The effect of graded monetary reward on cognitive event-related potentials and behavior in young healthy adults.
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Temporal correlates of the brain circuit underlying reward processing in healthy adults remain unclear. The current study investigated the P3 and contingent negative variation (CNV) as putative reward-related temporal markers. The effect of sustained monetary reward on these event-related potentials and on behavior was assessed using a warned reaction-time paradigm in 16 young healthy subjects. Monetary reward (0, 1 and 45 cents) varied across blocks of trials. While the CNV was unaffected by money, P3 amplitude was significantly larger for 45 than the 1 and 0 cent conditions. This effect corresponded to the monotonically positive subjective ratings of interest and excitement on the task (45>1>0). These findings suggest a difference between the P3 and CNV; the P3 is sensitive to the sustained effect of relative reward value, while the CNV does not vary with reward magnitude. (+info)
Cerebellar damage impairs detection of somatosensory input changes. A somatosensory mismatch-negativity study.
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Several recent studies support the view that the cerebellum's contribution to sensory processing is not limited to movement regulation. In a previous paper (Restuccia D, Valeriani M, Barba C, Le Pera D, Capecci M, Filippini V, Molinari M. Functional changes of the primary somatosensory cortex in patients with unilateral cerebellar lesions. Brain 2001; 124: 757-68) we showed that the cerebellum influences somatosensory input processing at very early stages. The present study was aimed at verifying whether an analogous influence is also exerted at higher levels. For some time it has been known that in the auditory modality a specific event-related potential (ERP), that is, mismatch negativity (MMN), reflects preattentive detection of changes in the incoming stimulus by comparing the new stimulus with sensory memory traces. To test the cerebellar influence on the processing of incoming somatosensory stimuli we first verified whether the electrical stimulation of fingers, according to an 'oddball' paradigm within a stimulus-ignored condition, was able to elicit event-related components specifically linked to the preattentive detection of change. We analysed scalp responses obtained from eight healthy volunteers during frequent and rare electrical stimulation of the first and fifth finger of the left hand, respectively. To ensure that responses to deviant stimuli were due to changes in detection mechanisms, rather than to activation of new afferents, we also analysed responses to rare stimulation alone ('standard-omitted' condition). The 'oddball' stimulation was able to elicit a parieto-occipital extra negativity that was different in scalp distribution and latency from the N140 response to the 'standard-omitted' stimulation. We considered that this response was related to changes in detection mechanisms and labelled it somatosensory mismatch negativity (S-MMN). When the same procedure was applied to six patients with unilateral cerebellar lesions we found that the S-MMN was clearly abnormal after stimulation of the affected hand (ipsilateral to the affected cerebellar hemisphere). Earlier ERPs, as well as ERPs elicited during the 'standard-omitted' condition, were fully normal. Present data indicate that cerebellar processing is involved in preattentive detection of somatosensory input changes. In conclusion, this study demonstrates the reliability of S-MMN recordings and indicates that subjects with cerebellar damage may be impaired in the cortical processing of incoming somatosensory inputs. (+info)
Neurophysiological endophenotypes of schizophrenia: the viability of selected candidate measures.
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In an effort to reveal susceptibility genes, schizophrenia research has turned to the endophenotype strategy. Endophenotypes are characteristics that reflect the actions of genes predisposing an individual to a disorder, even in the absence of diagnosable pathology. Individual endophenotypes are presumably determined by fewer genes than the more complex phenotype of schizophrenia and would, therefore, reduce the complexity of genetic analyses. Unfortunately, despite there being rational criteria to define a viable endophenotype, the term is sometimes applied indiscriminately to characteristics that are deviant in affected individuals. Schizophrenia patients exhibit deficits in several neurophysiological measures of information processing that have been proposed as candidate endophenotypes. Successful processing of sensory inputs requires the ability to inhibit intrinsic responses to redundant stimuli and, reciprocally, to facilitate responses to less frequent salient stimuli. There is evidence to suggest that both these processes are "impaired" in schizophrenia. Measures of inhibitory failure include prepulse inhibition of the startle reflex, P50 auditory evoked potential suppression, and antisaccade eye movements. Measures of impaired deviance detection include mismatch negativity and the P300 event-related potential. The purpose of this review is to systematically evaluate the endophenotype candidacy of these key neurophysiological abilities. For each candidate, we describe typical experimental procedures, the current understanding of the underlying neurobiology, the nature of the abnormality in schizophrenia, the reliability, stability and heritability of the measure, and any reported gene associations. We conclude with a discussion of the few studies thus far that have employed a multivariate approach with these candidates. (+info)
Error-related event-related potentials in children with attention-deficit hyperactivity disorder, oppositional defiant disorder, reading disorder, and math disorder.
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We studied error-related negativity (ERN) and error positivity (Pe) during a discrimination task in 319 unmedicated children divided into subtypes of ADHD (Not-ADHD/inattentive/combined), learning disorder (Not-LD/reading/math/reading+math), and oppositional defiant disorder. Response-locked ERPs contained a frontocentral ERN and posterior Pe. Error-related negativity and positivity exhibited larger amplitude and later latency than corresponding waves for correct responses matched on reaction time. ADHD did not affect performance on the task. The ADHD/combined sample exceeded controls in ERN amplitude, perhaps reflecting patients' adaptive monitoring efforts. Compared with controls, subjects with reading disorder and reading+math disorder performed worse on the task and had marginally more negative correct-related negativities. In contrast, Pe/Pc was smaller in children with reading+math disorder than among subjects with reading disorder and Not-LD participants; this nonspecific finding is not attributable to error processing. The results reflect anomalies in error processing in these disorders but further research is needed to address inconsistencies in the literature. (+info)
Affective visual event-related potentials: arousal, repetition, and time-on-task.
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Affective stimulus pictures that differed in valence (unpleasant, neutral, and pleasant) were repeated as targets in an oddball task to elicit event-related potentials (ERPs) in young female adults. Each picture target was repeated consecutively four times, with picture order counterbalanced and time-on-task influences assessed across subjects. Response time decreased from the first to second stimulus presentation and remained stable. Stimulus repetition was associated with voltage increases for N1, P2, N2, and P3, from initial to subsequent presentations. Arousal effects did not interact with stimulus repetition at any latency range. Time-on-task was associated with decreased voltages for the N2 and P3 potentials but was unaffected by stimulus valence. The findings suggest affective arousal, stimulus repetition, and time-on-task independently modulate ERP outcomes at overlapping time ranges. Theoretical implications are discussed. (+info)
Visual cues can modulate integration and segregation of objects in auditory scene analysis.
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The task of assigning concurrent sounds to different auditory objects is known to depend on temporal and spectral cues. When tones of high and low frequencies are presented in alternation, they can be perceived as a single, integrated melody, or as two parallel, segregated melodic lines, according to the presentation rate and frequency distance between the sounds. At an intermediate distance, in the 'ambiguous' range, both percepts are possible. We conducted an electrophysiological experiment to determine whether an ambiguous sound organization could be modulated toward an integrated or segregated percept by the synchronous presentation of visual cues. Two sets of sounds (one high frequency and one low frequency) were interleaved. To promote integration or segregation, visual stimuli were synchronized to either the within-set frequency pattern or to the across-set intensity pattern. Elicitation of the mismatch negativity (MMN) component of event-related brain potentials was used to index the segregated organization, when no task was performed with the sounds. MMN was elicited only when the visual pattern promoted the segregation of the sounds. The results demonstrate cross-modal effects on auditory object perception in that sound ambiguity was resolved by synchronous presentation of visual stimuli, which promoted either an integrated or segregated perception of the sounds. (+info)
Mismatch negativity contribution in multiple sclerosis patients.
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Mismatch Negativity is a functional index of the supratemporal auditory cortex. AIM: The aim of the present study on Mismatch Negativity (MMN) in multiple sclerosis (MS) patients was to evaluate if the MMN can be correlated with cognitive deficits assessed by the Paced Auditory Addition Task--PASAT. METHOD: a clinical study in forty females and 20 males separated in two groups: control individuals and those with a definite diagnosis of MS underwent a duration and frequency MMN. The MMN latencies and negative amplitudes obtained from the MS group were compared to the ones from the control group. The scores from the Paced Auditory Addition Task were correlated either with the presence or the absence of MMN. RESULTS: MMN was found in 60% of the individuals with multiple sclerosis within the auditory stimulation protocol with varied durations, and in 45 % within the auditory stimulation protocol with frequency variations. There were no statistically significant differences in latencies and amplitudes when compared to controls. We found a statistically significant correlation for the lack of MMN wave together with cognitive disorder asserted by the PASAT. CONCLUSIONS: The MMN correlated to the cognitive deficit assessed by the PASAT. (+info)
Preperceptual human number sense for sequential sounds, as revealed by mismatch negativity brain response?
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Humans and some other species can nonlinguistically operate on the quantities of things or events, including sounds. Whether this ability is restricted to conscious percepts of sounds developing in approximately 200 ms is, however, unclear. To this end, we recorded the mismatch negativity (MMN) brain response, an index of preperceptual auditory change detection, of adult humans who passively listened to rare sequences of four 50-ms tones ("deviants") interspersed among frequently repeated tones ("standards"). Each tone was either 1000 or 1500 Hz in frequency. Deviants differed from standards in a ratio of the tones of the 2 frequencies. MMN was found for deviants by 160 ms from the onset of their largest ratio difference from standards (2:2 vs. 4:0), suggesting some ability of the human brain to operate on the number of sequential sounds of specific frequencies at a preperceptual time scale. (+info)