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Your search keyword '"Murray, Micah M."' showing total 17 results
Start Over Author "Murray, Micah M." Publisher society for neuroscience
17 results on '"Murray, Micah M."'

14. How the Visual Brain Encodes and Keeps Track of Time.

Author

Salvioni, Paolo, Murray, Micah M., Kalmbach, Lysiann, and Bueti, Domenica

Subjects
*SENSORY evaluation, *NEUROPLASTICITY, *MEMORY, *SHORT-term memory, *CORTEX (Botany)
Abstract

Time is embedded in any sensory experience: the movements of a dance, the rhythm of a piece of music, the words of a speaker are all examples of temporally structured sensory events. In humans, if and how visual cortices perform temporal processing remains unclear. Here we show that both primary visual cortex (VI) and extrastriate area V5/MT are causally involved in encoding and keeping time in memory and that this involvement is independent from low-level visual processing. Most importantly we demonstrate that VI and V5/MT come into play simultaneously and seem to be functionally linked during interval encoding, whereas they operate serially (VI followed by V5/MT) and seem to be independent while maintaining temporal information in working memory. These data help to refine our knowledge of the functional properties of human visual cortex, highlighting the contribution and the temporal dynamics of VI and V5/MT in the processing of the temporal aspects of visual information. [ABSTRACT FROM AUTHOR]

Published
2013
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15. Learning-Induced Plasticity in Auditory Spatial Representations Revealed by Electrical Neuroimaging.

Author

Spierer, Lucas, Tardif, Eric, Sperdin, Holger, Murray, Micah M., and Clarke, Stephanie

Subjects
AUDITORY cortex, EVOKED potentials (Electrophysiology), BRAIN imaging, BRAIN, CEREBRAL dominance
Abstract

Auditory spatial representations are likely encoded at a population level within human auditory cortices. We investigated learning-induced plasticity of spatial discrimination in healthy subjects using auditory-evoked potentials (AEPs) and electrical neuroimaging analyses. Stimuli were 100 ms white-noise bursts lateralized with varying interaural time differences. In three experiments, plasticity was induced with 40 min of discrimination training. During training, accuracy significantly improved from near-chance levels to ∼75%. Before and after training, AEPs were recorded to stimuli presented passively with a more medial sound lateralization outnumbering a more lateral one (7:1). In experiment 1, the same lateralizations were used for training and AEP sessions. Significant AEP modulations to the different lateralizations were evident only after training, indicative of a learning-induced mismatch negativity (MMN). More precisely, this MMN at 195-250 ms after stimulus onset followed from differences in the AEP topography to each stimulus position, indicative of changes in the underlying brain network. In experiment 2, mirror-symmetric locations were used for training and AEP sessions; no training-related AEP modulations or MMN were observed. In experiment 3, the discrimination of trained plus equidistant untrained separations was tested psychophysically before and 0, 6, 24, and 48 h after training. Learning-induced plasticity lasted <6 h, did not generalize to untrained lateralizations, and was not the simple result of strengthening the representation of the trained lateralizations. Thus, learning-induced plasticity of auditory spatial discrimination relies on spatial comparisons, rather than a spatial anchor or a general comparator. Furthermore, cortical auditory representations of space are dynamic and subject to rapid reorganization. [ABSTRACT FROM AUTHOR]

Published
2007
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16. Occipital Transcranial Magnetic Stimulation Has Opposing Effects on Visual and Auditory Stimulus Detection: Implications for Multisensory Interactions

Author

Micah M. Murray, Vincenzo Romei, Lotfi B. Merabet, Gregor Thut, Romei, Vincenzo, Murray, Micah M., Merabet, Lotfi B., and Thut, Gregor

Subjects
Adult, Male, Visual perception, genetic structures, media_common.quotation_subject, medicine.medical_treatment, Stimulation, Stimulus (physiology), behavioral disciplines and activities, Primary visual cortex, Perception, Moro reflex, medicine, Reaction Time, Humans, Auditory, media_common, Visual Cortex, Neuroscience (all), Crossmodal, Multisensory, General Neuroscience, musculoskeletal, neural, and ocular physiology, Articles, Transcranial Magnetic Stimulation, eye diseases, Electric Stimulation, Transcranial magnetic stimulation, Visual cortex, medicine.anatomical_structure, Acoustic Stimulation, TMS, Auditory Perception, Visual Perception, Female, Visual, Psychology, Neuroscience, Photic Stimulation, Psychomotor Performance, psychological phenomena and processes, Human
Abstract

Multisensory interactions occur early in time and in low-level cortical areas, including primary cortices. To test current models of early auditory-visual (AV) convergence in unisensory visual brain areas, we studied the effect of transcranial magnetic stimulation (TMS) of visual cortex on behavioral responses to unisensory (auditory or visual) or multisensory (simultaneous auditory-visual) stimulus presentation. Single-pulse TMS was applied over the occipital pole at short delays (30-150 ms) after external stimulus onset. Relative to TMS over a control site, reactions times (RTs) to unisensory visual stimuli were prolonged by TMS at 60-75 ms poststimulus onset (visual suppression effect), confirming stimulation of functional visual cortex. Conversely, RTs to unisensory auditory stimuli were significantly shortened when visual cortex was stimulated by TMS at the same delays (beneficial interaction effect of auditory stimulation and occipital TMS). No TMS-effect on RTs was observed for AV stimulation. The beneficial interaction effect of combined unisensory auditory and TMS-induced visual cortex stimulation matched and was correlated with the RT-facilitation after external multisensory AV stimulation without TMS, suggestive of multisensory interactions between the stimulus-evoked auditory and TMS-induced visual cortex activities. A follow-up experiment showed that auditory input enhances excitability within visual cortex itself (using phosphene-induction via TMS as a measure) over a similarly early time-window (75-120 ms). The collective data support a mechanism of early auditory-visual interactions that is mediated by auditory-driven sensitivity changes in visual neurons that coincide in time with the initial volleys of visual input. Copyright © 2007 Society for Neuroscience.

Published
2007

17. Looming Signals Reveal Synergistic Principles of Multisensory Integration

Author

Céline Cappe, Vincenzo Romei, Antonia Thelen, Micah M. Murray, Gregor Thut, Cappe, Cã©line, Thelen, Antonia, Romei, Vincenzo, Thut, Gregor, and Murray, Micah M.

Subjects
Adult, Male, Auditory perception, Visual perception, Adolescent, media_common.quotation_subject, Stimulus (physiology), 050105 experimental psychology, Cuneus, Neural Pathway, Young Adult, 03 medical and health sciences, 0302 clinical medicine, Looming, Perception, Neural Pathways, Reaction Time, medicine, Humans, 0501 psychology and cognitive sciences, Evoked Potentials, media_common, Neuroscience (all), General Neuroscience, 05 social sciences, Multisensory integration, Articles, medicine.anatomical_structure, Acoustic Stimulation, Auditory Perception, Visual Perception, Female, Evoked Potential, Psychology, Neuroscience, Insula, Photic Stimulation, 030217 neurology & neurosurgery, Human
Abstract

Multisensory interactions are a fundamental feature of brain organization. Principles governing multisensory processing have been established by varying stimulus location, timing and efficacy independently. Determining whether and how such principles operate when stimuli vary dynamically in their perceived distance (as when looming/receding) provides an assay for synergy among the above principles and also means for linking multisensory interactions between rudimentary stimuli with higher-order signals used for communication and motor planning.Humanparticipants indicated movement of looming or receding versus static stimuli that were visual, auditory, or multisensory combinations while 160-channel EEG was recorded. Multivariate EEG analyses and distributed source estimations were performed. Nonlinear interactions between looming signals were observed at early poststimulus latencies (~75 ms) in analyses of voltage waveforms, global field power, and source estimations. These looming-specific interactions positively correlated with reaction time facilitation, providing direct links between neural and performance metrics of multisensory integration. Statistical analyses of source estimations identified looming-specific interactions within the right claustrum/insula extending inferiorly into the amygdala and also within the bilateral cuneus extending into the inferior and lateral occipital cortices. Multisensory effects common to all conditions, regardless of perceived distance and congruity, followed (~115 ms) and manifested as faster transition between temporally stable brain networks (vs summed responses to unisensory conditions). We demonstrate the early-latency, synergistic interplay between existing principles of multisensory interactions. Such findings change the manner in which to model multisensory interactions at neural and behavioral/perceptual levels. We also provide neurophysiologic backing for the notion that looming signals receive preferential treatment during perception. © 2012 the authors.

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