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In JoVE (1)
Other Publications (20)
- Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology
- Neuroreport
- Brain and Cognition
- Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology
- Brain Research. Cognitive Brain Research
- Neuropsychologia
- Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology
- The Journal of the Acoustical Society of America
- The European Journal of Neuroscience
- Brain Research
- Neuroreport
- Psychophysiology
- Neuroreport
- Psychophysiology
- Neuroreport
- Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology
- Neuropsychologia
- Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
- Brain and Language
- Neuropsychologia
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Articles by Blake W. Johnson in JoVE
JoVE General
Измерение Neuromagnetic функции мозга в Дети дошкольного возраста с настраиваемыми Sized MEG
Macquarie Centre for Cognitive Science, Macquarie University
Появление системы МЭГ размера для маленьких детей, открывает широкие новые возможности для изучения развития мозга. Новая система, вместе с протоколом, который выравнивает экспериментальные требования способностей детей, могут быть использованы для изучения когнитивных и языковых процессов у здоровых, проснись детей в возрасте от трех до шести.
Other articles by Blake W. Johnson on PubMed
Comparison of the N300 and N400 ERPs to Picture Stimuli in Congruent and Incongruent Contexts
The aim of this study was to examine the N300 and N400 effect to pictures that were semantically incongruous to a prior object name. Based upon theories of object identification, the semantic incongruity was manipulated to occur early or late in the object processing stream.
Cerebral Asymmetry for Mental Rotation: Effects of Response Hand, Handedness and Gender
We assessed lateralization of brain function during mental rotation, measuring the scalp distribution of a 400-600 ms latency event-related potential (ERP) with 128 recording electrodes. Twenty-four subjects, consisting of equal numbers of dextral and sinistral males and females, performed a mental rotation task under two response conditions (dominant non-dominant hand). For males, ERPs showed a right parietal bias regardless of response hand. For females, the parietal ERPs were slightly left-lateralized when making dominant hand responses, but strongly right-lateralized when making non-dominant hand responses. These results support the notion that visuo-spatial processing is more bilaterally organized in females. However, left hemisphere resources may be allocated to response preparation when using the non-dominant hand, forcing visuo-spatial processing to the right hemisphere.
A High Density ERP Comparison of Mental Rotation and Mental Size Transformation
To compare mental rotation and mental size transformation, 128-channel EEG was recorded while subjects performed both tasks using random two-dimensional shapes as stimuli. Behavioural results showed significant linear effects of both size transformation and mental rotation on reaction times. Rotation ERPs showed experimental effects at two latencies: a bilateral component distributed over posterior parietal electrodes at a latency of approximately 232-300ms and a second component at approximately 424-492ms distributed over right anterior parietal electrodes. The latency and spatial distribution of this second effect is consistent with previous research indicating a functional connection between this component and mental rotation. ERPs for the size-transformation task showed an effect at 180-228ms distributed bilaterally over occipital-temporal electrodes. These results are consistent with previous hemodynamic imaging studies that show involvement of parietal cortex in mental rotation and also the involvement of BA 19 in size-transformation tasks. However, the superior temporal resolution of the present data indicates that BA 19 activation may occur at a latency that is more likely related to apparent motion than to the size-transformation operation per se.
Neural Activity Associated with Binaural Processes for the Perceptual Segregation of Pitch
We measured late cortical potentials in a psychophysical procedure for binaural unmasking of a dichotically-embedded pitch.
Mu Rhythm Modulation During Observation of an Object-directed Grasp
Recent electrophysiological studies have shown that the human electroencephalographic mu rhythm is suppressed during the observation of actions performed by other persons, an effect that may be functionally related to the behaviour of so-called "mirror neurons" observed in area F5 of nonhuman primates. Because mirror neuron activity has been reported to be functionally specific to object-oriented actions, the present study was designed to determine if the human mu rhythm also exhibits this property. EEG measurements were obtained from 12 normal subjects while they observed either a precision grip of a manipulandum or an empty grip using the same hand position. Our results showed that the magnitude of the mu rhythm was significantly lower for the object grip condition than for the empty grip condition. These data support the notion that the human mu rhythm indexes a brain system that is functionally comparable to the monkey mirror neuron system. We propose that nonobject-directed actions may result in representational schemas that are either different or less salient than motorically equivalent actions that are directed toward objects.
One Good Turn Deserves Another: an Event-related Brain Potential Study of Rotated Mirror-normal Letter Discriminations
The time to decide if a letter is normal or backwards (mirror-reversed) increases as the letter is rotated away from the upright. It is widely accepted that this increase in time reflects the mental rotation of the stimulus to the upright orientation in order to determine the mirror-normal status of the stimulus. Although response times tend to be longer for mirrored stimuli than for normal stimuli, the difference is constant across orientation. Little work has been focused on why mirror-image stimuli produce longer response times than normal stimuli. This study examines the question of whether or not mirrored stimuli are rotated in the picture plane at the same time as normal stimuli, and if so, why response times to mirrored stimuli are longer than that for normal stimuli. Both the behavioural and electrophysiological findings suggest that the mirrored stimuli are not only rotated in the picture plane, but that they are subsequently rotated to the normal view. It is this additional rotation that produces, at least in part, the delayed response times for mirror-image stimuli.
Primary Motor Cortex Activation During Action Observation Revealed by Wavelet Analysis of the EEG
We characterised the spectral response of the EEG to median nerve stimulation using wavelet analysis, and compared the relative magnitudes of effect of several different action-observation conditions on the beta and mu 'rebound' rhythms.
Object-related Brain Potentials Associated with the Perceptual Segregation of a Dichotically Embedded Pitch
The cortical mechanisms of perceptual segregation of concurrent sound sources were examined, based on binaural detection of interaural timing differences. Auditory event-related potentials were measured from 11 healthy subjects. Binaural stimuli were created by introducing a dichotic delay of 500-ms duration to a narrow frequency region within a broadband noise, and resulted in a perception of a centrally located noise and a right-lateralized pitch (dichotic pitch). In separate listening conditions, subjects actively discriminated and responded to randomly interleaved binaural and control stimuli, or ignored random stimuli while watching silent cartoons. In a third listening condition subjects ignored stimuli presented in homogenous blocks. For all listening conditions, the dichotic pitch stimulus elicited an object-related negativity (ORN) at a latency of about 150-250 ms after stimulus onset. When subjects were required to actively respond to stimuli, the ORN was followed by a P400 wave with a latency of about 320-420 ms. These results support and extend a two-stage model of auditory scene analysis in which acoustic streams are automatically parsed into component sound sources based on source-relevant cues, followed by a controlled process involving identification and generation of a behavioral response.
Long-term Potentiation of Human Visual Evoked Responses
Long-term potentiation (LTP) is a candidate synaptic mechanism underlying learning and memory that has been studied extensively at the cellular and molecular level in laboratory animals. To date, LTP has only been directly demonstrated in humans in isolated cortical tissue obtained from patients undergoing surgery, where it displays properties identical to those seen in non-human preparations. Inquiry into the functional significance of LTP has been hindered by the absence of a human model. Here we give the first demonstration that the rapid repetitive presentation of a visual checkerboard (a photic 'tetanus') leads to a persistent enhancement of one of the early components of the visual evoked potential in normal humans. The potentiated response is largest in the hemisphere contralateral to the tetanized visual hemifield and is limited to one component of the visual evoked response (the N1b). The selective potentiation of only the N1b component makes overall brain excitability changes unlikely and suggests that the effect is due instead to an LTP process. While LTP is known to exist in the human brain, the ability to elicit LTP from non-surgical patients will provide a human model system allowing the detailed examination of synaptic plasticity in normal subjects and may have future clinical applications in the assessment of cognitive disorders.
Neural Processing of Observed Oro-facial Movements Reflects Multiple Action Encoding Strategies in the Human Brain
In this experiment, the oscillatory responses of the MEG were characterized during the observation of four viewing conditions: (a) observation of mouth movements, (b) observation of a non-biological motion stimulus (a mechanical aperture opening and shutting), (c) observation of object-directed mouth movements and (d) observation of speech-like mouth movements. Data were analyzed using synthetic aperture magnetometry (SAM) in three frequency bands, beta (15-35 Hz), gamma (35-70 Hz) and alpha/mu (8-15 Hz). Results showed that observations of biological motion resulted in beta desynchronization over lateral sensorimotor areas, while observations of non-biological motion resulted in a more medial desynchronization, an effect that may be related to the processing of a structured event sequence. Observation of linguistic movements resulted in less alpha/beta desynchronization in posterior brain regions in comparison to biological motion stimuli, suggesting that linguistically-relevant stimuli are processed with different neuronal systems than those recruited by normal action observation. We suggest that non-linguistic actions recruit dorsal systems while linguistic actions engage ventral processing systems. Object-directed movements showed the largest sensorimotor activations, suggesting that, as is the case for observations of hand movements, motoric processing is particularly sensitive to the viewing of goal-directed actions. Taken together, the results indicate that the brain utilizes multiple action encoding strategies, tailored to the function of the observed movement.
Differential Cortical Processing of Location and Pitch Changes in Dichotic Pitch
The objective of this study was to determine whether the auditory mismatch negativity can be elicited by changes in spatial and nonspatial cues within dichotic pitches. Participants were presented with blocks of standard dichotic pitch stimuli in which location or pitch was occasionally varied. A mismatch negativity was reliably elicited by deviant locations; in contrast, no measurable mismatch negativity response was found for deviant pitches. A separate psychophysical screening procedure ruled out the possibility that participants could not hear the pitch deviations. The results indicate that spatial and nonspatial features of dichotic pitch receive differential processing at a preattentive level of analysis within the auditory system and are supportive of recent notions of dual processing streams in audition.
Cerebral Processes During Visuo-motor Imagery of Hands
We investigated the role of cerebral motor structures during mental hand rotation. Neural activity was measured with event-related potentials (ERPs) in 16 healthy participants while they performed handedness judgments of visually presented hands. Mental rotation was associated with ERP amplitude modulations as early as 170 ms but most strongly during a time window of about 600-800 ms. Source analysis of ERPs during these time windows indicated generators in bilateral extrastriate and parietal cortices. The results do not support a direct involvement of anterior motor cortices in the neural computations underlying mental rotation. However, motor regions may play a role in providing ongoing kinaesthetic feedback during mental rotation or in checking the results of the imagined transformation.
Graded Cue Information in Dichotic Pitch: Effects on Event-related Potentials
To determine whether electroencephalogram components elicited by dichotic pitch stimuli are all-or-none threshold-like responses or graded responses that depend on the saliency of the stimuli, we recorded electroencephalograms while participants listened to dichotic pitch stimuli constructed with different signal-to-background ratios. The object-related negativity and P400 components were largest when the dichotic pitch was most salient (high signal-to-background ratio), and decreased in amplitude with decreasing signal-to-background ratio. These results are similar to those reported for mistuned harmonics, thereby providing additional evidence that the object-related negativity and P400 components observed for these disparate stimulus types reflect similar processing. They also support the notion that the object-related negativity and P400 amplitudes are dependent on the level of relevant cue-based stimulus information.
Sequential Processing of Interaural Timing Differences for Sound Source Segregation and Spatial Localization: Evidence from Event-related Cortical Potentials
Cortical processing of interaural timing differences (ITDs) was investigated with event-related potential (ERP) measurements in 16 human participants who were required in separate tasks to detect or to spatially localize dichotically embedded pitches. ITDs elicited three ERP components labeled ORN, N2, and P400. The ORN occurred at a latency of 150-250 ms and was elicited by ITDs regardless of location or task. In contrast, the N2 response (250-350 ms) was strongly modulated by location and showed larger amplitudes for the localization task than for the detection task. Finally, ITDs in the detection task elicited a P400 at a latency of 400-500 ms, but this response was entirely absent from ERPs elicited by identical stimuli in the localization task. These results are consistent with a sequential model of auditory perception in which segregation of concurrent sounds is followed by domain-specific processing of object location and identity.
Event-related Potentials for Interaural Time Differences and Spectral Cues
Dichotic pitches and mistuned harmonics can each lead to the perception of one or two auditory objects. Comparison of event-related potentials for the perception of one versus two objects reveals an early negative and a late positive component. The relationship of these components with auditory segregation was further investigated using stimuli containing monaural spectral cues to pitch, binaural timing cues to pitch, or a combination of both, interleaved with control stimuli (no pitch). Stimuli containing timing cues or a combination of timing and spectral cues reliably elicited both components, which were of larger amplitude when both cues were present. For stimuli containing only spectral cues, the early component was attenuated in amplitude and no measurable late component was detected.
Measurement of Brain Function in Pre-school Children Using a Custom Sized Whole-head MEG Sensor Array
Conventional whole-head MEG systems have fixed sensor arrays designed to accommodate most adult heads. However arrays optimised for adult brain measurements are suboptimal for research with the significantly smaller heads of young children. We wished to measure brain activity in children using a novel whole-head MEG system custom sized to fit the heads of pre-school-aged children.
Processing of Binaural Spatial Information in Human Auditory Cortex: Neuromagnetic Responses to Interaural Timing and Level Differences
This study was designed to test two hypotheses about binaural hearing: (1) that binaural cues are primarily processed in the hemisphere contralateral to the perceived location of a sound; and (2) that the two main binaural cues, interaural timing differences and interaural level differences, are processed in separate channels in the auditory cortex. Magnetoencephalography was used to measure brain responses to dichotic pitches--a perception of pitch created by segregating a narrow band of noise from a wider band of noise--derived from interaural timing or level disparities. Our results show a strong modulation of interhemispheric M100 amplitudes by ITD cues. When these cues simulated source presentation unilaterally from the right hemispace, M100 amplitude changed from a predominant right hemisphere pattern to a bilateral pattern. In contrast, ILD cues lacked any capacity to alter the right hemispheric distribution. These data indicate that intrinsic hemispheric biases are large in comparison to any contralaterality biases in the auditory system. Importantly, both types of binaural cue elicited a circa 200 ms latency object-related negativity component, believed to reflect automatic cortical processes involved in distinguishing concurrent auditory objects. These results support the conclusion that ITDs and ILDs are processed by distinct neuronal populations to relatively late stages of cortical processing indexed by the M100. However information common to the two cues seems to be extracted for use in a subsequent stage of auditory scene segregation indexed by the object related negativity. This may place a new bound on the extent to which sound location cues are processed in separate channels of the auditory cortex.
Premovement Brain Activity in a Bimanual Load-lifting Task
Even the simplest volitional movements must be precisely coordinated with anticipatory postural adjustments. Little is currently known about the neural networks that coordinate these adjustments in healthy adults. We measured brain activity prior to movement during a bimanual load-lifting task, designed to elicit anticipatory adjustments in a restricted and well-defined set of musculature in the arm. Electroencephalography and magnetoencephalography brain measurements were obtained from eleven participants while they performed a bimanual load-lifting task that required precise inter-limb coordination. Anticipatory biceps brachii inhibition in the loaded arm was associated with a robust desynchronization of the beta rhythm. Beamforming analyses localized beta band responses to the parietal lobules, pre- and post-central gyri, middle and medial frontal gyri, basal ganglia and thalamus. The current study shows that premovement brain activity in a bimanual load-lifting task can be imaged with magnetoencephalography. Future experiments will partition out brain activity associated with anticipatory postural adjustments and volitional movements. The experimental paradigm will also be useful in the study of motor function in patients with developmental or degenerative disorders.
How the Brain Responds to Any: an MEG Study
The word any may appear in some sentences, but not in others. For example, any is permitted in sentences that contain the word nobody, as in Nobody ate any fruit. However, in a minimally different context any seems strikingly anomalous: (*)Everybody ate any fruit. The aim of the present study was to investigate how the brain responds to the word any in such minimally different contexts - where it is permitted (licensed) and where it is not permitted (unlicensed). Brain responses were measured from adult readers using magnetoencephalography (MEG). The results showed significantly larger responses to permissible contexts in the left posterior temporal areas between 400-500 ms and 590-660 ms. These results clarify the anatomy and timing of brain processes that contribute to our judgment that a word such as any is or is not permitted in a given context.
"Shut Up!" An Electrophysiological Study Investigating the Neural Correlates of Vocal Inhibition
A neural biomarker that can be applied to studies of oral communication disorders would provide a boon to researchers. While there has been much research conducted on manual response inhibition, very few studies have examined vocal response inhibition. To date, no study has examined the temporal aspects of vocal inhibition. Therefore, the present study attempted to identify the neural correlates of vocal response inhibition by recording electroencephalographic activity during a modified version of the stop signal task. We included an ignore signal condition matched for frequency and visual stimulation to the stop signal which importantly, was included in the same block of trials as the typical go and stop trials. Behavioural results showed that participants were able to inhibit a vocal response within approximately 324ms. Statistical analysis of ERPs revealed that a positive component around 324ms was significantly larger in amplitude during successfully stopped trials compared to in an ignore condition, particularly over a cluster of fronto-central electrodes. These results support the notion that the P3 component is a reliable index of vocal inhibition.
