On September 1 I will be moving to the School of Psychology and Neuroscience at the University of St Andrews. Goodbye Germany, hello Scotland !
Using a sclera lens we induced a sustained rotation of the non-viewing, dominant eye, stimulating the extraocular muscle proprioceptors. While participants viewed a display with the non-dominant eye, this procedure improved visual detection in the hemifield located in the direction of this rotation.
This paper has the proofs already onlineDaniela Balslev, Hartwig R. Siebner, Olaf B. Paulson, Tanja Kassuba. (2012) The cortical eye proprioceptive signal modulates neural activity in higher-order visual cortex as predicted by the variation in visual sensitivity. Neuroimage (in press) http://www.ncbi.nlm.nih.gov/pubmed/22521251
... and this paper just got accepted, I uploaded my final version on the website:
Daniela Balslev, Marc Himmelbach, Hans-Otto Karnath, Svenja Borchers, Bartholomaeus Odoj (2012) Eye proprioception used for visual localization only if in conflict with the oculomotor plan. J Neuroscience (in press)
Eye muscle proprioceptive manipulation confirms spatial bias in visual attention towards the perceived direction of gaze
Daniela Balslev, William Newman, Paul C. Knox
My talk is scheduled on Thursday sept 1 at 15:30.
Our conclusion is that attention is involuntarily captured in the perceived direction of gaze. By using passive eye movement, this study provides more direct evidence of the role of eye proprioception in the allocation of attention, than my previous study where we interfered with the cortical processing of eye proprioception using repetitive transcranial magnetic stimulation (rTMS) over the somatosensory cortex.
The experiment was carried out at the University of Liverpool in collaboration with Drs. Knox and Newman. We used a scleral lens to manipulate the eye muscles and measured the consequences of this proprioceptive stimulus on visual accuracy. This proceedure was invented by Gabriel Gauthier and is considered "the golden standard" for testing the effects of eye proprioception on behavior in humans. I was very lucky to work with Paul Knox who is one of the few experts worldwide in using this method, and with William Newman, an ophthalmology consultant who kindly offered a chunk of his very busy time to make sure that the eyes of the experiment participants stayed safe.
The scleral lens is very similar with a hard contact lens that is used in patients. The lens is modified by attaching a tube - through which light suction is created to fix the lens to the cornea - and a stalk - which is fixed in a static holder. First the participant fixates laterally at 10 degrees, allowing us to block the dominant eye in this position. Then s/he is instructed to fixate centrally, causing the non-dominant, viewing eye to rotate back, whereas the non-viewing eye remains deviated. Although this eye returns centrally, its position is perceived to be slightly (~2 degrees) rotated in the direction of the dominant eye. This dissociates the real direction of gaze from the perceived direction of gaze and allows us to test visual detection for targets that are retinotopically equidistant, but presented at different distances from the perceived direction of gaze.
The procedure is not painful, only unpleasant - like putting contact lenses in and out of the eyes...
The abstract of my talk is here.
See you in Toulouse maybe...
Daniela will give a Young investigator talk at the Gordon Research Conference on Eye Movements on Monday 01 august 2011 at the University of New England http://www.grc.org/programs.aspx?year=2011&program=eyemove
Eye proprioception used for visual localization only if in conflict with
the oculomotor plan
Daniela Balslev1,2, Marc Himmelbach1, Hans-Otto Karnath1, Svenja Borchers1, Bartholomaeus Odoj1
1 Center of Neurology and Hertie Institute for Clinical Brain Research, University of Tuebingen , Germany; 2Department of Psychology, University of Copenhagen, Denmark
There are two hypotheses about how the efference copy of the motor command and the extraocular muscle proprioception are combined to locate retinal objects relative to the body: 1. only the efference copy is used whereas proprioception is a slow recalibrator of the forward model [Steinbach, 1987, Acta Psychologica, 63, 297-306] and 2. both signals are used together as a weighted average [Gauthier et al, 1990, Science, 249(4964), 58-61]. We tested these hypotheses in a patient (RW) with a circumscribed lesion of the right postcentral gyrus, that overlaps the eye proprioceptive representation [Balslev et al., 2011, Human Brain Mapping, 32, 624-631]. RW was as accurate and precise as the control group (n=19) in locating a lit LED that she viewed through the eye contralateral to the lesion (p > 0.6). However, when the task was preceded by a brief (<1s) and gentle push to the closed eye, which perturbs eye position and stimulates eye proprioceptors in the absence of a motor command, RW’s accuracy decreased (p<0.001). We suggest that eye proprioception is used only as a back-up during visual localization. Proprioception is compared with the efference copy and incorporated into the eye position estimate in conditions with a mismatch.
Acknowledgments: Funded by the Danish Medical Research Councils and a Marie Curie intra-european fellowship (DB). Grant numbers: 09-072209 and PIEF-GA-2009-252424.