Neglect is a possible
consequence of right-hemisphere brain damage and is characterised by a
dramatic failure to orient toward, explore and respond to stimuli
presented on the contralesional side, even when these items appear in
isolation or for sustained periods of time. For example, neglect
patients often only talk to people on their right and fail to eat food
from the left side of their plate. Interestingly, while neglect
patients fail to respond to certain regions of space, primary sensory
loss is not the main cause of neglect. In other words, neglect
represents a failure to perceive despite intact sensory processing. In
this lab we study the causal mechanisms and neural basis of this
neuropsychological syndrome using functional MRI, TMS and behavioural
studies in both neurological healthy subjects and neurological patients.
Berger M, Karnath H-O (2005). Spontaneous
eye and head position in patients with spatial neglect. J Neurol
H-O, Dieterich M (2006). Spatial neglect - a vestibular disorder? Brain
Extinction patients can
single stimulus at any spatial location. However, when two stimuli are
presented simultaneously, subjects are impaired at perceiving the
contralesional item. In other words, the contralesional stimulus is
extinguished when an ipsilesional stimulus is present. Extinction has
most commonly been associated with damage to the temporoparietal
junction of the right hemisphere. Extinction is often considered to be
the result of biased competitive interactions between the ipsilesional
and contralesional stimuli and is most commonly seen as an exaggeration
of the difficulty that normal subjects have while trying to attend to
multiple targets simultaneously. In this lab we study both
neurologically healthy subjects and neurological patients with the aid
of methods like TMS, fMRI, lesion mapping and behavioural studies to
resolve questions concerning the anatomy and the underlying mechanisms
H-O, Himmelbach M, Küker W (2003). The
cortical substrate of visual extinction. NeuroReport 14:
437-442, Erratum 14: 1189.
E, Karnath H-O (2007).
Incidence of visual extinction after left
versus right hemisphere stroke. Stroke
control and sensorimotor
Our rich behavioural repertoire
is based on the integration of spatial and temporal information about
the environment and internal states of movement effectors. It enables
us to react to environmental demands and challenges, actively explore
and investigate our surroundings, and manipulate objects and tools for
a specific purpose. Investigating neurological patients suffering from
movement coordination disorders, like apraxia or optic ataxia, our work
focuses on the system level of action control. We strive for functional
neuroanatomical models and hypotheses that agree with the patients'
behaviour thereby explaining the pathomechanism of the specific
disorder on the one hand and verifying respective models of action
control on the other hand. Acute and chronic neurological patients
after stroke are examined with state-of-the-art kinematic tracking
devices for eye, head, and hand movements. These investigations are
complemented by behavioural experiments in healthy humans and
M, Karnath H-O (2005). Dorsal and ventral stream interaction:
Contributions from optic ataxia. J Cogn Neurosci 17: 632-640.
-Goldenberg G, Hermsdörfer J,
Glindemann R, Rorden C, Karnath H-O (2007). Pantomime of tool use
depends on integrity of left inferior frontal cortex.
localization in space
Despite the movements of eyes,
head, and body, a healthy person perceives its environment as a
constant visual and acoustical unit. Humans also show a remarkable
ability to attend to and localise sounds. By means of functional MRI,
we search for the neural correlates underlying these mechanisms.
Likewise, in a soundproof room behavioral studies are carried out to
clarify the mechanisms of auditory localisation in multisound
environments. Our studies are carried out with healthy subjects as well
as stroke patients.
U, Lewald J, Karnath H-O (2003).
Disturbed sound lateralization in patients with spatial neglect.
J Cog Neurosci 15: 683-693.
U, Lewald J, Erb M, Karnath H-O (2006). Processing of auditory spatial
cues in human cortex: an fMRI study. Neuropsychologia 44:
Stroke patients may exhibit the
peculiar behavior of actively pushing away from the non-hemiparetic
side leading to lateral postural imbalance and a tendency to fall
towards the paralyzed side. This phenomenon has been called the "Pusher
Syndrome". We investigate the cognitive, visual, and vestibular
contributions to understand the mechanism leading to contraversive
Schematic drawing of pusher patients' perceived
with occluded eyes
(A) and while viewing their surroundings (B). The
patient's SPV shows a marked ipsiversive
deviation from the
earth-vertical with occluded eyes.
H-O (2007). Pusher syndrome - a frequent but little-known disturbance
orientation perception. J Neurol 254: 415-24.
Our ability to recognize objects
from many viewpoints is remarkable. To identify objects regardless of
scale or viewpoint, we must match them with mental representations of
seen objects. Patients with brain damage may have normal object
skills but an impaired sense of object orientation. This has been taken
as evidence that object recognition is processed independetly of our
of object orientation. Studies in patients with brain damage and in
subjects using functional MRI aim at clarifying these processes.
integration and simultanagnosia
Human object-perception has been
a major focus of perceptual investigation over the last decade. Besides
psychophysical methods, electrophysiological methods and functional
neuroimaging have provided a detailed map of areas located in the
occipito-temporal cortex that are involved in object recognition.
However, the perception of our environment not only requires the
perception of individual objects, but also the integration of multiple
objects to a global gestalt (e.g. the integration of individual trees
giving rise to the coherent perception of a forest). Patients with
brain-damage of the temporo-occipital cortex may show a deficit in
global gestalt perception involving complex visual arrays that consist
of multiple objects. This deficit has been termed simultanagnosia. The
mechanisms underlying disturbed global gestalt perception remain
largely unknown. We investigate such patients to reveal the parameters
that play a critical role in object integration and further improve our
understanding of the underlying mechanisms. In addition, functional
neuroimaging might allow for the identification of the contributing
cortical and subcortical structures.
S, Fruhmann Berger M, Klockgether T, Moskau S, Karnath H-O (2006).
Restricted ocular exploration does not seem to explain
simultanagnosia. Neuropsychologia 44: 2330-2336.
-Huberle E, Rupek P, Lappe M, Karnath H-O
(2009). Perception of global gestalt by temporal integration in
simultanagnosia. European Journal of Neuroscience 29: 197-204.
Patients with anosognosia for
hemiparesis typically are convinced that their limbs function normally
although they have obvious motor defects after stroke. They may
experience the paretic limbs as strange or as not belonging to them, or
even may attribute ownership to another person. We evaluate such
phenomena in stroke patients to elucidate the mechanisms leading to
anosognosia, the brain structures typically involved when patients
exhibit this behaviour, as well as its relation to unilateral spatial
H-O, Baier B, Naegele T
(2005). Awareness of the functioning of one’s own limbs
mediated by the insular cortex? Journal of
Neuroscience 25: 7134-7138.
B, Karnath H-O (2008). Tight link between our sense of limb
ownership and self-awareness of actions. Stroke 39: 486-488.
functions in the cerebellum?
The cerebellum is usually
associated with motor control and learning. However, accumulating
evidence suggests that it may also be involved in cognitive functions
and affect. This assumption is supported both by patient and functional
imaging studies. We investigate probable cognitive functions of the
cerebellum with the help of language, visuo-spatial and executive
tasks. Localisation of functions in the cerebellum is studied with the
help of lesion mapping procedures. We use 3D-MR images to precisely
localize the cerebellar lesion and associate its localisation and
extent with probable cognitive deficits.
Individual lesions in patients with posterior
(PICA) infarction (A), and superior
cerebellar (SCA) infarction (B)
superimposed on horizontal MR sections of a healthy adult brain.
S, Schoch B, Kaiser O, Groetschel H, Hein-Kropp C, Maschke M, Dimitrova
A, Gizewski E, Ziegler W, Karnath H-O, Timmann D (2005).
adolescents with chronic cerebellar lesions show no clinically relevant
signs of aphasia or neglect. Journal of Neurophysiology 94:
-Frank B, Schoch B, Richter S, Frings M,
Karnath H-O, Timmann D (2007). Cerebellar lesion studies of cognitive
function in children and adolescents – limitations
negative findings. Cerebellum 6: 242-253.
Patients with pure alexia suffer
from severe reading problems while other language-related skills such
as speaking, listening comprehension, or writing are typically intact.
One of the most characteristic clinical features of this acquired
reading disorder is laborious letter-by-letter reading, which results
in a disproportionate prolongation of reading times when the number of
letters per word is increased. We investigate this disorder with a
series of tasks that include systematic word-form manipulations and use
eye movement recordings to analyse the reading behaviour of patients
and healthy subjects.
Using diffusion-weighted (DWI),
fluid-attenuated inversion-recovery (FLAIR) magnetic resonance imaging
(MRI) as well as spiral computerized tomography (Spiral-CT) scans we
identify the lesion location(s) typically associated with specific
cognitive disorders. Statistical voxelwise lesion-behaviour mapping
(VLBM) is used to determine relationships between behavioral
measures/disorders and the location of brain injury, revealing the
function of brain regions. Together with Prof. Chris Rorden, University
of South Carolina, we improve and develop new VLBM approaches. Prof.
Rorden also developed software to implement these procedures (MRIcron),
made freely available to the scientific community. Statistical lesion
mapping can also correlate the effectiveness of neurosurgery with the
location of brain resection, identifying optimal surgical targets.
Moreover, brain regions identified via VLBM might serve as starting
points for research with healthy subjects using fMRT and/or TMS.
C, Karnath H-O (2004). Using human brain lesions to infer function: a
relic from a past era in the fMRI age? Nature Reviews
-Rorden C, Karnath H-O, Bonilha L (2007).
Improving lesion-symptom mapping. Journal of Cognitive Neuroscience 19:
perfusion-weighted Imaging (PWI)
In patients with stroke lesions,
we use PWI to identify the abnormally perfused brain area(s) that
receive enough blood supply to remain structurally intact, but not
enough to function normally. In order to recognize these common areas
in groups of patients, we analyse the increase of time-to-peak (or TTP)
lesion-inducted delays by using spatial normalization of PWI maps as
well as symmetric voxel-wise inter-hemispheric comparisons. These new
techniques allow comparison of the structurally intact but abnormally
perfused areas of different individuals in the same stereotaxic space,
and at the same time avoid problems due to regional perfusion
differences and to possible observer-dependent biases.
H-O, Zopf R, Johannsen L, Fruhmann Berger M, Nagele T, Klose U (2005).
Normalized perfusion MRI to identify common areas of
patients with basal ganglia neglect. Brain 128: 2462-9.
Magnetic Stimulation (TMS)
subjects a temporary brain lesion can be induced by transcranial
magnetic stimulation (TMS). A magnetic field induces
electrical activity in the cortex and disorganizes neural
thus the normal neural processes for a very short time. We use this
so-called „virtual lesion approach" to establish a more
detailed view of neuronal anatomy and the anatomical functions of
cortical regions identified in previous fMRI and/or lesion mapping
studies. The ability of TMS to elicit a very focal and transient
disruption of ongoing neural activation allows us the causal
investigation of brain function at a high spatial and temporal
studies in human and non-human primates
We compare the functional
neuroanatomy of attentional orienting between human and non-human
primates. We aim to bridge the gap between the vast amount of
neurophysiological data in monkeys on the one and the exponentially
growing functional imaging data in humans on the other side. The
long-range goal is to understand the neural mechanisms of selective
visual attention at the level of the individual neuron and the cortical
circuit and to relate these to perception and conscious awareness. We
seek to understand this selection process using a combination of fMRI
We use sensors in a pulsed
magnetic field to monitor movements of head, body and limbs. Multiple
sensors can be tracked in 3D with a temporal resolution of 10ms. The
sensors are connected to a multi-purpose measurement plattform. This
allows us to integrate the measurement of spatial position with eye
movements and other real-time data. A video tracking system based on
reflective markers is used to study limb movements. By attaching small
adhesive reflectors to points of interest, we can measure movements in
space, uninihibited by cables.
We use video- and coil based
tracking systems that allow us to monitor eye movements in subjects
with good temporal and spatial resolution. Analyzing the direction of
gaze is used to infer attentional processes and patterns, both common
and pathological. Further, eye and head tracking is used as a means of
- functional magnetic resonance imaging
Based on neuropsychological
hypotheses we use BOLD fMRI to localise neuroanatomical modules and
networks contributing to intact cognitive and sensorimotor functions.
Our research projects are conducted using 3 Tesla and 1.5 Tesla Siemens
scanners located at the university hospital Tuebingen. The close
vicinity to the Center of Neurology permits the safe inclusion of
neurological patients in neuroimaging experiments. The equipment
comprises diverse setups for stimulus presentation and response
collection including a state-of-the-art eye SMI eye tracker system and
custom build MR-compatible video cameras for motion tracking. Data
analysis is primarily conducted with the SPM package developed and
distributed by the Wellcome Trust Centre for Neuroimaging and