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Eye movements are inhibited prior to the onset of temporally-predictable visual targets. This oculomotor inhibition effect could be considered a marker for the formation of temporal expectations and the allocation of temporal attention in the visual domain. Here we show that eye movements are also inhibited before predictable auditory targets. In two experiments, we manipulate the period between a cue and an auditory target to be either predictable or unpredictable. The findings show that although there is no perceptual gain from avoiding gaze-shifts in this procedure, saccades and blinks are inhibited prior to predictable relative to unpredictable auditory targets. These findings show that oculomotor inhibition occurs prior to auditory targets. This link between auditory expectation and oculomotor behavior reveals a multimodal perception action coupling, which has a central role in temporal expectations.

Sensory organs are thought to sample the environment rhythmically thereby providing periodic perceptual input. Whisking and sniffing are governed by oscillators which impose rhythms on the motor-control of sensory acquisition and consequently on sensory input. Saccadic eye movements are the main visual sampling mechanism in primates, and were suggested to constitute part of such a rhythmic exploration system. In this study we characterized saccadic rhythmicity, and examined whether it is consistent with autonomous oscillatory generator or with self-paced generation. Eye movements were tracked while observers were either free-viewing a movie or fixating a static stimulus. We inspected the temporal dynamics of exploratory and fixational saccades and quantified their first-order and high-order dependencies. Data were analyzed using methods derived from spike-train analysis, and tested against mathematical models and simulations. The findings show that saccade timings are explained by first-order dependencies, specifically by their refractory period. Saccade-timings are inconsistent with an autonomous pace-maker but are consistent with a “self-paced” generator, where each saccade is a link in a chain of neural processes that depend on the outcome of the saccade itself. We propose a mathematical model parsimoniously capturing various facets of saccade-timings, and suggest a possible neural mechanism producing the observed dynamics.

Uses of molecular markers in the phylogenetic studies of various organisms have become increasingly important in recent times. This review gives an overview of different molecular markers employed by researchers for the purpose of phylogenetic studies. Availability of fast DNA sequencing techniques along with the development of robust statistical analysis methods, provided a new momentum to this field. In this context, utility of different nuclear encoded genes (like 16S rRNA, 5S rRNA, 28S rRNA) mitochondrial (cytochrome oxidase, mitochondrial 12S, cytochrome b, control region) and few chloroplast encoded genes (like rbcL, matK, rpl16) are discussed. Criteria for choosing suitable molecular markers and steps leading to the construction of phylogenetic trees have been discussed. Although widely practised even now, traditional morphology based systems of classification of organisms have some limitations. On the other hand it appears that the use of molecular markers, though relatively recent in popularity and are not free entirely of flaws, can complement the traditional morphology based method for phylogenetic studies.

28Eye movements are inhibited prior to the onset of temporally-predictable visual targets. This 29 oculomotor inhibition effect could be considered a marker for the formation of temporal 30 expectations and the allocation of temporal attention in the visual domain. Here we show 31 that eye movements are also inhibited before predictable auditory targets. In two 32 experiments, we manipulate the period between a cue and an auditory target to be either 33 predictable or unpredictable. The findings show that although there is no perceptual gain 34 from avoiding gaze-shifts in this procedure, saccades and blinks are inhibited prior to 35 predictable relative to unpredictable auditory targets. These findings show that oculomotor 36 inhibition occurs prior auditory targets. This link between auditory expectation and 37 oculomotor behavior, in combination with the results of our parallel study in the tactile 38 domain, reveals a multimodal perception action coupling, which has a central role in temporal 39 expectations. 40 41 100 asked to perform a 2-alternative forced choice (2AFC) discrimination task: report whether the chirp was 101 ascending or descending by pressing one of two buttons. Participants were instructed to be as accurate as 102 possible and to respond within the 4 seconds response window. Following the response, or after 4 s without 103 one, the fixation-cross changed color to gray for 200 ms to signal the end of the trial. B) The foreperiod was 104 either constant throughout the block (predictable condition) or changed randomly in different trials within the 105 same block (unpredictable condition). Thus, the cue acted as a 100% valid temporal cue in the predictable 106 condition but was uninformative regarding target timing in the unpredictable condition. The stimuli were 107 identical in the two conditions, and differed only in the validity of the temporal cue in predicting the time of the 108 target. Participants were not informed as to any predictability; therefore, all temporal expectations were 109 4 learned incidentally. 110 111 Results 112Behavioral performance: accuracy-rates and reaction times 113Accuracy-rates and reaction times (RT) were calculated separately for each participant, 114 condition and foreperiod. A two-way repeated measures ANOVA with factors Predictability 115 (predictable/unpredictable) and Foreperiod (1, 1.5, 2, 2.5, 3 s) revealed no evidence for 116 differences in accuracy-rates between predictability conditions (F(1,19) = 1.62, p = 0.22) or 117 foreperiods (F(4,76) = 0.81, p = 0.52), and no significant interaction between these two factors 118 (F(4,76) = 0.39, p = 0.746). The same analysis performed on RT of correct trials (secondary 119 variable) revealed a significant main effect of foreperiod (F(4,76) = 4.83, p = 0.006, ε = 0.708, 120 130 (blue bars) conditions. Error bars denote ± one standard error of the mean, corrected for within subjects 131 variability 13 . Source data are provided as a Source Data file. 133Saccades 134

Saccades shift the gaze rapidly every few hundred milliseconds from one fixated location to the next, producing a flow of visual input into the visual system even in the absence of changes in the environment. During fixation, small saccades called microsaccades are produced 1-3 times per second, generating a flow of visual input. The characteristics of this visual flow are determined by the timings of the saccades and by the characteristics of the visual stimuli on which they are performed. Previous models of microsaccade generation have accounted for the effects of external stimulation on the production of microsaccades, but they have not considered the effects of the prolonged background stimulus on which microsaccades are performed. The effects of this stimulus on the process of microsaccade generation could be sustained, following its prolonged presentation, or transient, through the visual transients produced by the microsaccades themselves. In four experiments, we varied the properties of the constant displays and examined the resulting modulation of microsaccade properties: their sizes, their timings, and the correlations between properties of consecutive microsaccades. Findings show that displays of higher spatial frequency and contrast produce smaller microsaccades and longer minimal intervals between consecutive microsaccades; and smaller microsaccades are followed by smaller and delayed microsaccades. We explain these findings in light of previous models and suggest a conceptual model by which both sustained and transient effects of the stimulus have central roles in determining the generation of microsaccades.

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BackgroundDuring visual exploration or free-view, gaze positioning is largely determined by the tendency to maximize visual saliency: more salient locations are more likely to be fixated. However, when visual input is completely irrelevant for performance, such as with non-visual tasks, this saliency maximization strategy may be less advantageous and potentially even disruptive for task-performance. Here, we examined whether visual saliency remains a strong driving force in determining gaze positions even in non-visual tasks. We tested three alternative hypotheses: a) That saliency is disadvantageous for non-visual tasks and therefore gaze would tend to shift away from it and towards non-salient locations; b) That saliency is irrelevant during non-visual tasks and therefore gaze would not be directed towards it but also not away-from it; c) That saliency maximization is a strong behavioral drive that would prevail even during non-visual tasks.MethodsGaze position was monitored as participants performed visual or non-visual tasks while they were presented with complex or simple images. The effect of attentional demands was examined by comparing an easy non-visual task with a more difficult one.ResultsExploratory behavior was evident, regardless of task difficulty, even when the task was non-visual and the visual input was entirely irrelevant. The observed exploratory behaviors included a strong tendency to fixate salient locations, central fixation bias and a gradual reduction in saliency for later fixations. These exploratory behaviors were spatially similar to those of an explicit visual exploration task but they were, nevertheless, attenuated. Temporal differences were also found: in the non-visual task there were longer fixations and later first fixations than in the visual task, reflecting slower visual sampling in this task.ConclusionWe conclude that in the presence of a rich visual environment, visual exploration is evident even when there is no explicit instruction to explore. Compared to visually motivated tasks, exploration in non-visual tasks follows similar selection mechanisms, but occurs at a lower rate. This is consistent with the view that the non-visual task is the equivalent of a dual-task: it combines the instructed task with an uninstructed, perhaps even mandatory, exploratory behavior.