Neil M. Drummond

Boston Scientific | BSCI · Neuromodulation

Background: Local field potentials (LFPs) represent the summation of periodic (oscillations) and aperiodic (fractal) signals. Although previous studies showed changes in beta band oscillations and burst characteristics of the subthalamic nucleus (STN) in Parkinson's disease (PD), how aperiodic activity in the STN is related to PD pathophysiology i...

Growing evidence suggests that both the medial prefrontal cortex (mPFC) and the subthalamic nucleus (STN) play crucial roles in conflict processing, but how these two structures coordinate their activities remains poorly understood. We simultaneously recorded electroencephalogram from the mPFC and local field potentials from the STN using deep brai...

Background: Parkinson’s disease (PD) is a common neurodegenerative disorder that results in movement-related dysfunction and has variable cognitive impairment. Deep brain stimulation (DBS) of the dorsal subthalamic nucleus (STN) has been shown to be effective in improving motor symptoms; however, cognitive impairment is often unchanged, and in some...

The interconnection of the angular gyrus of right posterior parietal cortex (PPC) and the left motor cortex (LM1) is essential for goal-directed hand movements. Previous work with transcranial magnetic stimulation (TMS) showed that right PPC stimulation increases LM1 excitability but right PPC followed by left PPC-LM1 stimulation (LPPC-LM1) inhibit...

The relative contributions of reticulospinal versus corticospinal pathways for movement production are thought to be dependent upon the type of response involved. For example, unilateral distal movements involving the hand and finger have been thought to be primarily driven by corticospinal output, whereas bilateral responses are considered to have...

Recent progress in targeted interrogation of basal ganglia structures and networks with deep brain stimulation in humans has provided insights into the complex functions the subthalamic nucleus (STN). Beyond the traditional role of the STN in modulating motor function, recognition of its role in cognition was initially fueled by side effects seen w...

Deep Brain Stimulation (DBS) has continuously gained popularity as a symptomatic treatment in diseases such as Parkinson’s Disease (PD), Essential Tremor (ET), and dystonia. For better understanding the mechanisms of DBS, a series of intraoperative Local Field Potential (LFP) recordings are acquired from patients during DBS. These recordings are va...

Corticospinal output pathways have typically been considered to be the primary driver for voluntary movements of the hand/forearm; however, more recently, reticulospinal drive has also been implicated in the production of these movements. While both pathways may play a role, the reticulospinal tract is thought to have stronger connections to flexor...

Response preparation in simple reaction time (RT) tasks has been modeled as an increase in neural activation to a sub-threshold level, which is maintained until the go-signal. However, the amount of time required for response preparation following a warning signal (WS) is currently unclear, as experiments typically employ long foreperiods to ensure...

Introduction The posterior parietal cortices (PPCs) engage in motor processing during reach and grasp. Yet, the neural substrates behind their connections to the motor cortex (M1) are still unknown. It has been postulated that right PPC (rPPC) acts directly on left PPC (lPPC), which then acts on left M1 (lM1). Alternately, rPPC may act on lM1 circu...

Humans are able to proactively inhibit a particular motor response when provided with a precue in a bimanual selective stopping task (e.g., Maybe Stop Right Hand). We investigated how preparation affects proactive selective inhibition, as previous experiments have been performed in a paradigm where the ability to prepare responses ahead of the go-s...

In a typical go/no-go task a single imperative stimulus is presented each trial, either a go or no-go stimulus. Participants are instructed to initiate a known response upon appearance of the go-signal and withhold the response if the no-go signal is presented. It is unclear whether the go-response is prepared in advance of the imperative stimulus...

Increased reaction times (RT) during choice-RT tasks stem from a requirement for additional processing as well as reduced motor-specific preparatory activation. Transcranial direct current stimulation (tDCS) can modulate primary motor cortex excitability, increasing (anodal stimulation) or decreasing (cathodal stimulation) excitability in underlyin...

During a simple reaction time (RT) task, movements can be initiated early and involuntarily through presentation of a loud startling acoustic stimulus (SAS), a phenomenon termed the StartReact effect. In order to infer that activity in startle-related structures led to the early response triggering, it is important to observe a concurrent startle r...

In a stop-signal task participants are instructed to initiate a movement in response to a go-signal, but to inhibit this movement if an infrequent stop-signal is presented after the go. Reaction time (RT) in a stop-signal task is typically longer compared to a simple-RT task, which may be attributed to a reduced readiness to initiate the response c...

When a startling acoustic stimulus (SAS) is presented during a simple reaction time (RT) task it can trigger the prepared response through an involuntary initiation pathway. Previous research modelling the effects of presenting a SAS at various intervals following a non-startling auditory imperative signal (IS) suggested that involuntary initiation...

Previous studies have used a secondary probe reaction time (RT) task to assess attentional demands of a primary task. The current study used a startling acoustic stimulus (SAS) in a probe RT paradigm to test the hypothesis that attentional resources would be directly related to limitations in response preparation. Participants performed an easy or...

The present study investigated whether differences in reaction time (RT) between movements initiated to a visual cue (directly cued) versus movements initiated to a location other than the visual cue (indirectly cued) arise because of varying levels of inhibition within the motor system during response preparation. Unlike typical visuomotor mental...

Previous research has shown that the supplementary motor area (SMA) is critical in movement inhibition. Recently it was shown that applying transcranial direct current stimulation (tDCS) over SMA affected participants' ability to inhibit their movement in a stop-signal reaction time task (Hsu et al., 2011). Of interest in the current study was whet...

Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformati...