EyeProprio

Alex and Daniela are attending the EPS Workshop on Oculomotor Readiness and Covert Attention organized by Dan Smith at University of Durham.

It was Alex first poster session – WELL DONE ALEX!

Summary of Daniela’s talk

Oculoproprioception
–
an eye position signal selective for coding the locus of attention?

The most commonly observed neural
representations for visual attention encode location relative to the direction
of gaze. Without information about the rotation of one’s own eyes in the orbits
cars around us in traffic or food on our plate would appear to change location
with every eye movement. Furthermore, gaze information is necessary to align visual
locations with sound or touch to enable cross-modal interactions. Despite
the importance of the gaze information in the brain’s representations for
spatial attention, the sources of this gaze input to the attention maps have
remained unknown.

There are two main signals of eye rotation. The
copy of the command sent to the extraocular muscles (corollary discharge, CD)
is predictive, therefore faster. The reafference from these muscles
(oculoproprioception, OP) is slower, but more accurate. In my talk I will
argue that these signals are used flexibly, depending on behavioral
goals. Locating objects relative to the body, for instance to guide a
pointing movement, relies mainly on the fast signal, CD. In contrast, OP seems
to be more important for perception, i.e, allocating attention in the
body-centered space.

Role of oculoproprioception in coding the locus of attention.

Barthel Odoj and Daniela Balslev’s paper has just been accepted for publication in Journal of Cognitive Neuroscience. This means two things:
1. Barthel’s PhD thesis is now ready to be submitted (fingers crossed!).
2. We are closer to understanding how eye and attention are related. The paper shows that the feedback signals from the eye movements (oculoproprioception) is incorporated into attention maps to align retinotopic snapshots to the world. Repetitive transcranial magnetic stimulation over the somatosensory cortex perturbs this signal and cause a 1 degree error in the perceived angle of gaze. The same intervention diverts attention away by 1 degree away from a target, without affecting the ability to locate the target for reaching. Feedback signals from eye movement appear more important for perception, whereas action relies more on the predictive signals, presumably because of the neural processing speed constraints.

Subcortical pathways for the gaze direction signals


We are advertising a 4-year PhD scholarship starting in September 2016 at the University of St Andrews. The fMRI project will identify subcortical structures that carry gaze direction signals for visual localization and spatial attention. The project is at the interface between cognitive neuroscience and medical physics. The student will be supervised by Dr Daniela Balslev from the University of St Andrews and Dr Ian Cavin from the University of Dundee & NHS Tayside Department of Medical Physics.

The project

How to apply

Contact
daniela.balslev@st-andrews.ac.uk
ian.cavin@nhs.net

Alex has done her undergraduate studies at the University of York and has just finished a Master in Cognitive Neuroscience at UCL. She will be joining the lab in October to study towards a PhD. Her research project uses fMRI in healthy population and patients with spatial neglect to investigate how spatial representations for attention and movement emerge from sensory input and the efferent copy of the motor command.

Welcome!

I am advertising a 3-year fully funded PhD position with start in september 2015 or as soon as possible after that. The student will use functional magnetic imaging (fMRI) in healthy participants and stroke patients to investigate how attention and the ocular sensorimotor signals are coupled and how errors in this coupling can lead to attention disorders such as spatial neglect.

Further details about the project, the supervisor, the environment and the application procedure are below:

The project:
The mind’s eye: the sensorimotor underpinnings of attention

A fundamental question in cognitive science is whether cognition and sensorimotor functions are entirely separate, as if the mind were a computer, or alternatively, whether the body influences the mind. The debate between advocates of the independent and the embodied views has been particularly heated in the discussion about the neural mechanisms of attention.

Attention is the ability to withdraw from some stimuli in order to deal effectively with others. Many of the brain areas that control attention also control eye movements. Is attention merely taking over some of the neural machinery evolved for gaze control, while operating completely independently? Or is attention nothing more than planned and withheld eye movements?

Recent breakthroughs in cognitive neuroscience allow now to design experiments that can answer these questions. I and others have mapped the pathways for the eye position signals in the central nervous system and provided tools to manipulate with these signals in the healthy human brain using transcranial magnetic stimulation (i.e. Balslev and Miall, J Neuroscience, 28:8968-72, 2008). There are two sources of eye position information: proprioception (the afferent input from the extraocular muscles) and corollary discharge (the copy of the oculomotor command). My work has shown that all interventions that change the oculoproprioceptive signal change the allocation of attention in space. This finding is crucial because it shows for the first time that a sensorimotor signal may have a specific function in attention (Balslev et al, J Neuroscience, 33:18311-8, 2013).

The aim of this research is to investigate how attention and the ocular sensorimotor input are coupled and how error in this coupling can cause spatial neglect.

The supervisor

I am an MD/PhD with 7 years postdoctoral experience, relocated to the UK one year ago to take up my first academic position. Personal fellowships from the Danish Medical Research Councils and the EU throughout the entire postdoctoral period have allowed me not only to develop an independent research agenda, but also to learn research methods in cognitive neuroscience from key experts. A list of my publications is here.

My lab has access to state-of-art equipment for transcranial magnetic stimulation (MagPro X100), eye tracking (EyeLink II) and functional magnetic resonance imaging (Siemens Trio, at the Clinical Research Centre, Ninewells Hospital Dundee). I would be happy to train the student to use these methods in healthy and patient populations. The oculomotor command and the re-afferent input for the eye muscles are fundamental building blocks in the neural representations that support movement, attention or object recognition. The goal is to understand how the brain represents space and how a breakdown in these representations in neurological patients can lead to disabilities such as optic ataxia, spatial neglect or simultanagnosia.

You can read more about my research here

The environment

The School of Psychology and Neuroscience at St Andrews has a strong Vision group using a variety of techniques (including psychophysics, eye movements, EEG, fMRI, TMS, neuropsychology and computational modelling) to study the human visual system. Ours is a highly multidisciplinary group, with members trained in biology, neuroscience, medicine, psychology, maths, physics and engineering. Potential students from these and related disciplines are welcome.

Funding

The PhD studentship covers tuition fees for UK/EU residents and provides a stipend of £13863/year. Candidates from overseas will have to find additional sources of support to cover the difference in the tuition fees
The project is funded via an award to Dr Daniela Balslev from the Wellcome Institutional Strategic Support Fund at the University of St Andrews.

Application procedure

Please send to daniela.balslev@st-andrews.ac.uk the following documents:
1. CV. This should include your personal details including your country of residence with a history of your education and employment to date.
2. Letter of motivation (half a page)
3. Two letters of reference
4. Copies of academic transcripts and degree certificates
5. Candidates who are not UK/EU residents will have to provide a statement about how they expect to cover the difference in the tuition fees (please see information about Funding above).

Applications will be accepted until the position is filled. Previous experience with Matlab, eye tracking, neuropsychology or functional magnetic resonance is not a prerequisite, but highly desirable.

Welcome to grad student Bobby Innes ! Bobby is joining the lab to investigate how the brain integrates the available sensorimotor signals to estimate the rotation of one’s own eyes in the orbits. This information is critical for our ability to reach or attend to visual objects.

There are two eye position signals. Each signal has its advantages. The copy of the oculomotor command or corollary discharge is fast, available even before the eyes have moved. The reafferent feedback from the eye muscles or proprioception takes about 100 ms to reach the cerebral cortex. Oculoproprioception is, however, the most accurate reflection of the current eye position.

We are asking whether these signals are combined or not in a multimodal estimate of eye position. If they are combined, what is the criterion for their optimization ? Is this criterion fixed or flexible, tailored to suit the behavioral goal best ? Is the eye special or does the integration of the oculomotor and oculoproprioceptive signals follow the same principles as the sensorimotor integration for hand control or for multisensory integration ?

Hopefully we should soon have some answers, so stay tuned.

Bobby is funded by a BBSRC/EASBIO PhD studentship (2014-2018) and is supervised by Daniela Balslev and Tom Otto.

We think we figured out the disease mechanism in simultanagnosia (a neuropsychological disease in which the patients see only one object at the time, and are unable to identify large visual scenes). This is a rare but a very invalidating disease: the patients can no longer read or orient themselves in unfamiliar surroundings. I hope my research will help towards better assessment and treatment for these patients. However, I must confess that I did it also for a selfish reason. I find neuropsychological puzzles cool and I think I solved this one.

In brief, simultanagnosia patients cannot see what they are directly looking at. Central and peripheral objects compete for attention and objects in the periphery win this competition. If multiple objects are instead presented in the visual periphery only, the patients are better able to perceive them simultaneously.
An abstract is below:

Abnormal center-periphery gradient in spatial attention in simultanagnosia

Daniela Balslev, Bartholomaeus Odoj, Johannes Rennig, Hans-Otto Karnath

Journal of Cognitive Neuroscience (in press)

Patients suffering from simultanagnosia cannot
perceive more than one object at a time. The underlying mechanism is incompletely
understood. One hypothesis is that simultanagnosia reflects “tunnel vision”, a
constricted attention window around gaze, which precludes the grouping of individual
objects. Although this idea has a long history in neuropsychology, the question
whether the patients indeed have an abnormal attention gradient around the gaze
has so far not been addressed. Here we tested this hypothesis in two simultanagnosia
patients with bilateral parieto-occipital lesions and two control groups, with
or without brain damage. We assessed the
subjects’ ability to discriminate letters presented briefly at fixation with
and without a peripheral distractor or in the visual periphery, with or without
a foveal distractor. A constricted span of attention around gaze would predict
an increased susceptibility to foveated versus peripheral distractors. Contrary
to this prediction and unlike both control groups, the patients’ ability to
discriminate the target decreased more in the presence of peripheral compared
to foveated distractors. Thus the attentional spotlight in simultanagnosia does
not fall on foveated objects as previously assumed, but rather abnormally
highlights the periphery. Furthermore, we found the same center-periphery gradient
in the patients’ ability to recognize multiple objects. They detected multiple,
but not single objects more accurately in the periphery than at fixation. These
results suggest that an abnormal allocation of attention around the gaze can disrupt
the grouping of individual objects into an integrated visual scene

Thursday 27th March 2014 at 4pm, School of Psychology, University of Leicester

Eye position signals in spatial cognition

The straightforward sense of where things are belies the hard problem of aligning input from mobile sensory organs with one another and with the action space of the body. Without information about the rotation of the eyes within the head, for instance, it would be virtually impossible to match an unknown face and a voice in a crowd or to reach to visual targets without seeing the hand.

There are two main signals of eye position. The copy of the command sent to the extraocular muscles (corollary discharge) is predictive, therefore faster. The reafference from these muscles (proprioception) is slower, but more accurate. In my talk I will present evidence that these signals are used flexibly, depending on behavioral goals. Locating objects relative to the body, for instance to guide a movement, relies mainly on the fast signal, corollary discharge. In contrast, eye proprioception seems to be more important for perception, ie allocating attention in the body-centered space.