Literature has long investigated the contributions of top-down and bottom-up processes in guiding search behavior. Recent findings suggest a modulatory role of top-down processes on attentional capture. However, results are contradictory, and whether and how top-down processes intervene has not been clearly established yet. Here, we approached the issue from the perspective of proactive top-down processes of distractor expectation and leveraged the Distractor Context Manipulation (DCM) paradigm to help characterizing their recruitment in visual search. Thus, we combined a feature search (i.e., search for a high-contrast target among no-contrast distractors) and a conjunction search (i.e., search for a high-contrast target among high-contrast distractors) with the DCM paradigm (Exp 1-4). Accordingly, blocks of trials were of three types: a Pure block containing no distractor-present trials, and two blocks containing frequent distractor-present trials (i.e., Mixed Feature and Mixed Conjunction). Subjects were instructed to look for the target on each trial. The comparison of distractor-absent trials of Mixed vs Pure blocks allowed detecting proactive top-down processes of distractor expectation. First, we investigated whether proactive top-down processes were recruited in distracting contexts of visual search and whether their potential recruitment was modulated by the type of search (Exp 1). Results attested for a proactive recruitment of top-down processes of distractor expectation in both feature and conjunction search. Such recruitment entailed a response time (RT) cost as well as a beneficial enhancement of the detection sensitivity (d’) to the target when distractors were expected, yet not presented. Overlapping results emerged in covert (Exp 1, 3) and overt (Exp 2, 4) variants of visual search. Since previous distracting experience shaped distractor expectation, we, also, sought to disentangle the role of expectation and experience in the activation of top-down processes. Results (Exp 2, 4) showed that the distractor expectation cost occurred regardless of whether or not distractors occurred in the immediately preceding trial. However, the magnitude of the cost was larger after distracting trials suggesting that these processes do not rely only on tonic expectation-based mechanisms but they are also contingently reinstated after a distracting experience occurred. Experiment 3 tried to characterize the implicit vs explicit nature of top-down mechanisms triggered by distracting experience. Results showed that RT-costs and d'-benefits did not change when distraction occurrence was unpredictable and when it was predictable. Therefore, top-down control setting triggered by recent distracting experience seems to be not subjected to explicit control. Experiment 4 further investigated the role of experience and expectations in order to disentangle their relative contributions. Here, also another type of top-down expectation was manipulated: the temporal certainty of incoming potentially distracting event. Results indicated a preponderant role of top-down expectations by showing that RT-costs followed the time course of temporal expectation of incoming potentially distracting events while temporal recency from a previous distracting experience had a smaller weight. Finally, Experiment 4 explored the EEG correlates of distractor expectation. An enhancement of the occipital P1 amplitude was elicited by both search and neutral stimuli but only when a temporal expectation of a potentially distracting event was induced indicating that distractor expectation modulates visual attentional processes in lower sensory areas. Overall, results suggested that in both feature and conjunction search preparatory top-down processes are proactively enrolled to face with expected task demands based on previous distracting experiences. These results help characterizing how top-down mechanisms intervene in different types of visual search.

La letteratura ha indagato il ruolo dei processi top-down e bottom-up nel guidare la ricerca visiva. Recenti studi hanno suggerito un ruolo modulatorio dei processi top-down sulla cattura attentiva. Tuttavia, i risultati sono contraddittori, e il ruolo dei processi top-down non è stato ancora chiaramente stabilito. In questo lavoro, abbiamo studiato se il controllo top-down fosse reclutato proattivamente quando c’è un’aspettativa di distrattori e abbiamo adottato il paradigma di Distraction Context Manipulation (DCM) per caratterizzare il loro reclutamento nella ricerca visiva. Pertanto, abbiamo combinato un compito di feature search e uno di conjunction search con il DCM (Esp 1-4). In linea con il DCM, i blocchi erano di tre tipi: un blocco Puro senza trial con distrattori, e due blocchi contenenti frequenti trial con distrattori (Mixed Feature e Conjunction). Il compito era individuare il target in ogni trial. Il confronto tra trial senza distrattori nei blocchi misti e nel blocco puro ha permesso di rilevare il reclutamento di processi top-down per l'aspettativa di distrattori. Inizialmente abbiamo indagato se i processi top-down fossero reclutati nei contesti distraenti e se il loro potenziale reclutamento fosse modulato dal tipo di ricerca (Exp 1). I risultati hanno mostrato un reclutamento proattivo dei processi top-down in caso di aspettativa di distrattori sia nel feature che nel conjunction search. Tale reclutamento è emerso come costo in termini di tempo di risposta nonché come beneficio della sensibilità di detezione del target quando i distrattori erano attesi ma non presentati. Risultati sovrapponibili sono emersi nelle varianti di ricerca visiva covert (Esp 1,3) e overt (Esp 2,4). Poiché le precedenti esperienze distraenti hanno mostrato di modellare l'aspettativa di distrattori nei trial successivi, abbiamo anche cercato di differenziare il ruolo delle aspettative da quello dell'esperienza nell'attivare i processi top-down. I risultati (Esp 1, 2 e 4) hanno indicato che il costo dovuto all’aspettativa di distrattori si verificava a prescindere che i distrattori fossero o meno presenti nel trial precedente. Tuttavia, l'entità di questo costo era maggiore dopo i trial con distrattori, suggerendo che questi processi non siano basati solo sull'aspettativa, ma siano anche rinforzati dopo un'esperienza distraente. L'esperimento 3 ha cercato di caratterizzare la natura implicita vs esplicita dei processi top-down innescati da esperienze distraenti. I risultati hanno mostrato che i costi e i benefici sui tempi di risposta non cambiano quando l'evento distraente è imprevedibile da quando è predicibile. I processi top-down innescati dalla esperienza distraente non sembrano essere soggetti al controllo esplicito. L'esperimento 4 ha ulteriormente tentato di elucidare i contributi relativi dell'esperienza e delle aspettative. Qui, anche un altro tipo di aspettativa top-down è stata manipolata: la certezza temporale che un evento potenzialmente distraente fosse in arrivo. I risultati hanno indicato un ruolo preponderante delle aspettative top-down mostrando che il costo sui tempi di risposta asseconda il decorso dell'aspettativa temporale di eventi potenzialmente distraenti mentre la prossimità temporale da una precedente esperienza distraente riveste un peso minore. Infine, l’esperimento 4 ha dimostrato che l'aspettativa dei distrattori modula i processi attenzionali. Le analisi EEG hanno indicato che l'aspettativa di distrattori aumenta l'ampiezza della componente occipitale P1 che viene elicitata sia da stimoli di ricerca che neutri, ma questo avviene solo quando viene indotta un'aspettativa temporale di un evento potenzialmente distraente. Nel complesso, i risultati suggeriscono che sia nel feature che nel conjunction search l’attenzione è modulata in maniera proattiva per meglio affrontare le aspettative rispetto alle richieste del compito formate sulle precedenti esperienze.

(2018). Proactive Top-Down Processes in Visual Search. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2018).

Proactive Top-Down Processes in Visual Search

PETILLI, MARCO ALESSANDRO
2018

Abstract

Literature has long investigated the contributions of top-down and bottom-up processes in guiding search behavior. Recent findings suggest a modulatory role of top-down processes on attentional capture. However, results are contradictory, and whether and how top-down processes intervene has not been clearly established yet. Here, we approached the issue from the perspective of proactive top-down processes of distractor expectation and leveraged the Distractor Context Manipulation (DCM) paradigm to help characterizing their recruitment in visual search. Thus, we combined a feature search (i.e., search for a high-contrast target among no-contrast distractors) and a conjunction search (i.e., search for a high-contrast target among high-contrast distractors) with the DCM paradigm (Exp 1-4). Accordingly, blocks of trials were of three types: a Pure block containing no distractor-present trials, and two blocks containing frequent distractor-present trials (i.e., Mixed Feature and Mixed Conjunction). Subjects were instructed to look for the target on each trial. The comparison of distractor-absent trials of Mixed vs Pure blocks allowed detecting proactive top-down processes of distractor expectation. First, we investigated whether proactive top-down processes were recruited in distracting contexts of visual search and whether their potential recruitment was modulated by the type of search (Exp 1). Results attested for a proactive recruitment of top-down processes of distractor expectation in both feature and conjunction search. Such recruitment entailed a response time (RT) cost as well as a beneficial enhancement of the detection sensitivity (d’) to the target when distractors were expected, yet not presented. Overlapping results emerged in covert (Exp 1, 3) and overt (Exp 2, 4) variants of visual search. Since previous distracting experience shaped distractor expectation, we, also, sought to disentangle the role of expectation and experience in the activation of top-down processes. Results (Exp 2, 4) showed that the distractor expectation cost occurred regardless of whether or not distractors occurred in the immediately preceding trial. However, the magnitude of the cost was larger after distracting trials suggesting that these processes do not rely only on tonic expectation-based mechanisms but they are also contingently reinstated after a distracting experience occurred. Experiment 3 tried to characterize the implicit vs explicit nature of top-down mechanisms triggered by distracting experience. Results showed that RT-costs and d'-benefits did not change when distraction occurrence was unpredictable and when it was predictable. Therefore, top-down control setting triggered by recent distracting experience seems to be not subjected to explicit control. Experiment 4 further investigated the role of experience and expectations in order to disentangle their relative contributions. Here, also another type of top-down expectation was manipulated: the temporal certainty of incoming potentially distracting event. Results indicated a preponderant role of top-down expectations by showing that RT-costs followed the time course of temporal expectation of incoming potentially distracting events while temporal recency from a previous distracting experience had a smaller weight. Finally, Experiment 4 explored the EEG correlates of distractor expectation. An enhancement of the occipital P1 amplitude was elicited by both search and neutral stimuli but only when a temporal expectation of a potentially distracting event was induced indicating that distractor expectation modulates visual attentional processes in lower sensory areas. Overall, results suggested that in both feature and conjunction search preparatory top-down processes are proactively enrolled to face with expected task demands based on previous distracting experiences. These results help characterizing how top-down mechanisms intervene in different types of visual search.
DAINI, ROBERTA
VisualSearch; TopDownExpectation; BottomUp; Distractor; ProactiveProcesses
VisualSearch,; TopDownExpectation,; BottomUp,; Distractor,; ProactiveProcesses
M-PSI/02 - PSICOBIOLOGIA E PSICOLOGIA FISIOLOGICA
English
20-feb-2018
PSICOLOGIA, LINGUISTICA E NEUROSCIENZE COGNITIVE - 77R
30
2016/2017
open
(2018). Proactive Top-Down Processes in Visual Search. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2018).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/199069
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