Neural control of fast-regular saccades and antisaccades: an investigation using positron emission tomography

Abstract

Regional cerebral blood flow changes related to the performance of two oculomotor tasks and a central fixation task were compared in ten healthy human subjects. The tasks were: (a) performance of fast-regular saccades; (b) performance of voluntary antisaccades away from a peripheral cue; (c) passive maintenance of central visual fixation in the presence of irrelevant peripheral stimulation. The saccadic task was associated with a relative increase in activity in a number of occipitotemporal areas. Compared with both the fixation and the saccadic task, the performance of antisaccades activated a set of areas including: the superior and inferior parietal lobules, the precentral and prefrontal cortex, the cingulate cortex, and the supplementary motor area. The results of the present study suggest that: (a) compared with self-determined saccadic responses the performance of fast regular, reflexive saccades produces a limited activation of the frontal eye fields; (b) in the antisaccadic task the inferior parietal lobes subserve operations of sensory-motor integration dealing with attentional disengagement from the initial peripheral cue (appearing at an invalid spatial location) and with the recomputation of the antisaccadic vector on the basis of the wrong (e.g., spatially opposite) information provided by the same cue.

Spatial Anisotropy of Saccadic Latency in Normal Subjects and Brain-Damaged Patients

“…This suggests that results obtained in the saccadic task were not due to differences in stability of fixation between the two groups. The fixation test showed a high degree of stability and a shift around the fixation point of the same order of magnitude as that reported in previous studies on normal subjects (Rohrschneider et al, 1995;Ukwade and Bedell, 1993;Eizenman et al, 1992).…”

“…Moreover, there are no data in normal subjects on the reaction time in oblique saccades. In fact, all studies on oblique saccades in humans dealt with parameters, such as amplitude, peak velocity, duration and trajectory (Bahill and Stark, 1977;Evinger et al, 1981;Oohira et al, 1983;van Gisbergen et al, 1985). Thus, the present investigation also adds new original data for normal subjects, at least for the latency of oblique saccades.…”

A non-invasive method to relate the timing of neural activity to white matter microstructural integrity

“…Only trials with saccades in the desired direction and latencies between 130 and 800 ms were considered correct, and only correct saccades were included in the regression analysis. The cutoff of 130 ms excluded anticipatory saccades, which are executed too quickly to be a valid response to the appearance of the target (Doricchi et al 1997;Fischer and Breitmeyer 1987;Straube et al 1999).…”

Schizophrenia Subjects Show Intact Success-Related Neural Activation but Impaired Uncertainty Processing during Decision-Making

“…Specifically, attentional processes that involve sustained, and possibly selective, attention (Coull et al, 1996), switching from task-relevant local to global targets (Fink et al, 1996;Lamb et al, 1989), voluntary attentional control (Hopfinger et al, 2000), and the distinction between taskirrelevant and task-relevant events (Downar et al, 2001;Kiehl et al, 2001;McCarthy et al, 1997) support the view that this area is critical for the extraction and selection of task-relevant information. Moreover, this area has been implicated in inhibitory control in a number of different paradigms (Garavan et al, 1999;Menon et al, 2001;Rubia et al, 2001b;Steel et al, 2001;Doricchi et al, 1997), that is, the allocation of resources to a response that has to compete with a highly overlearned and potentially habitual behavior. Several studies using decision-making paradigms have implicated the right posterior parietal cortex in autonomic arousal processes (Tranel and Damasio, 1994;Critchley et al, 2000), risk-taking decision-making (Ernst et al, 2002), and guessing (Elliott et al, 1999).…”