Papers by Andreas Sprenger
Journal of Cognitive Neuroscience, 2009
When simultaneous series of stimuli are rapidly presented left and right, containing two target s... more When simultaneous series of stimuli are rapidly presented left and right, containing two target stimuli T1 and T2, T2 is much better identified when presented in the left than in the right hemifield. Here, this effect was replicated, even when shifts of gaze were controlled, and was only partially compensated when T1 side provided the cue where to expect T2. Electrophysiological measurement revealed earlier latencies of T1- and T2-evoked N2(pc) peaks at the right than at the left visual cortex, and larger right-hemisphere T2-evoked N2(pc) amplitudes when T2 closely followed T1. These findings suggest that the right hemisphere was better able to single out the targets in time. Further, sustained contralateral slow shifts remained active after T1 for longer time at the right than at the left visual cortex, and developed more consistently at the right visual cortex when expecting T2 on the contralateral side. These findings might reflect better capacity of right-hemisphere visual working memory. These findings about the neurophysiological underpinnings of the large right-hemisphere advantage in this complex visual task might help elucidating the mechanisms responsible for the severe disturbance of hemineglect following damage to the right hemisphere.
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Experimental Brain Research, 2006
Non-consciously perceived arrow stimuli can speed up responses to similar stimuli that are shortl... more Non-consciously perceived arrow stimuli can speed up responses to similar stimuli that are shortly presented after a masked prime. Yet response facilitation may turn into a delay at particular intervals between masked primes and targets. In this case, the lateralized readiness potential, as a measure of the time course of differential activation between the primed and the unprimed motor cortices, consistently yielded two consecutive maxima of opposite polarity, at 250 and at 350 ms after prime onset. To further explore the mechanisms underlying inverse priming, we used single-pulse transcranial magnetic stimulation (TMS) of the left or right primary motor hand area (M1). Lateralized changes in corticomotor excitability induced by the masked prime were probed by assessing the effect of priming on the amplitude of the TMS-induced motor-evoked potentials (MEPs). In two experiments, MEPs increased and decreased, respectively, in the hand primed by the masked arrows when TMS was given at 250 and at 350 ms after prime onset, confirming the expectation that MEP changes may indicate the response tendencies induced by the masked primes. Both effects were more distinct with TMS of the left M1. However, there were also some differences between the patterns of results in the two experiments. We propose that the left M1 is activated for preparation of both right- and left-hand movements, and we relate the present results to current hypotheses about the nature of inverse priming.
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Computers & Geosciences, 1990
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Neuropsychologia, 2009
Patients with homonymous visual field defects (HVFD) are often crucially disabled during self-gui... more Patients with homonymous visual field defects (HVFD) are often crucially disabled during self-guided visual exploration of their natural environment. Abnormal visual search may be related to the sensory deficit, deficient spatial orientation or compensatory eye movements. We tested the hypothesis that visual search in HVFD is purely determined by the visual-sensory deficit by comparing nine patients with HVFD due to occipital stroke in an acute stage to nine healthy subjects with technically simulated "virtual" homonymous visual field defects (vHVFD) and to nine controls with normal visual fields. The simulated gaze-contingent visual field defects in vHVFD subjects were individually matched to the patients' HVFD with respect to their size and side. Eye movements were recorded while subjects searched for targets among distractors and indicated target detection by clicks. All patients, in particular those with lesions involving the inferior occipito-temporal (fusiform) gyrus, but also those with small lesions restricted to the visual cortex, showed longer search durations than vHVFD subjects. This was tightly related to the higher number of fixations and particularly "re-fixations" (repeated scanning of fixated items). Working memory across saccades during the search was intact (no increased "re-clicks"). Scanpath strategies were similar in patients and vHVFD subjects. For both groups amplitude and frequency of saccades did not differ between the hemifields. In HVFD patients with acute occipital brain lesions, visual input failure does not fully account for abnormal visual search. It might either result from disconnections of the primary visual cortex to associated occipital and temporal brain areas or reflect an early stage of compensatory eye movements which differ from chronic HVFD patients.
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Movement Disorders, 2006
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Neuroreport, 2002
Blinks are known to change the kinematic properties of fast eye movements, probably by changes in... more Blinks are known to change the kinematic properties of fast eye movements, probably by changes in the brain stem circuits. To determine whether slow disconjugate (slow vergence) eye movements are affected by blinks under natural viewing conditions, we elicited airpuff-evoked trigeminal blinks randomly during ongoing steady slow vergence eye movements. Lid and binocular eye movements were recorded by the scleral search coil method. Slow vergence eye movements showed a peak of vergence velocity during the final part of the blink, which depends on the stimulus direction. We propose that the direction-specific blink effect on slow vergence may be caused by changes in brain stem premotor circuits.
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Neuroimage, 2007
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Neuroimage, 2008
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Journal of Neurology Neurosurgery and Psychiatry, 2008
To investigate substantia nigra (SN) echogenicity in members of a family with homozygous and hete... more To investigate substantia nigra (SN) echogenicity in members of a family with homozygous and heterozygous PTEN induced kinase (PINK1) mutations with or without signs of Parkinson's disease (PD). Transcranial sonography (TCS) was used to investigate 20 members of a family with PINK1 mutations, including four homozygous and 11 heterozygous mutation carriers and five individuals with no mutation. For comparison, a healthy control group of 18 subjects without a positive family history of PD (control group) and a healthy control group of 15 subjects with a positive family history of sporadic PD (relative group) were investigated. For statistical analysis, the larger area of the two SNs echogenicity (aSNmax) of each individual was selected. A significantly increased aSNmax was found for all subgroups compared with the control group. The group of homozygous carriers of a PINK1 mutation had a significantly increased aSNmax compared with all of the other subgroups, except the group of heterozygous mutation carriers. These findings in carriers of a PINK1 mutation are comparable with those in carriers of Parkin mutations and non-genetic PD. The increased aSNmax in family members without a mutation suggests an additional contributing factor independent of the PINK1 mutation that may also play a role in relatives of patients with sporadic PD.
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Neuroimage, 2007
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Neuroreport, 2005
Recent studies have discussed the role of the cerebellum in not only motor but also cognitive fun... more Recent studies have discussed the role of the cerebellum in not only motor but also cognitive functions, and in particular, fronto-executive operations. Similar to a previous study on hemineglect patients, we recorded eye movements during a visual search task to investigate patients with isolated infarction of the cerebellum compared with controls. Patients showed longer search durations, associated with mild saccadic dysmetria, longer single fixation durations and a higher number of repeated fixations of items. Systematic search strategies were preserved, but less frequent in patients. In conclusion, though basic mechanisms of visual search including spatial memory were not affected by cerebellar lesions, patients' search behaviour was slower and less efficient, indicating a mild deficit of visual attention and motor planning.
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Progress in Brain Research, 2002
In patients with hemi-spatial neglect eye movement patterns during visual search reflect not only... more In patients with hemi-spatial neglect eye movement patterns during visual search reflect not only inattention for the contralesional hemi-field, but interacting deficits of multiple visuo-spatial and cognitive functions, even in the ipsilesional hemi-field. Evidence for these deficits is presented from the literature and from saccadic scan-path analysis during feature and conjunction search in 10 healthy subjects and in 10 patients with manifest or recovered left visual neglect due to right-hemispheric stroke. Deficits include (1) a rightward shift of spatial representation, (2) deficient spatial working memory and failure of systematic search strategies, leading to multiple re-fixations, more after frontal lesions, and (3) a reduced spotlight of attention and a deficient pop-out effect of color, more after temporo-parietal lesions.
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European Journal of Neuroscience, 2004
Smooth pursuit eye movements are evoked by retinal image motion of visible moving objects and can... more Smooth pursuit eye movements are evoked by retinal image motion of visible moving objects and can also be driven by the internal representation of a target due to extraretinal mechanisms (e.g. efference copy). To delineate the corresponding neuronal correlates, functional magnetic resonance imaging at 1.5 T was applied during smooth pursuit at 10 degrees /s with continuous target presentation and target blanking for 1 s to 16 right-handed healthy males. Eye movements were assessed during scanning sessions by infra-red reflection oculography. Smooth pursuit performance was optimal when the target was visible but decreased to a residual velocity of about 30% of the velocity observed during continuous target presentation. Random effects analysis of the imaging data yielded an activation pattern for smooth pursuit in the absence of a visual target (in contrast to continuous target presentation) which included a number of cortical areas in which extraretinal information is available such as the frontal eye field, the superior parietal lobe, the anterior and the posterior intraparietal sulcus and the premotor cortex, and also the supplementary and the presupplementary eye field, the supramarginal gyrus, the dorsolateral prefrontal cortex, cerebellar areas and the basal ganglia. We suggest that cortical mechanisms such as prediction, visuo-spatial attention and transformation, multimodal visuomotor control and working memory are of special importance for maintaining smooth pursuit eye movements in the absence of a visible target.
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Psychiatry Research, 2006
In obsessive–compulsive disorder (OCD), a dysfunction of neuronal circuits involving prefrontal a... more In obsessive–compulsive disorder (OCD), a dysfunction of neuronal circuits involving prefrontal areas and the basal ganglia is discussed that implies specific oculomotor deficits. Performance during reflexive and predictive saccades, antisaccades and predictive smooth pursuit was compared between patients with OCD (n = 22), patients with schizophrenia (n = 21) and healthy subjects (n = 24). Eye movements were recorded by infrared reflection oculography. In both patient groups, higher frequencies of anticipatory saccades with reduced amplitudes in the predictive saccade task were observed. Additionally, reduced smooth pursuit eye velocity and increased frequencies of saccadic intrusions during smooth pursuit as well as increased error rates in the antisaccade task were demonstrated for patients suffering from schizophrenia. Patients with OCD and schizophrenia revealed different patterns of oculomotor impairment: whereas increased anticipation of predictive saccades provides evidence for a dysfunction of the circuit between the frontal eye field and the basal ganglia in both groups, results from the antisaccade task imply additional deficits involving the dorsolateral prefrontal cortex in schizophrenic patients. Furthermore, the cortical network for smooth pursuit (especially the frontal eye field) is also assumed to be disturbed in schizophrenia.
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Brain, 2003
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Neuroimage, 2005
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Human Brain Mapping, 2008
In monkeys, areas in the intraparietal sulcus (IPS) play a crucial role in visuospatial informati... more In monkeys, areas in the intraparietal sulcus (IPS) play a crucial role in visuospatial information processing. Despite many human neuroimaging studies, the location of the human functional homologs of some IPS areas is still a matter of debate. The aim of the present functional magnetic resonance imaging (fMRI) study was to identify the distinct locations of specific human IPS areas based on their functional properties using stimuli adapted from nonhuman primate experiments, in particular, surface orientation discrimination and memory guided saccadic eye movements (SEM). Intersubject anatomical variability likely accounts for much of the debate. By applying subject by subject analysis, we can demonstrate that sufficient intersubject anatomical and functional commonalities exist. Both the lateral bank of the anterior part of IPS, the putative human homolog of the area AIP, and the caudal part of the IPS (putative CIP) showed activation related to spatial discrimination of surface orientation. Eye tracking conducted during fMRI data acquisition allowed us to show that both areas were separated by an area related to SEM. This area was located in the middle region of the IPS (most probably including LIP), i.e., similar to the location observed in nonhuman primates. In 10 of 11 subjects our putative CIP activation was located in a medial side branch of the posterior part of the IPS, on the opposite side as described in nonhuman primates, making this landmark a useful anatomical marker for the location of CIP. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc.
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Neuroimage, 2006
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Journal of Neurology, 2009
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Neuropediatrics, 2006
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Papers by Andreas Sprenger