Prospective controlled study on the effects of deep brain stimulation on driving in Parkinson's disease.

To explore the influence of bilateral subthalamic deep brain stimulation (STN-DBS) on car driving ability in patients with Parkinson's disease (PD), we prospectively examined two age-matched, actively driving PD patient groups: one group undergone DBS-surgery (PD-DBS, n = 23) and one group that was eligible for DBS but did not undergo surgery (PD-nDBS, n = 29). In PD-DBS patients, investigation at Baseline was done just prior and at Follow-up 6-12 month after DBS-surgery. In PD-nDBS patients, time interval between Baseline and Follow-up was aimed to be comparable. To assess the general PD driving level, driving was assessed once in 33 age-matched healthy controls at Baseline. As results, clinical and driving characteristics of PD-DBS, PD-nDBS and controls did not differ at Baseline. At Follow-up, PD-DBS patients drove unsafer than PD-nDBS patients. This effect was strongly driven by two single PD-DBS participants (9%) with poor Baseline and disastrous Follow-up driving performance. Retrospectively, we could not identify any of the assessed motor and non-motor clinical Baseline characteristics as predictive for this driving-deterioration at Follow-up. Excluding these two outliers, comparable driving performance between PD-DBS and PD-nDBS patients not only at Baseline but also at Follow-up was demonstrated. Age, disease duration and severity as well as Baseline driving insecurity were associated with poorer driving performance at Follow-up. This first prospective study on driving safety in PD after DBS surgery indicates that DBS usually does not alter driving safety but might increase the risk for driving deterioration, especially in single subjects with already unsafe driving prior to DBS surgery.

Oculomotor Fatigue and Neuropsychological Assessments mirror Multiple Sclerosis Fatigue.

Fatigue is a major complaint in MS. Up to now no objective assessment tools have been established which hampers any treatment approach. Previous work has indicated an association of fatigue with cognitive measures of attention. Oculomotor tests have been established in healthy individuals as a read-out of fatigue, and to some extent in MS patients. Based on these observations we compared two groups of MS patients, one with fatigue (n=28) and one without fatigue (n=21) and a group of healthy subjects (n=15) with a standardised computerised measure of alertness and an oculomotor stress test. Patients with fatigue showed highly significant changes of their saccade dynamics as defined by the Main Sequence and Phase Plane plots: They showed slowing of saccades, the characteristical fatigue double peak, and an asymmetrical phase plane. Oculomotor tests differentiated significantly between fatigue and fatigabiliy in our MS patients. They also showed significantly worse performance in the alertness test as well as in the oculomotor task. Significantly slower reaction times were observed for tonic alertness in 2 series without a cue (p=.025 and p=.037) but not in phasic alertness with a cue (p=.24 and p=.34). Performance was influenced by disability as well as by affective state. We conclude, when controlling for disability and depression, saccadic stress tests and alertness tests could be used as an objective read-out for fatigability and fatigue in MS patients.

Attention and Information Acquisition: Comparison of Mouse-Click with Eye-Movement Attention Tracking.

Attention is crucial as a fundamental prerequisite for perception. The measurement of attention in viewing and recognizing the images that surround us constitutes an important part of eye movement research, particularly in advertising-effectiveness research. Recording eye and gaze (i.e. eye and head) movements is considered the standard procedure for measuring attention. However, alternative measurement methods have been developed in recent years, one of which is mouse-click attention tracking (mcAT) by means of an on-line based procedure that measures gaze motion via a mouse-click (i.e. a hand and finger positioning maneuver) on a computer screen. Here we compared the validity of mcAT with eye movement attention tracking (emAT). We recorded data in a between subject design via emAT and mcAT and analyzed and compared 20 subjects for correlations. The test stimuli consisted of 64 images that were assigned to eight categories. Our main results demonstrated a highly significant correlation (p < 0.001) between mcAT and emAT data. We also found significant differences in correlations between different image categories. For simply structured pictures of humans or animals in particular, mcAT provided highly valid and more consistent results compared to emAT. We concluded that mcAT is a suitable method for measuring the attention we give to the images that surround us, such as photographs, graphics, art or digital and print advertisements.

Visual Attention and Saccadic Oculomotor Control in Parkinson's Disease.

BACKGROUND: In patients with Parkinson's disease (PD) we aimed at differentiating the relation between selective visual attention, deficits of programming and dynamics of saccadic eye movements while searching for a target and hand-reaction time as well as hand-movement time. Visual attention is crucial for concentrating selectively on one aspect of the visual field while ignoring other aspects. Eye movements are anatomically and functionally related to mechanisms of visual attention. Saccadic dysfunction might confound selective visual attention in PD. METHODS: We studied visual selective attention in 22 medicated PD patients (clinical ON status, mild to moderate disease severity) and 22 age matched controls. We looked for possible interferences through oculomotor deficits. Two tasks were compared: free viewing of photographs and time optimal visual search of a hidden target. Visual search times (VST), task related dynamics of saccades, and hand-reaction and hand-movement times were analyzed. RESULTS: In the free viewing task mild to moderately affected PD patients did not differ statistically from healthy subjects with respect to saccade dynamics. However, patients differed significantly from healthy subjects in the time optimal visual search task with 25% lower rates of successful searches. Hand movement reaction time did not differ in both groups, whereas hand movement execution time was significantly prolonged in PD patients. CONCLUSION: Saccadic oculomotor control and hand movement reaction times were intact, whereas in our less severely affected treated PD patients, visual selective attention was not. The highly reduced successful search rate might be related to disturbed programming and delayed execution of saccades during time optimal visual search due to decreased execution of serial-order sequential generation of saccades.

Effect of subthalamic nucleus deep brain stimulation on driving in Parkinson disease.

OBJECTIVE: To examine the influence of subthalamic nucleus (STN) deep brain stimulation (DBS) on driving in patients with Parkinson disease (PD). METHODS: Using a driving simulator setup proven to reflect on-road driving, 2 main analyses were performed: 1) comparison of driving performance among 23 patients with deep brain surgery (DBS patients), 21 patients without surgery (no-DBS patients), and 21 controls; and 2) analysis of the effect of stimulation vs levodopa on driving performance. To this end, 3 tests were run in the medicated DBS patient cohort, with 3 different conditions: "stimulation on" (STIM) (equated to daily treatment), "stimulation off" (OFF), and "stimulation off/levodopa" (LD) (dosage aimed at maintaining motor status). Differences in driving times and errors among conditions were analyzed. RESULTS: Age and cognitive deficits influenced driving performance negatively. The no-DBS patient group performed worse in driving time and driving errors than controls. DBS patients drove slower than controls and no-DBS patients. Driving safety was comparable to controls but higher than in no-DBS patients. Within the DBS patient group, driving was more accurate with STIM than with LD, although motor effects did not differ. Driving with STIM, but not with LD, was superior to driving in the OFF condition. CONCLUSION: DBS of the STN seems to have a beneficial effect on driving ability in patients with PD, potentially because of nonmotor driving-relevant aspects. Our data suggest that driving permission for DBS-treated patients with PD should not be handled more restrictively than permissions for patients with PD in general. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that STN-DBS in patients with PD is associated with a reduction in driving errors and improvements in driving accuracy in driving simulations.

Pupillary responses to single and sinusoidal light stimuli in diabetic patients.

We examined effects of diabetes mellitus (DM) on the pupillary light reflex (PLR). Phasic pupillary response to a single light stimulus (200 ms) (pPLR) and to continuous sinusoidal stimuli with four different frequencies (0.1, 0.3, 0.7, 1.3Hz) (cPLR) were examined in 52 DM patients and 21 control subjects. We asked: does recording and frequency analysis of cPLR together with short time fourier [STFT] analysis of pPLR differentiate better between DM patients and normal subjects than pPLR only?Initial pupil diameter was significantly decreased in the DM group. For pPLR. maximal contraction velocity (Vmax), Vmax of redilation 1, reflex-amplitude and pPLR latency were significantly reduced in those patients who also showed signs of diabetic autonomic neuropathy (DNP). Tests of dynamic pupillary light reflex (cPLR) revealed that all DM patients had a significantly reduced gain at lower frequencies. Pupil phase lag was greater at 0.1 and 0.3Hz and smaller at 0.7 and 1.3 Hz in the DNP group (p<0.001). Comparison of single pPLR recordings of 5 DNP patients with 5 subjects using short time fast fourier (STFT) analysis revealed a characteristic change from low frequency content in healthy subjects to high frequency content in DNP patients.Significant changes in the PLR in DM can be found only when symptoms of autonomic neuropathy have been shown. Both sympathetic and the parasympathetic nervous systems are affected by diabetic autonomic neuropathy. Only recording of cPLR, together with STFT of pPLR can identify significant pathological deficits of pupillary control in single cases.

Multiple memory-guided saccades: movement memory improves the accuracy of memory-guided saccades.

Memory-guided saccades (MGSs) with 3 s memorization delay were recorded in healthy subjects using four different paradigms: two "regular" MGS paradigms with the peripheral target lit for 0.2 s (MGS2) and for 1.8 s (MGS18); a multiple memory-guided saccade (MMGS) paradigm with the target lit for 1.8 s and the instruction to perform a visually guided saccade (VGS) towards it before the MGS; a trained memory-guided saccades (TMGSs) paradigm where the same target was presented so that the subjects should made 10 VGSs before the MGS. The longer target presentation interval (MGS18 paradigm) did not improve the accuracy of MGS. The execution of the VGSs improved the accuracy of the corrective saccades made after the first MGS to drive the eyes closer to the target, and this improvement was independent from the number of the VGSs (there was no difference between the MMGS and the TMGS paradigms). The VGSs provide a template that improves the capability of the corrective saccades to compensate for the residual position error at the end of the first saccade.

Foveal versus parafoveal scanpaths of visual imagery in virtual hemianopic subjects.

Sophisticated string analysis [compressed regional string analysis, cRSE] shows significant differences following therapeutical masking of the foveal region during a virtual hemianopia. The visual imagery scanpath is done over a compressed mental image that needs longer fixation duration but fewer saccades than the real image. Combination of different viewing tasks with types of pictures permits to show how scanpath top-down strategies can be enforced or decreased by proper combination of task and picture; this is influenced by the mask of fovea versus no-mask of fovea difference, with bottom up mechanisms becoming more important with loss of foveal viewing strategies in the mask condition.

Evoked potentials during active horizontal head rotations in patients with vertigo.

OBJECTIVES: The purpose of this study was to investigate whether evoked potentials by active head rotation help to verify and topographically differentiate patients with the major symptom vertigo. METHODS: Twenty-four healthy human subjects and 43 patients with either infratentorial or supratentorial brain lesions were analysed. RESULTS: The evoked response in normal subjects was composed of six peaks, indicated by polarization and time difference from the trigger points P100, N30, P0, N50, P155 and N320. The EEG pattern was independent of the direction, type of target and whether the eyes were open or closed. In contrast, the evoked response, especially P155, was dependent on the chosen trigger point and acceleration. P155 was the most stable and significant component of the evoked potentials. Thus, we chose P155 as the reference for studying patients with vertigo. DISCUSSION: In peripheral vestibular disorders, cerebellar and diffuse supratentorial cerebral lesions and P155 latencies remain non-significantly altered. However, P155 latencies significantly increase in pontine lesions homolaterally, and space occupying tumors contralaterally. CONCLUSION: Active horizontal head rotations differentially stimulate the vestibulocortical pathways and may contribute to the analysis of vertigo.

Eye movements in patients with Neglect show space-centred attention when fixating rotating objects.

OBJECTIVES AND METHODS: To determine whether attention operates in space-based or object-based coordinates, Neglect patients were confronted with a rotating object. After the object had undergone a 180-degree rotation a stimulus appeared on either side of the object and the reaction times were measured. The results of the present study showed that all patients performed worse on the contralateral side, both in the static as well as in the moving condition. This supports the theory that attention operates in space-centred reference frames. To bring some light into the discussion, the recording of eye movements was included. RESULTS: Our results showed three effects: (1) most eye movements started to the right of the midline; (2) some patients followed the moving object to the mid-line, before they returned to the ipsi-lesional side; (3) some patients followed the complete movement of the barbell. CONCLUSION: It is argued that patients recovering from Neglect consciously make more eye movements to the left to compensate for the deficit, but attention remains in the ipsi-lesional field.