Biomedical subjects

Anne B Sereno

Publications and source records attributed to Anne B Sereno.

11 recordsLinked to original sources

PubMed2006

Levodopa slows prosaccades and improves antisaccades: an eye movement study in Parkinson's disease.

BACKGROUND: The integrity of frontal systems responsible for voluntary control and their interaction with subcortical regions involved in reflexive responses were studied in patients with Parkinson's disease (PD). Previous studies have shown that patients with PD have impaired executive function, including deficits in attention, motor planning and decision making. METHODS: Executive function was measured through eye movements: reflexive (stimulus driven) prosaccades and voluntary (internally guided) antisaccades. Patients with advanced idiopathic PD, off and on their optimal levodopa therapy, were tested on a prosaccade and an antisaccade task and compared with matched controls. RESULTS: Levodopa significantly increased response time for reflexive prosaccades and reduced error rate for voluntary antisaccades. CONCLUSIONS: Consistent with our proposed model, patients with PD in the medicated state are better able to plan and execute voluntary eye movements. These findings suggest levodopa improves function of the voluntary frontostriatal system, which is deficient in PD.

Aged↗

PubMed2006

Comparison of shape encoding in primate dorsal and ventral visual pathways.

Ventral and dorsal visual pathways perform fundamentally different functions. The former is involved in object recognition, whereas the latter carries out spatial localization of stimuli and visual guidance of motor actions. Despite the association of the dorsal pathway with spatial vision, recent studies have reported shape selectivity in the dorsal stream. We compared shape encoding in anterior inferotemporal cortex (AIT), a high-level ventral area, with that in lateral intraparietal cortex (LIP), a high-level dorsal area, during a fixation task. We found shape selectivities of individual neurons to be greater in anterior inferotemporal cortex than in lateral intraparietal cortex. At the neural population level, responses to different shapes were more dissimilar in AIT than LIP. Both observations suggest a greater capacity in AIT for making finer shape distinctions. Multivariate analyses of AIT data grouped together similar shapes based on neural population responses, whereas such grouping was indistinct in LIP. Thus in a first comparison of shape response properties in late stages of the two visual pathways, we report that AIT exhibits greater capability than LIP for both object discrimination and generalization. These differences in the two visual pathways provide the first neurophysiological evidence that shape encoding in the dorsal pathway is distinct from and not a mere duplication of that formed in the ventral pathway. In addition to shape selectivity, we observed stimulus-driven cognitive effects in both areas. Stimulus repetition suppression in LIP was similar to the well-known repetition suppression in AIT and may be associated with the "inhibition of return" memory effect observed during reflexive attention.

Action Potentials↗

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↗

PubMed2005

Dissociating cognitive deficits involved in voluntary eye movement dysfunctions in Parkinson's disease patients.

In an attempt to distinguish and define the altered cognitive processes associated with Parkinson's disease (PD), we examine and try to dissociate the components of an effective voluntary saccade: (1) the planning and execution of a voluntary saccade; (2) the suppression of reflexive eye movements; and (3) the working memory processes required. We tested 14 PD patients (off their medications) and 11 control subjects on antisaccade (AS), delayed antisaccade (DAS), and remembered antisaccade (RAS) paradigms. The three tasks required identical responses, each task only differing in a single manipulation for direct comparison--a delay period was added in the DAS, and the target was removed during the delay period of the RAS--allowing us to study the specific cognitive processes involved in the execution of a voluntary saccade. Voluntary saccade response times were longer in the PD group compared to controls on all three tasks, suggesting difficulties in voluntary saccade execution. Furthermore, PD patients showed difficulty suppressing reflexive saccades (increased number of errors in the AS task and increased number of disinhibitions in the DAS task). Finally, our study did not show significant differences in either response time or error rate between the RAS and the DAS tasks for either control subjects or PD patients. In sum, we report evidence for voluntary saccade execution deficits together with problems inhibiting reflexive saccades in Parkinson's disease patients. These findings were correlated with each other and disease severity, suggesting that eye movement measurement may be a useful tool for studying higher cognitive function.

Aged↗

PubMed2005

Attention and memory-related responses of neurons in the lateral intraparietal area during spatial and shape-delayed match-to-sample tasks.

When a monkey attends to, remembers, and looks toward targets, the activity of some neurons in the lateral intraparietal area (LIP) changes. We recorded from isolated neurons during both a spatial and a shape match-to-sample task to examine and characterize voluntary active processes in LIP. Many LIP neurons show spatially selective activity during the delay period that depends on the location of the sample, but for most cells, this activity does not differ between the two tasks. Although much past work in posterior parietal cortex has explained responses in this region in terms of active processes such as decision-making and motor planning, our findings suggest that much of that activity represents more passive processing. Nevertheless, we do see a significant minority of units that demonstrate instruction-dependent activity during the delay period, suggesting that these units could represent the neural correlates of voluntary or active processes. Separately, we found that during the presentation of the sample stimulus and test array, some units show stronger responses to the stimulus in the shape-matching task when the animal must attend to the shape of a stimulus. This elevated response to the sample during the shape task provides evidence for feature-based attention in LIP. Attention to shape is a property that has not previously been described in primate cortex.

Animals↗

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↗

PubMed2004

Nicotine reduces antisaccade errors in task impaired schizophrenic subjects.

Nicotine and/or smoking have been shown to reduce various cognitive deficits associated with schizophrenia. Here, we examine the effects of nicotine gum on repeated performance on a simple eye movement task. Eight schizophrenic subjects and eight controls participated in three days of testing on saccade (S) and antisaccade (AS) tasks. On each testing day, subjects participated in four testing sessions and received both of two nicotine gum treatments (4 and 6 mg) and both of two control conditions (placebo gum and no gum), each followed by a recovery period. Overall, schizophrenics showed significant impairments on the AS task. However, upon individual examination only four schizophrenics showed significant differences in AS errors or reaction times (RTs) when compared to controls. The other four schizophrenic subjects showed control level performance. All schizophrenic subjects showed normal and better than control level performance on the simple S task. Furthermore, no effects of nicotine were seen on the simple S task. There were significant treatment effects on the AS task. Nicotine treatment significantly decreased errors in the task impaired schizophrenic group and this effect was most pronounced at the 6 mg level. No nicotine effects were demonstrated for non-impaired schizophrenic subjects or controls. This study demonstrates a benefit of short exposure to nicotine in cognitively impaired schizophrenic subjects. These results support previous findings of cognitive benefits of nicotine in schizophrenics.

Adult↗

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↗