Thomas Schenk

Ludwig-Maximilians-University of Munich | LMU · Department of Psychology

In the present study, we examined the extent of interference between a cognitive task (auditory n-back task) and different aspects of motor performance. Specifically, we wanted to find out whether such interference is more pronounced for aspects of planning as compared to programming. Here, motor planning is represented by a phenomenon called the “...

Weber's law states that our ability to detect changes in stimulus attributes decreases linearly with their magnitude. This principle holds true for many attributes across sensory modalities but appears to be violated in grasping. One explanation for the failure to observe Weber's law in grasping is that its effect is masked by biomechanical constra...

Background: There is growing interest in non-motor symptoms in Parkinson's disease (PD), due to the impact on quality of life. Anhedonia, the inability to experience joy and lust, has a prevalence of up to 46% in PD. The perception of pleasantness of an odor is reduced in anhedonia without PD. We previously showed a reduced hedonic olfactory perce...

A common set of tasks frequently employed in the neuropsychological assessment of patients with visuomotor or perceptual deficits are the card-posting and the perceptual orientation matching tasks. In the posting task, patients have to post a card (or their hand) through a slot of varying orientations while the matching task requires them to indica...

In their Perception–Action Model (PAM), Goodale and Milner (1992) proposed functionally independent and encapsulated processing of visual information for action and perception. In this context, they postulated that visual input for action is processed in an automatized and analytic manner, which renders visuomotor behaviour immune to perceptual int...

We describe a patient with acute herpes simplex encephalitis with left-hemispheric hippocampal, parahippocampal and insular lesions. Although prototypic language areas were unaffected, the patient suffered from an inability to name objects or animals displayed on pictures. This deficit was transient and gradually disappeared 8 weeks after the initi...

Ganel, Freud, Chajut, and Algom (2012) demonstrated that maximum grip apertures (MGAs) differ significantly when grasping perceptually identical objects. From this finding they concluded that the visual size information used by the motor system is more accurate than the visual size information available to the perceptual system. A direct comparison...

Delaying visual feedback to subjects adapting to a visuomotor cursor rotation has been found to enhance explicit and attenuate implicit learning. Dual task costs occur when a secondary task taps the same resources as the primary task. We here ask if these two phenomena interact and want to explore which aspect of motor learning is most affected by...

This commentary is the next in a chain of events. First, Striemer, Chapman, and Goodale (2009) argued, on the basis of a single case study testing a patient with hemianopia, that the primary visual cortex (V1) is not essential for successful obstacle avoidance behaviour. In the Cortex special issue on the “what and how-pathways”, we (Ross, Schenk,...

The violation of Weber's law in grasping has been presented as evidence for the claim that grasping is guided by visual information which is distinct from the information used in perceptual tasks. Previously, we contested this claim and argued that biomechanical constraints of the hand might explain why Weber's law cannot be reliably uncovered in g...

Although the neural underpinnings of visually guided grasping and reaching have been well delineated within lateral and medial fronto-parietal networks (respectively), the contributions of subcomponents of visuomotor actions have not been explored in detail. Using careful subtraction logic, here we investigated which aspects of grasping, reaching,...

Frames of reference play a central role in perceiving an object's location and reaching to pick that object up. It is thought that the ventral stream, believed to subserve vision for perception, utilises allocentric coding, while the dorsal stream, argued to be responsible for vision for action, primarily uses an egocentric reference frame. We have...

Rossit et al. (2011) showed that neglect patients perform normally in a propointing task but not in an antipointing task which requires pointing towards the mirrored position of a target. It is assumed that antipointing relies on information from the perceptual pathway of our visual brain. Therefore, this finding supports the notion that neglect is...

The perception-action model with its assumptions of distinct visual pathways for perception and visuomotor control has been highly influential but also contentious. The controversy largely focused on the evidence from studies on perceptual illusions and this scientific field has been reviewed quite a few times in recent years. In contrast another a...

Salient peripheral cues produce a transient shift of attention which is superseded by a sustained inhibitory effect. Cueing part of an object produces an inhibitory cueing effect (ICE) that spreads throughout the object. In dynamic scenes the ICE stays with objects as they move. We examined object-centred attentional facilitation and inhibition in...

Previous research found that a patient with cortical blindness (homonymous hemianopia) was able to successfully avoid an obstacle placed in his blind field, despite reporting no conscious awareness of it (Striemer, C. L., Chapman, C. S., & Goodale, M. A., 2009, PNAS, 106(37), 15996-16001). This finding led to the suggestion that dorsal stream areas...

Objectives: Disease-modifying therapies (DMTs) are applied to delay or prevent disease progression in multiple sclerosis (MS). While this has mostly been proven for physical symptoms, available studies regarding long-term effects of DMTs on cognitive functions are rare and sometimes inconsistent due to methodological shortcomings. Particularly in...

Numerous studies have addressed the issue of where people look when they perform hand movements. Yet, very little is known about how visuomotor performance is affected by fixation location. Previous studies investigating the accuracy of actions performed in visual periphery have revealed inconsistent results. While movements performed under full vi...

Salient peripheral cues produce a transient shift of attention which is superseded by a sustained inhibitory effect. Cueing part of an object produces an inhibitory cueing effect (ICE) that spreads throughout the object. In dynamic scenes the ICE stays with objects as they move. We examined object-centred attentional facilitation and inhibition in...

It has been suggested that goal-directed actions performed under full vision are immune to certain visual illusions, while movements relying on perception-based visual information are deceived by them (Milner & Goodale, 1995). Consequently, pointing movements should be deceived by visual illusions when a delay is introduced (memory demands) or when...

For grasping, Ganel, Chajut, and Algom(2008) demonstrated that the variability of the maximum grip aperture (MGA) does not increase with the size of the target object. This seems to violate Weber's law, a fundamental law of psychophysics. They concluded that the visual representations guiding grasping are distinct from representations used for perc...

Objectives: With an increasing number of disease-modifying treatments (DMTs) for multiple sclerosis (MS), patient preferences will gain importance in the decision-making process. We assessed patients' implicit preferences for oral versus parenteral DMTs and identified factors influencing patients' treatment preference. Methods: Patients with rel...

Background and purpose: A transient ischemic attack (TIA) involves temporary neurological symptoms but leaves a patient symptom-free. Patients are faced with an increased risk for future stroke, and the manifestation of the TIA itself might be experienced as traumatizing. We aimed to investigate the prevalence of posttraumatic stress disorder (PTS...

Previous studies have frequently applied a combination of line-bisection tasks (in which participants indicate the middle of a line) and obstacle avoidance tasks (in which participants move their hand between two obstacles) with the aim of revealing perception-action dissociations in certain neurological disorders, such as visual form agnosia and o...

Introduction: One-quarter of subarachnoid hemorrhage (SAH) survivors develop psychological distress. This impedes recovery. Limitations to existing care pathways mean that distress often goes undetected. We need to know how to better identify it. Objectives: Support groups for SAH exist in many countries. No research has been conducted on them....

Researchers and other stakeholders continue to express concern about the failure of randomized clinical trials (RCT) in subarachnoid hemorrhage (SAH) to show efficacy of new treatments. Pooled data may be particularly useful to generate hypotheses about causes of poor outcomes and reasons for failure of RCT in SAH, and strategies to improve them. I...

It has been suggested that while movements directed at visible targets are processed within the dorsal stream, movements executed after delay rely on the visual representations of the ventral stream (Milner and Goodale, 2006). This interpretation is supported by the observation that a patient with ventral stream damage (DF) has trouble performing a...

Observations of the visual form agnosic patient DF have been highly influential in establishing the hypothesis that separate processing streams deal with vision for perception (ventral stream) and vision for action (dorsal stream). In this context, DF's preserved ability to perform visually-guided actions has been contrasted with the selective impa...

Despite the high frequency of cognitive impairment in multiple sclerosis, its assessment has not gained entrance into clinical routine yet, due to lack of time-saving and suitable tests for patients with multiple sclerosis. The aim of the study was to compare the paradigm of visual search with neuropsychological standard tests, in order to identify...

. Homonymous visual field defects (HVFDs) are one of the most common consequences of stroke. Compensatory training encourages affected individuals to develop more efficient eye movements to improve function. However, training is typically supervised, which can be time consuming and costly. . To develop and evaluate the efficacy and feasibility of a...

Object: Patients with subarachnoid hemorrhage (SAH) and their close friends and family may be excessively fearful that the patient will have a recurrence, and such fears could play a critical role in the poor recovery shown by many patients The authors examined whether these fears could account for significant variance in psychosocial outcomes. M...

Receiving information that one has a dissected cervical artery, which can cause a stroke at any time, is obviously traumatic, but details about the psychiatric and psychosocial sequelae are not known. We investigated the prevalence of and risk factors for posttraumatic stress disorder (PTSD) in patients with spontaneous cervical artery dissection (...

Outcome of patients with aneurysmal subarachnoid hemorrhage (SAH) has improved over the last decades. Yet, case fatality remains nearly 40 % and survivors often have permanent neurological, cognitive and/or behavioural sequelae. Other than nimodipine drug or clinical trials have not consistently improved outcome. We formed a collaboration of SAH in...

Visuospatial neglect is a multicomponent syndrome, and one dissociation reported is between neglect for near (peripersonal) and far (extrapersonal) space. Owing to patient heterogeneity and extensive lesions, it is difficult to determine the precise neural mechanisms underlying this dissociation using clinical methodology. In this study, transcrani...

In this study we challenge the widely accepted suggestion that visual perception, but not visual control of action, processes object shape in a holistic manner (Ganel & Goodale, 2003, Nature). The finding that perceptual judgments but not visuomotor acts, such as grasping are affected by variations along an irrelevant object dimension (Garner-inter...

Background: Clinical prediction models can enhance clinical decision-making and research. However, available prediction models in aneurysmal subarachnoid hemorrhage (aSAH) are rarely used. We evaluated the methodological validity of SAH prediction models and the relevance of the main predictors to identify potentially reliable models and to guide...

In this study we investigated whether motor and perceptual tasks share common attentional resources. To this end, we used a dual-task paradigm requiring participants to perform grasping movements toward objects of varying size and at the same time to identify a perceptual target presented at the object's location. To ensure that both tasks were per...

Many neglect patients show deficits in the mental representation of their contralesional body side or body parts, termed personal neglect. These deficits include impairments in identifying body parts on schematic drawings of human bodies. Limb activation and alertness cues have been shown to modulate neglect transiently, and are effective treatment...

Human patients with visual field defects following damage to their primary visual cortex (V1) will often misperceive the midpoint of a horizontal line. They tend to shift the midpoint away from the real position towards their blind field. In patients with unilateral neglect, where midpoint shifts can also be observed, these perceptual errors do not...

Milner, Ganel and Goodale's (MGG) critique rests on the conjecture that object width is the only visual cue that determines grip size. I argue that, if other sensory cues are taken into account, D.F.'s grasping behaviour can be explained without assuming a distinction between vision for perception and action.

Covert attention is tightly coupled with the control of eye movements, but there is controversy about how tight this coupling is. The premotor theory of attention proposes that activation of the eye movement system is necessary to produce shifts of attention. In this study, we experimentally prevented healthy participants from planning or executing...

Goodale et al. (1991) reported a striking dissociation between vision for perception and action. They examined DF, a human patient who had damage to her ventral visual stream and suffered from visual form agnosia. She was unable to perceive an object's size but could match the opening of her hand to the object's size during grasping. It was conclud...

Spatial attention and eye-movements are tightly coupled, but the precise nature of this coupling is controversial. The influential but controversial Premotor theory of attention makes four specific predictions about the relationship between motor preparation and spatial attention. Firstly, spatial attention and motor preparation use the same neural...

Since Rossetti et al. (1998) reported that prism adaptation (PA) can lead to a substantial reduction of neglect symptoms PA has become a hot topic in neglect-research. More than 280 articles have been published in this area. Not all of those studies investigated the therapeutic potential of this technique, many studies examined the responsiveness t...

Spatial neglect is a characteristic sign of damage to the right hemisphere and is typically characterized by a failure to respond to stimuli on the left side. With about a third of stroke victims showing initial signs of neglect, it is a frequent but also one of the most disabling neurological syndromes. Despite partial recovery in the first months...

The perception-action model states that visual information is processed in different cortical areas depending on the purpose for which the information is acquired. Specifically, it was suggested that the ventral stream mediates visual perception, whereas the dorsal stream primarily processes visual information for the guidance of actions (Goodale &...

Patients with unilateral neglect tend to ignore sensory information from their contralesional hemispace. Many symptoms of neglect can be reduced by exposing patients to rightward-shifting prism goggles. It was noted that the effects on neglect symptoms last for at least two hours. This seems surprising in light of the fact that the after-effect of...

Successful interaction with the environment often involves the identification and localization of an item. Right posterior parietal cortex (rPPC) is necessary for the completion of conjunction but not feature visual search, regardless of the attentional requirements. One account for this dissociation is that the rPPC is primarily involved in proces...

Spatial priming allows memory for target locations to be evaluated, whereby when a target appears in the same location across trials, participants become more efficient at locating it and consequently their search times decrease. Previously, we reported priming effects when the location of a target was repeated with respect to the participant's bod...

The finding that in a patient with visual form agnosia (DF), the performance level varies in a visuomotor letter-posting task and a perceptual orientation matching task was considered as part of the evidence for the perception-action model (Milner and Goodale, 1995). In this study we examined an alternative interpretation of these findings. We spec...

Subarachnoid hemorrhage (SAH) patients illustrate a chronic fear of recurrence. A third of patients develop posttraumatic stress disorder (PTSD) after SAH, and PTSD after other conditions is associated with a more negative outlook on life. We examined whether recurrence fears are related to PTSD and whether this is associated with the patients maki...

Westwood and Goodale (this issue) review the evidence for distinct visual streams for action and perception. They argue that, on balance, both the neuropsychological and psychophysical data support this distinction. They claim that critical results were either statistically inconclusive (because they consisted of negative evidence) or based on a su...

Homonymous visual field defects are a frequent consequence of brain damage occurring in some 20-40% of stroke patients. They are often accompanied by a peculiar spatial bias termed "Hemianopic Line Bisection Error" (HLBE). Although known for more than 100 years the explanations for the HLBE put forward remain controversial. One explanation holds th...

How can we explain, that DF - a patient with a damaged ventral stream - can act normally in many everyday tasks despite her profound perceptual disability. The classical answer is that perception and action are based on separate visual streams. Here, I will explain why this view is problematic and offer an alternative answer. Specifically, I will a...

Post-traumatic stress disorder (PTSD) is common after subarachnoid haemorrhage (SAH) and causes poor outcome. Knowing which SAH events cause the stress leading to PTSD development could allow for their severity, and so the chances of PTSD, to be reduced. The dramatic nature of SAH onset has meant ictal events have been the presumed cause. Frequent...

Spatial priming in visual search is a well-documented phenomenon. If the target of a visual search is presented at the same location in subsequent trials, the time taken to find the target at this repeated target location is significantly reduced. Previous studies did not determine which spatial reference frame is used to code the location. At leas...

This study assesses the impairment in activities of everyday life using a novel test battery following subarachnoid hemorrhage (SAH) and its treatment. A one-off neuropsychologic assessment was conducted for all patients who agreed to participate in the study. The date of the interview was at least 12 months after the ictus. The aspects tested incl...

Patients with homonymous visual field defects experience disabling functional impairments as a consequence of their visual loss. Compensatory visual exploration training aims to improve the searching skills of these patients in order to help them to cope more effectively. However, until now the efficacy of this training has not been compared to tha...

Attention mediates access of sensory events to higher cognitive systems and can be driven by either top-down voluntary mechanisms or in a bottom-up, reflexive fashion by the sensory properties of a stimulus. The exact mechanisms underlying these different modes of attention are controversial, but both types of attention appear to be tightly coupled...

The perception-action model proposes that vision-for-perception and vision-for-action are based on anatomically distinct and functionally independent streams within the visual cortex. This idea can account for diverse experimental findings, and has been hugely influential over the past two decades. The model itself comprises a set of core contrasts...

In our review, we argued that the ubiquity and extent of inter-stream interactions suggests that the ventral and dorsal visual streams are not functionally independent processing pathways. Most commentaries agreed with our conclusions. However, the notion that the specializations of the two streams are relative, not absolute, was criticised. We add...

Peripheral cues trigger attention shifts, which facilitate perceptual processing and enhance visual awareness. However, this facilitation is superseded by an inhibition of return (IOR) effect, which biases attention away from the cued location. While the link between facilitatory effects of visual attention and awareness is well established, no stu...

Patients with subarachnoid hemorrhage (SAH) are younger than typical stroke patients. Poor psychosocial outcome after SAH therefore leads to a disproportionately high impact on patients, relatives, and society. Addressing this problem requires an understanding of what causes poor psychosocial outcome. Numerous studies have examined potential predic...

The high mortality rate associated with spontaneous subarachnoid haemorrhage (Hop et al, 1997) has meant that for a long time research on subarachnoid haemorrhage has focused on gross morbidity and survival time. However, improving survival over the last few decades (Nieuwkamp et al, 2009) has meant that it is now important to also examine subarach...

Room tilt illusion (RTI) – transient upside-down vision or apparent tilt of the visual scene on its side – has been described in patients with acute lesions of the brainstem, the parieto-occipital region, or the frontal lobe and in patients with epilepsy. Published cases so far have been based on patient histories taken after the event. A 31-year-o...

It is a key assumption of the perception/action model that the dorsal stream relies on current visual input and does not store visual information over an extended period of time. Consequently, it is expected that action which is guided by memorized visual information, so-called delayed action, cannot use information from the dorsal stream but must...

The contralesional line bisection error in hemianopia is a well-known clinical phenomenon. Its origin, however, is still unclear. We therefore investigated the causes of the hemianopic bisection error in 84 patients with unilateral homonymous hemianopia without visuospatial neglect. Our results suggest that the contralesional bisection error is nei...

Significant others (SOs), such as spouses and life partners, of patients who have survived subarachnoid hemorrhage (SAH) can experience psychiatric symptoms and psychosocial disability. The cause of such symptoms has not been established. Authors of the present study analyzed whether posttraumatic stress disorder (PTSD) subsequent to a loved one's...

A subarachnoid hemorrhage reduces patients' quality of life (QoL) in both the short and long term. Neurological problems alone cannot explain this reduction. We examined whether posttraumatic stress disorder (PTSD) and fatigue provide an explanation. We prospectively studied a representative sample of 105 subarachnoid hemorrhage patients. Patients...

The perception-action model proposes that vision for perception and vision for action are subserved by two separate cortical systems, the ventral and dorsal streams, respectively [Milner, A. D., & Goodale, M. A. (1995). The visual brain in action (1st ed.). Oxford: Oxford University Press; Milner, A. D., & Goodale, M. A. (2006). The visual brain in...

Humans are remarkably insensitive to large changes in a visual display if the change occurs simultaneously with a secondary perceptual event. A widely held view is that this change blindness occurs because the secondary perceptual event prevents the change from capturing attention. However, whereas some studies have shown that top-down attentional...