@article {4335, title = {Within-subject reaction time variability: Role of cortical networks and underlying neurophysiological mechanisms.}, journal = {Neuroimage}, volume = {237}, year = {2021}, month = {08/2021}, pages = {118127}, abstract = {

Variations in reaction time are a ubiquitous characteristic of human behavior. Extensively documented, they have been successfully modeled using parameters of the subject or the task, but the neural basis of behavioral reaction time that varies within the same subject and the same task has been minimally studied. In this paper, we investigate behavioral reaction time variance using 28 datasets of direct cortical recordings in humans who engaged in four different types of simple sensory-motor reaction time tasks. Using a previously described technique that can identify the onset of population-level cortical activity and a novel functional connectivity algorithm described herein, we show that the cumulative latency difference of population-level neural activity across the task-related cortical network can explain up to 41\% of the trial-by-trial variance in reaction time. Furthermore, we show that reaction time variance may primarily be due to the latencies in specific brain regions and demonstrate that behavioral latency variance is accumulated across the whole task-related cortical network. Our results suggest that population-level neural activity monotonically increases prior to movement execution, and that trial-by-trial changes in that increase are, in part, accounted for by inhibitory activity indexed by low-frequency oscillations. This pre-movement neural activity explains 19\% of the measured variance in neural latencies in our data. Thus, our study provides a mechanistic explanation for a sizable fraction of behavioral reaction time when the subject{\textquoteright}s task is the same from trial to trial.

}, keywords = {Adult, Algorithms, Alpha Rhythm, Cerebral Cortex, Connectome, Electrocorticography, Female, Gamma Rhythm, Humans, Male, Middle Aged, Nerve Net, Psychomotor Performance, Reaction Time, Young Adult}, issn = {1095-9572}, doi = {10.1016/j.neuroimage.2021.118127}, author = {Paraskevopoulou, Sivylla E and Coon, William G and Peter Brunner and Miller, Kai J and Schalk, Gerwin} } @article {3370, title = {Brain-computer interface (BCI) evaluation in people with amyotrophic lateral sclerosis.}, journal = {Amyotroph Lateral Scler Frontotemporal Degener}, volume = {15}, year = {2014}, month = {06/2014}, pages = {207-15}, abstract = {Brain-computer interfaces (BCIs) might restore communication to people severely disabled by amyotrophic lateral sclerosis (ALS) or other disorders. We sought to: 1) define a protocol for determining whether a person with ALS can use a visual P300-based BCI; 2) determine what proportion of this population can use the BCI; and 3) identify factors affecting BCI performance. Twenty-five individuals with ALS completed an evaluation protocol using a standard 6 {\texttimes} 6 matrix and parameters selected by stepwise linear discrimination. With an 8-channel EEG montage, the subjects fell into two groups in BCI accuracy (chance accuracy 3\%). Seventeen averaged 92 ({\textpm} 3)\% (range 71-100\%), which is adequate for communication (G70 group). Eight averaged 12 ({\textpm} 6)\% (range 0-36\%), inadequate for communication (L40 subject group). Performance did not correlate with disability: 11/17 (65\%) of G70 subjects were severely disabled (i.e. ALSFRS-R < 5). All L40 subjects had visual impairments (e.g. nystagmus, diplopia, ptosis). P300 was larger and more anterior in G70 subjects. A 16-channel montage did not significantly improve accuracy. In conclusion, most people severely disabled by ALS could use a visual P300-based BCI for communication. In those who could not, visual impairment was the principal obstacle. For these individuals, auditory P300-based BCIs might be effective.}, keywords = {Adult, Aged, Amyotrophic Lateral Sclerosis, Biofeedback, Psychology, brain-computer interfaces, Communication Disorders, Electroencephalography, Event-Related Potentials, P300, Female, Humans, Male, Middle Aged, Online Systems, Photic Stimulation, Psychomotor Performance, Reaction Time}, issn = {2167-9223}, doi = {10.3109/21678421.2013.865750}, url = {http://www.ncbi.nlm.nih.gov/pubmed/24555843}, author = {McCane, Lynn M and Sellers, Eric W and Dennis J. McFarland and Mak, Joseph N and Carmack, C Steve and Zeitlin, Debra and Jonathan Wolpaw and Theresa M Vaughan} } @article {2204, title = {Nonuniform high-gamma (60-500 Hz) power changes dissociate cognitive task and anatomy in human cortex.}, journal = {J Neurosci}, volume = {31}, year = {2011}, month = {02/2011}, pages = {2091-100}, abstract = {

High-gamma-band (\>60 Hz) power changes in cortical electrophysiology are a reliable indicator of focal, event-related cortical activity. Despite discoveries of oscillatory subthreshold and synchronous suprathreshold activity at the cellular level, there is an increasingly popular view that high-gamma-band amplitude changes recorded from cellular ensembles are the result of asynchronous firing activity that yields wideband and uniform power increases. Others have demonstrated independence of power changes in the low- and high-gamma bands, but to date, no studies have shown evidence of any such independence above 60 Hz. Based on nonuniformities in time-frequency analyses of electrocorticographic (ECoG) signals, we hypothesized that induced high-gamma-band (60-500 Hz) power changes are more heterogeneous than currently understood. Using single-word repetition tasks in six human subjects, we showed that functional responsiveness of different ECoG high-gamma sub-bands can discriminate cognitive task (e.g., hearing, reading, speaking) and cortical locations. Power changes in these sub-bands of the high-gamma range are consistently present within single trials and have statistically different time courses within the trial structure. Moreover, when consolidated across all subjects within three task-relevant anatomic regions (sensorimotor, Broca{\textquoteright}s area, and superior temporal gyrus), these behavior- and location-dependent power changes evidenced nonuniform\ trends\ across the population. Together, the independence and nonuniformity of power changes across a broad range of frequencies suggest that a new approach to evaluating high-gamma-band cortical activity is necessary. These findings show that in addition to time and location, frequency is another fundamental dimension of high-gamma dynamics.

}, keywords = {Acoustic Stimulation, Adolescent, Adult, Analysis of Variance, Brain Mapping, Brain Waves, Cerebral Cortex, Cognition Disorders, Electroencephalography, Epilepsy, Evoked Potentials, Female, Humans, Male, Middle Aged, Neuropsychological Tests, Nonlinear Dynamics, Photic Stimulation, Reaction Time, Spectrum Analysis, Time Factors, Vocabulary}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.4722-10.2011}, url = {http://www.ncbi.nlm.nih.gov/pubmed/21307246}, author = {Charles M Gaona and Sharma, Mohit and Zachary V. Freudenberg and Breshears, Jonathan and Bundy, David T and Roland, Jarod and Barbour, Dennis L and Gerwin Schalk and Leuthardt, E C} } @article {3093, title = {Trained modulation of sensorimotor rhythms can affect reaction time.}, journal = {Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology}, volume = {122}, year = {2011}, month = {09/2011}, pages = {1820{\textendash}1826}, abstract = {OBJECTIVE: Brain-computer interface (BCI) technology might be useful for rehabilitation of motor function. This speculation is based on the premise that modifying the EEG will modify behavior, a proposition for which there is limited empirical data. The present study examined the possibility that voluntary modulation of sensorimotor rhythm (SMR) can affect motor behavior in normal human subjects. METHODS: Six individuals performed a cued-reaction task with variable warning periods. A typical variable foreperiod effect was associated with SMR desynchronization. SMR features that correlated with reaction times were then used to control a two-target cursor movement BCI task. Following successful BCI training, an uncued reaction time task was embedded within the cursor movement task. RESULTS: Voluntarily increasing SMR beta rhythms was associated with longer reaction times than decreasing SMR beta rhythms. CONCLUSIONS: Voluntary modulation of EEG SMR can affect motor behavior. SIGNIFICANCE: These results encourage studies that integrate BCI training into rehabilitation protocols and examine its capacity to augment restoration of useful motor function.}, keywords = {brain-computer interface, EEG, Reaction Time}, issn = {1872-8952}, doi = {10.1016/j.clinph.2011.02.016}, url = {http://www.ncbi.nlm.nih.gov/pubmed/21411366}, author = {Chadwick B. Boulay and Sarnacki, W. A. and Jonathan Wolpaw and Dennis J. McFarland} } @article {3278, title = {T complex hemispheric asymmetries: effects of stimulus intensity.}, journal = {Hearing research}, volume = {34}, year = {1988}, month = {08/1988}, pages = {225{\textendash}232}, abstract = {The T complex component of the human auditory evoked potential (AEP) is thought to be produced in auditory cortex, on the posterior lateral surface of the temporal lobe. Recorded over temporal scalp, it consists of an 80-90 ms positive peak, Ta, and a 120-140 negative peak, Tb. As part of an effort to develop the clinical usefulness of the T complex in assessing auditory cortical function, we studied the effects of change in monaural stimulus intensity (20-80 dB SL) on T complex latency, amplitude, and hemispheric differences in normal adults. Ta and Tb peak latencies decreased as stimulus intensity increased. These latency changes were not dependent on ear or hemisphere. Right hemisphere Ta latency was shorter with contralateral than with ipsilateral stimulation; while left hemisphere Ta latency was not dependent on the ear stimulated. Tb latency was shorter over the left hemisphere, and over the contralateral hemisphere. Ta-b amplitude increased as stimulus intensity increased. This amplitude change was not dependent on ear or hemisphere. Ta-b amplitudes were larger over the right hemisphere and over the contralateral hemisphere. Hemispheric asymmetries were not significantly affected by stimulus intensity.}, keywords = {Reaction Time}, issn = {0378-5955}, doi = {10.1016/0378-5955(88)90002-0}, url = {http://www.ncbi.nlm.nih.gov/pubmed/3170365}, author = {Anthony T. Cacace and Dowman, R. and Jonathan Wolpaw} } @article {3336, title = {Single unit activity vs. amplitude of the epidural evoked potential in primary auditory cortex of awake cats.}, journal = {Electroencephalography and clinical neurophysiology}, volume = {47}, year = {1979}, month = {09/1979}, pages = {372{\textendash}376}, abstract = {The study investigated, in primary auditory cortex (AI) of awake cats, the relationship over a range of stimuli between the amplitude and latency of the initial positive deflection (P1) of the primary evoked potential and the intensity of concurrent underlying evoked single unit activity. Epidural evoked potentials and extracellular responses of 155 single units to monaural 100 musec clicks ranging from 45 to 110 dB were recorded. At low stimulus levels, considerable unit response could occur with a very small P1. At middle stimulus levels, unit response was directly proportional to P1 amplitude. At higher stimulus levels, P1 amplitude continued to increase while unit response began to saturate.}, keywords = {Reaction Time}, issn = {0013-4694}, doi = {10.1016/0013-4694(79)90288-8}, url = {http://www.ncbi.nlm.nih.gov/pubmed/90607}, author = {Jonathan Wolpaw} } @article {3342, title = {Hemispheric differences in the auditory evoked response.}, journal = {Electroencephalography and clinical neurophysiology}, volume = {43}, year = {1977}, month = {07/1977}, pages = {99{\textendash}102}, abstract = {The separation of the 80-250 msec portion of the AER to click stimulation into N1P2, produced by large areas of cortex, and the T complex, probably produced by secondary auditory cortex, was recently described (Wolpaw and Penry 1975). The present study investigated the ipsilateral vs. contralateral and right vs. left hemispheric differences in N1P2 and T complex latencies and amplitudes. One msec clicks at 60 dB above threshold were presented at 4.7 sec intervals monaurally to 32 normal adults and binaurally to 13 of the 32. AERs were recorded from vertex and temporal referred to a balanced non-cephalic reference electrode. For monaural stimulation, N1P2 and T complex amplitudes were significantly greater and T complex latency was significantly less over the contralateral and right hemispheres. The ipsilateral vs. contralateral and right vs. left hemispheric amplitude differences were significanlty greater for the T complex than for N1P2. Binaural results, which provided in additional measure of right vs. left hemispheric differences, were in agreement with the monaural findings. The results are consistent with neurophysiologic and behavioral findings in regard to ipsilateral vs. contralateral and right vs. left hemispheric differences and support the hypothesis that the T complex is produced by secondary auditory cortex.}, keywords = {Reaction Time}, issn = {0013-4694}, doi = {10.1016/0013-4694(77)90200-0}, url = {http://www.ncbi.nlm.nih.gov/pubmed/68878}, author = {Jonathan Wolpaw and Penry, J. K.} }