subjects were asked to respond to signals, presented in rapid succession, in one of two possible locations in space, on each side of central fixation point. The cue signal automatically oriented attention to one of the two locations in which a first stimulus was presented with 100% probability; 100 ms after the first response (RT1), a second response signal (RT2) was delivered either in the same location (valid condition) or in the opposite location (invalid condition). Four cue probabilities were manipulated for this second stimulus: 100%/0%, 80%/20%, 50%/50%, and 20%/80%. Two eccentricities of 3 degrees and 6 degrees were tested. RT2 data demonstrated that (1) there was no eccentricity effect; (2) the higher the cue probability, the greater were the attentional costs; (3) the attentional effects were smaller in the practiced subjects who faced attention-demanding situations daily, than in the other groups. Put together, these data suggest that automatic orienting of attention can be modulated by voluntary attentional processes, according to cue probability. Furthermore, experienced subjects seem to be able to better distribute their attentional resources in space, with increased task requirements. The adoption of an optimal criterion might lead to the use of a cost minimizing strategy.

Aging and the segregation of auditory stimulus sequences

This study aimed to clarify whether the age-related decline in selective attention widely reported in the literature can be attributed to a selective deficit in the segregation of relevant streams of sound from irrelevant ones. Young and older individuals responded to infrequent deviant stimuli (targets) mixed with distractors in situations that facilitated perception of one or two streams of sounds. Both young and older adults showed the same degree of improvement in performance under conditions that promoted auditory streaming. However, in both listening conditions young subjects were faster and more accurate than older subjects in responding to target zones. Thus, it appears that age-related declines in auditory selective attention cannot be attributed to a selective deficit in the segregation of auditory sequences, but occur in a subsequent stage of processing such as response selection and/or execution.

Middle latency auditory evoked potentials to tones of different frequency

The scalp distributions of middle latency auditory evoked potentials (MAEPs) elicited by tone bursts of 250 and 4000 Hz were compared in two experiments. Na (19.9 ms), Pa (29.8 ms), and Pb (51.4 ms) components elicited by tones of either frequency had fronto-central distributions, whereas the Nb component (38.4 ms) was maximal at parietal sites. Although the distributions of MAEP components varied as a function of the ear of stimulation, no significant differences were found as a function of tone frequency. The results are consistent with suggestions that MAEPs reflect activation of non-tonotopically organized generators.

Brain indices of automatic pattern processing

The extent to which the auditory system automatically encodes simple auditory patterns was investigated by recording event-related brain potentials (ERPs) to non-attended sounds in subjects reading a book. ERPs were recorded to tones alternating regularly in pitch and to rare breaks in the alternating sequence. In all conditions, breaks in the pattern elicited a right hemisphere dominant fronto-central mismatch negativity (MNN) at a latency of 140-220 ms. The MMN increased in amplitude and decreased in latency with increasing pitch separation and stimulus rate. The results suggest that the processing of auditory patterns occurs automatically and depends on a rapidly fading short-term acoustic memory.

Signal clustering modulates auditory cortical activity in humans

Auditory streaming and its relevance to attentional processing was examined using event-related brain potentials (ERPs) in situations facilitating perception of one or two streams of sounds. Subjects listened to sequences of brief tones of three different frequencies presented in random order. In evenly spaced (ES) conditions, the three frequencies were equidistant on the musical scale. In clustered, easy (CE) conditions, the attended frequency was distinct, while the middle and extreme distractor tones were clustered together. In clustered, hard (CH) conditions, the attended frequency was clustered with one of the distractors. The subjects pressed a button in response to occasional target tones of longer duration at a prespecified frequency. The subjects were faster and more accurate in CE conditions than they were in ES conditions, and ERP attention effects were enhanced in amplitude in CE conditions. Conversely, the subjects were slower and less accurate in CH conditions and ERP attention effects were delayed in latency and decreased in amplitude. Clustering effects suggest that the processing of stimuli belonging to the attended stream was promoted and the processing of those falling outside the stream was inhibited. The timing and scalp distribution of clustering-related changes in ERPs suggest that clustering modulates early sensory processing in auditory cortex.

On the Cognitive Processes Underlying Contextual Interference and Observational Learning

The main goal of the present study was to determine whether observation of an unskilled model learning a timing task enables the observer to develop a cognitive representation of the task similar to the one acquired through physical practice (Adams, 1986; Bandura, 1977; Lee & White, 1990). To reach that goal, we tested whether a contextual interference effect would be obtained in a retention test of subjects who had observed an individual practicing three variations of a timing task under a random or a blocked schedule of practice. Similar patterns of results in an immediate retention test were found following observation and physical practice. This suggests that observation indeed engaged the observers in the same type of cognitive activities as did physical practice. Moreover, a schedule of practice made up of 100% physical practice led to improved learning compared with a schedule of practice made up of 50% observation followed by 50% physical practice. This suggests that learning is enhanced more by numerous implementations of a motor program than by its mere construction or retrieval.

The effects of the amount and variability of practice on the learning of a multi-segmented motor task

Since the Shea, J.B. and Morgan (1979) study, investigators have repeatedly shown that the learning of a set of movement patterns (as evaluated in a retention test) is enhanced when acquisition occurred under a random rather than a blocked schedule of practice. Supposedly, this is the case because a random schedule of practice necessitates more elaborate cognitive activities than a blocked schedule before each acquisition trial can be initiated. Our main objective was to determine whether the advantage for learning found for random practice increases as a function of the number of acquisition trials. During acquisition, the results indicated a general tendency for smaller movement reproduction errors under a blocked rather than a random schedule of practice. However, this effect disappeared with larger amount of acquisition trials. In retention, larger errors were observed when acquisition occurred under a blocked rather than a random schedule of practice. Finally, the disadvantage for learning observed for the blocked schedule of practice disappeared under a block-repeated condition in which each movement pattern was first practiced under a blocked schedule which was then repeated a second time. The results are discussed in terms of the so-called contextual interference effect and indicates some of its limitations.

Perceptual context and the selective attention effect on auditory event-related brain potentials

Two experiments examined the effect of the perceptual context established through tonal grouping on neuroelectric responses during selective listening. Subjects monitored one of the extreme pitches in four-pitch tone sequences and detected rare longer tones of the designated pitch. In the first study, tonal grouping was manipulated by changing the tonal separation between the extreme pitches and their nearest neighbor, keeping the extreme pitches constant. Grouping increased the negativity of the attended-unattended difference potential. A second study examined the effect of grouping on the attention-related negativity when it opposed the effect of physical similarity. The proximity of extreme pitches varied, keeping the middle pitches constant. The effect of grouping on event-related potentials (ERPs) for the middle pitches was varied according to the tone being attended. ERPs for the middle tone adjacent to the attended tone became more negative with grouping, whereas ERPs for the distant middle tone became less negative with grouping. These effects suggest that the attention-related negativity is sensitive to contextual information.

Distractor clustering enhances detection speed and accuracy during selective listening

The effects of distractor clustering on target detection were examined in two experiments in which subjects attended to binaural tone bursts of one frequency while ignoring distracting tones of two competing frequencies. The subjects pressed a button in response to occasional target tones of longer duration (Experiment 1) or increased loudness (Experiment 2). In evenly spaced conditions, attended and distractor frequencies differed by 6 and 12 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1048-Hz distractors). In clustered conditions, distractor frequencies were grouped; attended tones differed from the distractors by 6 and 7 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1400-Hz distractors). The tones were presented in randomized sequences at fixed or random stimulus onset asynchronies (SOAs). In both experiments, clustering of the unattended frequencies improved the detectability of targets and speeded target reaction times. Similar effects were found at fixed and variable SOAs. Results from the analysis of stimulus sequence suggest that clustering improved performance primarily by reducing the interference caused by distractors that immediately preceded the target.

Feature processing during high-rate auditory selective attention

Auditory event-related brain potentials (ERPs) and reaction times were analyzed in a selective attention task in which subjects attended to tone pips presented at high rates (interstimulus intervals [ISIs] of 40-200 msec). Subjects responded to infrequent target tones of a specified frequency (250 or 4000 Hz) and location (left or right ear) that were louder than otherwise identical tones presented randomly to the left and right ears. Negative difference (Nd) waves were isolated by subtracting ERPs to tones with no target features from ERPs to the same tones when they shared target location, frequency, or both frequency and location cues. Nd waves began 60-70 msec after tone onset and lasted until 250-350 msec after tone onset, even for tones with single attended cues. The duration of Nd waves exceeded the ISIs between successive tones, implying that several stimuli underwent concurrent analysis. Nd waves associated with frequency processing had scalp distributions different from those associated with location processing, implying that the features were analyzed in distinct cortical areas. Nd waves specific to auditory feature conjunction were isolated. These began at latencies of 110-120 msec, some 30-40 msec after the Nds to single features. The relative timing of the different Nd waves suggests that auditory feature conjunction begins after a brief parallel analysis of individual features but before feature analysis is complete.

Frequency-related differences in the speed of human auditory processing

Three experiments were performed, two comparing the peak latencies of auditory evoked potentials (AEPs) elicited by 250 Hz and 4000 Hz tone pips and a third comparing simple reaction times (RTs) to the same stimuli. In the AEP experiments, the latencies of brainstem, middle and long-latency components were delayed following 250 Hz tone pips in comparison with the latencies of the same components evoked by loudness-matched 4000 Hz tones. Frequency-related latency differences increased with component latency, ranging from less than 1.0 ms for wave V of the brainstem AEP, to more than 20.0 ms for the cortical N1 component. Interpeak latency differences were also significantly lengthened following the 250 Hz tone pips. In the behavioral study, RTs were 14.6 ms slower following 250 than 4000 Hz tone pips. The results suggest that the time required for the sensory analysis of auditory signals varies inversely with their frequency.

Same-hand and different-hand finger pairings in two-choice reaction time: presence or absence of response competition?

Several two-choice reaction time experiments have compared conditions in which the two possible responses were from the same hand (same-hand pairing) or from different hands (different-hand pairing). Studies that used only the two relevant fingers on response keys reported shorter reaction times for the different-hand pairing. In other studies, two additional but irrelevant fingers were also in contact with response keys. These fingers were irrelevant in the sense that they never were required to respond. With this procedure, equivalent reaction times were found between same-hand and different-hand pairings. Reeve and Proctor (1988) recently have argued that using only two fingers results in response competition between the two fingers from the same hand, yielding shorter reaction times for the different-hand pairing condition. In contrast, when four fingers are placed on response keys, response competition should be absent for both the same-hand and the different-hand pairing conditions, resulting in equivalent reaction times. In the present work, reaction times associated with the same-hand pairing condition remained unchanged, irrespective of the number of fingers positioned on keys. In the different-hand pairing condition, reaction times were found to be longer when four fingers were used than when only two fingers rested on response keys. Thus, when four fingers are placed on keys, response competition appears to be present rather than absent. Other results showed that the response competition found in the different-hand pairing condition decreases with practice.

Study of decision-making in squash competition: a computer simulation approach

This paper describes how a computer simulation approach was used to specify some of the cognitive processes underlying decision-making in squash competition. The work presented in this article focused on the cognitive strategy of the defending player when choosing among three categories of preparation. (Total preparation for one particular event, partial preparation in favor of one event, and absence of biased preparation.) The defending player is viewed as in information processing system (IPS) placed in a problem-solving situation, the problem being what decision to reach. There are four steps inherent to the computer simulation approach: (a) obtaining the verbal protocol, (2) analyzing the protocol, (3) computer simulation, and (4) validation. This paper describes how each of those steps have been completed, with a special emphasis being placed on the first step of the procedure, that of obtaining the verbal protocol.

Additive latency effects of selective and nonselective restricted priming types

The purpose of this investigation was to examine further the contention of Alain et al. (1988) that a third priming type exists, called nonselective restricted (NSR) and controlled by response probability, which is distinct from those types influenced by foreperiod duration (nonselective general priming) and prediction probability (selective priming). In a four-choice reaction time (RT) task, prediction probability (.5, .7, & .9, indicating the likelihood of a particular response) and response probability (.5, .9, denoting the likelihood that a response would be needed at all) exerted significant but noninteractive effects on RTs for prepared responses (most probable), suggesting that each of these probabilities influence different priming types (Sternberg, 1969; selective and NSR, respectively). This was further indicated by the fact that prediction probability, but not response probability, significantly altered RTs for the unprepared (lesser probable) responses. Finally, the hypothesized nonselective character of NSR priming (i.e., all outputs controlled by response probability are equally affected by its value changes) was supported when responses were equiprobable, and, while the null effect of response probability just mentioned seemingly argued against this property when selective priming took place, the interpretation provided herein negated this opposition.