Motor Reaction Time Tasks Research Articles

High gamma coherence between task-responsive sensory-motor cortical regions in a motor reaction-time task.

Electrical activity at high gamma frequencies (70-170 Hz) is thought to reflect the activity of small cortical ensembles. For example, high gamma activity (often quantified by spectral power) can increase in sensory-motor cortex in response to sensory stimuli or movement. On the other hand, synchrony of neural activity between cortical areas (often quantified by coherence) has been hypothesized as an important mechanism for inter-areal communication, thereby serving functional roles in cognition and behavior. Currently, high gamma activity has primarily been studied as a local amplitude phenomenon. We investigated the synchronization of high gamma activity within sensory-motor cortex and the extent to which underlying high gamma activity can explain coherence during motor tasks. We characterized high gamma coherence in sensory-motor networks and the relationship between coherence and power by analyzing electrocorticography (ECoG) data from human subjects as they performed a motor response to sensory cues. We found greatly increased high gamma coherence during the motor response compared with the sensory cue. High gamma power poorly predicted high gamma coherence, but the two shared a similar time course. However, high gamma coherence persisted longer than high gamma power. The results of this study suggest that high gamma coherence is a physiologically distinct phenomenon during a sensory-motor task, the emergence of which may require active task participation.NEW & NOTEWORTHY Motor action after auditory stimulus elicits high gamma responses in sensory-motor and auditory cortex, respectively. We show that high gamma coherence reliably and greatly increased during motor response, but not after auditory stimulus. Underlying high gamma power could not explain high gamma coherence. Our results indicate that high gamma coherence is a physiologically distinct sensory-motor phenomenon that may serve as an indicator of increased synaptic communication on short timescales (∼1 s).

Event-related desynchronization of alpha and beta band neural oscillations predicts speech and limb motor timing deficits in normal aging

Normal aging is associated with decline of motor timing mechanisms implicated in planning and execution of movement. Evidence from previous studies has highlighted the relationship between neural oscillatory activities and motor timing processing in neurotypical younger adults; however, it remains unclear how normal aging affects the underlying neural mechanisms of movement in older populations. In the present study, we recorded EEG activities in two groups of younger and older adults while they performed randomized speech and limb motor reaction time tasks cued by temporally predictable and unpredictable sensory stimuli. Our data showed that older adults were significantly slower than their younger counterparts during speech production and limb movement, especially in response to temporally unpredictable sensory stimuli. This behavioral effect was accompanied by significant desynchronization of alpha (7−12 Hz) and beta (13−25 Hz) band neural oscillatory activities in older compared with younger adults, primarily during the preparatory pre-motor phase of responses for speech production and limb movement. In addition, we found that faster motor reaction times in younger adults were significantly correlated with weaker desynchronization of pre-motor alpha and beta band neural activities irrespective of stimulus timing and response modality. However, the pre-motor components of alpha and beta activities were timing-specific in older adults and were more strongly desynchronized in response to temporally predictable sensory stimuli. These findings highlight the role of alpha and beta band neural oscillations in motor timing processing mechanisms and reflect their functional deficits during the planning phase of speech production and limb movement in normal aging.

Pathological attenuation of the right prefrontal cortex activity predicts speech and limb motor timing disorder in Parkinson’s disease

Neurological deficits can cause a wide range of motor symptoms in patients with Parkinson’s disease (PD). However, our understanding about the effects of PD on the underlying neural mechanisms of motor function has remained elusive. In the present study, we investigated the relationship between PD pathology and neurological deficits in planning and execution mechanisms of motor timing during speech production and limb movement. We used a combination of behavioral and event-related potential (ERP) measures to characterize motor timing deficits in patients with PD compared with a neurologically intact matched control group during randomized speech vowel vocalization and button press motor reaction time tasks in response to temporally predictable and unpredictable sensory stimuli. Behavioral results indicated slower motor reaction times in PD regardless of motor modality or temporal predictability of sensory stimuli. In addition, our analysis indicated that slower motor reaction times in PD were correlated with pathological attenuation of neural activities within the right precentral and inferior frontal cortex only before the onset of speech production and limb movement. These findings highlight the role of a right-lateralized prefrontal cortical network in motor planning and its relationship with PD pathology during speech and limb movement timing control. Based on these data, we suggest that pathological attenuation of neural activities within this network is a neurophysiological biomarker of general and modality non-specific motor timing deficits in PD. We propose that this right-lateralized prefrontal network is a potential candidate for targeted treatment of speech and limb motor timing disorders in patients with PD.

Behavioral and neural correlates of normal aging effects on motor preparatory mechanisms of speech production and limb movement.

Normal aging is associated with decline of the sensorimotor mechanisms that support movement function in the human brain. In this study, we used behavioral and event-related potential (ERP) recordings to investigate the effects of normal aging on the motor preparatory mechanisms of speech production and limb movement. The experiment involved two groups of older and younger adults who performed randomized speech vowel vocalization and button press motor reaction time tasks in response to temporally predictable and unpredictable visual stimuli. Behavioral results revealed age-related slowness of motor reaction time only during speech production in response to temporally unpredictable stimuli, and this effect was accompanied by increased pre-motor ERP activities in older vs. younger adults during the speech task. These results indicate that motor preparatory mechanisms of limb movement during button press are not affected by normal aging, whereas the functional capacity of these mechanisms is reduced in older adults during speech production in response to unpredictable sensory stimuli. These findings suggest that the aging brain selectively compromises the motor timing of speech and recruits additional neural resources for motor planning and execution of speech, as indexed by the increased pre-motor ERP activations in response to temporally unpredictable vs. predictable sensory stimuli.

Sensorimotor Impairment of Speech and Hand Movement Timing Processing in Parkinson’s Disease

Models of motor control have highlighted the role of temporal predictive mechanisms in sensorimotor processing of speech and limb movement timing. We investigated how these mechanisms are affected in Parkinson’s disease (PD) while patients performed speech and hand motor reaction time tasks in response to sensory stimuli with predictable and unpredictable temporal dynamics. Results showed slower motor reaction times in PD vs. control in response to temporally predictable, but not unpredictable stimuli. This effect was driven by faster motor responses to predictable stimuli in control subjects; however, no such effect was observed in the PD group. These findings indicated the relationship between PD pathology and sensorimotor deficits in temporal predictive mechanisms of timing processing during speech production and hand movement.

Probing meaningfulness of oscillatory EEG components with bootstrapping, label noise and reduced training sets.

As oscillatory components of the Electroencephalogram (EEG) and other electrophysiological signals may co-modulate in power with a target variable of interest (e.g. reaction time), data-driven supervised methods have been developed to automatically identify such components based on labeled example trials. Under conditions of challenging signal-to-noise ratio, high-dimensional data and small training sets, however, these methods may overfit to meaningless solutions. Examples are spatial filtering methods like Common Spatial Patterns (CSP) and Source Power Comodulation (SPoC). It is difficult for the practitioner to tell apart meaningful from arbitrary, random components. We propose three approaches to probe the robustness of extracted oscillatory components and show their application to both, simulated and EEG data recorded during a visually cued hand motor reaction time task.

Cortical inhibition in attention deficit hyperactivity disorder: new insights from the electroencephalographic response to transcranial magnetic stimulation

Attention deficit hyperactivity disorder is one of the most frequent neuropsychiatric disorders in childhood. Transcranial magnetic stimulation studies based on muscle responses (motor-evoked potentials) suggested that reduced motor inhibition contributes to hyperactivity, a core symptom of the disease. Here we employed the N100 component of the electroencephalographic response to transcranial magnetic stimulation as a novel marker for a direct assessment of cortical inhibitory processes, which has not been examined in attention deficit hyperactivity disorder so far. We further investigated to what extent affected children were able to regulate motor cortical inhibition, and whether effects of age on the electroencephalographic response to transcranial magnetic stimulation were compatible with either a delay in brain maturation or a qualitatively different development. N100 amplitude evoked by transcranial magnetic stimulation and its age-dependent development were assessed in 20 children with attention deficit hyperactivity disorder and 19 healthy control children (8-14 years) by 64-channel electroencephalography. Amplitude and latency of the N100 component were compared at rest, during response preparation in a forewarned motor reaction time task and during movement execution. The amplitude of the N100 component at rest was significantly lower and its latency tended to be shorter in children with attention deficit hyperactivity disorder. Only in controls, N100 amplitude to transcranial magnetic stimulation was reduced by response preparation. During movement execution, N100 amplitude decreased while motor evoked potential amplitudes showed facilitation, indicating that the electroencephalographic response to transcranial magnetic stimulation provides further information on cortical excitability independent of motor evoked potential amplitudes and spinal influences. Children with attention deficit hyperactivity disorder showed a smaller N100 amplitude reduction during movement execution compared with control children. The N100 amplitude evoked by transcranial magnetic stimulation decreased with increasing age in both groups. The N100 reduction in children with attention deficit hyperactivity disorder at all ages suggests a qualitative difference rather than delayed development of cortical inhibition in this disease. Findings further suggest that top-down control of motor cortical inhibition is reduced in children with attention deficit hyperactivity disorder. We conclude that evoked potentials in response to transcranial magnetic stimulation are a promising new marker of cortical inhibition in attention deficit hyperactivity disorder during childhood.

Fluctuations in regional BOLD signal measured prior to trial presentation predict performance on a simple motor reaction time task

Fluctuations in regional BOLD signal measured prior to trial presentation predict performance on a simple motor reaction time task

Striatopallidal regulation of affect in bipolar disorder

Background Evidence from the neuroimaging literature suggests that the basal ganglia plays an important role in the regulation of affect. This conclusion stems almost exclusively from group comparisons and it remains unclear whether previous findings can be confirmed from a longitudinal study of mood change. The aim of this study was to increase our understanding of the functional role of the basal ganglia and thalamus in relation to change in affect in patients with bipolar disorder. Methods Ten bipolar disorder subjects participated in a functional MRI study. We used a simple motor reaction time task to probe subcortical regions bilaterally. Subjects were scanned twice, once when their self-reported mood ratings indicated hypomania or euthymia and then again when they were in depressed states. Results Subjects in their euthymic or hypomanic states exhibited increased caudate activity bilaterally and the globus pallidus of the left hemisphere. Longitudinal analyses revealed a significant association between an increase in severity of depression and a decrease in activity in the external segment of the right globus pallidus. Conclusions Our findings suggest that the globus pallidus is less responsive during a simple motor task in the depressed compared to the normal or euthymic states in patients with bipolar disorder. These results are consistent with current physiologic models of basal ganglia circuitry in which an increase in caudate activity results in an increase in inhibitory GABAergic outflow to the external globus pallidus and subsequent decrease in thalamocortical excitation and may underlie the clinical manifestations of depression in bipolar disorder. Limitations The findings of this study need to be interpreted with caution as correlation coefficients may be overestimated in this small study sample.

Reaction Times and Visuospatial Processing in Parkinson's Disease

Three motor reaction time tasks which differed in visuospatial complexity but not in motor demands were completed by a group of Parkinson's disease patients and a group of matched control subjects. Response initiation times increased with visuospatial difficulty, whereas movement times remained within a similar range. The two groups differed in response initiation and movement execution times across all reaction time conditions. However, there was no disproportionate increase in response initiation times between an initial nonspatial condition and more complex visuospatial conditions in Parkinson disease patients, and the patients did not make more errors than control subjects. The results do not give support to the hypothesis of a generalised visuospatial deficit in Parkinson's disease.

Measurement of neo-Pavlovian properties of higher nervous activity by motor reaction-time tasks

A preliminary study involving 80 paid subjects, 40 of each sex, investigated the usefulness of motor response-time tasks as measures of three neo-Pavlovian properties of higher nervous activity, excitatory strength, dynamism, and mobility. Six independent factors were extracted from a set of variables measuring those properties. These factors demonstrated the independence of the three properties, of the excitatory and inhibitory processes in dynamism and mobility, and of strength and sensitivity at least when such tasks are used as measures of properties in the auditory modality. These findings are promising, however, further investigation is required to validate these tasks against the classical tests of properties of higher nervous activity.

Computer analysis of the telemetered EEG in the study of epilepsy and schizophrenia.

Computation of power spectra from averaged brief epochs of spike free scalp EEG coincident with the subcortical spike has revealed a distinctive spectral configuration characterized by smooth monotonic decline in power from lowest to highest frequencies. Nine out of 10 patients with epilepsy display similar patterns preceeding long latency responses to a verbal motor reaction time task. Although subcortical spike activity has been recorded from the parasental region of patients with schizophrenia by several investigators half of our patients with schizophrenia displayed a different pattern which resembles a "white noise" spectrum during the delayed reaction time of incorrect response trials. Power spectra derived from 24-hour telemetered scalp EEGs from patients with epilepsy and schizophrenia are also sharply differentiated by similar criteria. These non-invasive methods for analysis of the scalp EEG in relation to careful and controlled behaviour observations may give useful information regarding subcortical activity when intracranial electrodes cannot be utilized.