Ioannis Evdokimidis (Department of Neurology, University of Athens) Is the distractibility factor for antisaccades a good predictor for developping psychosis ?

Abstract :

Several recent studies reported that the distractibility factor (the percentage of errors) in the antisaccade task was higher in psychotic patients and was considered as a further oculomotor trait of schizophrenia similar to the eye pursuit deficits (Holzman group studies). In order to reveal possible predisposing factors for developing psychosis we tested a sample of 2100 young subjects with a battery of oculomotor (reflex saccades, antisaccades, pursuit and fixations), cognitive (CPT, n2-back) and psychometric (RAVEN, PAS, TCI, SCL90) tests.
We present preliminary data concerning the antisaccade task and especially the relations between the distractibility factor, DF, the latencies and the PAS score (schizotypy). Our findings suggest that the DF shows a marginal correlation with the PAS score. In contrast, the variance of the correct antisaccade latency seems more rigid and meaningful. In addition we present a model for error prediction in healthy subjects.

Qing Yang (Shanghai Institute of Physiology, Chinese Academy of Sciences) Open-loop and Closed-loop Optokinetic Nystagmus (OKN) in Myasthenia Gravis and Nonmyasthenic Subjects

Abstract :

Open-loop (eye movement signal is not negatively feedbacked to affect the retinal slip) and closed-loop ( regular situation : eye signal is immediately negative feedbacked to control the retinal slip) Optokinetic nystagmus (OKN) were examined in 16 myasthenia gravis (MG), 8 nonmyasthenic ocular palsies and 4 normals. In MG patients, open-loop OKN gains increased significantly after the intramuscular injection of neostigmine. Both the closed-loop and open-loop OKN gains of nonmyasthenic subjects were not increased for the administration of neostigmine. Results indicated that only open-loop OKN gain could be sensitive to reflect the changes of the function of neuromuscular junction in MG patients.

Rich Krauzlis (The Salk Institute La Jolla, California, USA) How do pursuit and saccades select the same visual target ?

Areti Tzelepi (Lab. of Electrophysiology, Dept of Neurology, SUNY, Brooklyn, USA) High frequency oscillatory activity to visual pattern onset stimulation in man

Abstract :

Electrophysiological recordings with surface electrodes of the early visual evoked response revealed oscillatory activity in different frequency bands using the wavelet transform. Responses in beta and gamma frequency bands were affected differentially by stimulus properties. Topographic analysis of the response at the same time period using MEG recordings, showed simultaneous activation of the striate and extrastriate regions. Different frequency bands appear to be related to different aspects of visual processing.

Thomas Eggert (dept. of Neurology, Ludwig Maximilians Univ. of Munich, Germany) Background target interaction during saccade adaptation

Abstract :

Saccadic eye movements can be adapted by using a paradigm first described by McLaughlin (1967). When a target is systematically stepped backward/forward during the primary saccade, the saccade amplitude elicited by a primary target step of a given size decreases/increases within 100 to 300 trials. The question is how an intrasaccadic displacement of the target with respect to the retina can be distinguished from a displacement of the background and how the visual system determines an error signal for driving the adaptation.
In a first experiment the intrasaccadic displacement of a small foveal target was combined with a displacement of the background in the same or in the opposite direction as the target step. This had no influence on the adaptation. In a second experiment a new type of target was introduced. The subjects were asked to fixate the virtual middle of an open annulus of 4.8 deg diameter. Saccade adaptation to this type of target was clearly enhanced when the background stepped intrasaccadically in the same direction as the target. The sensitivity of saccade adaptation to displacements of the background differed depending on the type of target. We speculated that this sensitivity reflects the ability of the error signal to segregate the target from the background and that this ability might be related to the size of the attention focus around the time of the saccade. To test whether the attention focus was really larger on the annulus than on the foveal target, we measured the reaction times to small test stimuli flashed 100 ms after the end of the saccade at various distances from the fovea. There was clear evidence that the target size influences the size of the attention focus. This finding is in agreement with the view that the error signal for driving saccade adaptation is based on some kind of trans-saccadic iconic memory, not for the complete visual scene but for the part of the visual information that was selected for attention.
Since the presaccadic shift of attention is closely linked to the motor execution of the saccade, we addressed the further question of whether the size of the presaccadic attention shift is also adapted during short-term saccadic amplitude adaptation. Therefore we measured the presaccadic attention shift by means of a visual discrimination task during an adaptation paradigm. The adaptive gain change had no effect on the metrics of the presaccadic attention shift. This result suggests that the spatial information that is commonly accessed by the attention shift and the motor execution remains unaffected during short-term saccade adaptation, which most probably acts on a lower level of saccadic programming.

Nikos Smyrnis (Neurology Dept, Univ. of Athens, Eginition Hospital) Antisaccade performance in schizotypy versus anxiety and depression in 1251 healthy males

Abstract :

In recent years oculomotor tasks (smooth eye-pursuit, anti-saccades) have been extensively studied in relation to schizophrenia with the aim of identifying psychosis-related biological markers. In this report the anti-saccade task performance results are presented for a large sample of healthy males. These individuals were screened in eye-movement and cognitive tasks for the purposes of a prospective study on psychosis proneness (Athens Study of Psychosis proneness and Incidence of Schizophrenia, ASPIS). Methods: 1251 young males recruited from the Greek Air Force performed the anti-saccade task and completed the Perceptual Aberration Scale (PAS), the Schizotypal Personality Questionnaire (SPQ) and the Symptom Checklist 90-R.

Contacts :

Zoï KAPOULA Tél. 01 44 27 16 35
Isabelle ISRAEL Tél. 01 44 27 12 88
Françoise VITU Tél. 01 55 20 58 64