Switching, plasticity, and prediction in a saccadic task-switch paradigm

Abstract

Several cognitive processes are involved in task-switching. Using a prosaccade/antisaccade paradigm, we manipulated both the interval available for preparation between the cue and the target and the predictability of trial sequences, to isolate the contributions of foreknowledge, an active switching (reconfiguration) process, and passive inhibitory effects persisting from the prior trial. We tested 15 subjects with both a random and a regularly alternating trial sequence. Half of the trials had a short cue-target interval of 200 ms, and half a longer cue-target interval of 2,000 ms. When there was only a short preparatory interval, switching increased the latencies for both prosaccades and antisaccades. With a long preparatory interval, switching was associated with a smaller latency increase for prosaccades and, importantly, a paradoxical reduction in latency for antisaccades. Foreknowledge of a predictable sequence did not allow subjects to reduce switch costs in the manner that a long preparatory cue-target interval did. In the trials with short preparatory intervals, the effects on latency attributable to active reconfiguration processes were similar for prosaccades and antisaccades. We propose a model in which the passive inhibitory effects that persist from the prior saccadic trial are due not to task-set inertia, in which one task-set inhibits the opposite task-set, but to inhibition of the saccadic response-system by the antisaccade task, to account for the paradoxical set-switch benefit for antisaccades at long cue-target intervals. Our findings regarding foreknowledge show that previous studies used to support task-set inertia may have conflated the effects of both active reconfiguration and passive inhibitory processes on latency. While our model of response-system plasticity can explain a number of effects of dominance asymmetry in switching, other models fail to account for the paradoxical set-switch benefit for antisaccades.

The use of working memory for task prediction: What benefits accrue from different types of foreknowledge?

“…Another possibility is that one might not know which stimulus will appear, but know the type of response that will be required. In the saccadic paradigm, one may then be uncertain as to which side the target would appear, but know from the trial sequence that an antisaccade was the required response (Barton et al, 2005;Sohn and Anderson, 2001;Tornay and Milan, 2001). This would be a 'set-foreknowledge.'…”

“…Our recent investigations have focused on the benefits of set foreknowledge in a saccadic paradigm (Barton et al, 2005). Set-foreknowledge in particular is revealed during instances where the set changes from one trial to the next.…”

“…To study this, we recently performed an experiment in which subjects performed blocks of trials that contained mixtures of prosaccades and antisaccades (Barton et al, 2005). In one group of blocks the mixture was randomized.…”

Stimulation of the Frontal Eye Field Reveals Persistent Effective Connectivity after Controlled Behavior

“…In a Stroop paradigm in which subjects switch between automatic word reading and controlled color naming tasks, a greater switch cost is observed on a word-reading trial after color naming than on a color-naming trial after word reading (Allport et al, 1994). Also, when switching between prosaccade and controlled antisaccade, that is, when switching between rules to make a saccade to and away from a visual target, a greater switch cost is observed on a prosaccade trial that follows an antisaccade trial than on an antisaccade trial that follows a prosaccade trial (Cherkasova et al, 2002;Fecteau et al, 2004;Barton et al, 2006). Moreover, responses become faster when switching from prosaccade to antisaccade than when repeating antisaccade.…”

“…These results cannot be accounted for by the extra neural processing to establish the rule representation for controlled behavior, as this would result in an increase in RTs when switching from automatic to controlled behavior rather than vice versa. It is also shown that the effect cannot be eliminated with ample task preparation time of several seconds (Allport et al, 1994;Rogers and Monsell, 1995;Meiran, 2000;Barton et al, 2006), suggesting that a mechanism involved in the aftereffect of controlled behavior cannot be updated during a task preparation period on the next trial.…”