Biomedical subjects

Kevin A Briand

Publications and source records attributed to Kevin A Briand.

6 recordsLinked to original sources

PubMed2006

Dissociating sensory and motor components of inhibition of return.

Two explanations for inhibition of return (IOR) have been proposed. The first is that IOR reflects inhibition of attentional processing at previously cued locations, resulting in altered sensory analysis. The second is that IOR reflects the inhibition of responses directed towards those previously cued locations. We used a variant of a double-saccade paradigm to dissociate these two proposed effects of IOR and attempted to reveal both effects within the context of a single experimental task. Subjects viewed a series of exogenous cues and then made a localization response to subsequent targets with either a target-directed saccade or a pointing response. Results were similar for both response modes. An important finding was that the pattern of IOR depended critically on how subjects reacted to the exogenous cues. Subjects either oriented to the cued locations (via saccades or pointing) prior to responding to the target (Respond), or passively viewed the cues before responding (Ignore). In the Respond condition, IOR was observed at the most recently cued position. Although this could be consistent with an altered sensory interpretation, it would also be consistent with a spatiotopic representation. In the Ignore condition, the sole inhibited location was not the most recently cued position, but the first cued position. This finding is surprising and in conflict with previous work with multiple exogenous cues. The data are discussed in relation to a number of prominent issues in the area of IOR and suggest important new constraints and boundary conditions.

Adult↗

PubMed2006

Disruption of reflexive attention and eye movements in an individual with a collicular lesion.

The superior colliculus (SC) plays a central role in the control of saccadic eye movements and has also been implicated in control of covert spatial attention. While there is a growing body of evidence from studies of awake behaving primates that supports these proposals, direct evidence from humans has been sparse. In the present study we tested a patient with thiamine deficiency and a lesion of the SC, who performed both eye movement tasks (prosaccades and antisaccades, with or without a gap) and a covert spatial attention task assessing inhibition of return (IOR). For eye movements, the gap effect was disrupted, and abnormal saccade metrics occurred, with reflexive eye movements being disrupted moreso than voluntary eye movements. Each of these effects resolved coincident with thiamine treatment. The covert attention task revealed a complete absence of IOR. The unequal disruption of voluntary and reflexive eye movements supports the idea that oculomotor responses can be generated in an independent fashion by frontal cortical and lower level neural systems. The role of the SC and other structures in these orienting processes is discussed.

Attention↗

PubMed2004

Nicotine improves antisaccade task performance without affecting prosaccades.

Although there is ample evidence for a cognitive-attentional benefit of the stimulant nicotine, the source of this benefit is not as well understood. One approach is to address what aspects of performance nicotine affects at a functional systems level. It is currently debated whether the benefits produced by nicotine are the effect of enhanced higher cognitive function or reflect an overall increase in general arousal. In order to address this question, the effects of nicotine on two simple eye movement tasks were studied: the saccade (S) and antisaccade (AS) tasks. Because the S and AS tasks utilize identical sensory stimuli (peripheral targets) and require identical motor responses (eye movements) but differ significantly in their cognitive demands, the use of these two tasks should enable a parsing of nicotine effects on cognitive versus sensory-motor processes. In this study, the S and AS tasks were performed by two experimental groups, task naïve subjects and highly practised subjects. For the first group, that of the task naïve subjects, nicotine gum administration resulted in a decrease in AS errors. For the second group, that of two experienced subjects tested repeatedly over a 3 week period, nicotine also produced a significant decrease in AS task errors, as well as resulting in a significant decrease in AS response times. Neither task naïve nor experienced subjects showed any effects of nicotine on the S task. Examining the effects of nicotine on highly controlled and constrained tasks such as the S and AS task may provide another level of insight into the mechanisms underlying the beneficial cognitive effects of nicotine.

Humans↗

PubMed2003

Voluntary spatial attention has different effects on voluntary and reflexive saccades.

Although numerous studies have investigated the relationship between saccadic eye movements and spatial attention, one fundamental issue remains controversial. Some studies have suggested that spatial attention facilitates saccades, whereas others have claimed that eye movements are actually inhibited when spatial attention is engaged. However, these discrepancies may be because previous research has neglected to separate and specify the effects of attention for two distinct types of saccades, namely reflexive (stimulus-directed) and voluntary (antisaccades). The present study explored the effects of voluntary spatial attention on both voluntary and reflexive saccades. Results indicate that voluntary spatial attention has different effects on the two types of saccades. Antisaccades were always greatly facilitated following the engagement of spatial attention by symbolic cues (arrows) informing the subject where the upcoming saccade should be directed. Reflexive saccades showed little or no cueing effects and exhibited significant facilitation only when these cues were randomly intermixed with uncued trials. In addition, the present study tested the effects of fixation condition (gap, step, and overlap) on attentional modulation. Cueing effects did not vary due to fixation condition. Thus, voluntary spatial attention consistently showed different effects on voluntary and reflexive saccades, and there was no evidence in these studies that voluntary cues inhibit reflexive saccades, even in a gap paradigm.

Adolescent↗

PubMed2002

The role of response in spatial attention: direct versus indirect stimulus-response mappings.

Recent research has suggested that inhibition of return (IOR) develops more quickly when subjects must respond with an eye movement than when they make a manual response to the target (Perception and Psychophysics 62 (2000) 1512-1524). Four spatial cueing experiments were conducted where subjects had to indicate the location of visual targets. Within each of the oculomotor and manual modalities, responses could be either directed towards the target (saccade or pointing) or had a more complex stimulus-response (S-R) mapping. For both saccadic and manual responses, IOR onset was delayed as the required S-R mapping became more indirect. This finding further emphasizes the role of response-related processes in spatial attention. Possible explanations for this pattern of results are considered, including the notion that activity in prefrontal cortex, needed for execution of such abstract S-R mappings, may influence the time course of reflexive spatial cueing effects.

Analysis of Variance↗

PubMed2002

Delayed onset of inhibition of return in schizophrenia.

Peripheral visual cues occuring before a subsequent target result in an almost immediate facilitatory and then a later inhibitory effect on target detection. In a detailed parametric investigation, the authors compared schizophrenic subjects (SCZ) and control subjects (CONT) to examine whether they showed any differences in the time course of these nonpredictive peripheral cuing effects. Subjects fixated a central position and made saccadic responses to visual targets. Targets were presented 10 degrees to the left or right of fixation and were preceded at various time intervals by visual cues. Targets occurred with equal probability in either the same position as the cue or in the opposite, uncued location, and 10 delay periods were used corresponding to stimulus onset asynchronies (SOAs) of 66, 79, 106, 133, 159, 226, 305, 505, 705, and 1000 ms. All subjects showed facilitation for short cue-target delays and inhibition of return (IOR) for longer delays. SCZ, however, showed an apparent shift in the time course of cuing effects in the form of a delayed onset of IOR. Using a task of reflexive orienting, these results support findings of a delayed rather than an absent inhibitory process in medicated SCZ.

Adult↗