Saccade Programming

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Jeffrey D Schall - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic dissociation of visual selection from Saccade Programming in frontal eye field.
    Journal of neurophysiology, 2001
    Co-Authors: Aditya Murthy, Kirk G Thompson, Jeffrey D Schall
    Abstract:

    Previous studies of visually responsive neurons in the frontal eye fields have identified a selection process preceding Saccades during visual search. The goal of this experiment was to determine whether the selection process corresponds to the selection of a conspicuous stimulus or to preparation of the next Saccade. This was accomplished with the use of a novel task, called search-step, in which the target of a singleton visual search array switches location with a distracter on random trials. The target step trials created a condition in which the same stimulus yielded Saccades either toward or away from the target. Visually responsive neurons in frontal eye field selected the current location of the conspicuous target even when gaze shifted to the location of a distractor. This dissociation demonstrates that the selection process manifest in visual neurons in the frontal eye field may be an explicit interpretation of the image and not an obligatory Saccade command.

  • Dissociation of Visual Discrimination From Saccade Programming in Macaque Frontal Eye Field
    Journal of neurophysiology, 1997
    Co-Authors: Kirk G Thompson, Narcisse P. Bichot, Jeffrey D Schall
    Abstract:

    Thompson, Kirk G., Narcisse P. Bichot, and Jeffrey D. Schall. Dissociation of visual discrimination from Saccade Programming in macaque frontal eye field. J. Neurophysiol. 77: 1046–1050, 1997. To d...

  • perceptual and motor processing stages identified in the activity of macaque frontal eye field neurons during visual search
    Journal of Neurophysiology, 1996
    Co-Authors: Kirk G Thompson, Narcisse P. Bichot, Doug P. Hanes, Jeffrey D Schall
    Abstract:

    1. The latency between the appearance of a popout search display and the eye movement to the oddball target of the display varies from trial to trial in both humans and monkeys. The source of the delay and variability of reaction time is unknown but has been attributed to as yet poorly defined decision processes. 2. We recorded neural activity in the frontal eye field (FEF), an area regarded as playing a central role in producing purposeful eye movements, of monkeys (Macaca mulatta) performing a popout visual search task. Eighty-four neurons with visually evoked activity were analyzed. Twelve of these neurons had a phasic response associated with the presentation of the visual stimulus. The remaining neurons had more tonic responses that persisted through the Saccade. Many of the neurons with more tonic responses resembled visuomovement cells in that they had activity that increased before a Saccade into their response field. 3. The visual response latencies of FEF neurons were determined with the use of a Poisson spike train analysis. The mean visual latency was 67 ms (minimum = 35 ms, maximum = 138 ms). The visual response latencies to the target presented alone, to the target presented with distractors, or to the distractors did not differ significantly. 4. The initial visual activation of FEF neurons does not discriminate the target from the distractors of a popout visual search stimulus array, but the activity evolves to a state that discriminates whether the target of the search display is within the receptive field. We tested the hypothesis that the source of variability of Saccade latency is the time taken by neurons involved in Saccade Programming to select the target for the gaze shift. 5. With the use of an analysis adapted from signal detection theory, we determined when the activity of single FEF neurons can reliably indicate whether the target or distractors are present within their response fields. The time of target discrimination partitions the reaction time into a perceptual stage in which target discrimination takes place, and a motor stage in which Saccade Programming and generation take place. The time of target discrimination occurred most often between 120 and 150 ms after stimulus presentation. 6. We analyzed the time course of target discrimination in the activity of single cells after separating trials into short, medium, and long Saccade latency groups. Saccade latency was not correlated with the duration of the perceptual stage but was correlated with the duration of the motor stage. This result is inconsistent with the hypothesis that the time taken for target discrimination, as indexed by FEF neurons, accounts for the wide variability in the time of movement initiation. 7. We conclude that the variability observed in Saccade latencies during a simple visual search task is largely due to postperceptual motor processing following target discrimination. Signatures of both perceptual and postperceptual processing are evident in FEF. Procrastination in the output stage may prevent stereotypical behavior that would be maladaptive in a changing environment.

Kirk G Thompson - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic dissociation of visual selection from Saccade Programming in frontal eye
    2014
    Co-Authors: Aditya Murthy, Kirk G Thompson, D. Schall
    Abstract:

    namic dissociation of visual selection from Saccade Programming in frontal eye field. J Neurophysiol 86: 2634–2637, 2001. Previous studies of visually responsive neurons in the frontal eye fields have identified a selection process preceding Saccades during visual search. The goal of this experiment was to determine whether the selection process corresponds to the selection of a conspicuous stimulus or to preparation of the next Saccade. This was accomplished with the use of a novel task, called search-step, in which the target of a singleton visual search array switches location with a distracter on random trials. The target step trials created a condition in which the same stimulus yielded Saccades either toward or away from the target. Visually responsive neurons in frontal eye field selected the current location of the conspicuous target even when gaze shifted to the location of a distractor. This dissociation demonstrates that the selec-tion process manifest in visual neurons in the frontal eye field may be an explicit interpretation of the image and not an obligatory Saccade command

  • Dynamic dissociation of visual selection from Saccade Programming in frontal eye field.
    Journal of neurophysiology, 2001
    Co-Authors: Aditya Murthy, Kirk G Thompson, Jeffrey D Schall
    Abstract:

    Previous studies of visually responsive neurons in the frontal eye fields have identified a selection process preceding Saccades during visual search. The goal of this experiment was to determine whether the selection process corresponds to the selection of a conspicuous stimulus or to preparation of the next Saccade. This was accomplished with the use of a novel task, called search-step, in which the target of a singleton visual search array switches location with a distracter on random trials. The target step trials created a condition in which the same stimulus yielded Saccades either toward or away from the target. Visually responsive neurons in frontal eye field selected the current location of the conspicuous target even when gaze shifted to the location of a distractor. This dissociation demonstrates that the selection process manifest in visual neurons in the frontal eye field may be an explicit interpretation of the image and not an obligatory Saccade command.

  • Dissociation of Visual Discrimination From Saccade Programming in Macaque Frontal Eye Field
    Journal of neurophysiology, 1997
    Co-Authors: Kirk G Thompson, Narcisse P. Bichot, Jeffrey D Schall
    Abstract:

    Thompson, Kirk G., Narcisse P. Bichot, and Jeffrey D. Schall. Dissociation of visual discrimination from Saccade Programming in macaque frontal eye field. J. Neurophysiol. 77: 1046–1050, 1997. To d...

  • perceptual and motor processing stages identified in the activity of macaque frontal eye field neurons during visual search
    Journal of Neurophysiology, 1996
    Co-Authors: Kirk G Thompson, Narcisse P. Bichot, Doug P. Hanes, Jeffrey D Schall
    Abstract:

    1. The latency between the appearance of a popout search display and the eye movement to the oddball target of the display varies from trial to trial in both humans and monkeys. The source of the delay and variability of reaction time is unknown but has been attributed to as yet poorly defined decision processes. 2. We recorded neural activity in the frontal eye field (FEF), an area regarded as playing a central role in producing purposeful eye movements, of monkeys (Macaca mulatta) performing a popout visual search task. Eighty-four neurons with visually evoked activity were analyzed. Twelve of these neurons had a phasic response associated with the presentation of the visual stimulus. The remaining neurons had more tonic responses that persisted through the Saccade. Many of the neurons with more tonic responses resembled visuomovement cells in that they had activity that increased before a Saccade into their response field. 3. The visual response latencies of FEF neurons were determined with the use of a Poisson spike train analysis. The mean visual latency was 67 ms (minimum = 35 ms, maximum = 138 ms). The visual response latencies to the target presented alone, to the target presented with distractors, or to the distractors did not differ significantly. 4. The initial visual activation of FEF neurons does not discriminate the target from the distractors of a popout visual search stimulus array, but the activity evolves to a state that discriminates whether the target of the search display is within the receptive field. We tested the hypothesis that the source of variability of Saccade latency is the time taken by neurons involved in Saccade Programming to select the target for the gaze shift. 5. With the use of an analysis adapted from signal detection theory, we determined when the activity of single FEF neurons can reliably indicate whether the target or distractors are present within their response fields. The time of target discrimination partitions the reaction time into a perceptual stage in which target discrimination takes place, and a motor stage in which Saccade Programming and generation take place. The time of target discrimination occurred most often between 120 and 150 ms after stimulus presentation. 6. We analyzed the time course of target discrimination in the activity of single cells after separating trials into short, medium, and long Saccade latency groups. Saccade latency was not correlated with the duration of the perceptual stage but was correlated with the duration of the motor stage. This result is inconsistent with the hypothesis that the time taken for target discrimination, as indexed by FEF neurons, accounts for the wide variability in the time of movement initiation. 7. We conclude that the variability observed in Saccade latencies during a simple visual search task is largely due to postperceptual motor processing following target discrimination. Signatures of both perceptual and postperceptual processing are evident in FEF. Procrastination in the output stage may prevent stereotypical behavior that would be maladaptive in a changing environment.

Sarah J White - One of the best experts on this subject based on the ideXlab platform.

  • eye movement control during reading effects of word frequency and orthographic familiarity
    Journal of Experimental Psychology: Human Perception and Performance, 2008
    Co-Authors: Sarah J White
    Abstract:

    Word frequency and orthographic familiarity were independently manipulated as readers’ eye movements were recorded. Word frequency influenced fixation durations and the probability of word skipping when orthographic familiarity was controlled. These results indicate that lexical processing of words can influence Saccade Programming (as shown by fixation durations and which words are fixated). Orthographic familiarity, but not word frequency, influenced the duration of prior fixations. These results provide evidence for orthographic, but not lexical, parafoveal-on-foveal effects. Overall, the findings have a crucial implication for models of eye movement control in reading: There must be sufficient time for lexical factors to influence Saccade Programming before Saccade metrics and timing are finalized. The conclusions are critical for the fundamental architecture of models of eye movement control in reading— namely, how to reconcile long Saccade Programming times and complex linguistic influences on Saccades during reading.

  • Running head: WORD FREQUENCY AND ORTHOGRAPHIC FAMILIARITY
    2008
    Co-Authors: Copy Of: White, S J, Sarah J White
    Abstract:

    eye movements were recorded. Word frequency influenced fixation durations and the probability of word skipping when orthographic familiarity was controlled. These results indicate that lexical processing of words can influence Saccade Programming (as shown by fixation durations and which words are fixated). Orthographic familiarity, but not word frequency, influenced the duration of prior fixations. These results provide evidence for orthographic, but not lexical, parafoveal-on-foveal effects. Overall, the findings have a crucial implication for models of eye movement control in reading: there must be sufficient time for lexical factors to influence Saccade Programming before Saccade metrics and timing are finalised. The conclusions are critical for the fundamental architecture of models of eye movement control in reading, namely, how to reconcile long Saccade Programming times and complex linguistic influences on Saccades during reading. Key words / phrases: Reading. Eye movements. Word frequency. Orthography. Models of eye movement control in reading. Word frequency and orthographic familiarity 1 As we read, the linguistic characteristics of words influence the duration of fixations and which words are fixated Word frequency effects The influence of word frequency on word processing is an established finding both for isolated word response time tasks (Monsell, 1991) and sentence reading Word frequency effects during sentence reading are usually spatially localised to the word Word frequency and orthographic familiarity 2 that induced those effects (Henderson & Ferreira, 1990, 1993 Raney & Rayner, 1995) and in other cases there are effects of word frequency both on the word itself and on subsequent spillover fixations (Kennison & Clifton, 1995; The influence of word frequency on eye movement behaviour during reading suggests that lexical word recognition processes can influence when and where the eyes move. However, of the large number of studies that manipulated word frequency, a very small proportion of these have attempted to control for the orthographic characteristics of the words. It is easy to confound word frequency with orthographic familiarity because frequent words are necessarily orthographically familiar whereas many infrequent words are orthographically unfamiliar. A few studies have attempted to control for orthographic characteristics using the measure of type frequency, which is the number of words that contain a particular letter sequence. Rayner and Duffy (1986) undertook post-hoc analyses which showed higher trigram type frequencies for frequent than infrequent target words, but they found that word frequency effects still held for those items in which differences in type frequency were reversed. Word frequency and orthographic familiarity 3 Importantly, previous reading studies only attempted to control for orthography by using type frequency counts. As type frequency is simply the number of words that contain a particular letter sequence, it is effectively a measure of lexical informativeness or redundancy. For example, the trigram "pne" at the word beginning has a very low type frequency and is very informative because it highly constrains the number of possible word candidates (pneumatic, pneumonia). Importantly, type frequency does not reflect letter sequence familiarity. For example, there are a number of words that begin with the letter sequence "irr", but very few of these are very frequent; hence although "irr" has a relatively high type frequency it actually has quite low orthographic familiarity. Manipulations of only type frequency or informativeness should therefore reflect processing at the level of lexical candidates. A better measure of orthographic familiarity is token frequency, which is the sum of the frequencies of words that contain a particular letter sequence 1 . Critically, effects of orthographic familiarity may involve processing at a sub-lexical or even visual level (see next section). Note that other studies have tested for effects of word frequency, and the type and token frequency of word initial letters, in multiple isolated word processing tasks (Kennedy, 1998; Kennedy, Pynte, & Ducrot, 2002) and sentence reading (Kennedy & Pynte, 2005; Pynte & Kennedy, 2006). However the orthographic characteristics beyond the word initial letters were not controlled in these studies and consequently they do not test whether word frequency effects occur independently of differences in orthographic familiarity. To summarise, although previous studies of word frequency have attempted to control for orthography to some extent, these studies do not eliminate the Word frequency and orthographic familiarity 4 possibility that differences in orthographic familiarity could have produced, or at least influenced, the word frequency effect. The issue of whether orthographic familiarity may be contributing to the word frequency effect is of particular importance for the case of word skipping. Critically, the linguistic characteristics of skipped words must be processed in parafoveal vision (where stimuli are degraded due to acuity limitations) which reduces the speed of linguistic processing of those words (Rayner & Morrison, 1981; which may reduce the time (or resources) available within a fixation for processing of the parafoveal word (e.g. Morrison, 1984). Of the studies that have shown word frequency effects on word skipping, only one study controlled for type bigram frequency (Rayner et al., 1996). Not only was orthographic familiarity not controlled, but orthographic processing of trigrams, not just bigrams, could have contributed to the effect. Furthermore, the fact that some studies have not shown word frequency effects on word skipping (Calvo & Meseguer, 2002; Henderson & Ferreira, 1993) Basically, given that this issue is so critical for models of eye movement control during reading, it is absolutely essential that a thorough analysis of the effects of word frequency and orthographic familiarity be undertaken. The present study does this by testing the effects of word frequency on eye movement behaviour whilst controlling for monogram, bigram and trigram token orthographic frequencies. Orthographic effects Studies using isolated word tasks have investigated a wide range of factors related to orthographic processing of words (Henderson, 1982). A number of early studies were undertaken into the effects of bigram frequency and word frequency during reading (Gernsbacher, 1984). These studies used isolated word methods such as tachistoscopic presentation of words, naming and lexical decision and bigram frequency was controlled only by type frequency counts such as those reported by Mayzner and Tresselt (1965). However the findings of such studies using low frequency words have been contradictory with some indicating that words with high frequency bigrams are more difficult to process Word frequency and orthographic familiarity 6 than those with low frequency bigrams A number of studies using eye tracking methodologies have examined the role of the informativeness of letter sequences (confounded with orthographic familiarity). Pynte, Kennedy and Murray (1991) showed longer fixation durations on informative parts of words (see also Holmes & O'Regan, 1987). In sentence reading, Lima and Inhoff (1985) showed that first fixation durations were longer on words which began with constraining (e.g. dwarf) compared to less constraining (e.g. clown) letter sequences. Other experiments have shown that the orthographic familiarity of the initial letters of long words can influence where they are first fixated (Hyönä, 1995; Radach, Inhoff, & Heller, 2004; Orthographic familiarity may impact on visual, sub-lexical or lexical levels of processing. Processing of text at a visual, rather than linguistic, level may modulate the familiarity of visual information such that frequent letter strings may develop higher visual familiarity than infrequent letter strings (Findlay & Walker, 1999). Therefore any effects of orthographic familiarity must be interpreted as a reflection of processing at least at the level of visual familiarity. However differences in orthographic familiarity may also be associated with differences in informativeness or constraint (type frequency) and orthographically unfamiliar words may also tend to have more irregular phonology and Word frequency and orthographic familiarity 7 fewer orthographic neighbours. Consequently, any effects of orthographic familiarity could also be driven by sub-lexical or even lexical processes. The present study manipulates the orthographic familiarity of the entire word, and it examines whether orthographic familiarity influences fixation durations and word skipping. Models of eye movement control during reading Models of eye movement control vary in the extent to which they suggest that linguistic processing can influence eye movement behaviour. Some suggest that eye movements are driven by linguistic processing at least at the level of lexical access (Just & Carpenter, 1980; Morrison, 1984; In contrast, it has been suggested (Deubel, O'Regan, & Radach, 2000; Nazir, 2000), and models have proposed (McConkie & Yang, 2003; O'Regan, 1990 O'Regan, , 1992 Linguistic factors therefore have a critical role in influencing eye movement behaviour during reading and visual and/or oculomotor based models can not fully account for reading eye movement behaviour. However, the issue of precisely how linguistic processing influences when and where the eyes move during reading is far from resolved. The most comprehensive implemented models of eye movement behaviour during reading, the E-Z reader model The issue of how linguistic processing can influence Saccade Programming, whilst taking account of Saccade Programming times, is one of the most critical issues for the design of models of eye movements in reading. The present study tests whether lexical Word frequency and orthographic familiarity 10 factors (word frequency) influence Saccade Programming (fixation durations and word skipping) independent of sub-lexical factors (orthographic familiarity). If the lexical factor of word frequency influences fixation durations or word skipping, then this must either be explained by an early linguistic influence on when Saccade Programming is initiated, or else a later influence during, or at the end of, the labile stage of Saccade Programming. Both the E-Z reader and SWIFT models suggest that word frequency impacts on Saccade Programming, and so they predict that this influences both fixation durations and word skipping. However, both models are vague about precisely how word frequency impacts on the difficulty of word processing. Given the timing constraints of the proposal that linguistic factors trigger the initiation of Saccade Programming, it is quite plausible that the sub-lexical factor of orthographic familiarity, and not the lexical factor of word frequency, might influence Saccades within such a framework. Nevertheless, if the present study shows that word frequency does have an influence, for example on how long words are first fixated, then this would suggest that the linguistic processes that occur prior to Saccade Programming in these models must be of a lexical nature. Parafoveal-on-foveal effects of word frequency and orthograph

Clare Press - One of the best experts on this subject based on the ideXlab platform.

  • manual response preparation and Saccade Programming are linked to attention shifts erp evidence for covert attentional orienting and spatially specific modulations of visual processing
    Brain Research, 2006
    Co-Authors: Martin Eimer, Jose L Van Velzen, Elena Gherri, Clare Press
    Abstract:

    The premotor theory of attention claims that attentional shifts are triggered during response Programming, regardless of which response modality is involved. To investigate this claim, event-related brain potentials (ERPs) were recorded while participants covertly prepared a left or right response, as indicated by a precue presented at the beginning of each trial. Cues signalled a left or right eye movement in the Saccade task, and a left or right manual response in the manual task. The cued response had to be executed or withheld following the presentation of a Go/Nogo stimulus. Although there were systematic differences between ERPs triggered during covert manual and Saccade preparation, lateralised ERP components sensitive to the direction of a cued response were very similar for both tasks, and also similar to the components previously found during cued shifts of endogenous spatial attention. This is consistent with the claim that the control of attention and of covert response preparation are closely linked. N1 components triggered by task-irrelevant visual probes presented during the covert response preparation interval were enhanced when these probes were presented close to cued response hand in the manual task, and at the Saccade target location in the Saccade task. This demonstrates that both manual and Saccade preparation result in spatially specific modulations of visual processing, in line with the predictions of the premotor theory.

Narcisse P. Bichot - One of the best experts on this subject based on the ideXlab platform.

  • Dissociation of Visual Discrimination From Saccade Programming in Macaque Frontal Eye Field
    Journal of neurophysiology, 1997
    Co-Authors: Kirk G Thompson, Narcisse P. Bichot, Jeffrey D Schall
    Abstract:

    Thompson, Kirk G., Narcisse P. Bichot, and Jeffrey D. Schall. Dissociation of visual discrimination from Saccade Programming in macaque frontal eye field. J. Neurophysiol. 77: 1046–1050, 1997. To d...

  • perceptual and motor processing stages identified in the activity of macaque frontal eye field neurons during visual search
    Journal of Neurophysiology, 1996
    Co-Authors: Kirk G Thompson, Narcisse P. Bichot, Doug P. Hanes, Jeffrey D Schall
    Abstract:

    1. The latency between the appearance of a popout search display and the eye movement to the oddball target of the display varies from trial to trial in both humans and monkeys. The source of the delay and variability of reaction time is unknown but has been attributed to as yet poorly defined decision processes. 2. We recorded neural activity in the frontal eye field (FEF), an area regarded as playing a central role in producing purposeful eye movements, of monkeys (Macaca mulatta) performing a popout visual search task. Eighty-four neurons with visually evoked activity were analyzed. Twelve of these neurons had a phasic response associated with the presentation of the visual stimulus. The remaining neurons had more tonic responses that persisted through the Saccade. Many of the neurons with more tonic responses resembled visuomovement cells in that they had activity that increased before a Saccade into their response field. 3. The visual response latencies of FEF neurons were determined with the use of a Poisson spike train analysis. The mean visual latency was 67 ms (minimum = 35 ms, maximum = 138 ms). The visual response latencies to the target presented alone, to the target presented with distractors, or to the distractors did not differ significantly. 4. The initial visual activation of FEF neurons does not discriminate the target from the distractors of a popout visual search stimulus array, but the activity evolves to a state that discriminates whether the target of the search display is within the receptive field. We tested the hypothesis that the source of variability of Saccade latency is the time taken by neurons involved in Saccade Programming to select the target for the gaze shift. 5. With the use of an analysis adapted from signal detection theory, we determined when the activity of single FEF neurons can reliably indicate whether the target or distractors are present within their response fields. The time of target discrimination partitions the reaction time into a perceptual stage in which target discrimination takes place, and a motor stage in which Saccade Programming and generation take place. The time of target discrimination occurred most often between 120 and 150 ms after stimulus presentation. 6. We analyzed the time course of target discrimination in the activity of single cells after separating trials into short, medium, and long Saccade latency groups. Saccade latency was not correlated with the duration of the perceptual stage but was correlated with the duration of the motor stage. This result is inconsistent with the hypothesis that the time taken for target discrimination, as indexed by FEF neurons, accounts for the wide variability in the time of movement initiation. 7. We conclude that the variability observed in Saccade latencies during a simple visual search task is largely due to postperceptual motor processing following target discrimination. Signatures of both perceptual and postperceptual processing are evident in FEF. Procrastination in the output stage may prevent stereotypical behavior that would be maladaptive in a changing environment.