Sequence Of Auditory Stimuli Research Articles

Rapid extraction of auditory feature contingencies

Contingent relations between sensory events render the environment predictable and thus facilitate adaptive behavior. The human capacity to detect such relations has been comprehensively demonstrated in paradigms in which contingency rules were task-relevant or in which they applied to motor behavior. The extent to which contingencies can also be extracted from events that are unrelated to the current goals of the organism has remained largely unclear. The present study addressed the emergence of contingency-related effects for behaviorally irrelevant auditory stimuli and the cortical areas involved in the processing of such contingency rules. Contingent relations between different features of temporally separate events were embedded in a new dynamic protocol. Participants were presented with the auditory stimulus sequences while their attention was captured by a video. The mismatch negativity (MMN) component of the event-related brain potential (ERP) was employed as an electrophysiological correlate of contingency detection. MMN generators were localized by means of scalp current density (SCD) and primary current density (PCD) analyses with variable resolution electromagnetic tomography (VARETA). Results show that task-irrelevant contingencies can be extracted from about fifteen to twenty successive events conforming to the contingent relation. Topographic and tomographic analyses reveal the involvement of the auditory cortex in the processing of contingency violations. The present data provide evidence for the rapid encoding of complex extrapolative relations in sensory areas. This capacity is of fundamental importance for the organism in its attempt to model the sensory environment outside the focus of attention.

Regularity Extraction and Application in Dynamic Auditory Stimulus Sequences

Traditional auditory oddball paradigms imply the brain's ability to encode regularities, but are not optimal for investigating the process of regularity establishment. In the present study, a dynamic experimental protocol was developed that simulates a more realistic auditory environment with changing regularities. The dynamic sequences were included in a distraction paradigm in order to study regularity extraction and application. Subjects discriminated the duration of sequentially presented tones. Without relevance to the task, tones repeated or changed in frequency according to a pattern unknown to the subject. When frequency repetitions were broken by a deviating tone, behavioral distraction (prolonged reaction time in the duration discrimination task) was elicited. Moreover, event-related brain potential components indicated deviance detection (mismatch negativity), involuntary attention switches (P3a), and attentional reorientation. These results suggest that regularities were extracted from the dynamic stimulation and were used to predict forthcoming stimuli. The effects were already observed with deviants occurring after as few as two presentations of a standard frequency, that is, violating a just emerging rule. Effects of regularity violation strengthened with the number of standard repetitions. Control stimuli comprising no regularity revealed that the observed effects were due to both improvements in standard processing (benefits of regularity establishment) and deteriorations in deviant processing (costs of regularity violation). Thus, regularities are exploited in two different ways: for an efficient processing of regularity-conforming events as well as for the detection of nonconforming, presumably important events. The present results underline the brain's flexibility in its adaptation to environmental demands.

Left temporal impairment of auditory information processing in prematurely born 9-year-old children: An electrophysiological study

Children born preterm more than average display cognitive difficulties that are significant enough to prevent normal schooling. The aim of our study was to provide better understanding of the long-term neuropathological processes associated with preterm injury, through the hypothesis that mild cognitive disorders might be related to slight deficits in primary functions such as attention and perception. Assessment of auditory pre-attentive processes was performed by recording the obligatory sensory response (N250) and the change-detection response (Mismatch Negativity, MMN). Topographic study of these responses was performed in fifteen 9-year-old children born preterm (27–33 weeks gestational age) matched to fifteen control children born at term. The auditory stimulus sequence consisted of 1000 Hz standard and 1100 Hz deviant tones (15%) delivered binaurally with an interstimulus interval of 700 ms. The results showed that MMN was similar in both groups. Analysis of the responses to standard repetitive tones demonstrated significantly smaller N250 wave amplitude in children born preterm. Scalp current density maps showed that this reduction in amplitude was associated with lower activity of both frontal and left supratemporal generators. Although the functional significance of the N250 wave in children remains to be clarified, our results indicate a disorder of auditory processes related to prematurity that might have consequences on the development of higher-level processes.

Directional motion contrast sensitivity in developmental dyslexia

The present study compared the perception of visual motion in two dyslexia classification schemes; the [Boder, E. (1973). Developmental dyslexia: a diagnostic approach based on three atypical reading-spelling patterns. Developmental Medicine and Child Neurology, 15, 663–687.] dyseidetic, dysphonetic and mixed subgroups and [Williams, M. J., Stuart, G. W., Castles, A., & McAnally, K. I. (2003). Contrast sensitivity in subgroups of developmental dyslexia. Vision Research, 43, 467–477.] surface, phonological and mixed subgroups by measuring the contrast sensitivity for drifting gratings at three spatial frequencies (1.0, 4.0, and 8.0 c/deg) and five drift velocities (0.75, 3.0, 6.0, 12.0, and 18.0 cyc/s) in a sample of 32 children with dyslexia and 32 matched normal readers. The findings show that there were no differences in motion direction perception between normal readers and the group with dyslexia when dyslexia was taken as a homogeneous group. Motion direction perception was found to be intact in the dyseidetic and surface dyslexia subgroups and significantly lowered in both mixed dyslexia subgroups. The one inconsistency in the findings was that motion direction perception was significantly lowered in the [Boder, E. (1973). Developmental dyslexia: a diagnostic approach based on three atypical reading-spelling patterns. Developmental Medicine and Child Neurology, 15, 663–687.] dysphonetic subgroup and intact in the [Williams, M. J., Stuart, G. W., Castles, A., & McAnally, K. I. (2003). Contrast sensitivity in subgroups of developmental dyslexia. Vision Research, 43, 467–477.] phonological subgroup. The findings also provide evidence for the presence of a disorder in sequential and temporal order processing that appears to reflect a difficulty in retaining sequences of non-meaningful auditory and visual stimuli in short-term working memory in children with dyslexia.

Increased attention for computer-tailored health communications: An event-related potential study.

The authors tested whether individually tailored health communications receive more attention from the reader than nontailored health communications in a randomized, controlled trial among student volunteers (N = 24). They used objective measures of attention allocation during the message exposure. In a between-subjects design, participants had to read tailored or nontailored nutrition education messages and at the same time had to pay attention to specific odd auditory stimuli in a sequence of frequent auditory stimuli (odd ball paradigm). The amount of attention allocation was measured by recording event-related potentials (ERPs; i.e., N100 and P300 ERPs) and reaction times. For the tailored as opposed to the nontailored group, results revealed larger amplitudes for the N100 effect, smaller amplitudes for the P300 effect, and slower reaction times. Resource allocation theory and these results suggest that those in the tailored group allocated more attention resources to the nutrition message than those in the nontailored group.

The effect of visual task difficulty and attentional direction on the detection of acoustic change as indexed by the Mismatch Negativity

Näätänen's model of auditory processing purports that attention does not affect the MMN. The present study investigates this claim through two different manipulations. First, the effect of visual task difficulty on the passively elicited MMN is assessed. Second, the MMNs elicited by stimuli under attended and ignored conditions are compared. In Experiment 1, subjects were presented with mixed sequences of equiprobable auditory and visual stimuli. The auditory stimuli consisted of standard (80 dB SPL 1000 Hz), frequency deviant (1050 Hz), and intensity deviant (70 dB SPL) tone pips. In a first instance, subjects were instructed to ignore the auditory stimulation and engage in an easy and difficult visual discrimination task (focused condition). Subsequently, they were asked to attend to both modalities and detect visual and auditory deviant stimuli (divided condition). The results indicate that the passively elicited MMN to frequency and intensity deviants did not significantly vary with visual task difficulty, in spite of the fact that the easy and difficult tasks showed a wide variation in performance. The manipulation of the attentional direction (focused vs. divided conditions) did result in a significant effect on the MMN elicited by the intensity, but not frequency, deviant. The intensity MMN was larger at frontal sites when subjects' attention was directed to both modalities as compared to only the visual modality. The attentional effect on the MMN to the intensity deviants only may be due to the specific deviant feature or the poorer perceptual discriminability of this deviant from the standard. Experiment 2 was designed to address this issue. The methods of Experiment 2 were identical to those of Experiment 1 with the exception that the intensity deviant (60 dB SPL) was made to be more perceptible than the frequency deviant (1016 Hz) when compared to the standard stimulus (80 dB SPL 1000 Hz). The results of Experiment 2 also demonstrated that the passively elicited MMN was not affected by large variations in visual task difficulty; this provides convincing evidence that the MMN is independent of visual task demands. Similarly to Experiment 1, the direction of attention again had a significant effect on the MMN. In Experiment 2, however, the frequency MMN (and not the intensity MMN) was larger at frontal sites during divided attention compared to focused visual attention. The most parsimonious explanation of these results is that attention enhances the discriminability of the deviant from the standard background stimulation. As such, small acoustic changes would benefit from attention whereas the discriminability of larger changes may not be significantly enhanced.

Sensorimotor synchronization: A review of the tapping literature

Sensorimotor synchronization (SMS), the rhythmic coordination of perception and action, occurs in many contexts, but most conspicuously in music performance and dance. In the laboratory, it is most often studied in the form of finger tapping to a sequence of auditory stimuli. This review summarizes theories and empirical findings obtained with the tapping task. Its eight sections deal with the role of intention, rate limits, the negative mean asynchrony, variability, models of error correction, perturbation studies, neural correlates of SMS, and SMS in musical contexts. The central theoretical issue is considered to be how best to characterize the perceptual information and the internal processes that enable people to achieve and maintain SMS. Recent research suggests that SMS is controlled jointly by two error correction processes (phase correction and period correction) that differ in their degrees of cognitive control and may be associated with different brain circuits. They exemplify the general distinction between subconscious mechanisms of action regulation and conscious processes involved in perceptual judgment and action planning.

Mismatch negativity responses in schizophrenia: a combined fMRI and whole-head MEG study.

Mismatch negativity is an event-related brain response sensitive to deviations within a sequence of repetitive auditory stimuli. It is thought to reflect short-term sensory memory and is independent of higher-level cognitive processes. Mismatch negativity response is diminished in patients with schizophrenia. Little is known about the mechanisms of this decreased response, the contribution of the different hemispheres, and its locus of generation. Patients with schizophrenia (N=12) and matched comparison subjects (N=12) were studied. A novel design to measure mismatch negativity responses to deviant auditory stimuli was generated by using the switching noises from the functional magnetic resonance imaging (fMRI) scanner, thus avoiding any interfering background sound. Stimuli included deviants of amplitude (9 dB lower) and duration (76 msec shorter) presented in a random sequence. The scanner noise was recorded and applied to the same subjects in a whole-head magnetoencephalography (MEG) device. Neuromagnetic and hemodynamic responses to the identical stimuli were compared between the patients and comparison subjects. As expected, neuromagnetic mismatch fields were smaller in the patient group. More specifically, a lateralization to the right for duration deviance was only found in comparison subjects. For the relative amplitude of the blood-oxygen-level-dependent signal (measured with fMRI), differences emerged in the secondary (planum temporale), but not primary (Heschl's gyrus), auditory cortex. Duration deviants achieved a right hemispheric advantage only in the comparison group. A significantly stronger lateralization to the left was found for the deviant amplitude stimuli in the patients. The data support the view of altered hemispheric interactions in the formation of the short-term memory traces necessary for the integration of auditory stimuli. This process is predominantly mediated by the planum temporale (secondary auditory cortex). Altered interaction of regions within the superior temporal plane and across hemispheres could be in part responsible for language-mediated cognitive (e.g., verbal memory) and psychopathological (hallucinations, formal thought disorder) symptoms in schizophrenia.

Neurophysiological correlates of error correction in sensorimotor-synchronization

In a sensorimotor synchronization task requiring subjects to tap in synchrony with an auditory stimulus, occasional perturbations (i.e., interval changes) in an otherwise isochronous sequence of auditory metronome stimuli are known to be compensated remarkably swift and with surprising precision, even when they are too small to be consciously perceived. To investigate the neural substrate and the informational basis of error correction in sensorimotor synchronization, we recorded movement-related, auditory-evoked, and error-related EEG potentials. Experiment 1 confirmed rapid adjustment to stimulus phase shifts, with faster correction of large (50 ms) compared to small (15 ms) shifts. In addition to being corrected faster, there was overcorrection of the 50 ms shifts, attributed to engagement of period correction mechanisms. For +50 ms shifts, a neural correlate of period correction was identified in the form of medial frontal cortex activation, preceded by an error-related brain potential (ERN). Auditory-evoked potential (AEP) amplitudes were sensitive to stimulus phase shifts of both large and small magnitude. Further experiments with a smaller magnitude 10 ms phase shift (Experiment 2) and passive auditory stimulation (Experiment 3) provided evidence that the modulation of AEP amplitudes is not due to metronome interval changes, but may represent auditory-somatosensory activation. Together, behavioral and neurophysiological data support the hypothesis that phase correction is a largely automatic process, not dependent on conscious perception of changes in timing. By contrast, perceivable phase shifts may invoke timekeeper adjustments accompanied by medial frontal cortex activity.

Deficits in automatically detecting changes in conjunction of auditory features in patients with schizophrenia

Disturbances in processing simple acoustic changes in a stream of stimuli have been widely reported in patients with schizophrenia, but little is know about auditory feature conjunction in these individuals. This study was designed to examine the extent to which patients with schizophrenia automatically process changes in conjunction of auditory features by using event‐related brain potentials. Seventeen patients and 17 age‐matched controls were presented with frequent low pitch tones at 45° to the left of center and frequent high pitch tones at 45° to the right of center while performing a continuous visual serial‐choice reaction time task. The sequence of auditory stimuli included rare conjunction‐deviants comprised of a different combination of features (e.g., low pitch tone at 45° right) and double‐deviant tones that differed from the standard tones in both pitch and location (i.e., middle pitch at 0° azimuth). Conjunction‐deviant stimuli elicited an MMN wave that was maximum at frontocentral sites. Compared with controls, the MMN to conjunction‐deviant was reduced in patients and was more centrally distributed. Double‐deviant sounds generated a biphasic MMN followed by a P3a wave at central sites. Both MMN and P3a were reduced in patients compared with controls. These results show that patients with schizophrenia have difficulty in automatically detecting changes in a combination of auditory features as well as orienting to what “normally” would be considered salient by healthy individuals.

Mismatch responses to randomized gradient switching noise as reflected by fMRI and whole-head magnetoencephalography.

The central auditory system of the human brain uses a variety of mechanisms to analyze auditory scenes, among others, preattentive detection of sudden changes in the sound environment. Electroencephalography (EEG) and magnetoencephalography (MEG) provide a measure to monitor neuronal cortical currents. The mismatch negativity (MMN) or field (MMNm) reflect preattentive activation in response to deviants within a sequence of homogenous auditory stimuli. Functional magnetic resonance imaging (fMRI) allows for a higher spatial resolution as compared to the extracranial electrophysiological techniques. The image encoding gradients of echo planar imaging (EPI) sequences, however, elicit an interfering background noise. To circumvent this shortcoming, the present study applied multi-echo EPI mimicking an auditory oddball design. The gradient trains (SOA = 800 msec, 94.5 dB SPL, stimulus duration = 152 msec) comprised amplitude (-9 dB) and duration (76 msec) deviants in a randomized sequence. Moreover, the scanner noise was recorded and applied in a whole-head MEG device to validate the properties of this specific material. Robust fMRI activation patterns emerged in response to the deviant gradient switching. Changes in amplitude activated the entire auditory cortex, whereas the duration deviants elicited right-lateralized signal increase in secondary areas. The recorded scanner noise evoked reliably right-lateralized mismatch MEG responses. Source localization was in accordance with activation of secondary auditory cortex. The presented paradigm provides a robust and feasible tool to study the functional anatomy of early cognitive auditory processing in clinical populations such as schizophrenia.

An analysis of audio-visual crossmodal integration by means of event-related potential (ERP) recordings

Crossmodal integration was studied in humans by presenting random sequences of auditory (brief noise bursts), visual (flashes), and audiovisual (simultaneous noise bursts and flashes) stimuli from a central location at irregular intervals between 600 and 800 ms. The subjects’ task was to press a button to infrequent and unpredictable ( P=0.15) target stimuli that could be either a more intense noise burst, a brighter flash, or a combination of the two. In accordance with previous studies, behavioral data showed that bimodal target stimuli were responded to much faster and were identified more accurately than the unimodal target stimuli. The neural basis of this crossmodal interaction was investigated by subtracting the ERPs to the auditory (A) and the visual (V) stimuli alone from the ERP to the combined audiovisual (AV) stimuli (i.e. interaction=AV−(A+V)). Using this approach, we replicated previous reports of both early (at around 40 ms) and late (after 100 ms) ERP interaction effects. However, it appears that the very early interaction effects can be largely accounted for by an anticipatory ERP that precedes both the unimodal and bimodal stimuli. In calculating the ERP interaction this slow shift is subtracted twice, resulting in an apparent shift of the opposite polarity that may be confounded with actual crossmodal interactions.

Some measures of verbal and spatial working memory in eight- and nine-year-old hearing-impaired children with cochlear implants.

The purpose of this study was to examine working memory for sequences of auditory and visual stimuli in prelingually deafened pediatric cochlear implant users with at least 4 yr of device experience. Two groups of 8- and 9-yr-old children, 45 normal-hearing and 45 hearing-impaired users of cochlear implants, completed a novel working memory task requiring memory for sequences of either visual-spatial cues or visual-spatial cues paired with auditory signals. In each sequence, colored response buttons were illuminated either with or without simultaneous auditory presentation of verbal labels (color-names or digit-names). The child was required to reproduce each sequence by pressing the appropriate buttons on the response box. Sequence length was varied and a measure of memory span corresponding to the longest list length correctly reproduced under each set of presentation conditions was recorded. Additional children completed a modified task that eliminated the visual-spatial light cues but that still required reproduction of auditory color-name sequences using the same response box. Data from 37 pediatric cochlear implant users were collected using this modified task. The cochlear implant group obtained shorter span scores on average than the normal-hearing group, regardless of presentation format. The normal-hearing children also demonstrated a larger "redundancy gain" than children in the cochlear implant group-that is, the normal-hearing group displayed better memory for auditory-plus-lights sequences than for the lights-only sequences. Although the children with cochlear implants did not use the auditory signals as effectively as normal-hearing children when visual-spatial cues were also available, their performance on the modified memory task using only auditory cues showed that some of the children were capable of encoding auditory-only sequences at a level comparable with normal-hearing children. The finding of smaller redundancy gains from the addition of auditory cues to visual-spatial sequences in the cochlear implant group as compared with the normal-hearing group demonstrates differences in encoding or rehearsal strategies between these two groups of children. Differences in memory span between the two groups even on a visual-spatial memory task suggests that atypical working memory development irrespective of input modality may be present in this clinical population.

Nonspatial intermodal selective attention is mediated by sensory brain areas: Evidence from event‐related potentials

The present study focuses on the question of whether inter‐ and intramodal forms of attention are reflected in activation of the same or different brain areas. ERPs were recorded while subjects were presented a random sequence of visual and auditory stimuli. They were instructed to attend to nonspatial attributes of either auditory or visual stimuli and to detect occasional target stimuli within the attended channel. An occipital selection negativity was found for intramodal attention to visual stimuli. Visual intermodal attention was also manifested in a similar negativity. A symmetrical dipole pair in the medial inferior occipital areas could account for the intramodal effects. Dipole pairs for the intermodal attention effect had a slightly more posterior location compared to the dipole pair for the intramodal effect. Auditory intermodal attention was manifested in an early enhanced negativity overlapping with the N1 and P2 components, which was localized using a symmetrical dipole pair in the lateral auditory cortex. The onset of the intramodal attention effect was somewhat later (around 200 ms), and was reflected in a frontal processing negativity. The present results indicate that intra‐ and intermodal forms of attention were indeed similar for visual stimuli. Auditory data suggest the involvement of multiple brain areas.

Nonspatial intermodal selective attention is mediated by sensory brain areas: Evidence from event-related potentials

The present study focuses on the question of whether inter- and intramodal forms of attention are reflected in activation of the same or different brain areas. ERPs were recorded while subjects were presented a random sequence of visual and auditory stimuli. They were instructed to attend to nonspatial attributes of either auditory or visual stimuli and to detect occasional target stimuli within the attended channel. An occipital selection negativity was found for intramodal attention to visual stimuli. Visual intermodal attention was also manifested in a similar negativity. A symmetrical dipole pair in the medial inferior occipital areas could account for the intramodal effects. Dipole pairs for the intermodal attention effect had a slightly more posterior location compared to the dipole pair for the intramodal effect. Auditory intermodal attention was manifested in an early enhanced negativity overlapping with the N1 and P2 components, which was localized using a symmetrical dipole pair in the lateral auditory cortex. The onset of the intramodal attention effect was somewhat later (around 200 ms), and was reflected in a frontal processing negativity. The present results indicate that intra- and intermodal forms of attention were indeed similar for visual stimuli. Auditory data suggest the involvement of multiple brain areas.

Decay time of the auditory sensory memory trace during wakefulness and REM sleep

In a repetitive auditory stimulus sequence, deviant infrequent tones typically elicit a component of auditory event-related potentials termed mismatch negativity (MMN). The elicitation of MMN is assumed to reflect the existence of a memory trace of the standard stimulus that has a decay time of about 10 s and is strengthened by repetition of the standards. The main aim of the present study was to test the decay time of the sensory memory trace during rapid-eye movement (REM) sleep vs. wakefulness, as indexed by the MMN. Subjects were presented 10 tone trains, separated by 3, 6, or 9 s of silence, during waking and REM sleep. Each train consisted of 9 standards of 1000 Hz and 1 deviant of 2000 Hz that occurred at position 1, 2, 4, or 6. The waking deviants elicited a frontocentral negativity with a scalp topography equivalent to the MMN component. During REM sleep, the negative component showed the same scalp distribution only for the 3-s intertrain interval (ITI). In this brain state, the MMN amplitude was smaller and decreased with prolongation of the ITI. These results suggest a weaker sensory memory trace formation and a premature decay time of such a memory trace during REM sleep as compared with wakefulness.

The emergence of cross-modal complex temporal-processing abilities in children

Studies of temporal processing of multi-item visual, auditory, and tactile stimulus sequences in children with central auditory-processing disorders have shown considerable variability even among the children in the normal control group, suggesting that some aspects of complex temporal processing may continue to develop throughout childhood. In the present study, two experiments were performed. In the first, groups of normally developing children aged 8, 10, 12, and 14 years were tested with three-item sequences of auditory tones (analogous to the pitch pattern sequence test widely used in assessing central auditory-processing abilities), sequences of colored boxes, and sequences of tactile vibrations presented to different locations on the forearm. Children were asked to identify the sequence presented. Results showed significant improvements in performance with age, with most of the difference between the 8- and 10-year-old groups. A second experiment examined younger children, aged 6, 7, and 8 years, with slightly modified versions of the same tasks. Again, a significant improvement in performance with age was observed. These improvements were evident for all sensory modalities, although overall performance levels were highest for the visual task and lowest for the tactile task. Results are discussed in terms of more general development of perceptual and cognitive abilities in childhood. [Work supported by NIH.]

Neuromagnetic studies of human auditory cortex function and reorganization.

Much of our present understanding of sensory processing by the human brain is obtained from studies of patients with sensory impairments. Past auditory studies have focused strongly on the peripheral mechanisms of hearing disorders, and have led to an overuse of stimuli that are good for testing the transfer functions of simple acoustic features but are not suitable for understanding the perception of complex auditory stimuli or stimulus sequences. Magnetoencephalography (MEG) is a non-invasive method for studying how the human brain processes and stores auditory information. The long-term groundwork in building up the basic understanding of cortical dynamics during various "simple" stimulations now allows the use of more complex, real-life-like stimuli, and clinical applications.

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.

Lesions of frontal cortex diminish the auditory mismatch negativity

Event-related brain potentials to non-attended auditory stimuli were recorded from patients with dorsolateral prefrontal cortex (DPFCx) lesions and from age-matched control subjects as they performed a visual reaction time task. Auditory stimuli consisted of monoaural sequences of repetitive standard tones (1000 Hz) and occasional deviant tones of a higher frequency (1300 Hz). In comparison with control subjects, DPFCx patients showed enhanced P1 amplitudes (mean peak latency 50 msec), consistent with reduced frontally mediated gating of sensory input to the auditory cortex. The mismatch negativity (MMN) elicited by deviant tones was reduced in DPFCx patients over a broad latency range (130–210 msec), especially over the lesioned hemisphere and for tones delivered to the ear ipsilateral to the lesion. The results suggest that DPFCx and DPFCx-temporal projections play a critical role in involuntary orienting to physical changes in sequences of non-attended auditory stimuli.