Is Motion Perception Deficit in Schizophrenia a Consequence of Eye-Tracking Abnormality?

Abstract

Background Studies have shown that schizophrenia patients have motion perception deficit, which was thought to cause eye-tracking abnormality in schizophrenia. However, eye movement closely interacts with motion perception. The known eye-tracking difficulties in schizophrenia patients may interact with their motion perception. Methods Two speed discrimination experiments were conducted in a within-subject design. In experiment 1, the stimulus duration was 150 msec to minimize the chance of eye-tracking occurrence. In experiment 2, the duration was increased to 300 msec, increasing the possibility of eye movement intrusion. Regular eye-tracking performance was evaluated in a third experiment. Results At 150 msec, speed discrimination thresholds did not differ between schizophrenia patients (n = 38) and control subjects (n = 33). At 300 msec, patients had significantly higher thresholds than control subjects (p =.03). Furthermore, frequencies of eye tracking during the 300 msec stimulus were significantly correlated with speed discrimination in control subjects (p = .01) but not in patients, suggesting that eye-tracking initiation may benefit control subjects but not patients. The frequency of eye tracking during speed discrimination was not significantly related to regular eye-tracking performance. Conclusions Speed discrimination, per se, is not impaired in schizophrenia patients. The observed abnormality appears to be a consequence of impairment in generating or integrating the feedback information from eye movements. This study introduces a novel approach to motion perception studies and highlights the importance of concurrently measuring eye movements to understand interactions between these two systems; the results argue for a conceptual revision regarding motion perception abnormality in schizophrenia.

Efference Copy Failure during Smooth Pursuit Eye Movements in Schizophrenia

“…Moreover, the group ϫ gain interaction from the mixed model confirmed that patients not only failed to benefit significantly from tracking, but could actually be differentiated from controls on this measure. Hong et al (2009) reported that patients benefitted from pursuit eye movements. However, this occurred in the context in which subjects were asked to fixate, but pursuit movements were observed during fixation.…”

“…Characteristics of smooth pursuit in schizophrenia are deficits in predictive pursuit (Thaker et al, 1996(Thaker et al, , 1999(Thaker et al, , 2003Sweeney et al, 1998;Lencer et al, 2004;Hong et al, 2008) and a global decrease in pursuit smoothness and accuracy (Yee et al, 1987;Clementz and McDowell, 1994;Levy et al, 2000;Kathmann et al, 2003;Ettinger et al, 2004;Lencer et al, 2004), particularly during the closed-loop pursuit phase. Whereas open-loop pursuit, the initial 100 -150 ms of the response, is driven exclusively by feedforward image motion signals originating in the retina (Lisberger et al, 1987;Lisberger, 2010), closed-loop pursuit depends upon both retinal motion signals and extraretinal feedback information, such as an efference copy or "corollary discharge" of the oculomotor output.…”

“…The schizophrenia pursuit deficit could be caused by impairments in low-level motion processing (Stuve et al, 1997;Chen et al, 1999Chen et al, , 2003Chen et al, , 2008Butler and Javitt, 2005;Slaghuis et al, 2005;Chen, 2011;Nagel et al, 2012) and/or higher-level predictive mechanisms Thaker et al, 1996Thaker et al, , 1999Sweeney et al, 1998;Keedy et al, 2006;Hong et al, 2008), such as an inability to generate or use efference copy information.…”

An eye-tracking investigation of intentional motion perception in patients with schizophrenia

“…33,34 However, eyetracking still provides a useful insight into early, implicit and online information pro cesses as well as an opportunity to disentangle them from later reflexive and decisional processes. A second limitation comes from the fact that deficits in the perception of nonsocial motion, including detection of coherent motion 35 and speed 36,37 or direc tion discrimination, 38 have also been demonstrated in individ uals with schizophrenia. Further explorations are needed to clarify whether the intentional motion detection deficit demon strated in this study can be explained by a general deficit in mo tion perception in individuals with schizophrenia or whether it is more specific to the social domain.…”

Long range frontal/posterior phase synchronization during remembered pursuit task is impaired in schizophrenia

“…FEF are a likely source to relay the efference copy information to the two extrastriate visual areas (MT/MST), where it is integrated with the visual sensory input (i.e., corollary discharge) to form a motion perception (Nuding et al, 2008). Motion perception relies on the efference copy for adapting the visual receptive field in accordance with motion (Hong et al, 2009; Sommer and Wurtz, 2002; Turano and Massof, 2001). Converging lines of evidence suggest that schizophrenia probands and their relatives have impaired predictive pursuit (Thaker et al., 2003).…”