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ABSTRACT: An important prerequisite for the development of animal models of human auditory evoked potentials (AEP) is the accurate identification of homology. Prior research has revealed some remarkably similar response properties between rat and human AEPs, although there remains little consensus regarding the nature or validity of this correspondence. In the present study we seek to extend this research by examining the response properties of rat AEP as a function of stimulus repetition and interval. The aim being to determine whether rat AEP components show the same paradoxical reversal of repetition suppression observed for the human N100 AEP component at brief stimulus intervals. To achieve this, AEPs were recorded epidurally at the vertex in the freely moving rat in response to acoustic stimuli presented at random stimulus intervals between 50 and 5000ms. Using stimulation and analysis techniques to remove AEP waveform distortion due to overlapping AEP responses, the present results show that rat AEP components can be successfully resolved at intervals as brief as 50ms. The results also demonstrate several fundamental types of correspondence between human and rat AEP components in terms of the sensitivity to stimulus interval and acoustic stimulus type. However the results found no evidence that rat AEP components show the reversal of repetition suppression at brief, relative to long, stimulus intervals as demonstrated for the N100 component in humans. The results are discussed in terms of EEG recording and AEP analysis procedures that provide promising avenues for future research.
Brain research 12/2012; · 2.46 Impact Factor
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ABSTRACT: The capacity of the human brain to detect deviance in the acoustic environment pre-attentively is reflected in a brain event-related potential (ERP), mismatch negativity (MMN). MMN is observed in response to the presentation of rare oddball sounds that deviate from an otherwise regular pattern of frequent background standard sounds. While the primate and cat auditory cortex (AC) exhibit MMN-like activity, it is unclear whether the rodent AC produces a deviant response that reflects deviance detection in a background of regularities evident in recent auditory stimulus history or differential adaptation of neuronal responses due to rarity of the deviant sound. We examined whether MMN-like activity occurs in epidural AC potentials in awake and anesthetized rats to high and low frequency and long and short duration deviant sounds. ERPs to deviants were compared with ERPs to common standards and also with ERPs to deviants when interspersed with many different standards to control for background regularity effects. High frequency (HF) and long duration deviant ERPs in the awake rat showed evidence of deviance detection, consisting of negative displacements of the deviant ERP relative to ERPs to both common standards and deviants with many standards. The HF deviant MMN-like response was also sensitive to the extent of regularity in recent acoustic stimulation. Anesthesia in contrast resulted in positive displacements of deviant ERPs. Our results suggest that epidural MMN-like potentials to HF sounds in awake rats encode deviance in an analogous manner to the human MMN, laying the foundation for animal models of disorders characterized by disrupted MMN generation, such as schizophrenia.
Frontiers in psychology. 01/2011; 2:367.
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ABSTRACT: Temporal and spectral sound information is processed asymmetrically in the brain with the left-hemisphere showing an advantage for processing the former and the right-hemisphere for the latter. Using monaural sound presentation we demonstrate a context and ability dependent ear-asymmetry in brain measures of temporal change detection. Our measure of temporal processing ability was a gap-detection task quantifying the smallest silent gap in a sound that participants could reliably detect. Our brain measure was the size of the mismatch-negativity (MMN) auditory event-related potential elicited to infrequently presented gap sounds. The MMN indexes discrimination ability and is automatically generated when the brain detects a change in a repeating pattern of sound. MMN was elicited in unattended sequences of infrequent gap-sounds presented among regular no-gap sounds. In Study 1, participants with low gap-detection thresholds (good ability) produced a significantly larger MMN to gap sounds when sequences were presented monaurally to the right-ear than to the left-ear. In Study 2, we not only replicated a right-ear-advantage for MMN in silence in good temporal processors, but also showed that this is reversed to a significant left-ear-advantage for MMN when the same sounds are presented against a background of constant low-level noise. In both studies, poor discriminators showed no ear-advantage, and in Study 2, exhibited no differential sensitivity of the ears to noise. We conclude that these data reveal a context and ability-dependent asymmetry in processing temporal information in non-speech sounds.
Neuropsychologia 10/2010; 49(1):69-82. · 3.64 Impact Factor
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Linda E Campbell,
Matthew Hughes, Timothy W Budd,
Gavin Cooper,
W Ross Fulham,
Frini Karayanidis,
Mary-Claire Hanlon,
Wendy Stojanov,
Patrick Johnston,
Vanessa Case,
Ulrich Schall
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ABSTRACT: Feedforward inhibition deficits have been consistently demonstrated in a range of neuropsychiatric conditions using prepulse inhibition (PPI) of the acoustic startle eye-blink reflex when assessing sensorimotor gating. While PPI can be recorded in acutely decerebrated rats, behavioural, pharmacological and psychophysiological studies suggest the involvement of a complex neural network extending from brainstem nuclei to higher order cortical areas. The current functional magnetic resonance imaging study investigated the neural network underlying PPI and its association with electromyographically (EMG) recorded PPI of the acoustic startle eye-blink reflex in 16 healthy volunteers. A sparse imaging design was employed to model signal changes in blood oxygenation level-dependent (BOLD) responses to acoustic startle probes that were preceded by a prepulse at 120 ms or 480 ms stimulus onset asynchrony or without prepulse. Sensorimotor gating was EMG confirmed for the 120-ms prepulse condition, while startle responses in the 480-ms prepulse condition did not differ from startle alone. Multiple regression analysis of BOLD contrasts identified activation in pons, thalamus, caudate nuclei, left angular gyrus and bilaterally in anterior cingulate, associated with EMG-recorded sensorimotor gating. Planned contrasts confirmed increased pons activation for startle alone vs 120-ms prepulse condition, while increased anterior superior frontal gyrus activation was confirmed for the reverse contrast. Our findings are consistent with a primary pontine circuitry of sensorimotor gating that interconnects with inferior parietal, superior temporal, frontal and prefrontal cortices via thalamus and striatum. PPI processes in the prefrontal, frontal and superior temporal cortex were functionally distinct from sensorimotor gating.
European Journal of Neuroscience 11/2007; 26(8):2327-33. · 3.63 Impact Factor
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ABSTRACT: Behavioural evidence suggests that individuals with schizophrenia may exhibit impairment in the encoding of cues to sound location. There are three primary cues used by the auditory system to locate the position of a sound in space: interaural differences in the arrival-time (ITD), phase (IPD), and the loudness (ILD) of the sound at the two ears. The goal in this study was to obtain an electrophysiological index of preattentive detection of change in sound lateralization created by these cues.
The amplitude of mismatch negativity (MMN) was measured in 18 individuals with schizophrenia and 19 healthy comparison subjects to changes in sound lateralization produced by interaural temporal cues (ITD and IPD) and interaural loudness cues (ILD). Performance was also investigated on a target detection task, where targets were defined by ITD, IPD, or ILD cues.
Individuals with schizophrenia had reduced MMN amplitudes and decreased hit rates when deviants were created by interaural temporal cues, but not when loudness cues were used.
Results from both the MMN and behavioural task revealed a selective impairment in the use of temporal cues to sound lateralization in individuals with schizophrenia.
This finding supports previous research that suggests impairment in the encoding of the temporal information in schizophrenia.
Clinical Neurophysiology 05/2007; 118(4):833-44. · 3.41 Impact Factor
