Effects of Stimulus-Driven and Goal-Directed Attention on Prepulse Inhibition of Brain Oscillations.

OBJECTIVE: Prepulse inhibition (PPI) is an operational measure of sensory gating. PPI of cortical response to a startling pulse is known to be modulated by attention. With a time-frequency analysis, we sought to determine whether goal-directed and stimulus-driven attention differentially modulate inhibition of cortical oscillations elicited by a startling pulse. METHODS: An electroencephalogram (EEG) was recorded in 26 healthy controls performing an active acoustic PPI paradigm. Startling stimuli were presented alone or either 400 or 1000 ms after one of three types of visual prepulse: to-be-attended (goal-directed attention), unexpected (stimulus-driven attention) or to-be-ignored (non-focused attention). We calculated the percentage PPI for the auditory event-related spectral perturbation (ERSP) of theta (4-7 Hz), alpha (8-12 Hz), beta1 (13-20 Hz) and beta2 (20-30 Hz) oscillations and changes in inter-trial coherence (ITC), a measure of phase synchronization of electroencephalographic activity. RESULTS: At 400 ms: (i) PPI of the ERSP of alpha, theta and beta1 oscillation was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta2 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. At 1000 ms: (i) PPI of alpha oscillations was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta1 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. The ITC values did not vary according to the type of prepulse. CONCLUSIONS: In an active PPI paradigm, stimulus-driven and goal-directed attention each have differential effects on the modulation of cortical oscillations.

Predictive factors for improvement of gait by low-frequency stimulation in Parkinson's disease.

BACKGROUND: After several years duration of Parkinson's disease, with or without deep brain stimulation, axial signs (such as postural instability, freezing of gait) may worsen. High-voltage, low-frequency stimulation has been shown to improve severe gait disorders in some patients. OBJECTIVE: To identify predictive factors for the efficacy of low-frequency stimulation. METHODS: We assessed the respective effects of low- and high-frequency stimulation using an acute stand-walk- sit test, and on motor performance in 22 patients with longstanding, bilateral sub-thalamic nucleus stimulation. We calculated the difference in the number of steps (delta steps) between high and low -frequency stimulation during the stand-walk-sit test. Our aim was to establish a profile for low-frequency responders, which was defined by a positive value for delta steps. RESULTS: Low frequency responders presented higher age, a severe axial phenotype five years after surgery and a lower L-dopa responsiveness of (i) the Unified Parkinson's Disease Rating Scale part III score and its akinesia subscore before surgery and (ii) the axial subscore one year after surgery. CONCLUSION: Here we defined a specific and severe axial profile of minority of patients who could benefit from low frequency stimulation parameters. Our findings challenge the conventional treatment approach (i.e. high-frequency stimulation) in patients who develop gait disorders after several years of stimulation.

Effects of stimulus-driven and goal-directed attention on prepulse inhibition of the cortical responses to an auditory pulse.

OBJECTIVE: Inhibition by a prepulse (prepulse inhibition, PPI) of the response to a startling acoustic pulse is modulated by attention. We sought to determine whether goal-directed and stimulus-driven attention differentially modulate (i) PPI of the N100 and P200 components of the auditory evoked potential (AEP) and (ii) the components' generators. METHODS: 128-channel electroencephalograms were recorded in 26 healthy controls performing an active acoustic PPI paradigm. Startling stimuli were presented alone or either 400 or 1000ms after a visual prepulse. Three types of prepulse were used: to-be-attended (goal-directed attention), unexpected (stimulus-driven attention) or to-be ignored (non focused attention). We calculated the percentage PPI for the N100 and P200 components of the AEP and determined cortical generators by standardized weighted low resolution tomography. RESULTS: At 400ms, the PPI of the N100 was greater after an unexpected prepulse than after a to-be-attended prepulse, the PPI of the P200 was greater after a to-be-attended prepulse than after a to-be ignored prepulse. At 1000ms, to-be-attended and unexpected prepulses had similar effects. Cortical sources were modulated in areas involved in both types of attention. CONCLUSIONS: Stimulus-driven attention and goal-directed attention each have specific effects on the attentional modulation of PPI. SIGNIFICANCE: By using a new PPI paradigm that specifically controls attention, we demonstrated that the early stages of the gating process (as evidenced by N100) are influenced by stimulus-driven attention and that the late stages (as evidenced by P200) are influenced by goal-directed attention.

Modulation of dysarthropneumophonia by low-frequency STN DBS in advanced Parkinson's disease.

BACKGROUND: Parkinsonian dysarthria (as typically characterized by hypophonia, monotony of pitch, and rhythm abnormalities) is often accompanied by gait disturbances. The long-term effect of subthalamic nucleus deep brain stimulation (STN DBS) on dysarthria remains unclear. METHODS: Given STN DBS's known improvement of gait disorders, we analyzed speech intelligibility and aerodynamic and acoustic parameters in 11 advanced PD patients in three double-blind, randomized conditions: "defined Off," 60 Hz STN DBS and 130 Hz STN DBS. RESULTS: An improvement in aerodynamic speech parameters during 60 Hz STN DBS was accompanied by significant clinical benefit. CONCLUSIONS: Chronic treatment with low-frequency STN DBS may have a beneficial impact on dysarthropneumophonia, even in advanced PD patients.

Parkinsonism in Gaucher's disease type 1: ten new cases and a review of the literature.

Parkinsonism has been described in patients with Gaucher's disease (GD). We reviewed the 10 cases of patients with both parkinsonism and GD recorded in the French national GD registry, as well as 49 previously published cases. Relative to the general population, parkinsonism in GD patients (1) was more frequent, (2) occurred at an earlier age, (3) responded less well to levodopa, and (4) was more frequently associated with signs of cortical dysfunction. Enzyme replacement therapy (ERT) and substrate reduction therapy (SRT) were ineffective on GD-associated parkinsonism, suggesting that parkinsonism itself is not an indication for ERT or SRT in this setting.