Region-Specific Summation Patterns Inform the Role of Cortical Areas in Selecting Motor Plans.

Given an instruction regarding which effector to move and what location to move to, simply adding the effector and spatial signals together will not lead to movement selection. For this, a nonlinearity is required. Thresholds, for example, can be used to select a particular response and reject others.

Reach preparation enhances visual performance and appearance.

We investigated the impact of the preparation of reach movements on visual perception by simultaneously quantifying both an objective measure of visual sensitivity and the subjective experience of apparent contrast. Using a two-by-two alternative forced choice task, observers compared the orientation (clockwise or counterclockwise) and the contrast (higher or lower) of a Standard Gabor and a Test Gabor, the latter of which was presented during reach preparation, at the reach target location or the opposite location. Discrimination performance was better overall at the reach target than at the opposite location.

Manipulations of the relationship between response alternatives and exogenous saccade latencies.

The relationship between the latencies of saccadic eye movements and the number of response alternatives is complex. Previously, we have found a decrease in exogenous saccade latencies with an increase in the number of response alternatives (i.e.

An anti-Hick's effect for exogenous, but not endogenous, saccadic eye movements.

Previously, we have shown that the reaction times (RTs) of exogenously generated saccadic eye movements decrease with an increase in the number of response alternatives (Lawrence et al. in J Vis 8(26):1-7, 2008; Lawrence and Gardella in Exp Brain Res 195(3):413-418, 2009). Because this pattern of RTs is in the direction opposite that predicted by Hick (Q J Exp Psychol 4:11-26, 1952), we termed the effect an "anti-Hick's" effect.

The responses of visual neurons in the frontal eye field are biased for saccades.

Previous research suggests that visually responsive neurons in the frontal eye field (FEF) respond to visual targets even when they are not the goal of a saccadic eye movement. These results raise the possibility that these neurons respond to visual targets independent of the effector that is to be used to acquire the target locations. In the present study, we examined whether a plan to execute a saccade or a reach to a visual target influenced the response to and the representation of targets in the FEF.

Saccades and reaches, behaving differently.

Previously, we have shown, both in humans and monkeys, that the latencies of exogenously generated saccades decrease with an increase in the number of response alternatives (Lawrence et al. in J Vis 8:26, 1-7, 2008). Because this pattern of latencies was in the direction opposite that predicted by Hick (Q J Exp Psychol 4:11-26, 1952), we termed the effect an "anti-Hick's" effect.

An anti-Hick's effect in monkey and human saccade reaction times.

In order to execute movements to targets in the environment, we must first select a target in which to move, generally from an array of alternatives. Hick's Law states that reaction time (RT) increases as the number of response alternatives increases. Violations of this law, however, generally in the form of the absence of a relationship between response alternatives and RT have been reported in the literature.

Comparison of effector-specific signals in frontal and parietal cortices.

We previously demonstrated that the activities of neurons in the lateral intraparietal area (LIP) and the parietal reach region (PRR) of the posterior parietal cortex (PPC) are modulated by nonspatial effector-specific information. We now report similar modulation in FEF, an area of frontal cortex that is reciprocally connected with LIP. Although it is possible that these effector-specific signals originate in LIP and are conveyed to FEF, it is also possible that these signals originate in FEF and are "fed back" to LIP.

Delay-period activity in visual, visuomovement, and movement neurons in the frontal eye field.

In the present study, we examined the role of frontal eye field neurons in the maintenance of spatial information in a delayed-saccade paradigm. We found that visual, visuomovement, and movement neurons conveyed roughly equal amounts of spatial information during the delay period. Although there was significant delay-period activity in individual movement neurons, there was no significant delay-period activity in the averaged population of movement neurons.

Interference with spatial working memory: an eye movement is more than a shift of attention.

In the present experiments, we examined whether shifts of attention selectively interfere with the maintenance of both verbal and spatial information in working memory and whether the interference produced by eye movements is due to the attention shifts that accompany them. In Experiment 1, subjects performed either a spatial or a verbal working memory task, along with a secondary task requiring fixation or a secondary task requiring shifts of attention. The results indicated that attention shifts interfered with spatial, but not with verbal, working memory, suggesting that the interference is specific to processes within the visuospatial sketchpad.

Don't go there.

Response inhibition, or impulse control, is critical for normal cognitive function. In this issue of Neuron, Hasegawa and colleagues use a spatial nonmatch-to-sample task to reveal neurons in and around the frontal eye fields that encode where an animal should not look.

Eye-hand coordination: saccades are faster when accompanied by a coordinated arm movement.

When primates reach for an object, they very often direct an eye movement toward the object as well. This pattern of directing both eye and limb movements to the same object appears to be fundamental to eye-hand coordination. We investigated interactions between saccades and reaching movements in a rhesus monkey model system.

The effects of eye and limb movements on working memory.

Three experiments examined the role of eye and limb movements in the maintenance of information in spatial working memory. In Experiment 1, reflexive saccades interfered with memory span for spatial locations but did not interfere with memory span for letters. In Experiment 2, three different types of eye movements (reflexive saccades, pro-saccades, and anti-saccades) interfered with working memory to the same extent.